Minutes of the LIS Section meeting held on 20th October 2008
Present: G. Arduini, J. Barranco, E. Benedetto, A. Blas, R. Calaga, C. Carli, M. Chanel, A. Franchi, W. Fischer, S. Gilardoni, M. Martini, S. Maury, E. Métral, B. Mikulec, Y. Papaphilippou, D. Quatraro, B. Salvant
General Information (Gianluigi)
Gianluigi reminded the deadline for the submission of request for fellows (3/11)
A special CAS course mainly oriented for CERN engineers and technical engineers will take place in Divonne at the end of February. Proposal for candidates should be sent to Gianluigi.
An interim report on the LHC Sector 34 incident has been issued and is available on the web.
Some invitations for the LHC fest are still available.
Tune shift and instabilities measurement at PS-Booster (D. Quatraro) - slides
Diego presented the results of some measurements conducted in the PSB. The detuning with intensity in the PS-Booster has been measured at two different energies and the energy dependence and values seem to indicate that space charge is the main source of detuning. This is particularly evident in the vertical plane although it is less obvious in the horizontal plane. This would indicate that the contribution to the low frequency impedance is mainly dominated by space charge and the impedance of the machine is in the few MOhm/m at most. Measurements at even higher energy (e.g. 1.4 GeV) could help in further reducing this upper limit.
Measurements have been conducted for two rings (2 and 4) and give similar results.
Preliminary measurements have been taken to study a horizontal instability developing in ring 4 when the transverse feedback is switched OFF. The rise-time of the instability has been determined.
The instability seems to occur at well defined timings for a given intensity. The tests have been done with the damper off and therefore the intensity has been limited to about 5 × 1012 p.
It was suggested to investigate the possible additional points:
Dependence of the rise-time and timing of the instability as a function of intensity and/or bunch length. The possibility to keep the damper on for some time and then to switch it off at different timings should be used to study this dependence.
The temporal evolution of the transverse signals and the spectral content should be studied as well in order to characterize the instability.
Round Table (all)
MDs and SPS (Benoit, Elena, Elias, Rama)
The status of the MDs (Elias) can be found here.
The wire scanners with the new electronics are far from being operational and more tests are certainly necessary.
The Ionization Profile Monitor is not yet working. Elias is following that up with BI (J. Koopman) and with F. Arnold for the application software.
The last test with the SPS matching monitor was not successful due to some timing problems. Preparations for the next test at the beginning of November are ongoing with the support of E. Bravin, T. Lefevre and A. Guerrero.
Some measurements have been performed with bunches 12 ns long and with RF off in order to identify the frequencies at which the beam is getting unstable transversally. Additional measurements will be taken with longer bunches (possibly > 20 ns) in order to improve the resolution in frequency.
Rama is analyzing the data on the localization of impedance. Measurements with local bumps have been performed as well.
PS (Simone, Yannis)
A fixed target beam with h=16 structure has been injected into the SPS and the dependence of the capture losses in the SPS as a function of the h=16 voltage at extraction in the PS has been studied. The preliminary results indicate that the a maximum voltage of few kV can be tolerated in the SPS.
Gianluigi suggested to measure the losses (extraction efficiency or beam loss monitor signals in Septum 16) as a function of the h=16 voltage in the PS.
Problems have been experienced again with the CODD system. These problems seem to be related to the real time task, a fix has been found but the real origin has not been identified.
Simone is discussing with Ray about the replacement of the vacuum chamber for QFO105
LINAC4 (Christian)
Masamitsu has been working on the minimization of the beta beating induced by the injection bump in the PSB.
Preliminary runs with ORBIT and acceleration have been performed but some more work is required to understand some observed features.
P
Collimation studies are continuing and will be the subject of one of the next LIS section meeting presentations. In particular the dependence of the collimation efficiency on the collimator material is being addressed.
A. Vivoli (fellow) is trying to use the MOCAC program (for IBS calculations) at CERN.
A request for a fellow will be submitted for the neutrino factory activity.
Next meeting
Monday, 17th November 2008 at 10:00 in room 354-1-001
Agenda
General Information (Gianluigi)
Electron cloud simulations for the beam dump kickers in the SPS (Giovanni)
Round Table (all)
A.O.B.
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