Summary notes of the HSS meeting on 17/02/2014

Present: RB, HB, RDM, MHF, MF, MG, PH, SR, EQ, MS, GV, FZ, RR, RW, CH, DH

Report from meetings

• SLM and general information -> MG
  There has been no SLM since lasts meeting.
  Welcome to Roberto Rossi who will work as technical student with the collimation team. He also introduced Cédric Hernalsteens who works with him on resonant extraction and Raymond Wasef who works on the modeling of space-charge in MAD-X.
  
• PS-LIU -> SG
  Baseline 2 operational since Friday.
  Cost to completion (without options) slightly increased mainly due to:
  a) inclusion of requested BI activities: new IPM, turn-by-turn acquisition for ring semgrids
  b) controls of the KFA53 - New contact for vacuum group is Jan Hansen since Paolo now GL.
  LIU day the 11th April, agenda available here: https://indico.cern.ch/event/299470/other-view?view=standard. Public meeting, all invited.
  Raymond : improvement of simulation analysis for the normal sextupolar resonance (exp. in collaboration with GSI). The data are given by the frozen-model SC module coupled to MADX. IMPACT simulation progressing.
  Alexander : presentation to the LAGUNA-LBNO meeting of last results concerning the analysis of HI beams. Paper for injection oscillation in preparation to be submitted to PRSTAB.
  Injection studies: Yuanyuan produced the first result on the bump desynchronization study. Now moved to tracking with time varying fields for the existing bump. Then simulations of the new bump.
  Mauro Migliorati back to CERN until end of summer. Will work on the impedance model, impedance identification and coupled bunch instabilities.
  New extra sextupoles for Chromaticity control should be installed this week. The two extra octupoles are in preparation for installation. The ECR for them should be circulated soon.
  FINEMET cavities: review in September for the HW and performances (9-10/09) with colleagues from outside labs. The cavity should be installed soon. Only two final amplifiers will be installed for testing and not the full set to avoid irradiating elements not needed during the commissioning.
  New student in the group will arrive in March to work with Gianni and Giovanni on e-cloud for the PS. New optical detector and pickup nearly finished to be installed in MU98 before startup.
  TDR: progressing, hope for first draft by the end of the month.
• Collimation status -> SR
  Stefano said that 4 collimators with BPMs were approved, 2 of which are made house and the other two have been ordered and accepted. RdM asks about the dump collimators,  ATS optics compatibility, and if we have a baseline ATS optics for RUN2. Massimo says ATS requires further discussion and will more likely be introduced after 2015. Still, we should aim to be ATS compatible. The issue if collimators have to move in the squeeze. Now, dump collimators only move during the ramp. Special arrangements for ATS in MDs are possible.
  Roderik will follow up on the work of Luisella of asynchronous dump simulations. 
• SixTrack status -> RdM
  SixTrack is now included as a project together with GEANT / PH-SFT to allow for Google support for students.

Loss maps for new IR7 optics -> DM (slides)

Daniele Mirarchi presented his work related to collimation on IR7 for the post LS1 optics. He performed tracking simulations for Beam 1 and Beam 2 at the nominal beam energy of 7 TeV. As discussed previously, quadrupoles in IR7 are strongly irradiated, some of which (MQWB) were run at low strength and will now be completely off and could later be used as spares or for tests.
His results for Beam 2 are very similar to those for previous optics due to very similar optical conditions.
For Beam 1 he finds increased loss peaks in IR8. Looking at details particle by particle he finds that these originate in off momentum particle, mostly generated by single diffractive scattering with typically dp/p = 1.e-2. These new peaks are due to the fact that the dispersion for Beam 1 has been reduced (from 50 cm to about 10 cm), thus changing the cut in momentum performed by the collimators. A revised optics with larger dispersion for Beam 1, so to mimic the original optical solution, shows lower peaks.

Progress on power converter ripple effects and specifications for HL-LHC -> MF (slides)

Miriam recalled the main ideas which had been discussed before in the LCU meeting on 26/11/2013.
She studies the ripple generated in the triplet for the present and planned powering after LS3. The effects increase with the maximum beta which will be higher than at present for the upgrade optics. The high magnet inductance of the triplets works as low-pass filter to suppress higher ripple frequencies possibly induced by the powering for the magnetic fields seen by the beam.
There are uncertainties from the simulation of Eddy currents and the limited knowledge of the actual conductivity of the tungsten used. The most relevant effects are expected at multiples of 50Hz and in particular at 600 and 300 Hz. She determined the dynamic aperture using SixTrack. Without beam-beam, she observes reductions from 18 sigma down to 9 - 10 sigma in the worst cases.
The next steps will be to finalised the list of possible frequencies that could affect the power converter, massive numerical simulations, and the evaluation of the transfer function between ripple in the power converter and magnetic ripple seen by the beam.

AOB 

Last update: 25-Feb-2014

MG & HB

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