Ad-Hoc Meeting #63 (PSB Injection Revolution Frequency)

Tuesday 20 Oct 2020, 09:00 → 09:30 Europe/Zurich

Vydo Meeting (CERN)

Present: M-E. Angoletta, D. Barrientos, A. Findlay, M. Jaussi, J. Molendijk, H. Damerau, S. Albright, H. Bartosik, P. Skowronski, G.P. Di Giovanni, B. Mikulec.

 

Introduction:

Parts of Linac4 are synchronised with the PSB injection revolution train (e.g. chopper, Linac4 RF cavities), but certain parts are not (source, klystron modulators). The ’test’ was made a couple of weeks ago to change the PSB injection revolution frequency with the consequence that Linac4 tripped.

Last week the Linac4 LLRF team confirmed this situation.

There are 2 options to enable to perform Linac4-PSB energy matching during PSB post-LS2 restart:

1. Understand all essential dependencies and fix the outstanding synchronisation issues
2. Fix the PSB injection revolution frequency and vary the Linac4 energy with PIMS11/12 (amplitude) during the energy matching.

 

Historically pre-LS2 the PSB injection revolution frequency was changed to perform energy matching checks with Linac2 (G.P. Di Giovanni).

 

Discussion points:

• M-E. Angoletta mentions that on the LLRF technical side there is no issue to either change or maintain fixed the frequency.
• S. Albright asked if the resolution of energy steps would be sufficient adapting PIMS11/12. B. Mikulec said she believes this was no issue, and J. Molendijk supported this, saying that the amplitude should be a 16-bits register.
• S. Albright added that in the longer term it might be beneficial to stay flexible; an example could be injecting onto a ramp with different revolution frequencies per ring. H. Bartosik said that we should always keep the injection frequency fixed anyway and adapt the Bdls.
• B. Mikulec asked if there could be an issue with the tomoscope/tomogram. S. Albright and H. Damerau said this was not the case as long as the measurements are done taking into account that the beam has to first be at the central orbit. The energy matching procedure, relying on tomography and the turn-by-turn closed orbit measurement, should account for this comment and be added to the PSB beam commissioning document.
• B. Mikulec mentioned that the debuncher phase might need adaptation when the Linac4 energy is changed, but that this was a quick adjustment that would take around 15-20 minutes once at the end of the energy matching. P. Skowronski said that a Makerule could also be prepared that would link the debuncher phase change to the energy change. Remark from B. Mikulec after the meeting: it would need to be checked if this would be compatible with long. painting.
• Answering to a question, if the amplitude/energy variation of PIMS11/12 could be verified, P. Skowronski replied that this should be possible through phase measurement of e.g. the last BPM in LTB.
• B. Mikulec said that the PSB injection frequency should be non-ppm; M. Jaussi will implement this change. A. Findlay said that it is not important to keep historic settings and that the currently used value should be set. There is also some clean-up needed for some timings (TPROT should be renamed TREV and the 2 dependent timings should not be able to be set from the working sets).

09:00 → 09:30 Discussion

Speakers: Alan James Findlay (CERN), Bettina Mikulec (CERN), Diego Barrientos (CERN), Gian Piero Di Giovanni (CERN), Hannes Bartosik (CERN), Heiko Damerau (CERN), John Molendijk (CERN), Maria Elena Angoletta (CERN), Michael Jaussi (CERN), Piotr Krzysztof Skowronski (CERN), Simon Albright (CERN)