Minutes of the ICE section
98th meeting on Wednesday 11/12/2013 (08:40-10:30, 6/2-004)
ICE members: Adrian Oeftiger (AO), Andrea Passarelli (AP), Benoit Salvant (BS), Carlo Zannini (CZ), Danilo Banfi (DB), Daria Astapovych (DA), Elias Metral (EM), Elena Wildner (EW), Frank Schmidt (FS), Giovanni Iadarola (GI), Giovanni Rumolo (GR), Javier Barranco (JB), Kevin Shing Bruce Li (KL), Nicolo Biancacci (NB), Nicolas Mounet (NM), Olav Ejner Berrig (OB), Serena Persichelli (SP), Tatiana Pieloni (TP), Xavier Buffat (XB).
Present/Excused: AO, AP, BS, CZ, DB, DA, EM, EW, FS, GI, GR, JB, KL, NB, NM, OB, SP, TP, XB, HannesB, AndreaP, ElenaB, KlausH, MichaelB, FreddyB, AlanF, SimonW, FritzC.
1) Newcomers / visitors
- None.
2) Comments on the minutes of the previous 97th meeting + Actions
- No comment.
3) General infos
- No particular comment from anyone.
- SL meeting:
- Nothing special.
- Request from AntoineL for some impedance studies for HPPS => To be added to the list.
- WP2 Task Leader meeting => Next steps sent to the team: slides (status of Task 2.4).
- PS dummy septum: Sim. made for both BTV IN and OUT; Meas. made without BTV;Yesterday SP and JosephK went there and the BTV was not inserted.
- Next optics work for the PSB lines: discussion with BettinaM about the work plan => To be discussed with OlavB when he is back in January.
- LHC MKI review on Monday 09/12/13.
- EM gave a seminar at TUD on Monday 02/12/13 and discussed with OliverBF about possible collaborations between CERN and TUD (students who could be shared between TUD and CERN at ~ 50%) => To be thought about and discussed with OliverBF for instance when he is at CERN for the special ecloud meeting on 16/12/13.
- Info from StefanoR => The SLAC collimator has been received and the impedance measurements are being planned.
- Nice preliminary results by XB et al. about the LHC EOSI with an imperfect damper… Next step to benchmark with HEADTAIL, etc.
- Discussion with / request from MassimoG about the possible effects of chromatic aberrations (chromatic beta-beating) on collective instabilities => Action 1 below.
- Next step for the LIU PS impedance studies => Simulate the TMCI at transition with the updated impedance model => Action 2 below.
4) PSB LIU requests (Elena Benedetto): pdf
- ElenaB reviewed the different requests for the beam dynamics activities and discussed a preliminary planning.
- 2015: HW needs to go into production => 2014 is the last chance.
- Final reports => EDMS docs is the best.
- Transverse damper => They anticipated so it is already in upgrade.
- Refurbish equipment which is aging.
- Power => Times 4 as intensity is times 2.
- Bandwidth? => Times 2. 11 MHz at the moment and in the future 22 MHz.
- Proposition of an Intermediate Review ~ June 2014 to see the status of the studies.
- Discussion after the meeting with Freddy Blas about a contact person for the injection errors in the PSB => Kevin Li.
- Next step => EM to discuss with ElenaB to finalize the detailed planning of activities and deadlines (Action 3 below).
5) Status of the PSB impedance model (CZ): ppt
- CZ reviewed all the activities linked to the PSB impedance model, mentioning that the first main significant difference between the PSB and the other machines is that the relativistic velocity factor is very small at injection (~ 0.3) and that therefore the use of 3D EM simulations in this regime of beta different from 1 had to be investigated in some detail => In particular, the direct space charge contribution has to be removed.
- CZ already considered:
- Indirect SC
- RW
- Extraction kicker (inlcuding cables) => Kicker in open-short configuration which should be close to reality => Suggested by MikeB. The coupling is only in H and not in V.
- Transitions
- CZ then showed the plots of the total horizontal and vertical driving impedances at both injection and top energies, and estimated the effective impedances (and detailed contributions of the different components) at 160 MeV, 1 GeV and 1.4 GeV. Comparing these results to past measurements, CZ concluded that:
- Measurements at 1 and 1.4 GeV are consistent with a missing effective impedance of ~ 2 MOhms/m.
- Measurements at 160 MeV suggest a missing effective impedance of ~ 4 MOhms/m.
Note: A 20% error in the estimation of the indirect SC impedance could explain the discrepancy on the missing impedance => The calculation will be refined.
- Other devices have also been studied:
- Inconel undulated chamber or ceramic chamber => More or less the same from the impedance point of view => No real preference.
- Finemet cavities => The impedance does not depend on the relativistic beta and therefore the work done by SP in the PS can be re-used.
- The longitudinal impedance model will also be developed in the future.
6) Very partial analysis of the PSB instability measurements of January 2013 (NM): pdf
- NM reminded some previous work on the subject and the measurements which have been done in January 2013.
- More than 1 month of studies in the PSB, essentially on the 1st instability, with many systematic scans. A new scan has been made (compared to the past): sextupole current, i.e. chroma changed.
- The growth rates from RW impedance are orders of magnitude smaller than measurements!
- A typical "1st instability" has been analysed in some detail, in particular the growth rates as a function of chromaticity.
- Work still to be be done:
- Still one month of data to look at carefully.
- Still many unexplained features of the instabilities:
- Why only a specific times during the cycle?
- Magnitude of the growth rates.
- Bunch profile and chroma dependency.
7) Actions to be taken for the next meeting
- Old actions.
- New actions:
- Action 1 (all the team to think about): Possible effects of chromatic aberrations (chromatic beta-beating) on collective instabilities.
- Action 2 (NB): Next step for the LIU PS impedance studies => Simulate the TMCI at transition with the updated impedance model.
- Action 3 (EM): Finalize with ElenaB the detailed planning and deadlines for the PSB-LIU beam dynamics activities.
8) Miscellaneous
- Deadlines and important dates for ICE.
- The next (99th) meeting will take place on 18/12/2013 => Agenda:
1) LHC single-bunch instabilities observed in 2012: simulations vs. measurements (DA).
- See preliminary agendas for the next meetings.
- See List of Actions.
Minutes by E. Metral, 10/01/2014.