Oct 20 – 25, 2019
Europe/Zurich timezone

Status of the neutron lifetime experiment $\tau$SPECT

Oct 22, 2019, 4:54 PM
WHGA/001 - Auditorium (PSI)

WHGA/001 - Auditorium



Jan Kahlenberg Kim Ulrike Ross (Johannes-Gutenberg-University Mainz)


The $\tau$SPECT experiment aims to measure the neutron lifetime $\tau_n$ using a 3D magnetic storage technique. Due to the neutron’s magnetic moment, very low-energetic neutrons (ultracold neutrons, UCN) with a maximum energy of $\approx 50\,\mathrm{neV}$ can be stored in the magnetic trap with a volume of $\approx 8$ litres. $\tau$SPECT is designed to determine $\tau_n$ using two independent measurement methods. In phase I, surviving UCN in the storage volume after varying storage times are counted. Phase II involves the in-situ detection of decay protons.
A proof-of-principle measurement using the magnetic field of the former $a$SPECT spectrometer (double hump structure) for longitudinal confinement and a fused silica tube for radial storage has been performed in July 2015 [1]. Since then, besides the successful upgrade of the UCN D source at the pulsed research reactor Mainz [2], the 3D magnetic trap using a magnetic octupole for the radial confinement has been installed and commissioned. Other relevant components are a movable neutron guide system with an adiabatic fast passage (AFP) spin flipper as well as a custom-designed UCN detector (boron-coated ZnS:Ag scintillator).
We will present the current status of the experiment and the progress of the initial commissioning runs.

[1] J. Karch, PhD thesis, Johannes Gutenberg University Mainz, 2017
[2] J. Kahlenberg et al., Eur. Phys. J. A 53, 226 (2017)

Funding acknowledgement
This work has been supported by the Cluster of Excellence ''Precision Physics, Fundamental Interactions, and Structure of Matter'' (PRISMA+ EXC 2118/1) funded by the German Research Foundation (DFG) within the German Excellence Strategy (Project ID 39083149)

Primary authors

Jan Kahlenberg Kim Ulrike Ross (Johannes-Gutenberg-University Mainz)


Dr Peter Bluemler (Johannes-Gutenberg-University Mainz) Prof. Martin Fertl (Johannes Gutenberg Universitaet Mainz) Werner Heil (Institute of Physics) Dieter Ries (Johannes Gutenberg Universitaet Mainz) Christian Schmidt (Johannes Gutenberg-Universität Mainz)

Presentation materials