Minutes of the LIS Section meeting held on 14^th July 2008

Present: G. Arduini, S. Aumon, J. Barranco, E. Benedetto, O. Berrig, C. Carli, M. Chanel, A. Franchi, S. Gilardoni, M. Martini, E. Métral, Y. Papaphilippou, D. Quatraro, G. Rumolo

General Information (Gianluigi)

Gianluigi has circulated the list of expected arrivals and departures of students between the members of the section in order to provide Lauriane with an estimate of the office space requirements in the near future. Feedback is welcome.

Gianluigi reminded about the possibility of having Estonian or Turkish students. Proposal for work subjects should be sent to him.

Documents to be scanned should be given to Nicole who is sitting in the office close to that of Lauriane.

The whole LHC is now cold. HW commissioning of Sector 7-8 and 8-1 is almost completed and it has not been stopped temporarily in order to allow an intervention on the controls electronics of the Cryogenic System in Pt. 8. HW Commissioning of Sector 2-3 is progressing and it should be completed by the end of next week.

An LHC injection tests is planned for the beginning of August. Beam 1 will be injected from TI2 to LSS3 where it will be stopped by the collimators.

MTE status (Simone) - slides

The preliminary setting-up of the capture has been completed after having measured the matrix for the correction of tune and chromaticity based 5-current mode of operation and the matrix for the correction of the tune using low energy quadruples. During the setting-up a polarity error of the extraction octupoles has been identified. The model of the machine at 14 GeV/c seems to provide a good image of the real machine.  The capture process still needs further optimization in particular for the uniformity of the population of each of the beamlets.

The capture has been performed by controlling the working point with the Pole-Face Windings instead of the low-energy quadrupoles as the quadrupoles are heavily used at injection for the fixed target and CNGS beams and the rms current in the enlarged low energy quadrupoles is larger than the maximum acceptable.

The operation of the high intensity beams occurs with particularly low tunes at injection. Elias noted that this has been the case also in the past but careful adjustment of the injection is needed to allow operation at nominal tunes. See slides and link for past experience (from Elias).

For the above reason the correction of the detuning as a function of the slow-bump amplitude might require the use of the pole face windings instead of the low energy quadrupoles.

After the PS stop due to the magnet repair it should be possible to start the extraction and therefore the measurement of the TT2-TT10 line. Gianluigi reminded that a 14 GeV/c cycle is required in the SPS in order to characterize the matching including the TT10 line.

An OP application is now available for the measurement of the non-linear chromaticity.

OASIS signals are available for the tuning of the multi-turn extraction but there are not sufficient channels if work is ongoing on other users.

Round table

Simone and Yannis for the PS

The PS magnet unit 25 failed on Thursday evening as a result of a fault to ground of the figure of 8 loop. The magnet has to be changed but there is not spare with the special windings required in that area (ion injection) and for that reason the ion injection line will be disconnected. A similar problem would be encountered in the proton injection area.

Measurements of the orbit have been performed before the stop and they seem to show that the deterioration of the orbit during acceleration seems to be the consequence of a dipole error in section 25. The orbit should be re-measured after the magnet change to see whether the fault on the magnet is the cause of the deterioration of the orbit during acceleration.

The measurements available so far seem to indicate the orbit measurement is now working properly. A measurement of the dispersion shown by Simone present important deviations from the expected value but according to Elias, Simone and Yannis the quality of the agreement has not been better in the past.

PS controls issues:

• unreliable acquisition results
• a lot of reboots are required to operate the wire scanners
• The new wire scanner electronics cannot be used as there is no application available to access it.

Elena

Elena is completing the analysis of some of the data taken during the TI2 test as there will be a presentation on the results of the TI2 commissioning at t the next LTC. She is also continuing the analysis of the matching monitor MD performed in the SPS last year. A note should be written to describe this work.

Michel Martini

ORBIT simulations and comparison with the results of the experiments performed by Michel Chanel last year are in pretty good agreement. This was not the case for ACCSIM simulations for the same number of macroparticles although the algorithms for the space charge calculations should be very similar. Michel will discuss this with F. Jones during his visit. New studies are needed in the PSBooster with more emittance measurements at 160 MeV in order to study the dependence of the emittance blow-up on the working point.

Sandra

Sandra is progressing in the study of the losses at injection in the PS. The losses responsible for the radiation under the Goward Road are not generated by losses in the injection line but very likely by those occurring at the injection septum after one turn. Measurements of the injection matching with the PS SEM grids have been performed and are being analyzed. Dispersion measurement in the line and at injection will be performed too in order to verify the injection matching.

The machine development sessions on the transition studies should start soon as well.

Javier

He is working on the collimation for the PS2. The space available for collimation is very limited and the space requirements are being investigated.

Gianluigi asked whether he has progressed with writing an article on the CT losses in the PS. Javier replied that he needs some additional data on the losses occurring during the CT extraction. Gianluigi noted that it is very important to summarize all the work done in a report for publication in a journal.

Christian

Preliminary studies of the injection optics of the PSB at injection indicate that the effect of the injection bump cannot be neglect in particular for the asymmetric bump option. Steering magnets at injection need to be added in the LINAC4 to PSB injection region. They were not included in the design already they are installed in the PSBooster now.

Michel Chanel and Giovanni will start studies soon both to continue the bench-mark of the space charge codes and to evaluate the impact of the choice of the working point on the beam performance (Michel) and to start the characterization of the PSB impedance and the study of the collective effects (Michel and Giovanni).

P. Jackson (doctoral student from Oxford) will arrive in the middle of the week and she will start to work on LINAC4-PSB performance issues and in particular on a preliminary collimation scheme.

Discussions on the instrumentation in the PSBooster (with LINAC4) have also started.

Diego

(in collaboration with Benoit) has completed the work on the interface between Z-base and HEADTAIL. The latter can now use as input Z-base wake-field outputs.

The work on the transverse impedance for non-relativistic beams will continue now,

Giovanni

The test of new coatings to suppress the electron cloud by reducing the secondary emission yield (SEY) of the surface of the vacuum chamber is progressing well and a new coating (Carbon deposited in Neon atmosphere) has shown low SEY and electron cloud build-up lower than NEG.

Yannis

During the EPAC conference Yannis has discussed with people from JPARC. They would be interested in inviting people during the commissioning of the high energy ring (which has a lattice with Negative Momentum compaction factor). They have already injected into this machine and they did not find any particular problem. Commissioning will continue in December.

More space is required for injection and extraction in the PS2 lattice. Yannis is going to investigate a possible structure allowing for that. He is also going to make a preliminary investigation for a machine with three-fold symmetry.

Yannis has also discussed about the PS2 studies with U. Wienands (SLAC) in the frame of LARP. Giovanni is the contact person for the impedance and collective effects issues.

Yannis (in collaboration with Rende) has tested with beam in the PS a long LHC cycle in with slower ramp as required in case of a breakdown of the PS rotating machine. Performance close to nominal have been obtained. No quadruple bunch splitting at high energy could be applied due to a timing problem, only triple splitting could be applied at low energy. Yannis is going to follow-up on this issue.

Elias

The wire scanner 517 should now be working. The issue of the calibration of the WS 414 is still open. Gianluigi suggested to calibrate the wire scanner with orbit bumps. This could be done by operators if instructed.

LHC beams: some work has been done in the PS at transition and the transverse emittance seems now to be smaller.

Next meeting

Monday, 28^th July 2008 at 10:00 in room 354-1-001

Agenda

General Information (Gianluigi)

Highlights from conferences and workshops (Elena, Giovanni, Michel, Simone, Yannis)

Round Table (all)

A.O.B.

Back to Minutes