Summary notes of LCU meeting on 26/02/2007

Present: IA, RA, GB, CB, RB, HB, FC, SF, AG, WH, JJ, MM, EM, YP, TP, VP, TR, RT, TW, FZ

 Follow up of actions

• Correction of the chromatic behaviour of the V6.500 lattice in collision -> TR
  Chromatic behaviour of V6.500 in collision : The issue of x/y tune crossing as function of delta p was discussed, which is potentially a problem for example for the dispersion measurement. It is followed up by Thys who is more generally looking at correction with sextupoles. Using four sextupole families normally already gives good results. A further follow up is needed, with a check of beta-beating and phase advances in the insertions. RA expressed a concern on possible consequences on the collimation optics in IR3, 7.
  Two slides, see b_beat6.5H and b_beat6.5V.

Report from meetings

• FiDeL -> MG
  MG reported on FiDeL magnet modelling. An issue was MQX triplet magnet data. MQXA (KEK) can be based on data from 2001-2002 and should be under control. MQXB (Fermilab) needs further follow-up. MQYs (large aperture magnets) require further work on warm data (currently not available) to derive warm cold correlations in presence of non-nominal magnetic permeability.

Review of the RLC open actions relevant for LCU activities -> FZ

MG recalled that the LCU mandate now includes impedance and collective effects for LHC.
Open issues were summarised by FZ.  Please see his table and give feedback to him in case of corrections.
TCTV impedance was on the list and can be considered as closed according to RA since the TCTV design is now finalised.
Septa are followed up impedance-wise by EM.
TDI impedance: AG says this is closed for calculations to the extend that things the could be modelled were all done. FC said the TDI impedance was measured, found to be worse than calculated and that this is followed up with possible hardware modifications.
A remaining issue on a comparison of longitudinal geometric wakes and resitive wall longitudinal wakes will be followed up (EM contacting AK,  and FeRo and FC for measurements).
RA said impedance support is needed for phase 2 collimators.
Electron cloud: FZ follows up on the possibility to include ecloud in MadX.
Incoherent ecloud effects need further follow up with help expected from outside of LCU section.
Beam-beam compensation is included in the PhD work by UD.
More general impedance issues: Nonlinear wakes are followed up by FZ and EM and FZ consider a review of Landau damping.

AG says he would prefer to attend the meeting only for the impedance issues. MG suggests to look at the agenda and choose his presence accordingly.

Progress in IR8 matching for beta* squeeze -> YP

YP recalled why changes are needed in optics V6.500 compared to V6.5. A change was needed to allow for Beam 1/Beam 2 phase advance differences in IR3, 7 as presented by Oliver Bruning in the LTC of the 31/03/2004. YP studied rematching of the squeeze using MadX with the Jacobian algorithm and showed preliminary results for beta* between 10 m and 2 m. Aperture still need verification, while the crossing schemes (one for each beta* value) still need to be computed. SF suggests to gain further by including the MQX strength in the matching strategy.
For slides see squeeze.ppt.

HB reminded that Q5 at injection is common to the transfer lines and the LHC. The Q5 strength was not modified from V6.5 to V6.500. This may become an issue in a modified injection optics for V6.501.

Last update: 27-Feb-07

MG & HB

Back to LCU Minutes