Minutes of the LIS Section meeting held on 11^th June 2007.

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

General information (G. Arduini)

As a follow-up the Group Meeting G. Arduini asked whether there is an interest in reviving the Group Fora and whether there are subjects which are of interest for the section. M. Chanel noted that there are already many meetings and it is difficult to find time to attend others. C.Carli was of the opinion that it would be good to keep these meeting in order to favour exchanges among the people working in the different sections of the group. E-mail exchanges and discussions after the meeting seem to indicate that the majority of the members (in particular staff) are not in favour of continuing the Group Fora. It seems also that the CLIC and the recent modification of its main parameters is the subject which is interesting more people

Measurement and Correction of the trajectories of the 5-turns of the Continuous Transfer Extraction (A. Franchi) - slides

M. Chanel asked whether the position of the trajectories of the 5 slices could be measured in TT2. G. Arduini and A. Franchi replied in the negative.

Status of the machines

PSB (M. Chanel)

M. Chanel reported that the observed abnormal heating of the SBDL cables has been identified. Each dipole magnet (with the exception of 15B1 and 16B2 (special magnets at the injection and extraction regions) is equipped with 1 coil per ring ion order to equalize te integral of the dipole fields in the 4 rings. The coils corresponding to each ring are powered in series. Recently M. Chanel has discovered that each power supply is connected to the coil circuit by two pair of cables having different cross-section. The preliminary investigation seem to indicate that one pair of cables has inverted polarity and therefore the trim coils are short-circuited so that during the ramp current is flowing although the power supply seem not to deliver any current. After the meeting an access took place: no polarity error was found but it was observed that the cable of smaller cross-section was short-circuited on the magnet side but it was not at the power supply side. This resulted in having the coils short-circuited as suspected. The error has now been corrected (the cables with smaller cross section have been short-circuited also on the power converter side). M. Chanel continued saying the the replacement of te electronics for the orbit acquisition in the PSB is ongoing and the quality of the acquisitions is improving. It is not yet clear whether a realignment will be necessary as the problem of the SBDL cabling must be solved first as the suspected fault could induce orbit distortion (due to the absence of correction coils in 2 dipole magnets.

PS (S. Gilardoni)

The problems observed with the main power supplies and pole face windings have been fixed. The samplers for the Pole Face Windings power supplies are still noisy and show a delay in the measurements. Tests have been performed with the slow extraction using the sextupole in 1 instead of that in SS3. Although the extraction efficiency achieved with the new scheme was close (88 %) to the extraction efficiency obtained with the scheme implemented in 2006 (92%) it was decided to go back to the previous scheme because there were doubts about the behaviour of the extraction electrostatic septum 23. It must be noted that the previous scheme was using two sextupoles in SS3 and SS7 + the ODE octuppoles. The new scheme using the sextupoles in SS1 and SS7 was studied on OP request in order to avoid using the octupoles.

Simone added that there might be a spare for the slim quadrupole QFO105 at the beginning of the TT2 line, initially it was thought that there was no spare.

SPS (E. Métral)

The machine is running smoothly. From time to time the so-called ghost (slow losses in the second part of the ramp)  is appearing. Investigations are ongoing and it seems that this is related to an RF HW problem.

The setting-up of the injection and acceleration of the LHC beam on the MD cycle with acceleration from 26 to 37 GeV/c has been performed. A machine study has been conducted to determine the energy dependence of the vertical e-cloud instability.

MD (E. Métral)

E. Métral gave a preliminary summary of the MDs (summary)

Next meeting

Monday, 2^nd July 2007 at 09:00 in room 354-1-001

Agenda

General information (G. Arduini)

Preliminary results of the MDs performed on the energy dependence of the vertical e-cloud instability in the SPS (G. Rumolo)

Status of the PS magnet model (M. Juchno - to be confirmed)

Status of the machines (supervisors)

Status of the MD studies (E. Métral)

A.O.B.

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