xBPM

Tuesday 25 Feb 2020, 13:30 → 14:30 Europe/Zurich

WSLA/008 (PSI)

Uwe Flechsig

working group meeting

13:30 → 13:50 Electronics for feedback

Speaker: Boris Keil (Paul Scherrer Institut)

2020_0225__Keil_SLS2_Photon_BPM_FOFB_Aspects.pdf

2020_0225__Keil_SLS2_Photon_BPM_FOFB_Aspects.pptx

Boris presented the current SLS feedback system,

• we have a "fast feedback system": some key parameters: 500 Hz, 74 (electron) BPMs, 4k samples/s allows orbit corrections up to 100Hz (0 dB point),
• and a "slow system" with input from (photon) XBPMs which allows feedback up to 1 Hz by changing the reference orbit. 
• the reference for the fast feedback  comes from beam based alignment where the electron beam is centered in the quadrupols
• the "slow system" is used to correct relative drifts, the reference orbit for the slow system can be changed to some extend by user input 
• important to note: the (electron) BPMs use RF electronics, one advantage: allows spectral filtering
• SLS 2.0: similar electron BPM system is forseen (similar principles but better parameters and additional features)
• fast XBPMs would be a big benefit for SLS 2.0 and should be seriously considered

13:50 → 14:00 SiC XBPM update

status, strategy after Massimos resignment

Speaker: Maria Carulla

2020_02_25_Feb_Meeting.pdf

2020_02_25_Feb_Meeting.pptx

Mar has taken over the SiC detector project from Massimo, she works in the framework of a cross-proposal more or less alone with part time support of one technician. Status:

• she prepared a new wafer (2 \mu m thick active membrane) with 30 XBPMs of different kind (see attached material), the wafer is not yet separated
• some results from the last measurements at X05DA have been shown, monochramtic data at 12  keV look good, pink beam data show some features which are not yet fully understood
• a 2d detector has been tested at microXAS- the feasibility for a "slow" feedback has been demonstrated
• fast readout was not on the task list so far

14:00 → 14:10 FE XBPM strategy

current strategy for XBPMs in the frontends of SLS 2.0

Speaker: David Marco Just

20_Strategy for XBPMs located in SLS 2.0 FEs.pdf

20_Strategy for XBPMs located in SLS 2.0 FEs.pptx

David presented the current XBPM related concepts for the frontends of SLS 2.0, keywords:

• no XBPMs at bending magnets are forseen (at SLS 1.0 we have staggered pair monitors which are rarely used), this is an open issue from our first meeting see https://indico.psi.ch/event/7329/attachments/13835/18186/190308_minutes.pdf
• IDs: the upstream blade based XBPM will be kept (some minor upgrades may be required to match the beam shape of perhaps new IDs)
• IDs: the downstream blade based XBPM will be removed- the chamber can be kept or the space reserved to install a new XBPM version later. UF: the position of this monitor should be checked- perhaps more upstream would be better.
• fast readout was not considered so far

14:10 → 14:30 Discussion

Remarks by Volker and others. Summary about open issues, todo list:

• XBPMs at bending magnets - is it OK to follow DJ concept to skip them?
  • Juraj (after the meeting): the XBPMs at bending magnet were very useful during the initial commissioning and optimization of SLS 1.0 - he strongly recommends to have them also for  SLS 2.0.    email JK Feb 26, 2020: Hi Uwe, just to remind you on the discussion on SPMs concerning the bending magnets. It is true that currently the users do not care about them, but historically these SPMs were used to realign the girders (I mentioned that during my first presentation). This confirmed my observations during the commissioning – namely that we had a systematic misalignment pointing the beam downwards. Therefore I suggest their use also for SLS-2. Cheers, Juraj
• is DJ concept for the monitors in the ID frontends OK?
• do we want/must-have fast XBPMs - I (UF) see advantages but do not fully overlook the problems and difficulties

As an outcome  we should prepare and agree on some key specifications for the XBPMs in the frontends of SLS 2.0 which we can submit to the project management. In particular for developments which need additional resources.