Minutes of the LIS Section meeting held on 18th May 2009
Present: G. Arduini, J. Barranco, H. Bartosik, O. Berrig, C. Carli, C. Hansen, P. Jackson, J. Jowett, M. Martini, S. Maury, E. Métral, N. Mounet, Y. Papaphilippou, G. Prior, D. Quatraro, G. Rumolo, B. Salvant, M. Scholz, E. Wildner, C. Zannini
General Information (Gianluigi)
Gianluigi introduced a new member of the team: M. Scholz who will work on the LINAC4 injection into the PSB as technical student under the supervision of C. Carli
Gianluigi announced that Vittorio Vaccaro is at CERN and he is going to give two seminars on impedance aspects on Tue 19 May at 11:00 and on Wed 20 May at 14:00 in room 354-1-001.
From IEFC:
During the intervention on the AD target during the shut-down it was found that it was longitudinally displaced by 6 cm because of an error in the installation. This could be the reason for the lower antiproton yield in 2008. The target longitudinal position is remotely controllable. It would be interesting to do a longitudinal scanin the target position in order to optimize the antiproton yield.
PSB
Sieve: a water leak
has been detected. The sieve is not
available for the moment. A project will start in
2010 for new design. The design should possibly take into
account of the operation with LINAC4 and input should be provided to EN/STI
in that respect
č
Christian will be the contact
The LINAC4
construction could result in movements of up to 10
mm in a service gallery for LINAC2 and could result in
damage of cooling pipes serving the PS Complex. The movement will be
continuously monitored and the civil engineering work will be stopped in
case movements larger than 1 mm are detected.
nToF could be ready to take beam during this
week or the following
Volunteers are required to help with the
access in the LHC
LHC status:
Sector 23 cool-down is
progressing. HW commissioning
should start middle of June
Measurements at room temperature revealed some bad welding with discontinuity in the copper stabilizer for the dipole bus bar connections in sector 12 and 67. Much better in 34. In 56 no evident outliers have been identified but investigations are ongoing around some magnets that quenched during the training quench campaign. Measurements on the quadrupoles bus-bar are being performed. In the sectors which are at room temperature. The same measurement will be tried at 80 K in sector 45.
Gianluigi mentioned that C. Bhat is going to be at CERN in the period 7/7/2009-20/8/2009. Elena Wildner mentioned that she would be interested in collaborating with C. Bhat for the Beta Beam Study for his experience in longitudinal gymnastics and in particular for the Barrier buckets. Gianluigi suggested Elena to contact C. Bhat directly.
The DG will visit India. Paul Collier is collecting input for possible collaborations for Indian Institutes. Gianluigi asked for feedback from the Section Members, he also added that TRIUMF would like to extend the collaboration with CERN for the LHC and the upgrade programmes. E. Wildner noted that she is using the ACCSIM code for the Beta-Beam study. ACCSIM included in fact the decay of the radioactive ion beams. Gianluigi warned that ACCSIM contains some bugs in the module for the simulation of the beam behaviour in the presence of space charge for bunched beams. So far no fix has been found by F. Jones. He could work on the correction of such bug but no benchmarking effort can be provided by LIS.
Status of the nominal beam in LEIR (Michel Chanel) - slides
Michel Chanel presented the parameters and status of the nominal LHC beam in LEIR. The nominal beam can be accumulated at injection but losses are observed at low energy and in particular at the beginning of the ramp. Space charge is suspected to be at the origin of the losses (the space charge tune spread is ~0.07 in the vertical plane) and for that it is planned to flatten the bunches with a second harmonic (this is possible thanks to large bandwidth of the RF cavities) and to optimize the working point. Gianluigi asked whether sign of instabilities are observed. Michel replied that detailed studies have not been conducted yet but the transverse feedback is certainly needed. He also added that the observed relative losses increase with intensity.
Round table (all)
Elias mentioned that aperture measurements have been performed with the wire scanner 51995 and it seems that the measured aperture is still smaller than the theoretical one (for a perfect machine) by at least 20% (in sigmas). A main bending magnet (MBB50070) had to be changed due to an inter-turn short. Problems have been also encountered with a vacuum valve that closed, preventing the beam to circulate, while it was appearing as open.
Yannis said that there are still problems with the chromaticity and tune correction because of problems with the reading of the samplers for the reading of the Pole-Face Windings currents and of the radial position. Operation is following that up. The values of the tune returned by the BI expert program differ from those available on the sampler (these are used in the application for the tune/chromaticity measurement and correction). Gianluigi suggested to profit of the present PS-Booster stop (injection septum leak) to progress on the studies for the LHC and Fixed-Target cycles with low ramp rates required in case of a failure of the PS rotating machine.
Benoit said that the reason for the discrepancy between the estimates of the transverse impedance for a rectangular chamber with resistive walls provided by Particle Studio and theoretical results has been understood. CST has solved the problem but the solution will be implemented only in the 2010 version of Particle Studio. The simulations of the transverse impedance of the SPS Beam Position Monitors were also affected by such a bug. CST is running the jobs prepared by Benoit to have the correct results for the BPMs. Benoit will then run HEADTAIL to include the latest impedance data for the BPMs (together with the resistive wall due to the vacuum chamber and the kickers).
Diego is summarizing the observations of the PS-Booster instability in a note.
Hannes is conducting tuneability studies for the PS2
Penny and Christian have started very preliminary studies on the feasibility of a collimation system for the PS-Booster with LINAC4
Olav has generated the LHC survey files. SPS sequence files have been generated from the layout
Space charge simulations for the injection process are progressing (Michel Martini). Gianluigi asked whether the ORBIT programme is installed on the new cluster. Christian replied that Masamitsu has been working on that. Michel Martini pointed-out that the post-processing of the data generated by ORBIT is not trivial (ACCSIM is superior in that respect). Christian said that SNS people (J. Holmes) could be interested in improving that.
Elena Wildner is preparing the a presentation for the SPC on the Beta-Beams. She would ba also interested in studying the possible use of crystals for the collimation of ions. Gianluigi suggested Elena to contact Walter Scandale.
Michel Chanel said that a leak on a primary pump valve was at the origin of the pressure rise observed in the electron cooler section. Restarting the pump has solved the problem. Modifications are being studied.
Gersende said that there are some discrepancies between the HARP data and the simulation codes for the pion production. Furthermore there are no data from HARP below 3 GeV. There are hints that the present energy of the SPL (4 GeV) is not optimum and higher energies might be more favourable.
Next meeting
Monday, 15th June 2009 at 14:00 in room 354-1-001
Agenda:
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