Minutes of the LIS Section meeting held on 10^th December 2007.

Present: G. Arduini, S. Aumon, J. Barranco, O. Berrig, R. Calaga, A. Franchi, S. Gilardoni, E. Métral, Y. Papaphilippou, D. Quatraro, G. Rumolo, B. Salvant.

General information (Gianluigi)

Muriel will leave CERN by the end of January

A new CERN unit led by L. Evans should be created for LHC and LHC Injector upgrades

R. Losito will take over from J. Lettry as ATB Group Leader from 1/1/2008.

Deadline for BEAM07 papers: 12/12. Paper should be sent to Gianluigi for approval before submission.

Deadline for the submission of EPAC abstract to Oliver: 13/12 morning.

NA61 has asked to investigate the possibility of having Sulphur ions for Fixed target physics in 2010. S. Maury is following that up.

Main Unit 76 PFW failed during HV test. Need to check radiation level in that area. There will be a presentation on the results of radiation survey at the APC in January 2008.

Head-tail instability in the PS on the long injection flat-bottom (Elias) - slides

A slow horizontal head-tail instability in the PS is affecting the LHC beam in the 1.2 s injection plateau when the machine is uncoupled (or with low coupling). the difference in horizontal and vertical chromaticity (typically -0.9 -H- and -1.3 -V) explains why the instability is developing first in the horizontal plane. Due to this asymmetry coupling can be used to stabilize the beam.

Simulations with HEADTAIL reproduce well observations performed in the nineties by Elias and expectations from Sacherer theory on the dependence of the instability pattern and growth time on chromaticity. The simulations reproduce well also the effect of coupling as observed from measurements and from theory (http://doc.cern.ch/archive/electronic/cern/preprints/ps/ps-99-011.pdf).

Results have been presented at PAC07 (http://doc.cern.ch/archive/electronic/cern/preprints/ab/ab-2007-032.pdf ).

In the slides K0 is the integrated skew quadrupole  strength over the whole machine. Space charge is not included in the simulation.

Very small losses are visible in the injection plateau and could be due to the effect of space charge and the trapping-detrapping in resonance islands as a result of the synchrotron motion. This phenomenon could be enhanced by chromaticity.

The availability of a transverse feedback could allow to operate at low (in absolute value) chromaticity which could help in reducing these slow losses.

A.O.B.

LINAC4: So far help received from FNAL (F. Ostiguy) limited to issues with ESME. No feedback/help received on space charge simulations. C. Carli will gett in touch with F. Ostiguy for ORBIT simulations (distribution functions, grid granulariy, number of macroparticles). M. Aiba is working on simulating the injection painting. No summary has been produced so far on the work done with ORBIT. Acceleration has not been tested yet in ORBIT. Benchmarking between ORBIT and the experiments conducted at the PS booster needs also to be done.

Optics models:

• The SPS aperture model needs to be checked in LSS5 against the layout drawings ==> Done. Changes are foreseen also in 2008. Needs to be followed up with J. Ramillon ==> Olav.
• Not clear whether MADX can cope with requirements to describe properly all the features of the aperture for the PS-SPS Complex ==> Olav to discuss with F. Schmidt.
• The transition optics for the PS should be added ==> Still to be done
• It was pointed out that the TT2-TT10 optics for the CT transfer has not been modified (the QKE58 is not used for this type of extraction). On the other hand the optics for the AD transfer has been rematched to take into account the suppression of the QKE58 in the PS ring ==> Updated.
• The definition of the orbit correctors in the PS ring should be verified ==> Olav.
• The LEIR injection line optics and aperture model is still missing ==> Olav.
• Gianluigi will pass to Olav the latest TT20 optics files. Still to be done.
• The organization of the files needs to reviewed to facilitate the navigation ==> Olav.

Bi-polar power converter for DHZ60: Simone said that the PO people will do it if time permits. Having a bi-polar power converter is important to provide and adequate closed orbit correction at high energy for AD and LHC beams

Next meeting

Monday, 14^th January 2008 at 09:00 in room 354-1-001

Agenda

General information (G. Arduini)

MTE Commissioning (M. Giovannozzi)

Issues with the orbit correction in MADX in the PSB (O. Berrig)

A.O.B.

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