Minutes of the ICE section
30th meeting on Wednesday 01/06/2011 (08:40-10:30, 6/2-004)
ICE members: Benoit Salvant (BS), Christian Hansen (CH), Carlo Zannini (CZ), Hugo Alistair Day (HD), Elena Benedetto (EB), Ewen Hamish Maclean (EHM), Elias Metral (EM), Elena Wildner (EW), Frank Schmidt (FS), Giovanni Rumolo (GR), Jean-Luc Nougaret (JLN), Kevin Shing Bruce Li (KL), Maria Carmen Alabau Pons (MCAP), Nicolo Biancacci (NB), Nicolas Mounet (NM), Olav Ejner Berrig (OB), Tatiana Pieloni (TP), Werner Herr (WH), Xavier Buffat (XB).
Present/Excused: BS, CH, CZ, HD, EB, EHM, EM, EW, FS, GR, JLN, KL, MCAP, NB, NM, OB, TP, WH, XB, Georges Trad, Javier Cardona, Raymond Wasef, Rogelio Tomas.
1) Newcomers / visitors
- None.
2) Comments on the minutes of the previous 28th and 29th meetings + Actions
- Still needs to write the last two minutes (28th and 29th).
3) General infos
- BS + GR + some other people => Big effort put on wire scanner measurements these days to try and understand in particular a factor 2 in the PS. Will be discussed in the next LIU SPS meeting.
- SL meeting: Nothing special.
- News on the LHC:
- Fill # 1815 broke all the previous records: ~ 1.25E33 peak and ~ 38 pb^-1 integrated. All bunches of B2 OK and only 1 batch of B1 had some transverse emittance blow-up.
- We reached the 0.5 fb^-1.
- Plan for the week: Again 1092b with batches of 108b and then with 144b.
- Marie Curie Initial Training Network Invisibles => It is official, we are funded (EW).
- LHC MKI heating => To be followed up (HD). Meeting on Tuesday with HD + MikeB + FritzC + EM to discuss the next steps. Interlock put at ~ 50 deg at the moment and there is no cooling.
- Comment from FritzC about the ferrite properties measured by CZ => Might be worth to re-discuss it altogether.
- SPS MDs:
- Coast at 120 GeV/c => Still emittance growth observed in both planes, with small losses and roughly independent of tunes => External excitations suspected. Next MD will be done at 270 GeV/c.
- Very good results with Q26 this year (i.e. much better than last year) which are similar to Q20: ~ 3E11 p/b within ~ 2 microm.
- SPS longitudinal instability depending on the radial steering (see ThomasB's talk at last MSWG meeting) => No instability above a certain steering, which needs to be understood.
- PTCORBIT code is running for the 3 machines (PSB, PS and SPS) => It seems that the most critical issue was to obtain the MADX files and "flat files" of the different machines.
- Yesterday's LBOC: Talk by WolfgangH on possible impact of longitudinal oscillations on transverse plane => Can a spread of chromaticity explain the transverse emittance blow-up we observe? Discussion also about the nonlinear chromaticity, which was also discussed in the next talk by FS. Finally, WolfgangH showed than even with the roll-off of the transverse damper gain above few MHz, there is no problem with the instability rise-times we expect.
- Question from FrankZ to be answered: Do we know the electrical field at the surface of the primary collimators for the nominal LHC? There could be electron(-cloud) field emission for high field in the LHC. Action 1: Impedance team.
- REMINDER: We should try and discuss during ICE meetings all the talks we are asked to present in other committees (LBOC, SPSU, LMC, Chamonix, etc.).
4) Main activities and news from the Impedance WG (BS): pptx
- This is the first presentation of the impedance working group activity and the idea was (as it will be for the other coming presentations of the different working groups' activities) to explain what an impedance is, what the main activities are (since the creation of this working group), what the available tools are, what the collaborations are, what the hot topics are and what the current issues and future work are.
- In particular it is worth mentioning that we have 4 tools:
- Theory.
- Electro-magnetic simulations codes like CST Particle Studio in time domain or CST Microwave Studio in frequency domain. Note that the codes T3P (in time domain) and Omega3P (in frequency domain) are from the US and seem to be better optimized for particle accelerators. They are also designed to be run on parallel computers.
- Bench measurements using wires.
- Beam-based measurements.
- The hot topics are the LHC injection kicker (MKI) heating, the design of the dispersion suppressor and phase 2 collimators, SPS enamel flanges, material characterization etc.
- Several collaborations:
- GSI, TU Darmstadt and CST,
- La Sapienza and Frascati Rome,
- IHEP Beijing,
- KEK and J-PARC,
- New collaboration with India
- Impedance meetings usually on Friday mornings, on average once in 3 weeks => http://impedance.web.cern.ch/impedance/. It can also be accessed from the ICE section web page: https://espace.cern.ch/be-dep/ABP/ICE/default.aspx.
5) FFT corrections for tune measurements (NB): pptx
- Nicolo has been invited to give a 15-min talk (Refined techniques for phase measurements) at the Optics Measurements, Corrections and Modelling for High-Performance Storage Rings workshop (OMCM) which will take place at CERN on June 20-22 => He will mainly discuss what he is presenting today.
- Nicolo reminded us with the DFT (Discrete Fourier Transform) of harmonic signals, first in the continuous case and then in the discrete case => Having a finite number of samples corresponds to windowing with a rect function r[n] the sampled signal, which corresponds to a convolution in the discrete frequency domain.
- Amplitude, phase and frequency resolutions depend on the error in localizing the spectrum maximum => To overcome these limits and recover the real parameters for the harmonic signals different methods were proposed, which are compared in the following:
- CFFT = Corrected FFT => Used to correct the amplitude, phase and frequency. Based on analytical properties of windowing functions.
- ApFFT = All phase - FFT => Used to improve the phase resolution. Based on properly preprocessing the measured signal in order to cancel phase errors.
- Sussix => Used to improve the frequency resolution. Based on iterative routines to get the frequency of the tune.
- Conclusions and outlook:
- Sussix speed can be improved by implementing the analytical corrections (single shot corrections vs. iterative loops).
- The corrected FFT can be improved in order to detect subsequent harmonics in the betatron signal.
- The NAF algorithm could also be looked at.
- Sussix is not optimized for the phase and the amplitude => It could/should be upgraded for both the phase and the amplitude.
6) Actions to be taken for the next meeting
- Old actions.
- New actions:
- Action 1 (impedance team): Do we know the electrical field at the surface of the primary collimators for the nominal LHC? There could be electron(-cloud) field emission for high field in the LHC (question from FrankZ to be answered).
7) Miscellaneous
- The next (31th) meeting will take place on 08/06/2011 => Agenda:
1) Main activities and news from the Ecloud (FZ)
2) Beta-Beams WG (EW)
- See preliminary agendas for the next meetings.
Minutes by E. Metral, 05/06/2011.