NIUS2012 - ESS Neutron Imaging User Symposium

15 Apr 2012, 08:00 → 18 Apr 2012, 18:30 Europe/Zurich

"Himmelrych" (Hotel zur Therme, Bad Zurzach)

Anders Kaestner (Paul Scherrer Institut), Eberhard Lehmann (Paul Scherrer Institut)

Scope

The purpose of this meeting is to provide a forum for an active exchange of knowledge and experiences gained from neutron imaging experiments in the past years. Users from different European neutron sources (SINQ, BER-2, FRM-II …) are kindly invited to participate. In an intense dialog with the facilities’ operators and with the other participants of the symposium we want to identify the current state of the art in neutron imaging. This will define further requests for technical and scientific improvements of the method. An important part of the symposium is to brainstorm about how the image data best can be evaluated to gain most information from neutron imaging experiments.
Furthermore, we want to focus your interest to the options at the upcoming European Spallation Neutron Source ESS that will be built in Lund (Sweden) until 2019. The opportunities and challenges for different neutron imaging techniques should also be discussed during the meeting.

Sunday 15 April

Registration

Dinner

Monday 16 April

Introduction

Convener: Dr Nikolay Kardjilov (Helmholtz-Zentrum Berlin)

1 Introduction to the ESS-NIUS Symposium

NIUS has been initiated by three institutions (PSI, HZB and TUM) in order to have a platform for the users and the operators of the neutron imaging facilities to exchange knowledge about the recent research results and the new and improved options in the imaging techniques. In addition, the European Spallation Neutron Source ESS to be built in Lund, Sweden, comes into the game as a potential site to host an advanced neutron imaging facility as early as ESS comes into operation. Based on the experience gained during previous and running studies a forecast and brainstorming about future demands and options at the existing neutron imaging beam lines but also for ESS should be initiated during the workshop. Despite of the wide range of research topics we hope for mutual understanding of the imaging procedures and the research results presented by the participants. Their feedback is very welcome during and at the end of the workshop in order to define the right scientific arguments and technical layout of the future ESS facility for neutron imaging.

Speaker: Dr Eberhard Lehmann (Paul Scherrer Instiut)

Slides Lehmann.pdf

2 Prospects for neutron imaging at the ESS long pulse source

Beside the powerful tool of conventional attenuation contrast imaging with a broad thermal or cold energy spectrum a number of novel imaging methods exploiting a monochromatic beam or energy resolved approaches have become available within the last decade [1]. These developments have the potential and do extend the range of applications of neutron imaging significantly. Modern short pulse spallation neutron sources are advantageous as compared to continuous sources especially for methods requiring relatively high wavelength resolution, which are those utilizing Bragg scattering for imaging contrast and providing spatially resolved information about crystalline structures present in a sample. The planned long pulse target station of the ESS on the other hand provides the potential to serve most to date available neutron imaging contrast methods with an outstanding efficiency [2,3] including (i) conventional attenuation contrast [1], (ii) energy resolved attenuation contrast imaging exploiting Bragg scattering [3,4], (iii) phase contrast imaging addressing the refractive index distribution of the sample, (iv) polarized neutron imaging with the aim to investigate magnetic structures, fields and phenomena [5,6] as well as (v) dark-field contrast imaging with the potential to investigate (magnetic) microstructures beyond real space resolution [7,8]. The potential of wavelength resolved application of the latter methods, i.e. polarized neutron imaging, phase and dark-field contrast imaging but also Bragg edge imaging has been outlined [2,3]. However, the development of such techniques as well as their specific requirements and information output are still a task for intense engagement and further exploration. The state-of-the-art as well as directions of progress will be presented and discussed. Additionally, the design of an efficient future instrument with such a range of flexibility, in particular concerning wavelength resolution, at the long pulse target station constitutes a significant challenge. This conveys (i) especially an appropriate chopper system, a novel task for imaging instruments [2,3], required to achieve such wavelength resolution as well as to define the utilized wavelength band, (ii) an appropriate transport of a useful divergence, flux and spectrum via neutron guides and optics, but also (iii) novel technological solutions especially for time resolved high spatial resolution image detection [9]. First approaches and ideas for such an instrument as well as its potentials for future science cases will be presented and discussed. [1] M. Strobl, N. Kardjilov, A. Hilger, I. Manke, J. Banhart, J. Phys. D 42 (2009) 243001 [2] M. Strobl, Nucl. Instr. and Meth. A 604 (2009) 646–652 [3] M. Strobl, N. Kardjilov, A. Hilger, D. Penumadu, I. Manke, NIMA, 651, 1 (2011) 57-61 [4] Santisteban J R, Edwards L, Steuwer A and Withers P J 2001 J. Appl. Cryst. 34 289-97 [5] N. Kardjilov et al. Nature Physics, 4 (2008) [6] M. Strobl et al., Phys. B 404 (2009) 2611 [7] M. Strobl et al, PRL 101, 123902 (2008) [8] I. Manke et al. Nat. Commun. 1, 125, DOI:10.1038/ncomms1125 (2010) [9] A.S. Tremsin, et al., Nucl. Instr. and Meth. A 592 (2008) 374

Speaker: Dr Markus Strobl (ESS-AB, Science Division, Lund, Sweden)

Slides Strobl.pdf

3 IAEA Activities Related to Neutron Imaging

The use of neutron imaging at research reactors (RRs) or spallation neutron sources for industrial applications such as non-destructive examination and testing has already been proven in industrialized countries. This technique allows for studies of a material’s characterization, strength, integrity, and durability without inflicting permanent damage to the material itself. The advantage of neutrons, compared to X-rays, is that they are sensitive to many light elements, have deeper penetration length, and are also sensitive to magnetic structures. Furthermore, as neutron imaging technology has advanced, its techniques have become more precise, efficient and much faster, specifically in the incorporation of digital radiography (2D), computed tomography (3D), energy-selective neutron imaging or dynamic (real-time) neutron imaging. These new techniques, in addition to advanced capabilities, also eliminate the need for consumables like films and other potentially hazardous chemical compounds used in film-based radiography. Today the major fields of neutron imaging application include the mining, oil and petroleum industries, car and aviation industries, archaeology, cultural heritage, environment, biology, medicine, physics, including energy sector that ranges from nuclear power industry to new technologies such as hydrogen cells and lithium batteries. The IAEA RR Database (RRDB, http://nucleus.iaea.org/RRDB/ indicates that more than 50 RRs (out of ~240 facilities operational) operate film-based or digital neutron radiography station. In this paper we will present the strategy and concrete actions how the IAEA is assisting its Member States in neutron imaging related activities that certainly has a great potential to contribute to the enhanced and more sustainable RR utilization. Our efforts include but are not limited to organization of Technical Meetings, Workshops and Schools, coordination of Coordinated Research Projects, support of Facility and Users’ Networks, collection of facility specifications, facilitation of Round Robin exercises, publication of Technical Documents and promotional brochures. Last but not the least, through technical cooperation assistance, the IAEA provides technical and financial support for modernization of existing or construction of new neutron imaging facilities in the developing countries. It is expected that at least 5 neutron imaging facilities world-wide will receive such assistance in 2012-2013. Since very recently some joint activities are under discussion with the international Society of Neutron Radiology (ISNR).

Speaker: Dr Danas Ridikas (IAEA)

Slides Ridikas.pdf

4 Neutron Imaging Facilities at PSI

Neutron imaging capabilities are allocated at the Swiss spallation neutron source SINQ since the beginning of its operation in 1997. The first beam line for this kind of studies – NEUTRA - has been built at a thermal beam port with low gamma background and a well defined neutron distribution. Investigations for different research groups and also for industry have been performed by using several kinds of digital imaging detection systems with their well-known superior performance. In particular, NEUTRA enables neutron tomography on different size scales, time-dependent studies and the investigation of highly activated material in the NEURAP configuration of NEUTRA. Recently, we implemented an X-ray tube too with high voltages until 320 kV with the aim to enable pixel-wise referenced imaging in combination with the neutron image data. ICON is a second imaging facility at a cold beam port with the direct view to the cold D2-moderator. The beam can be tuned in respect to collimation or intensity by means of different apertures in a selection wheel. With the help of an optional turbine-type energy selector or with an implemented Be-filter the neutron spectrum can be modified. A band filter type device (TESI) based on the reflection at single crystals is under completion and will be used for the further narrowing of the spectrum. Furthermore, a grating interferometer has been built for phase-contrast type and dark field imaging studies. ICON is equipped with three different camera based detection systems, among them a micro-setup with presently highest spatial resolution. The test beam line BOA which is designed for methodical studies and used only PSI internally is already equipped with an imaging detection system. The beam at BOA is polarized and has a quite high intensity of very cold neutrons. These properties look very promising for future interesting studies and developments at PSI.

Speaker: Dr Christian Grünzweig (Paul Scherrer Institut)

Slides Gruenzweig.pdf

5 Non-imaging instruments at SINQ – The future may include hybrids

Neutron scattering is a key experimental tool for experimental studies ranging from modern topics in condensed matter physics and materials science to pressing questions in energy research and health care. I will present the current suite of instruments at SINQ and activities in the Laboratory for Neutron Scattering (LNS) and in the Laboratory for Developments and Methods (LDM) on future instrumentation for the ESS. A consortium including Switzerland and Denmark is working on a hybrid instrument combining neutron imaging, powder diffraction and small-angle scattering to probe different length scales simultaneously. The development of this novel concept requires input from the respective communities and may be of great interest to the attendees of the symposium.

Speaker: Dr Christian Rüegg (Paul Scherrer Institut)

coffee break

Plant / Soil interaction

Convener: Dr Nikolay Kardjilov (Helmholtz-Zentrum Berlin)

6 Imaging water flow in soils and roots

Plants need continuous and adequate supply of water from soils. How do plant roots can sustain the water demand set by transpiration, in particular when water becomes limited and heterogeneously distributed? This is a central question in hydrology and agriculture, in particular in times of climate change, when precipitation is expected to become more irregular and rare. Our understanding of plant-soil water relations suffers from the lack of experimental methods to directly measure root water uptake in-situ. Nowadays, advances in imaging techniques such as X-ray CT, NMR, and neutron radiography and tomography offer new possibilities to image root and water distribution in soils. In particular, neutron radiography of water distribution near roots of transpiring plants revealed an unexpected behavior of the soil near roots, the so called rhizosphere (Carminati et al., 2010). In contrast to the existing theory, rhizosphere was wetter than the adjacent bulk soil during drying. Interestingly, after irrigation the rhizosphere remained markedly dry. The consequence of such unexpected properties of the rhizosphere are not known and need complementary experiments. In particular, a method to measure the fluxes of water from soil to roots is needed. Here we present a new method to directly image water flow across the root-soil interface and along roots. We used neutron radiography to trace the transport of heavy water (D_2O) from soil to roots of transpiring plants. The flow rate of D_2O into the roots was modeled with a diffusion-convection equation. Comparison between model and observations gave: 1) the permeability of roots and 2) the local root water uptake. The model was validated by independent measurements of flow along roots. With this new method we measured for the first time the water flow across the soil-root interface. Our results were based on two-dimensional images, from which we extrapolated the profile of D_2O across the roots. The estimations, as well as the validation of the model, would be much more accurate if three-dimensional images of D_2O transport into roots were available. The half time of D_2O flow into roots was in the order of 2-3 minutes. Our next objective/wish is to monitor D_2O transport in soil and roots at high resolution in three-dimensions by means of neutron tomography. Such results will bring new insights on how water enters the roots.

Speaker: Prof. Andrea Carminati (Georg-August-University Goettingen)

Slides Carminati.pdf

7 Contribution of neutron imaging to assess key processes at the root-soil interface

Imaging with neutrons has been shown the last years to be a powerful and precise tool to address not only water content dynamics in soil and sediments, but also to identify and track root structures and root growth. The recent developments have seen a special focus on zooming into the root-soil interface, but also to broaden the perspective by introducing additional methodological procedures for neutron imaging or by coupling to other imaging techniques. The latter is, for example, aiming to measure life-controlling parameters such as oxygen and pH dynamics in the soil ecosystem. For that aim we coupled neutron radiography with novel fluorescence imaging techniques to study the dynamics of these two essential biogeochemical parameters in the root-zone of plants in combination with water content. Measuring the real-time distribution of water, oxygen concentration and pH enables us to understand where the active parts of the roots are located in respect to water uptake, respiration and output of acids or bases. Roots performance itself is variable as a function of age and local conditions such as water and oxygen availability in soil, and the same is true for micro-organisms living in the root-zone. It is technically challenging to monitor these dynamics in such a small distance from the roots without disturbing them. Moreover, this process network with various links and feed-backs can be interpreted the better, the more aspects of the root-soil interaction can be assessed in the same sample during a particular period of time. We will present results of thin boron-free glass containers filled with fine sand of different grain sizes (inner size 10cm x 10cm x 1cm) with a growing lupine plant, and a built in sensor foil for O2, during night and day cycles of different water content and oxygen deficit. Another focus is on the spatial distribution of water uptake in the root system. Several factors, e.g. modified hydraulic properties of the soil around the roots, vary along the root system and may change with time. To address the spatial heterogeneity of root water uptake and its reasons water balances and water fluxes need to be quantified for different sections of the root system. One approach here is the hydraulically separate parts of the root system, to allow for local water balances by neutron radiography. Another is to visualize water movement by adding substances that can act as neutron radiography tracers, for example heavy water or Gadolinium complexes. These approaches have to be tested to judge their ability to quantitatively determine water fluxes from soil into the root, or even the other way round.

Speaker: Prof. Sascha Oswald (University of Potsdam)

Slides Oswald.pdf

8 The influence of heterogeneous water and phosphorus supply on root growth in soil

Phosphorus (P) and water are the two most limiting resources for plant growth in natural and agricultural ecosystems. Water and P distribution in soil varies over time and space and is heterogeneous on the scale of a root system. Temporal and spatial adaptation of root growth to these heterogeneities is crucial for nutrient and water uptake, plant fitness and plant production. Many plant species which are adapted to P-poor soil, develope root modifications like cluster roots to increase P uptake. Cluster roots are densely packed rootlets with increased organic acid exudation. P is considered to be the main factor determining cluster root production. The effect of water on cluster root production has not been elucidated yet. We conducted to growth chamber experiments using neutron radiography (NR) to investigate root and cluster root allocation patterns in soil with heterogeneous P and water distribution. We used the neutron imaging facility NEUTRA for thermal neutrons at PSI (Villigen). In the first experiment, we supplied P fertilized soil to single root tips of Lupinus albus to investigate the effect of localized P supply on cluster root initiation. The roots were tracked in NR images on 20 day old root systems The soil around the root tips was thoroughly removed and replaced with unfertilized or fertilized soil (15, 40 or 100 mg P/ kg soil). We established six replicates. Ten days after soil replacement we washed the soil from the roots and counted the number of cluster roots produced on the treated root tips. Three root tips treated with 100 mg P/ kg soil, produced cluster roots. Only one tip treated with 40 or 15 mg P or the unfertilized control soil produced a cluster root. In the second experiment, we used L. albus to investigate root growth allocation in soil with heterogeneous water and P distribution. Therefore we established heterogeneous P and/or water distributions by implementing vertical bands of soil fertilized with P (30 mg kg-1) and/or with increased available water capacity (AWC). Treatments with homogeneous water and P distribution served as controls. The root system was imaged using NR on day 12, 19 and 35 after seeding. When water availability was limiting plant growth, cluster roots were preferentially allocated in the soil parts with lower water content (and lower AWC). Heterogeneous P distribution had no effect on cluster root allocation, neither at high, nor at low water availability. Results demonstrate that heterogeneous water distribution is more important for cluster root allocation than heterogeneous P concentration in soil. Locally increased water availability hindered cluster root production, while locally increased P concentrations tended to promote cluster root production. This opposite effect of water and P is surprising because P diffusivity in soil and consequently P availability increases with water content. Results suggest that water content or other soil physical parameters influenced cluster root production independently from P availability.

Speaker: Mr Bernd Felderer (ETHZ)

Slides Felderer.pdf

Lunch

Building materials

Convener: Dr Markus Strobl (ESS-AB)

9 Moisture movement and durability of cement-based composite materials

Service life of most reinforced concrete structures exposed to agressive environment is not sufficient. In many countries this fact is both an economical and an ecological serious problem. Frequently transport of aqueous salt solutions is at the origin of early deterioration. Neutron imaging has proved to be a unique test method to determine moisture movement in the micro-porous structure of concrete. It will be shown that the ingress of salt solutions such as seawater can be significantly reduced by water repellent surface treatment. The influence of frost action on moisture migration will be outlined. Special emphasis will be placed on the role of cracks in moisture transport. Results obtained so far serve as solid basis for further investigations.

Speaker: Prof. Folker Wittmann (Aedificat Institute Freiburg (AIF) and Qingdao Tech)

Slides Wittmann.pdf

10 PATCHY MICROSTRUCTURE OF CEMENT PASTE INVESTIGATED BY NEUTRON AND SYNCHROTRON X-RAY TOMOGRAPHY

It has previously been shown [1-2] that concretes and mortars exhibit a patchy microstructure of hardened cement paste (hcp), i.e. a microstructure in which dense areas of hcp are sharply delineated from porous areas. Similarly, patchy microstructure has also been observed in samples of hardened cement pastes with embedded water-saturated light-weight aggregates [3,4] and superabsorbent polymers [5]. While the presence of the patchy microstructure in hcp influences macroscale material properties, the reasons for its occurrence are yet to be fully understood. Here we report on the results of combined neutron (NT) and synchrotron X-ray (SRμCT) tomography investigation of one sample of early-age cement paste of water to cement ratio (wcr) of 0.28. The cement paste was tomographed by X-rays (TOMCAT beamline, PSI) and neutrons (ICON beamline, PSI) both before and after setting. The patch domains revealed by SRμCT correspond to areas that exhibit higher than the average signal for the cement paste in the NT acquired before cement paste setting. These areas of higher porosity exhibit major decrease in the neutron tomography signal in the experiments performed after the setting time. Based on these observations, we suggest that the inhomogeneity that leads to the patchy porosity observable in the cement pastes in the hardened state is present in the material structure already at the very early ages after mixing/casting and that the porous patch domains originally exhibit higher than average wcr. Some possible mechanisms of occurrence of the observed patchy microstructure are proposed. REFERENCES [1] S. Diamond, The patchy structure of cement paste in conventional concretes, Concrete Science and Engineering: A Tribute to Arnon Bentur, RILEM Proc. PRO, vol. 36, RILEM Publications S.A.R.L, Paris, 2004, pp. 85– 94. [2] S. Diamond, E. Landis, Microstructural features of a mortar as seen by computed microtomography, Materials and Structures, Vol. 40, 2007, p. 989–993 [3] P. Trtik, B. Münch, W.J. Weiss, A. Kaestner, I. Jerjen, L. Josic, E. Lehmann, P. Lura, P. Release of internal curing water from lightweight aggregates in cement paste investigated by neutron and X-ray tomography, Nuclear Instruments and Methods in Physics Research A, 651 (2011) 244–249 [4] P.Trtik, B. Münch, W.J. Weiss, I. Jerjen, A. Kaestner, E. Lehmann, P. Lura, Patchy microstructure of hardened cement pastes – an insight by the combination of neutron and X-ray tomographies, poster, WCNR-9, Kwa Maritane, South Africa, 2010 [5] P. Trtik, B. Münch, W.J. Weiss, G. Herth, A. Kaestner, E. Lehmann, P. Lura, Neutron tomography investigation of water release from superabsorbent polymers in cement paste, International RILEM Conference on Material Science (MatSci), Aachen, Germany, 2010

Speaker: Dr Pavel Trtik (EMPA Dubendorf)

11 Neutron imaging of transport in porous materials: rocks, gypsum, asphalt, clay brick, wood, and fruits

We use neutron imaging to acquire the spatial distribution of water, or other fluids, in porous materials during wetting (in liquid or vapor phase), redistribution, drying, with or without the presence of temperature gradients. In addition, we impose different boundary conditions such as control air flow above the porous material, using a micro windtunnel, or controlled changes in relative humidity using an environmental chamber. We have documented sedimentary stones, gypsum, porous asphalt, clay brick, hard and soft wood, apples and pears. Neutron imaging provides invaluable quantitative information, of very high resolution in moisture content, space and time. Such information is used for identifying the physics of the transport processes, material properties determination and for validation of computer models. In terms of modeling, we have developed a comprehensive framework using a fully coupled transport, chemical and poromechanical approach. Its multiscale implementation provides the capacity to take into account heat and mass transport, swelling and mechanical behavior at different material scales. The air, heat and moisture flow above the porous medium and the interaction with the porous medium is modeled by coupling the porous material model to a computational fluid dynamics code. We will present the different types of experiments that we have run at Neutra and Icon, PSI, Villigen, some insights from the analysis of the data and examples of numerical simulations.

Speaker: Dr Dominique Derome (Empa)

Slides Derome.pdf

Short presentations (Poster session)

Convener: Dr Markus Strobl (ESS-AB)

12 TIPSI hybrid spectrometer at the planned European Spallations Neutron Source ESS: Probing different length scales simultaneously

On going material performance improvement leads to incorporate advance ceramics/polymer/metals/ into diverse heterogeneous system (metallic matrix, carbon, nanofiber etc…). The behavior and performances of these systems usually depends on the interplay between atomic, nano/meso and macros/microscopic structure. Traditionally the structural information on these length is determined separately by wide angle diffraction techniques (atomic/nanoscopic in reciprocal space Q=[0.3, 10] Å-1), by small angle diffraction (nano/meso Q[0.002, 0.1]Å-1) experiments and direct space technique like imaging/SeSANS one for submicronics to millimeter sizes. The goal of the proposed hybrid instrument at ESS, TIPSI, is to study these materials in operandi and in situ at multiple length scales with high time resolution to obtain a multi-length scale coherent picture. The idea is to use simultaneous or quasi simultaneous neutron powder diffraction (NPD), small angle neutron scattering (SANS/SeSANS) and neutron imaging (NI) to cover a broad range of length scales. Technique Diffraction Small angle scattering Imaging Length scale ~0.01-5 nm ~1-1000 nm ~0.01-100 mm The challenge in combining the different methods is simultaneous optimization. The different techniques have significantly different requirements regarding optimal working conditions. The challenges will be met by using two neutron sources – both a cold and a thermal source. The instrument is envisioned to have a length of 180 m; this is a sweet spot for placing a resolution chopper at 6 m distance from the moderator and allows sufficient space for directing two beams onto the same sample spot by curved guides. Chopper pulse selectors will alternately send pulses from the cold and the thermal source to avoid confusing the detector. However it is possible that frame overlap can be handled and in this case every pulse can be used.

Speaker: Dr Nadir ALIOUANE (Paul scherrer Institut, Laboratory for neutron scattering)

Slides Aliouane.pdf

13 Neutron Imaging at IBR-2 Pulsed Reactor: First Results and Neutron Imaging Instrument Project

The method of neutron imaging is considered as an important technique for non-destructive testing and as research tool in physics, material science, geology, archaeology, etc. Therefore shortly after the launch of the IBR-2 pulsed reactor after modernization the first test experiments were performed on beamline Nr. 12 of the reactor. The first obtained results confirmed the good perspectives of this method at the IBR-2 reactor. For further development of neutron imaging (including radiography and tomography techniques) in Dubna a project for construction of “conventional” thermal neutron imaging station at FLNP JINR was started. The instrument will be installed on the beamline Nr. 14 of the IBR-2 pulsed reactor and it will be equipped with common neutron radiography components like aperture wheel, shutter, collimation tubes, goniometer for sample positioning, CCD-camera based detector and beam dump with adequate shielding around. The IBR-2 reactor as an existing long pulsed neutron source can provide energy selection option combined with high neutron flux which gives unique opportunities in many scientific and industrial applications.

Speaker: Gizo Bokuchava (FLNP JINR, Dubna, Russia)

Slides Bokuchava.pdf

14 Neutron imaging options for the Institut Laue Langevin (ILL)

The high flux reactor source at the ILL, Grenoble provides the highest continuous neutron fluxes current available worldwide. To exploit this position in 2002 the NEUTROGRAPH instrument for dynamic radiography and tomography was constructed. It is set up at the H9 beam line was operational since October 2002, as a collaboration between the ILL and the University of Heidelberg. With a high-intensity thermal neutron beam of about 3x109 n cm-2 s-1, NEUTROGRAPH is dedicated to real-time, snapshot and stroboscopic radiography with time resolution down to a few microseconds, as well as dynamic tomography on a sub-minute time scale. The high intensity also allows the visualization of thick and strongly absorbing materials. This allows investigation of larger samples with extremely low contrast, as in some fields of material science and archaeology. However the neutron imaging field has evolved over the past decade and hence there is an opportunity for a new generation of instrument to be conceived that can exploit the high flux to help push the current boundaries of spatial and time resolution. As part of this process, a concept for a new instrument has been developed but requires significant contribution from the community. An overview of the state of the art of imaging at the ILL will be presented, followed by a vision concept for a new instrument, IMAGEN. Feedback from the community will be greatly appreciated to direct the focus of the concept which will be advanced to a proposed new instrument at the ILL.

Speaker: Dr Alexander Evans (Institut Laue Langevin)

Slides Evans.pdf

15 Energy-selective neutron imaging on IMAT

A new facility for neutron imaging and neutron diffraction called IMAT (Imaging and Materials Science) is currently being built at the pulsed neutron spallation source ISIS. IMAT will be available for a wide range of materials science applications with a main emphasis on engineering science. The special feature of IMAT will be energy-dependent imaging combined with neutron diffraction. The pulsed source operation facilitates a very flexible selection of neutron wavelength bands and a good energy resolution. Energy-selective imaging applications on IMAT will take advantage of the Bragg edge features in the total cross sections of many engineering materials. High-resolution Bragg edge mapping will allow visualizing structure properties in a material, for example strain and texture components, and show features which are invisible in conventional white-beam radiography data. An interesting aspect of IMAT will be tomography-driven diffraction for studying structurally and geometrically complex samples. The structures and materials inside engineering-sized samples can be more effectively analysed if the diffraction scans are guided by radiographic data. Vice versa, diffraction data may be indispensable for a physical interpretation of the wavelength-dependent attenuation features in radiography data.

Speaker: Winfried Kockelmann (ISIS Facility, Rutherford Appleton Laboratory)

Slides Kockelmann.pdf

16 Characterization of Japanese Helmets through Neutron Imaging Techniques

Investigation of the forging and assembly of armour is one of the most interesting topics in ancient Japanese technology. In this work, we present novel results from a non-invasive approach to the study of two Japanese helmets (kabuto) made in the 17th Century. There are many different types of Japanese helmets, but they can be grouped into three main categories: those made from a single sheet of metal, those assembled from a small number of sheets, and those assembled from a number (varying between 8 and 128) of lamellar plates arranged in a circular fashion around the crown of the head. One of the helmets studied (H1) is a Horagai Bachi, an example of the first of the three helmet types. This is a Tetsu bari shiki kawari-bachi (wonderfully shaped steel helmet) made, in the form of a shell, by Ryōei - Ohara Katsunari from Hiroshima province at the end of the 17th Century. This helmet was made available by the Stibbert Museum in Florence. The second Kabuto (H2) is an example of the third type. It is a Saotome Bachi made in the 1st half of the 17th Century. It is made up of 62 lamellar plates finished with a visor decorated with two opposing gold dragons. The components are joined by rivets, which are invisible to outside inspection, and the entire surface is lacquered. This helmet was kindly provided by a private collector. (It was formerly part of the H.R. Robinson collection) Such ancient armours are quite rare and when found in museums, are usually in an excellent condition of conservation. Thus, traditional (invasive) analytical methods cannot generally be applied, and, a non invasive approach is mandatory. Neutron techniques, which are able to identify the morphology and the inner structure of artefacts have been applied in order to determine their methods of manufacture. Thanks to their high powers of penetration [G. L. Squires, 1996; V. F. Sears, 1992], neutrons represent an almost unique method for the non-invasive characterization of the microstructure of massive metal objects. These techniques have been recently applied to the study of metal artefacts of archaeological [S. Siano et al., 2002] and historical [F. Grazzi et al., 2009] origin, and have given detailed information on bulk properties (e.g. phase composition, texture, residual strain distribution) which has allowed us to obtain information about their manufacturing techniques. On a different scale, neutron tomography techniques can add useful information about the bulk conservation status [E. Lehmann el al., 2005] and the inner structure (when present) of the artefact [E. Lehmann el al., 2010]. We will discuss here the results of neutron imaging experiments (radiography and tomography) carried out at the ICON and NEUTRA beamlines operating at the neutron source SINQ (CH), applied to helmets H1 and H2 respectively. A preliminary test measurement was carried out on the helmet H1 by irradiating it for 60 seconds and measuring the gamma emission spectrum. The activation level was measured and, from the analysis of the gamma spectrum, we were able to gain information about the elemental composition, excluding iron. In order to limit the activation level induced by the presence of copper, the helmet H1 was investigated by only 13 neutron radiographs in total, taken at different positions of the helmet. As a result of the radiography, we have identified a circular brazing, close to the top, connecting the upper to the lower parts of the helmet, and a linear brazing used to secure the single plate forming the lower part of the helmet. Those brazing were invisible at a visual inspection. Concerning the helmet H2 a full neutron tomography was possible. Tomographic reconstruction of the inner volume of the helmet in 3D, with preliminary treatment of the images obtained, has allowed us to acquire further information about the structure and methods of assembly. In particular the actual arrangement of the lamellar plates, and the location of hidden rivets. SQUIRES, G. L., 1996. Introduction to the theory of Thermal Neutron Scattering, Dover Publication Inc., (NEW YORK). SEARS, V. F., 1992. Neutron scattering lengths and cross sections. Neutron News 3, 26-37. SIANO, S. ET. AL., 2002. Quantitative multiphase analysis of archaeological bronzes by neutron diffraction. Applied Physics A, 74, S1139-S1142. GRAZZI, F. ET AL., 2009. Neutron diffraction characterization of Japanese artworks of Tokugawa age. Anal. Bioanal Chem. 395,1961–1968. LEHMANN, E.H. ET AL., 2005. Non-invasive studies of objects from cultural heritage. Nucl. Instr. and Meth. A 542, 68-75. LEHMANN, E.H., HARTMANN, S., SPEIDEL, M. O., 2010. Investigation of the content of ancient Tibetan metallic Buddha statues by means of Neutron Imaging Methods. Archaeometry 52, 416–428.

Speaker: Ms Filomena Salvemini (Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, 50019 Sesto Fiorentino (FI), Italy)

Slides Salvemini.pdf

17 Neutron imaging and the destroyed nuclear fuels from Fukushima-1 nuclear power plant accidents

The non-destructive techniques, as mentioned in the followings, are to be applied usefully for non-destructive analysis of failed core fuels and materials in the reactors no.1-3 and spent fuels in the fuel pools no.1-4 in the Fukushima-Daiichi PPTs. Heavy elements like as actinides have commonly a sharp neutron resonance absorption. Resonance energy depends intrinsically on nuclide structure. So different resonance energy is observed among its isotopes. Using neutron radiographic imaging, 3-dimmensional distribution of isotopes in the material may be visualized individually. This can be applied to the post-irradiation examination of nuclear fuel elements containing various actinides and their isotopes. This work is concerned to neutron radiographic post-irradiation examinations of nuclear fuel materials by using a newly proposed, designed and fabricated “gamma-ray insensitive” Imaging Plate. Some experimental results are characterisation of the newly fabricated imaging plate (Dy-IP) and its application for experimental neutron radiography test under realistic post-irradiated conditions. The gamma-ray fogging is suppressed by the direct imaging technique using a Dy-containing imaging plate. Imaging procedures of Dy-IP is modelled as (1)neutron(and gamma-ray) exposure, (2)erasure by visible light, (3)self-exposure by radio-activated Dy, and (4)readout of photo-stimulated luminescence (PSL). The realistic post-irradiated NR experiment using the Dy-IP has been conducted in a usual manner at the NEURAP installation of SINQ, PSI. This setup enables the inspection of rod-type samples within a well -shielded facility, where the positioning in height and angular position can be handled precisely. Just after neutron exposure (for 24 min) and erasing the direct exposure image (for about 15 min), the PSL material of the IP is exposed auto-radiographically for 120 min by the Dy-165 decay in the Dy-IP sheet, which results in -fog free NR imaging. The direct technique image by Dy-IP is very clear and high contrast. Spatial resolution is 0.200mm. Gamma-fog free NR images have been obtained for the post irradiation nuclear fuel pin. Hydrogen precipitates in the cladding and inter-fuel pellet gap are clearly observed. The method is very useful for the inspection and even quantitative analysis of highly activated probes as spent fuel, reactor core components and spallation target rods. Details are found in the references. References 1)M.TAMAKI et al., “Record and display methods of neutron radiographic imaging”, Japan patent Heisei_11-23799(1999). 2)M. TAMAKI et al., ”The direct dysprosium(Dy) imaging technique and its experimental test under realistic conditions during the NEURAP-18 run”, PSI Scientific Report 2003,3,187 (2004). 3)M.TAMAKI et al., “Dy-IP Characterization and its Application for Experimental Neutron Radiography Tests under Realistic Conditions”, Nucl.Instrum. Meth. A, 542,320-323(2005). 4)M.TAMAKI et al., “Post-irradiation Analysis of SINQ Target Rods by Thermal Neutron Radiography”, J.Nucl.Mater., 356, 162-167(2006). 5) M.TAMAKI et al., “Post-Irradiation Examination using Neutron Imaging Technique for Visualization of Hydride Precipitates in Nuclear Fuel Cladding” Proc. of Symposium on Water Chemistry and Corrosion in Nuclear Power Plants in Asia 2009, October , 2009, Nagoya, Japan.

Speaker: Dr Masayoshi Tamaki (TAMAKI Memorial Institute)

Slides Tamaki.pdf

18 From the ANCIENT CHARM Project to the future combined PGAI-NT station at FRM II

In frame of the ANCIENT CHARM project in 2006-2009 we have built a testing Prompt Gamma Activation Imaging installation combined with a Neutron Tomography set-up. Although the divergence of our beam is due to an elliptical end of the beam guide not optimal for tomography purposes, we have got an image-resolution smaller than 500 um. This resolution was sufficient in order to navigate the sample in the scanning mode for PGAI purposes (with ca. 2.3 mm x 2.3 mm large neutron beam). The knowledge we have learned during the ANCIENT CHARM project was a motivation to build a more precise PGAI-NT instrument with a better PGAI resolution of down to 1 mm x 1 mm neutron beam. The PGA-NT instrument should be installed at the end of 2012.

Speaker: Dr Kudejova Petra (Technische Universität München, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II))

Slides Kudejova.pdf

19 Magnetic resonance and neutron imaging of infiltration into heterogeneous soil

The subject of the contribution is to show the possibilities of combining the three-dimensional magnetic resonance imaging (MRI) and neutron imaging (NI) to investigate the complex water flow dynamics in natural soil. The infiltration outflow experiment was conducted on undisturbed soil samples with concurrent imaging by i) MRI and ii) NI. Despite the experiment was conducted on two different samples, the experimental concept, type of soil and observed behaviour was the same. Additionally, both NI and MRI were used to image selected soil samples at various static water saturations. MRI of porous system and of soils in particular, is specific due to many issues related to the complex internal structure, varying pore sizes, interface interaction, etc. In small pores, due to very fast relaxation of hydrogen spins on solid-liquid interfaces, the MRI signal is difficult or impossible to detect with use of current MR scanners. On the other hand, the relaxation properties can be used to increase the image contrast between water contained in different pore size classes or distinguish between the water and tracer. The acquisition time increases with the image resolution, therefore, depending on the process dynamics the image resolution can be sometimes sacrificed in favour of capturing fast processes. During repeated ponded infiltration (RPI) experiment on undisturbed soil sample of coarse sandy loam (dia. 5.5 cm, height 11.2 cm) the process of infiltration and nickel nitrate transport was investigated combining MR imaging and MR relaxometry measurements. The RPI experiment consisted of two consecutive infiltration runs separated by drainage phase and differed in initial water content. Fast processes were imaged by a fast, low resolution MR sequence. The wetting, steady state flow and drainage phases as well as the nickel tracer breakthrough of each experimental run were monitored by multi-echo multi-slice magnetic resonance sequence. Mapping of relaxation parameters, which is substantially time consuming, was performed during steady state conditions. The RPI experiment reveals complicated water regime and flow instability characterized by a decrease of the steady state flow rates between the first infiltration run conducted into drier soil and the second infiltration run into wet soil. It was hypothesized that the discrete air phase entrapped in large pores causes substantial decrease of inflow/outflow flux density in the case of the second infiltration run. The spatial distribution and the volume of the entrapped air were extracted from MR image. The tracer breakthrough patterns showed significantly different flow trajectories during first and second infiltration run. In highly heterogeneous soil under study the pathways which conducted the dominant portion of the water/solute during the first infiltration run were the ones strongly affected by trapped air bubbles during the second run. Undisturbed samples (dia. 36 mm, height 100 mm) of the same soil type were investigated by NI likewise. Particular phases of ponded infiltration were imaged by neutron radiography (fast processes) to image fast processes in 2D and by neutron tomography to monitor slow processes in 3D. Identically to MRI the NI was able to detect the increase of the trapped air volume between first and second infiltration run and to identify the distribution of individual bubbles; however these air structures could be identified only in the voids larger than the voxels size. The study shows strengths of each of imaging methods and the potential of combining these two non-invasive methods for investigation of water phenomena in natural porous media.

Speaker: Ms Vladimira Jelinkova (Faculty of Civil Engineering, Czech Technical Univ. in Prague, Czech Republic)

Slides Jelinkova.pdf

20 The New Beamline for Neutron Optics and other Approaches BOA

The purpose of the instrument is to test new kinds of neutron optics and other applications e.g. in the field of neutron imaging and detector development. Presently the neutron beamline BOA is in the final commissioning phase at PSI/SINQ. The beamline is a redesign of the former fundamental physics instrument FUNSPIN. BOA is a 18 m long instrument located at beam channel 51 looking on the SINQ cold source. The existing primary polarization of the former FUNSPIN instrument is not changed because research with polarized neutrons is one of the key interests of the neutron community. The position of the beamline close to the cold source effects the performance of the instrument: The measured polarized neutron flux is around 2x108 n (cm2 s mA)-1. The secondary instrument is equipped with three turn able axes with flexible translation tables and aperture units. The maximum available space along the beam path is 12 m. An area sensitive CCD-camera system, a He-3 2d PSD neutron detector and a single He-3 neutron detector are available for the data acquisition.

Speaker: Dr Tobias Panzner (Paul Scherrer Institut , LDM)

Slides Panzner.pdf

21 Combined in-situ neutron diffraction and imaging for strain investigations

Wavelength dependent neutron transmission imaging has recently gained attention for the potential to spatially resolve texture, crystallographic phase and lattice strain. Especially promising is the time-of-flight (TOF) approach that takes maximum advantage of the new generation of pulsed spallation neutron sources, such as the SNS, JSNS and ESS. Compared to traditional (neutron) residual stress diffractometers, imaging approaches can obtain strain information over large areas simultaneously in one direction, while only one (gauge) volume at a time can be probed using traditional diffraction techniques. In practice, the majority of neutron diffraction experiments utilize gauge volumes on the order of millimeters and this limitation gets exacerbated with the use of radial collimators at TOF sources. Because of the need to use larger gauge volumes due to geometric complexities associated with slits and alignment, one cannot capture large strain gradients occurring over stress concentration areas effectively. Experiments with sub millimeter gauge volumes have been performed at residual stress instruments occasionally, but are extremely time intensive due to the small volume of diffraction and are prone to problems associated with partial scattering volume being occupied by air. Furthermore, the instrument alignment and sample positioning required for sub millimeter experiments are extremely important and can only be achieved if specialized equipment, such as laser alignment tracking systems with specialized software (for example SScanSS), is available. Neutron transmission imaging can overcome some of these limitations. The authors have undertaken measurements using the TOF engineering diffractometer (SMARTS) at Los Alamos Neutron Scattering Center (LANSCE), where two detector banks were used at 2θ of ±90° and a MCP (Multichannel Plate) detector in transmission geometry (2θ=180°). A tensile test was performed while acquiring data with all three detector systems, providing measurement of three separate strain components simultaneously. A torsion test was carried out, where imaging and diffraction was carried out separately, due to the non-uniform strain field in a torsion sample. Example data, experimental details and associated challenges will be discussed, which will be of relevance for current and future coupled imaging/diffraction beamlines and experiments.

Speaker: Mr Robin Woracek (University of Tennessee & Helmholtz Zentrum Berlin)

Slides Woracek.pdf

22 High Resolution Dual Modality (Neutron and X-ray) Imaging of Partially Saturated Sand and Direct Numerical Simulation Technique Application of Flow through Porous Media

High spatial resolution dual modality (neutron and X-ray) tomography was performed on partially water-saturated silica sand specimens with two different grain shape morphologies (round and angular) at Helmholtz-Zentrum-Berlin. Partially saturated sand specimens were placed in custom developed granular material compaction molds. Partially saturated silica sand is a three phase material consisting of solid phase (Silica: SiO2), gas phase (air), and liquid phase (water). Due to different attenuation characteristics of neutrons and X-rays to these three phases of interest, neutron and X-ray images provided unique but complementary information. While the water phase contrast is well identified using high resolution (~13.7 µm/voxel) cold neutron images without using a contrast agent, the detailed structure of silica phase is much clearly shown in higher resolution (~11.2 µm/voxel) X-ray images due to low attenuation of air/water phases to X-rays. Such dual modality image characteristics make the detailed spatial analysis of the three phases with high confidence by utilizing both contrasts. Image registration technique was further applied to align the neutron and X-ray data to the same location, and the three phases were quantified more precisely. Direct numerical simulation based on the actual pore geometry of a dry sand specimen obtained from X-ray tomography. Capillary pressure – saturation curves and the water distribution at different capillary pressures were obtained from the simulations. The data presented in this research is of critical importance to many disciplines that involve multi-phase flow visualization and analysis, granular mechanics that considers quantitative 3-D distribution of voids (gas and liquid phases) and solids, geotechnical and petroleum engineering, and contaminant transport through vadose zone. The dual modality imaging was presented as an effective tool to study partially saturated porous medium at micro scale. The technique has potential to be applied to experiments involving in-situ fluid flow and solid deformation, and the experimental results can be directly compared with image based simulation results.

Speaker: Mr Felix Kim (University of Tennessee)

Slides Kim.pdf

23 Energy-selective neutron imaging: methods and applications

Neutron radiography and its extension to tomography is based on transmission contrast by varying macroscopic cross sections in the sample of interest. Traditionally, a polychromatic beam is used, which enables to discriminate between different sample materials and thicknesses. By using a tunable monochromatic, cold neutron beam one can scan in transmission polycrystalline samples over the cold energy range, where so-called Bragg edges dominate the cross section. Those edges can be understood in the context of the Bragg law 2dhklsin(θhkl)=λ, where coherent elastic scattering at the hkl lattice plain is possible until 2dhkl=λ, after which a sharp increase in transmission intensity is observed because of decreased sample scattering out of the beam. In energy selective neutron imaging around these Bragg edges lays a new source of image contrast that contains microstructural information on the sample. It has the potential of becoming a new tool for material research complementary to existing diffraction techniques. The approach can also be extended to 3D tomography studies on request. A first part of this poster is dedicated to a study on the use of two monochromator types for energy selective imaging: the neutron velocity selector and a newly developed monochromator called TESI. The first features a large field-of-view and a monochromaticity Δλ/λ=15% realized through mechanical selection of the desired neutron energies. TESI uses a set of single crystals to scatter neutrons of unwanted energies out of the direct beam, to obtain a final monochromaticity of Δλ/λ=2%-5%. The second part of the poster deals with applications of energy-selective neutron imaging, with special focus on the combination with neutron diffraction imaging.

Speaker: Mr Steven Peetermans (Paul Scherrer Institut)

24 Quantified neutron and x-ray imaging in geomechanics

The understanding of the mechanics of geomaterials (i.e., soils and rocks) is central to many civil and research engineering projects. However the deformation of these materials is very complex with multi-scale phenomena (from interactions of individual grains to the evolution of deformation structures). Furthermore, these materials have inherent heterogeneity, both from their formation and in their mechanical behaviour with the evolution of localised deformation features such as fractures and shear-bands. In the presence of such heterogeneity, standard experimental measures (where stresses and strains are measured at points on a specimen boundary) loose their pertinence as they can only, at best, provide some average macroscopic response, which is not representative of the actual material behaviour. So-called "full-field" methods overcome many of the limitations of standard experimental approaches in that properties and processes can be characterised throughout test specimens as opposed to at discrete points at the surface. In this context, neutron and x-ray imaging techniques play a central role, as they permit 3D characterisation of the interior of samples including during experiments where the samples might be contained within some experimental device (thus allowing 4D imaging of the sample evolution). However to fully exploit the power of these methods requires data analysis procedures that can pull out quantified information on the properties and processes of interest. In this presentation, examples from a number of projects where neutron and x-ray imaging have been used to explore the mechanics of geomaterials will be provided. The examples include: in-situ x-ray tomography of sand undergoing triaxial compression; 3D Digital Image Correlation to derive continuum displacement and strain fields from time-lapse 3D images; discrete image-based grain tracking to derive full particle kinematics for many thousands of sand grains; tracking of fluid-flow through localised deformation features in a sandstone.

Speaker: Dr Stephen Hall (Division of Solid Mechanics, Lund University, Lund, Sweden and European Spallation Source AB, Lund, Sweden)

Slides Hall.pdf

25 Close future plans for radiography driven PGAA at FRM II in Munich

Prompt gamma activation analysis (PGAA), as well as neutron radiography are known as non-destructive neutron techniques. While in PGAA, the average elemental composition of the irradiated volume can be obtained, with neutron radiography one can visualise the internal structure of an inhomogeneous sample with a high resolution. With combining the two methods, the chemical composition of the sample details with different image contrasts can be determined and thus the spatial elemental distribution can be reconstructed, too. The PGAA instrument at FRM II was upgraded in 2011. The high-flux focussed beam provides a unique opportunity for high-resolution elemental mapping and the medium-flux homogeneous beam is ideal for radiography of objects with the size of a few centimetres. First, the neutron radiography part will be installed and tested in the characterisation of these neutron beams, then the radiography image of selected test objects will be measured and the resolution determined.

Speaker: Mr Stefan Söllradl (Paul Scherrer Institute & University of Bern)

Slides Soellradl.pdf

26 A new software protocol for high-throughput tomography using attenuation-contrast and phase-contrast

The Helmholtz-Zentrum Geesthacht is operating beamlines using neutrons at the FRM2, Munich and using synchrotron radiation at the Deutsches Elektronen-Synchrotron DESY, Hamburg. At the storage rings DORIS III and PETRA III four different beamlines are equipped to perform attenuation-contrast and phase-contrast microtomography. For the efficient use of beamtime and to increase the sample throughput a new data format is defined within the Helmholtz Foundation. Especially in tomography using SR and neutrons the close interaction of sample information, the experimental control, together with the reconstruction software is required. Therefore, a new software protocol for SR and neutron tomography is suggested. The concept and the status of the implementation will be given.

Speaker: Dr Felix Beckmann (Helmholtz-Zentrum Geesthacht)

Slides Beckmann.pdf

Poster session/ Coffee break

Fuel cells / Battery electro-chemistry

Convener: Dr Markus Strobl (ESS-AB)

27 Neutron Imaging of Water in Fuel cells – State of the Art and Future Opportunities

In situ neutron imaging of operating Polymer Electrolyte Fuel Cells (PEFCs) has been increasingly used in the past 10 years in order to visualize and quantify the distribution of liquid water. The Paul Scherrer Institute (PSI) could bring an important contribution to this field, thanks to the long term collaboration between the Electrochemistry Laboratory (ECL) and the Neutron Imaging and Activation Group (NIAG), both being part of PSI. Application to fuel cell has been a strong driver for improvements. In the last years, unprecedented spatial resolution could be reached [1-3], allowing in plane imaging (side view) of the cells besides the "traditional" through plane imaging. High resolution imaging was used to draw correlations between liquid water and mass transport losses [4], to study water transport characteristics with isotope labeling [5] and to observe the water/ice behavior in sub-zero fuel cell startup [6]. In current and future experiments, the use of limited beam time is optimized using a newly developed setup for the simultaneous imaging of 6 operating fuel cells [7]. The possibilities of detecting different phases of water (liquid/ice) with energy-selective imaging [8] in operating PEFCs will also be investigated. [1] P. Boillat, G. Scherer, A. Wokaun, G. Frei, and E. Lehmann, Electrochem. Commun. 10, 1311 (2008). [2] P. Boillat, G. Frei, E. H. Lehmann, G. G. Scherer, and A. Wokaun, Electrochem. Solid-State Lett. 13, B25 (2010). [3] E. Lehmann, G. Frei, G. Kühne, and P. Boillat, Nucl. Instr. Meth. A 576, 389 (2007). [4] P. Boillat, P. Oberholzer, R. Perego, R. Siegrist, A. Kaestner, E. Lehmann, G. Scherer, and A. Wokaun, ECS Transactions 41, 27 (2011). [5] P. Boillat, P. Oberholzer, B. C. Seyfang, A. Kaestner, R. Perego, G. G. Scherer, E. H. Lehmann, and A. Wokaun, J. Phys.: Condens. Matter 23, 234108 (2011). [6] P. Oberholzer, P. Boillat, R. Siegrist, R. Perego, A. Kastner, E. Lehmann, G. G. Scherer, and A. Wokaun, J. Electrochem. Soc. 159, B235 (2012). [7] P. Oberholzer, P. Boillat, R. Siegrist, A. Kaestner, E. Lehmann, G. Scherer, and A. Wokaun, Electrochem. Commun. , submitted for publication. [8] L. Josic, E. Lehmann, D. Mannes, N. Kardjilov, and A. Hilger, Nucl. Instr. Meth. A 670, 68 (2012).

Speaker: Dr Pierre Boillat (Paul Scherrer Institut (PSI))

Slides Boillat.pdf

28 Modeling of Li-Ion-batteries to optimize the results gained by neutron imaging

Monochromatic neutron beams or neutrons corresponding to a small wavelength band close to Bragg-edges are used to discriminate between different phases of materials or to gain a spatially resolved map of stress and strain inside a sample. Standard neutron radiography and tomography experiments on the contrary are acquired with a white neutron beam most of the time. This is done in order to improve the neutron statistics of the recorded transmission images by the increased neutron flux reaching the sample or the detector, respectively. In certain cases this may not yield the desired effects. It will be exemplified by measurements and calculations of the transmission through a Li-Ion-battery that a white neutron beam (thermal/cold) is not always the best choice for standard neutron radiography and tomography. A restricted band width of the neutron spectrum may not only give better results but also help to reduce the activation of the sample.

Speaker: Mr Martin Muehlbauer (TU-Darmstadt)

Slides Muehlbauer.pdf

29 Neutron imaging into an operating lithium-ion battery

Neutron imaging is a valuable tool for in situ characterizations, similar to x-ray radiography. Using time series of neutron images, the change in attenuation of a neutron beam passing through a sample can be used to follow a change in the material over time. The utilization of neutron imaging for fuel cell liquid water metrology has been demonstrated at PSI [1] and NIST [2]. A similar approach can be applied to measure the Li movement and degradation process of electrolyte between the positive and negative electrodes of an operating lithium-ion battery. Due to the high neutron cross-section of the hydrocarbon-based solvents, neutron radiography has been used to see the absorption of the electrolyte during cycling [3]. The neutron imaging experiment was performed at the spallation neutron source (SINQ) at PSI using the cold neutron imaging beam-line ICON to investigate the electrolyte decomposition processes in an electrochemical cell. With the experimental setup neutron imaging offers the ability of viewing directly in the processes between the two electrodes. This method allows us to observe the gaseous releases indirectly by a displacement of electrolyte through the gas emission. We have compared different cell chemistries to get a better understanding of the involved processes. Finally, it was possible to observe the gas evolution process during the first charge and discharge, which clearly shows that the SEI formation on graphite leads to gas releases. In addition, gas formation was observed for the high voltage spinel due to the decomposition reaction of electrolyte at high voltages. References: [1] E. Lehmann, P. Boillat, G. Scherrer, G. Frei, Methods Phys. Res., Sect. A, vol. 605, 123 – 126, 2009. [2] D. S. Hussey, D. L. Jacobson, M. Arif, K. J. Coakley, D. F. Vecchia, J. Fuel Cell Sci. and Tech.,7, no. 2, 021024, 2010. [3] M. Lanz, E. Lehmann, R. Imhof, I. Exnar, P. Novák, J. Power Sources, vol. 101, no. 2, 177 – 181, 2001. [4] A.P. Kaestner, S. Hartmann, G. Kuehne, G. Frei, C. Gruenzweig, L. Josic, F. Schmid, E.H. Lehmann, NIMA, vol 659(1), 387-393, 2011.

Speaker: Dr Heino Sommer (BASF SE)

Slides Sommer.pdf

30 Summary & Discussion

Dinner

Tuesday 17 April

Material research / Metallurgy

Convener: Dr Burkhard Schillinger (TU München FRM II)

31 Chemical diffusion in liquid metallic alloys

Mechanisms of diffusion are well understood in solids with a large database of diffusion coefficients available. For liquids the situation is less clear. An experimental database with accurate diffusion coefficients even for comparatively simple binary systems is currently not available. Hence, it is difficult to test existing theories, models, or data obtained by numerical modelling against experimental data. The reason for the absence of experimental data has a number of origins: i) Many metallic liquids are highly reactive and show a comparatively high melting point. ii) Capillary experiments used to determine chemical diffusion coefficients can be affected by convective flow in the liquid and segregation and sedimentation as well as microstructure formation during heating and cooling, respectively. As a results diffusion coefficients can easily vary by a factor of 2 to 4. Real-time monitoring of the capillary sample during diffusion overcomes part of the problems. The diffusion couple is monitored in real-time by using radiographic methods. The recorded grey values can be converted into sample concentration. Using X-ray radiography it was shown recently that accurate diffusion coefficients can be obtained for a binary alloy [1]. Here, we discuss results of recent experiments determining diffusion coefficients in-situ making use of neutron radiography [2]. For the discussed material combination neutron radiography compared with X-ray radiography offered sufficient contrast. Future requirements for neutron radiography to study self- and chemical-diffusion in liquids are discussed. [1] B. Zhang, A. Griesche, A. Meyer Phys. Rev. Lett. 104, (2010) 035902. [2] F. Kargl et al. J. Phys.: Cond. Matter 23, (2011) 254201.

Speaker: Dr Florian Kargl (Deutsches Zentrum für Luft- und Raumfahrt (DLR))

Slides Kargl.pdf

32 Combining diffraction and imaging for the study of structural phase transitions

Reciprocal-space techniques, among them neutron diffraction, are a common tools for the investigation of structural phase transitions. Neutron imaging, which provides direct-space information on the macro-scale, is still a rarity for this kind of studies. Here we present an example demonstrating the potential of combining both techniques. We will illustrate it with a temperature dependent study of the phase transformations, melting and re-crystallization of a heavy eutectic alloy containing gold and lead [1]. Besides complementary insight on the volume anomalies at the transitions, we show that neutron imaging provides unique, time-resolved information on the spatial fluctuations of the alloy density and composition across the melting point [2]. This information, impossible to obtain from x-ray imaging, is of enormous relevance for the understanding and modelling of crystallization processes, many of them of high technological relevance in metallurgy and engineering. [1] M. Medarde et al., J. Nucl. Mater. 441, 72-82 (2011), [2] R. Simons et al., in preparation.

Speaker: Dr Marisa Medarde (Laboratory for Developments and Methods, Paul Scherrer Institut)

Slides Medarde.pdf

33 Studies of hydrogen diffusion in steels with neutron radiography

The purpose of the present study is to show the feasibility of examining hydrogen desorption in steels using neutron radiography at the ANTARES facility of the FRM II research reactor, TU Munich. It has been shown that this method is appropriate for in situ determination of hydrogen desorption. Experiments were carried out in the temperature range from room temperature up to 260°C. Measurement was based on direct comparison between electrochemically hydrogen-loaded steel samples and hydrogen free reference samples at the same temperature. This enables the determination of hydrogen concentration as a function of time and temperature. Ex situ carrier gas hot extraction experiments using the same temperature–time profiles as the neutron radiography experiments have been used to calibrate the greyscale values of the radiographs to defined hydrogen concentrations. It can be stated that hydrogen desorption correlates with sample temperature.

Speaker: Dr Thomas Kannengiesser (BAM Federal Institute for Materials Research and Testing)

Slides Kannengiesser.pdf

34 Neutron Depolarisation Imaging Of The Kondo Cluster Glass Formation In CePd(1-x)Rh(x)

At the neutron imaging beam line ANTARES at FRM II, Munich, we have recently developed the Neutron Depolarisation Imaging (NDI) technique [1,2]. The NDI method, which is a combination of neutron radiography and polarisation analysis, allows mapping of variations of magnetic properties over a sample on a length scale of about 300 µm. These may, for instance, result from variations of the chemical composition of the sample [3]. A closed cycle cryostat in combination with a 3He/4He dilution insert has enabled us to reach temperatures as low as 75 mK in such measurements. A study on the metallurgically inhomogenous Kondo lattice system CePd(1-x)Rh(x) [4,5] has been performed to demonstrate the potential of the NDI technique at such low temperatures. Additional magnetic fields applied at the sample position allowed us to identify spin glass behaviour in CePd(1-x)Rh(x) at low temperatures for moderate Rh concentration x. In our contribution we will discuss the experimental technique as well as its application to disordered, ferromagnetic materials that undergo quantum phase transitions. References: [1] M. Schulz et al., "A polarizing neutron periscope for neutron imaging", Nucl. Instr. and Meth. in Phys. Res. A, Vol. 605, 2009, p.43-46 [2] M. Schulz et al., "Neutron depolarisation imaging: Stress measurements by magnetostriction effects in Ni foils", Physica B, Vol. 406, 2011, p.2412-2414 [3] C. Pfleiderer et al., "Search for Electronic Phase Separation at Quantum Phase Transitions", J. Low Temp. Phys., Vol. 161, 2010, p.167-181 [4] T. Westerkamp et al., "Kondo-Cluster-Glass State near a Ferromagnetic Quantum Phase Transition", Phys. Rev. Lett., Vol. 102, 2009, 206404. [5] J. G. Sereni et al., "Ferromagnetic quantum criticality in the alloy CePd1−xRhx", Phys. Rev. B, Vol. 75, 2007, 024432

Speaker: Philipp Schmakat (Physik-Department E21, Technische Universität München, D-85748 Garching, Germany)

Slides Schmakat.pdf

coffee break

Cultural heritage

Convener: Dr Burkhard Schillinger (TU München FRM II)

35 Neutron imaging, a non destructive method for the study of mobile cultural heritage objects. Survey on 10 years of close collaboration with the NIAG team at PSI

The scientific staff at the Laboratory for Conservation Research at the Swiss National Museum performs non-destructive or minimally invasive analysis of cultural heritage by means of micro X-ray fluorescence spectrometry, atom-absorption spectrometry, and infra-red and Raman spectrometry, in order to determine the composition of metal alloys, adhesives, pigments, coloring, precious and semi-precious stones, products of corrosion and preservatives. For specific studies, other methods are required to get knowledge about inner hidden structures or state of conservation. The common approach for this kind of investigations is to use X-rays, thermal and/or cold neutrons rays. We performed in close collaboration with PSI studies within several projects. Bronze sculptures from roman origin collected in Switzerland were studied with neutron tomography, in total about 200 pieces [1]. Because alloys in the Roman period were heavily loaded with lead, neutron imaging is preferred to all X-ray methods. The process of wood conservation is strongly related to the penetration depth of the resin or other agents into the wood structure. With neutron imaging techniques we were able to visualize and to quantify the amounts over the full process of injection, distribution, solvent evaporation and solidification [2]. The flanged axe of Thun-Renzenbühl dated to the early bronze age axe decorated with numerous inlays of a golden metal was investigated by neutron tomography in order to obtain virtual cuts of the axe in all three dimensions. This allowed studying the casting and decoration technique. [1] Deschler-Erb E, Lehmann EH, Pernet L, et al, The complementary use of neutrons and X-rays for the non-destructive investigation of archaeological objects from Swiss collections , in: ARCHAEOMETRY 46: 647-661 Part 4 NOV 2004 [2] E. Lehmann, S. Hartmann and P. Wyer, Neutron radiography as visualization and quantification method for conservation measures of wood firmness enhancement, in: Nuclear Instruments and Methods in Physics research section A- Accelerators spectrometers detectors and associated equipment, 542 (1-3): 87-94 APR 21 2005. [3] K. Hunger, D. Berger, E. Lehmann, F. Müller, S. Hartmann and M. Wörle; Zerstörungsfreie Untersuchungen des frühbronzezeitlichen Randleistenbeils aus Thun-Renzenbühl (Kanton Bern) mittels Mikro-Röntgenfluroeszenzanalyse und Neutronentomographie, Beitrag zum Erwerbungsbericht „Die Sammlung“ 2008/2009, 124-127.

Speaker: Dr Marie Wörle (Swiss National Museum, Laboratory for Conservation Research, Collection Centre Affoltern a. A.)

Slides Woehrle.pdf

36 An example of the application of combined use of Neutron Imaging and Time of Flight Neutron Diffraction: characterization of Japanese ancient swords

A total of five fragments of Japanese swords, pertaining to a period ranging from 15th until 17th century [1], have been analyzed through neutron imaging and neutron diffraction techniques. The samples represent the lower part of ancient swords, purposely broken approximatively at 50-60 mm from the beginning of the blade, at the end of second world war in Japan. Most of them are signed and the authorship and attribution have been accurately identified. The samples have been made available by the Stibbert Museum staff as test samples for non destructive characterization through innovative methods. A white beam and energy resolved neutron imaging study have been performed using the ICON beamline at the spallation neutron source SINQ in Switzerland [2] on all the five samples. The sword fragments have been analyzed with white beam in order to create a 3D map of the different components: metal, mineralization products, slag inclusions and empty volumes. Martensitic rich areas inside the metal have been also identified. By exploiting the ICON energy selector, we used two distinct wavelengths, immediately before and after the 110 ferrite Bragg edge, to map the distribution of ferrite and cementite inside the metallic volumes of the samples [3]. We have hence performed two tomographic reconstructions using the two different wavelengths previously described. The two tomographic reconstructions have been combined together in order to maximize the ferrite phase contrast compared with all the other phases, and showing the distribution of the ferrite phase inside the samples. Neutron diffraction has been performed on the selected samples by using the INES diffractometer at the ISIS pulsed neutron source in UK [4]. The measurements have been done on the average gauge volume, both in the tang and in the blade, in order to determine the quantitative distribution of the metallic and non-metallic phases. Moreover, the cementite to ferrite ratio has been used to quantify the carbon content. The comparative analysis of the phase distribution among the samples (together with the results of tomography) allowed us to identify the peculiar characteristics related to the forging traditions and periods of the Japanese history. I.e. the carbon content, the fayalite amount, the presence of wuestite and troilite have been comparatively checked. On few selected samples a diffraction scan has been performed dividing the blade into three different sections: the edge, the core and the ridge, thus determining the inner phase distribution and confirming the highly differentiate specialization of the single parts of this kind of swords already seen through neutron imaging. The shape of the ferrite peak has also been studied in order to semiquantitatively determine the texture level, the strain level and the domain size of the grains, to gain knowledge about the several forging methods used by the different Japanese schools and traditions. The combination of the two techniques (neutron tomography and neutron diffraction) allowed us to quantitatively characterize the morphology and composition of the samples in a totally non destructive way, giving invaluable information about forging methods and thermal treatments applied to Japanese swords. [1] K. Nagayama, The Connoisseur’s Book of Japanese Swords, Kodansha International Press (1997). [2] E. Lehmann, L. Josic, and G. Frei, Neutron News 20, 20 (2009). [3] L. Josic, A. Steuwer, E. Lehmann, Appl. Phys. A 99, 515 (2010). [4] F. Grazzi, M. Celli, S. Siano, and M. Zoppi, Nuovo Cimento C 30, 59 (2007).

Speaker: Dr Francesco Grazzi (CNR-ISC)

Slides Grazzi.pdf

37 Non-destructive investigation of "The violinist", a lead sculpture by the Spanish artist Pablo Gargallo, using the neutron imaging facilities of the Paul Scherrer Institute.

"The violinist" (1920) is one of the few sculptures made by Gargallo during the so called lead period (from 1920 to 1923). It was created using a wooden kernel onto which several layers of lead sheet were fixed with nails and soldered. In the last few years the outburst of some blisters on both legs has made it clear for the first time that the lead was severely attacked by carbonation, most probably due to the organic vapours from the wood, a material which is not chemically compatible with lead. Before treatment, a complete exploration and diagnosis of the sculpture using non-destructive techniques was necessary in order to assess its real state of conservation and the manufacturing technique used by the artist. Industrial X-ray facilities cannot easily go through such thickness of lead without totally burning away all the information about the inner wood kernel. This was a case study perfectly suited for neutron imaging although the size of the wooden kernel could pose some serious limits to the technique. Tomography and 3D reconstruction were also the aim of the investigation. This project, selected in the last call by SINQ, was carried out in NEUTRA, the thermal neutron radiographic facility in PSI. A scintillator and a CCD camera were used for neutron detection and neutron imaging respectively. Some 2250 radiographic projection images were captured. Once filtered, the data were processed to obtain the computed tomography showing all the structural information inside the sculpture. The series of cross sections were stacked to form a three-dimensional volume image which could be moved around, cross sectioned and segmented. All the different materials of the sculpture can be seen in the images, both in projection and in tomography. The results show some highly attenuated areas, due either to the geometry of the sculpture or to the attenuation coefficient of materials. Some areas of the lead sculpture which never appear on the silhouette do not have much information, specially where wood is rather thick. Some interesting information about the artist’s technique has been revealed: how the wooden kernel was carved and the different ways the lead sheets were fixed on to the wooden kernel using iron nails and low temperature soldering. Lead corrosion has shown up clearly in the projections, in the tomography and in the 3D reconstruction allowing us to map the location and extension of corroded areas behind the lead surface and to better understand the dynamics of this specific pathology. Finally, the new technical knowledge acquired through neutron imaging about the manufacturing process of the sculpture and the materials used, and its present state of corrosion will be of great value when it comes to set the strategies for future restoration.

Speaker: Mr ALEX MASALLES (MNAC Museu Nacional d'Art de Catalunya, Barcelona (Spain))

Slides Masales_The_violinist.pdf

Lunch

Archeology / Paleontology

Convener: Dr Winfried Kockelmann (Rutherford Appleton Laboratory)

38 The IMAT imaging system at ISIS

IMAT will be a cold neutron radiography and diffraction instrument for engineering applications, with a large single-frame neutron bandwidth of 6 Å taking advantage of the 10Hz operation on ISIS TS-2. IMAT will enable conventional neutron radiography, tomography and neutron diffraction applications. In addition, it will offer novel energy-selective neutron imaging techniques as well as combined imaging-strain-texture studies. IPCF-ME, in collaboration with ISIS staff, has been involved in the preliminary tests for individuating the better up-to-date solutions to be adopted for the final imaging device. Now the final design of the imaging camera has been produced and the device is currently under construction in the laboratories of IPCF-ME. The timetable requires that the camera must be ready and tested from the optical and mechanical stability point of view within the end of November 2012. At the end of the same year the camera will be transferred at ISIS for the first tests on the neutron beam. The project had to fulfill a number of preliminary requests, frequently contrasting between themselves. Among them we can mention: a large field of view; a design suitable to obtain a compact, light and transportable camera box; a minimization of the volumes of materials directly exposed to the neutron flux; good stability of the optical alignment (or self-alignment ability); a safe position of the CCD, far enough from the neutron beam; the possibility of selecting different magnification ratios with a minimum spatial resolution of 50 microns; a high temporal resolution and TOF capability; a user friendly design. Furthermore, the instrument must be as versatile and flexible as possible to enable swift interchanges between imaging and diffraction modes and to allow for future upgrades of neutron imaging technology. We will present the results of the preliminary tests which have lead to the final design of the camera. The detailed project of the imaging system will be presented and discussed.

Speaker: Dr Francesco Aliotta (Istituto per i Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche)

Slides Aliotta.pdf

39 Natural Science meets the Humanities - The study of Roman bronzes found in Switzerland by the combination of different methods

Many Bronzes of archaeological relevance found in Switzerland are from Roman origin. Their uniqueness means, in most cases, any investigation of samples must be performed as good as possible non-destructively. Transmission experiments performed either with X-rays or neutrons, depending on the structure and size of the objects, can help to identify inner structures, composition, defects or the manufacture process. Furthermore, in some cases the treatment by conservators and restorers also becomes visible. Second, the composition of the alloy used for the Bronzes can be obtained with non-invasive analytical tools, which means by X-ray fluorescence (XRF) and atomic absorption analysis (AAS). This report describes three examples from such investigations, pointing the archaeologist in the direction of which conclusions can be drawn from such experiments whilst highlighting the problems in interpretation which still exist. The combination of these methods together with a classical archaeological analysis can deliver best possible results in the investigation of Roman Bronzes.

Speaker: Dr Eckhard Deschler-Erb (University of Zurich, CH-8006 Zurich, Switzerland)

Slides Deschler-Erb.pdf

40 New insights into hearing of early synapsids

The ability to hear air-borne sound has evolved independently in at least five vertebrate groups such as frogs, lizards, turtles, crocodiles and mammals (Müller & Tsuji 2007). Among these groups mammals are unique because they are able to hear high frequencies of air-borne sound. This might be a consequence of the very efficient impedance matching mechanism of the mammalian middle ear apparatus. This leverage system amplifies low pressure air-borne sound into higher pressure water-borne sound to the inner ear (Kemp 2005). However, this was not the ancestral condition, because the earliest land-living vertebrates were direct descendants of water-living vertebrates and, thus, were unable to hear air-borne sound. Nevertheless, the first land-living vertebrates were not completely deaf and could detect vibrations of the ground mainly via the mandible and probably by the air-filled thorax cavity. The origin of tympanic hearing in the synapsid lineage is far from clear. It has been assumed that some advanced therapsids - the ancestors of mammals - had an eardrum at the caudal part of the mandible and were probably able to hear low-frequency air-borne sound. The bones of the jaw articulation in these animals transmitted sound vibrations from the eardrum to the inner ear. Consequently, the ancestors of mammals utilized the lower jaw not only for feeding, but also for hearing. In modern mammals this jaw articulation is reduced to the ear ossicles, but still functions for hearing in the same way. In the transition from therapsids to mammals this sound conducting apparatus was further optimized, whereby the auditory ossicles were functionally decoupled from the mandible and were miniaturized (Allin 1975). Although this evolutionary process is well documented in the fossil record, the hearing capabilities of non-mammalian synapsids, the presence or absence of an eardrum and a middle ear cavity are still subjects to debate, because soft tissue structures are not preserved. Moreover, the internal cranial anatomy of most therapsids is almost completely unexplored. Our first examinations of skulls of non-mammalian synapsids by neutron tomography shed new light on the origin of tympanic hearing and the auditory capabilities of non-mammalian synapsids. 3D reconstructions of cephalic structures provided fundamental new insights into the anatomy of the inner ear, the middle ear apparatus and the otic region. References: Allin, E.F. 1975. Evolution of the mammalian middle ear. J. Morph 147: 403-438. Kemp, T.S. 2005. The origin & evolution of mammals. Oxford Univ. press, New Yorck, 331 S. Müller, J., Tsuji, L.A. 2007. Impedance-Matching Hearing in Paleozoic Reptiles: Evidence of Advanced Sensory Perception at an Early Stage of Amniote Evolution. PLoS ONE 2(9): e889. doi:10.1371/J..pone.0000889.

Speaker: Mr Michael Laaß (Staatliches Museum für Naturkunde Karlsruhe)

coffee break

Nuclear engineering

Convener: Dr Winfried Kockelmann (Rutherford Appleton Laboratory)

41 Investigating the thermalhydraulics of nuclear fuel bundles and functional spacers using cold-neutron tomography at the ICON beamline

Neutron imaging of industrial two-phase flows, being a promising technique, has gained increasing attention in the last two decades. We focus on annular flows in nuclear fuel bundles. For annular flows, occurring typically at the upper part of the fuel bundles of boiling water reactors (BWRs), the potential dryout of the coolant liquid film constitutes a safety concern and is a limiting factor in the thermal power and thus for the economy of the reactor. We investigate adiabatic, air-water annular flows in a scaled-up model of two neighboring subchannels as found in BWR fuel assemblies using cold-neutron tomography. The imaging of the double subchannel has been performed at the ICON beam line at the neutron spallation source SINQ at the Paul Scherrer Institute, Switzerland. Cold-neutron tomography is proven here to be an excellent tool for investigating annular flows and the influence of functional spacers on such flows. Different fuel bundle geometries and as well spacer geometries have been investigated in a series of experiments. The high-resolution, high-contrast measurements provide the spatial distributions of the coolant liquid film thickness on the fuel pin surfaces as well as on the surfaces of the spacers, including the vanes. Monte Carlo simulations of the imaging have also been performed to be able to optimize the measurement accuracy and to avoid biasing effects.

Speaker: Dr Robert Zboray (Paul Scherrer Institute)

Slides BWRbundle_Neutrontomo_NIUS2012_zboray.pdf

42 What happens during nuclear accidents? – Contributions of neutron imaging to nuclear safety

The hydrogen uptake during steam oxidation of the nuclear fuel cladding made from zirconium alloys is very important for the development of nuclear accidents. It changes the time scale of hydrogen release and degrades the mechanical properties of the fuel cladding. The hydrogen uptake results in an embrittlement of the zirconium alloy connected with a strong reduction of the thermo-shock stability. If emergency cooling successes, the cladding can be destroyed and the nuclear fuel can be redistributed with strong consequences for the coolability of the damaged reactor core. At Karlsruhe Institute of Technology the processes occurring during loss of coolant accidents (LOCA´s) and severe accidents (accidents beyond LOCA) were simulated experimentally at bundle scale in the large scale QUENCH experiments. The study of the hydrogen release and uptake during the accident scenario simulated are a main goal of these tests. Parallel to the large scale experiments separate effect tests are performed to study the hydrogen uptake and diffusion in various zirconium alloys applied for cladding tubes. Neutron radiography and tomography was applied to examine the hydrogen concentration in different samples. The hydrogen distribution and diffusion in samples from the separate effect tests and in samples prepared from the large-scale tests. The correlations between the total macroscopic neutron cross section and the hydrogen concentration were determined using calibration specimens. This calibration makes a fully quantitative analysis possible. The kinetics of the hydrogen uptake in steam and hydrogen containing atmospheres and the hydrogen diffusion at temperatures above 850°C were investigated in-situ. The post test examinations of samples prepared from QUENCH-LOCA tests show the formations of hydrogen enriched bands oriented non-perpendicular to the tube axis. As the main parameters that control the hydrogen uptake during the time between burst of the cladding rods and quenching and the temperatures occurring in these time intervals were indentified. Different commonly used cladding alloys show strong differences in the hydrogen uptake during severe accident simulation test. Very important for the hydrogen uptake is the oxide layer morphology. The formation of the so-called “breakaway” oxide results in nearly one order of magnitude higher hydrogen concentration after the test compared to samples with a compact oxide layer.

Speaker: Mr Mirco Grosse (Karlsruhe Institute of Technology)

Slides Grosse.pdf

43 Recent developments at the CONRAD instrument at the Helmholtz Centre Berlin

In recent years several new techniques have enlarged the area of applications of neutron imaging; among the most important of these are Bragg-edge mapping, polarised neutron imaging and interferometric imaging. In this talk an overview will be given on recent developments in these methods at CONRAD, the neutron imaging instrument at the Helmholtz Centre Berlin. Polycrystalline materials exhibit significant wavelength-related variation in neutron transmission around the Bragg cut-off for polycrystalline materials. Polarised neutron imaging uses analysis of the spin rotation around magnetic field distributions to directly visualise magnetic phenomena [1]. Applications in this field might become one of the most important areas in future, strengthening the position of neutron imaging in science and technology. Interferometric imaging exploits interference effects to simultaneously measure attenuation, phase/refraction and (U)SANS/dark-field signals [2,3]. This opens the way to imaging nano/microscopic structures in bulk materials (e.g. fissures/voids in engineering materials) and magnetic domain structures inside macroscopic objects [4,5]. Examples for 3D imaging of magnetic domains will be given [4]. The wavelength dependence of the small angle scattering signal will be discussed. Another focus will be laid on imaging of fuel cell and other engineering materials, especially with monochromatic neutrons. [1] Kardjilov, N. et al. Nat. Phys. 4, 399-403 (2008). [2] Pfeiffer, F. et al. Nat. Mater. 7, 134-137 (2008). [3] Strobl, M. et al. Phys. Rev. Lett. 101, 123902 (2008). [4] Manke, I. et al. Nature Communications 1, 125, DOI: 10.1038 /ncomms1125 (2010) [5] N. Kardjilov et al. Materials Today 14, 6, p. 248-256 (2011)

Speaker: Dr Nikolay Kardjilov (Helmholtz-Zentrum Berlin)

Slides Kardjilov.pdf

44 Summary & Discussion

Dinner

Wednesday 18 April

Water transport I

Convener: Dr Eberhard Lehmann (Paul Scherrer Instiut)

45 ANTARES Upgrade - The New Imaging Beam Line at FRM II

The well known ANTARES beam line at beam port SR4b at FRM II had to be completely dismantled to give way to a neutron guide to a new neutron guide hall. The newly built beam line ANTARES Upgrade will be commissioned in spring/summer 2012 and will, in addition to nearly identical possible parameters as the old ANTARES, offer many extended new capabilities, such as a second experimental chamber closer to the reactor for higher flux and low background for small samples, and six instead of two selectable collimators for higher flux or higher resolution. The beam forming components located in a separately acessible chamber will include a velocity selector, a double crystal monochromator, several neutron optical periscopes to cut direct sight, one of them built as a highly efficient magnetic polariser. Linear phase contrast grids will be added soon. A high-resolution scientific CMOS camera will allow for high-speed and high-resolution measurements. We will present the new features and possible applications of ANTARES Upgrade.

Speaker: Michael Schulz (FRM II)

Slides Schulz.pdf

46 Quantitative in-situ neutron imaging of non-equilibrium soft and complex matter systems using cold neutrons

The movement of solvents in and through soft and complex matter is not only of fundamental interest but is also important for applications as wide-ranging as drug-delivery, food packaging, oil recovery and water uptake in plants. Solvent flux results in changes in the local composition of a material which can be measured using neutron imaging. The concentration profiles extracted from the images can yield fundamental details about the diffusion behaviour of the solvent. By deuterating one component, e.g. the solvent, and using cold neutrons, the neutron contrast in the sample can be improved significantly. Together with the recent technical improvements in neutron imaging instrumentation, especially the scintillators used, this allows quantitative in-situ measurements on such systems with a resolution of a few tens of micrometers and seconds. In this presentation I will give an overview of our results from the neutron radiography instruments ICON (PSI) and ANTARES (FRMII) and describe a few examples from the wide range of samples we have investigated to date. These include biologically-relevant systems, nanoporous materials, amphiphiles and polymers. I will also present details of the practical considerations specific to our systems and the consequences for instrument design such as suitable neutron wavelength distributions, beam intensities and camera-scintillator combinations.

Speaker: Dr Helen Hermes (Heinrich-Heine-University Düsseldorf)

Slides Hermes.pdf

47 Influence of pore size and fluid-wall interactions on the imbibition of a fluid in silica mesoporous materials

Imbibition is the phenomenon by which a liquid is able to penetrate and rise-up into a porous media. This process is often found in everyday life (for instance when a cube of sugar is dipped into coffee) and is of great interest to many areas, from biology and industrial applications through to nanofluidics. Imbibition kinetics have been well known on a macroscopic level since the 19th century: the liquid height depends on the square root of time and on pre-factors related to the liquid investigated, such as the surface tension, the contact angle and the viscosity. The first step to understanding the imbibition process on a nanoscopic scale is to determine the role of the pre-factors. Moreover, an understanding of how this is modified by using different liquids and porous media can yield important information about the interaction between the liquid and the pore walls. We have investigated the imbibition of water into several mesoporous MCM-41 silica matrices, in order to determine the transport coefficients, such as the viscosity, in small pores and to gain an understanding of this process on a nanoscopic scale. These matrices have a well-known structure: a long range ordered framework with uniform mesopores, tunable mean pore diameter and a large surface area (about 1000 m2/g). We synthesized and characterized different mesoporous MCM-41 matrices with mean pore diameters between 2nm and 4nm, about ten times the diameter of the molecules inside the pores. In order to understand a possible contribution of a pre-adsorbed layer, we have also compared the imbibition of dodecane and toluene, which differ in their vapour pressure, with that of water. Neutron radiography experiments on the ICON instrument, at the Paul Scherrer Institute, allowed us to follow the liquid front rising in the sample. We found that even on a nanoscopic scale the height of the liquid depends on the square root of time, with a strong dependence of the pre-factor on the confinement conditions. For all the liquids this depends on the MCM41 pore size and is larger for smaller pores. As expected, the process also depends on the liquid properties and, for example, is almost twice as fast for water as for dodecane. In addition, marked differences in the imbibition behaviour in hydrophilic and hydrophobic matrices were observed.

Speaker: Dr Claudia Pantalei (Laboratoire Léon Brillouin, CEA Saclay, F-91191 Gif-sur-Yvette, France)

coffee break

Water transport II

Convener: Dr Eberhard Lehmann (Paul Scherrer Instiut)

48 Imaging Chemistry (and Physics) in Space and Time: New Opportunities by Dynamic Neutron and X-ray micro-Imaging

Reactive transport phenomena in porous media are of fundamental relevance not only in hydrology or environmental sciences, but also in a broad range of other scientific disciplines as well as in numerous engineering processes. For most chemically active porous materials or composite systems, their physical structure and chemical reactivity is directly reflected in the spatial distribution of chemical properties. Key chemical properties include chemical composition (distribution of chemical elements), chemical speciation (atomic coordination of a specific chemical element), or chemical states (e.g. redox state). Chemical information of this kind provides key knowledge about chemical reactivity as well as structural properties of heterogeneous materials. Consequently, current demands on imaging extend beyond traditional structural (physical) imaging. The ability to visualize the distribution of chemical properties at the (sub)micrometer scale as well as chemical dynamics in materials and reactions is of fundamental interest and importance. Thus, the need for „chemical microscopes“ is growing rapidly. Over the most recent years, micro-analytical facilities based on neutron beams as well as synchrotron x-ray beams advanced to indispensable instruments in the context of micro-analytical, non-destructive imaging. Both types of beams are nowadays used for multi-dimensional structural micro-analysis (physical imaging) as well as chemical and crystallographic micro-imaging. Advantageously, based on their characteristic and generally non-destructive interaction with matter, neutrons and x-rays provide complementary analytical contrast mechanism. X-ray microprobe facilities posses several intrinsic advantages concerning chemical imaging. Most important, the element-specific absorption resonances accessible within the x-ray energy range provide an element-specific chemical sensitivity. Moreover, the fine structure of an absorption edge reveals information on the chemical speciation of the absorber. Quite commonly, different oxidation states are readily identified based on their characteristic spectroscopy signatures of the absorption edges. Furthermore, any specific chemical environment around the absorber (chemical speciation) will lead to specific bound-bound transitions at the low-energy side of the edge, while the coordination geometry will result in characteristic scattering phenomena above the Fermi level. These speciation-dependent features represent chemical contrast which can be used to record up to three-dimensional chemical images documenting the spatial variation of oxidation states, specific mineral phases, or different molecular species, for example. Complementary to x-rays, neutron radiation exhibits a unique penetration power and a particular sensitivity for lowest Z elements. Neutron radiography and tomography is the most suitable non-destructive tool for dense objects when a certain size of the object is reached. Compared to the more common X-ray approaches, even heavy elements can be penetrated and distinguished from other materials. Moreover, due to the large cross section of low Z elements, small amounts of aqueous liquids or organic materials can be detected with a high contrast even within a dense body. Neutron imaging corresponds indeed to a highly specialized method allowing the observation of hidden structures and features in bulk objects. In this presentation, recent progress and achievements in the field of 2D/3D chemical imaging and speciation analysis using various neutrons and synchrotron radiation x-ray microprobe techniques will be demonstrated. The reactive transport of Cs in natural Opalinus Clay Rock material will serve as an example of scientific application. Clearly, Opalinus Clay Rock represents a chemically and physically heterogeneous medium. The complementary use of different microprobe techniques allows characterizing the physical structure and chemical nature of the porous medium. Moreover, the effect of the observed heterogeneities on the evolution of reactive transport pattern can be visualized. Most advantageous, the employed neutron and x-ray techniques can be considered as being of non-invasive nature (in most cases, at least). This important feature allows the non-disturbing recording of multiple, subsequent images as a function of evolution – making up a “reactive transport movie”. In the presented case, we used such time-resolved chemical imaging to conduct dynamic, in-situ investigations elucidating the diffusion of water and an inert tracer, as well as the mobility of reactive aqueous species. Notably, the evolution of Cs contaminant plumes in various micro-structured natural porous media differing in physical and chemical complexity could be monitored. Finally, through a model based interpretation of experimental results we grasp the mechanisms of transport phenomena and chemical interactions in porous media. In this context, the rapid development of analytical imaging techniques goes along with novel data analysis and modeling approaches. Available time resolved 3D chemical imaging and structure analysis opens opportunity for advanced 3D transport modeling taking into account compositional heterogeneity of the samples at a (sub)-micrometer scale consistently with the experimental observations.

Speaker: Dr Daniel Grolimund (Paul Scherrer Institute, Swiss Light Source)

Slides Grolimund.pdf

49 Neutron imaging of recurrent ponded infiltration into heterogeneous soil

Ponded infiltration is a hydrological process in which water remaining at the soil surface infiltrates under positive pressures into the soil profile which becomes nearly or fully saturated. For most natural sites this condition occurs only for a short period of time, mostly during extreme precipitations, still a large fraction of the total water and chemical fluxes in the soil profile are transferred during these events. Under the close-to-saturation conditions, a preferential flow may take place in heterogeneous soils. There is also the experimental evidence that a significant steady state flow rate drop may occur during a recurrent ponded infiltration indicating changes/instability of the saturated hydraulic conductivity of soil (Cislerova et al, 1988). These variations are often ascribed to a changing fraction of the entrapped air. The effect is not considered in standard theory of water flow in porous media. In presented study we were able to reproduce variation of quasi steady state flow during ponded infiltration experiment on three small undisturbed samples of coarse sandy loam and to visualize the process by neutron imaging (NI). Two main flow irregularities typical for soil under study were detected on two soil samples during recurrent ponding experiment: (1) gradual decrease of the quasi-saturated hydraulic conductivity (Kqs) soon after the outflow appeared; (2) the Kqs was even lower that at the end of the first infiltration run and remained relatively steady. The third sample didn’t produce variability of quasi steady state hydraulic conductivity. Series of NI tomography images of the sample taken during the quasi steady state stage of the first infiltration run showed the air trapped in many of large pores and cavities in the samples affected by the temporal variations of Kqs. Furthermore, many of entrapped air bubbles increased in volume during the course of the first infiltration run. Further entrapped air redistribution has been detected during the second run. The fraction of the entrapped air visible in images was calculated and plotted against the Kqs. The increase of volumetric fraction of entrapped air bubbles by only 0.005 was accompanied by the decrease of quasi-saturated hydraulic conductivity by up to 50% of the initial value. The experimental results support the hypothesis stated earlier (Snehota et al., 2010) that the effect of the gradual decrease of the flow rates is caused by entrapped air redistribution and gradual build-up of bubbles in preferential pathways. The trapped air may thus restrict the preferential flow pathways and cause the overall lower infiltration and outflow flux rates. When the same experiment was repeated on undisturbed sample of the same soil but taken from a more compact part of soil without continuous preferential pathways, the described effect didn’t occur. The results of the NI tomography study have shown the close connection between preferential flow and temporal variations of quasi-saturated hydraulic conductivity. The neutron imaging has been performed in NEUTRA, PSI and the research project has been supported by the European Commission under the 7th Framework Programme through the 'Research Infrastructures'

Speaker: Dr Michal Snehota (Faculty of Civil Engineering, Czech Technical Univ. in Prague, Czech Republic)

Slides Snehota.pdf

50 High resolution neutron radiography and microtomography with fast MCP-Timepix detector operating at >1Khz frame rates

The unique capability of MCP detectors to count neutrons with high detection efficiency (70% for cold and 50% for thermal), high spatial resolution (sub-15 um) and no readout noise can be very attractive for some applications where relatively small area of the detector (currently 28x28 mm^2) is acceptable. The recent development of fast parallel readout electronics for a 2x2 Timepix readout enabled high resolution imaging with event centroiding at ~MHz counting rates. In addition to imaging resolution, the dynamical studies can be performed by time tagging of every neutron with accuracy of 1 us (for 55 um spatial resolution) and sub-ms for sub-15 um spatial resolution. Another advantage of MCP detectors is their high dynamic range, allowing simultaneous event detection in case of very low neutron fluxes (<10 n/cm^2/s) and fluxes as high as 10^8 n/cm^2/s with 1 KHz frames/s readout rates. Our latest imaging experiments conducted at ICON and BOA beamlines will be presented, demonstrating not only the capabilities of the detection system, but also the excellent quality of those beamlines for high resolution neutron radiography and tomography. We will also describe the performance of the latest micropore neutron collimators used for scatter rejection in neutron radiography of samples with considerable neutron scattering, e.g. quantification of water content at a close distance to the detector required for high resolution imaging.

Speaker: Dr Anton Tremsin (University of California at Berkeley)

Slides Tremsin.pdf

51 Summary & Discussion

Transportation to PSI

52 test

test

Speaker: Dr Anders Kaestner

Slides PSI-areal-a4.pdf

Lunch

Excursion to PSI

Convener: Dr David Mannes (Paul Scherrer Institut)

Departure