MPP meeting (02 Jul 2008)
Present: Mateusz Bednarek, Juan Casas-Cubillos; Nuria Catalan Lasheras; Giorgio D'Angelo; Sandor Feher; Carlos Fernandez Robles; Robert Henry Flora; Piotr Jurkiewicz, Glyn Kirby; Michele Modena; Vittorio Parma; Mirko Pojer; Vittorio Remondino; Roberto Saban; Rüdiger Schmidt; Walter Venturini Delsolaro; Antonio Vergara Fernandez; Louis Walckiers
Chaired by: Dr. SIEMKO, Andrzej
General information
Sector 5-6 has been given to operation after re-qualifying the RB circuit for 5.5 TeV equivalent current. The complete analysis and release of the circuits in MTF is still missing. A dicussion on what is left to do in MTF will take place in the next MPP meeting.
Sector 7-8. The R circuit was brought back to 5.025 TeV equivalent current after the multiple quench seen last on week 25. A cryogenic stop is schedule for this week. The circuit will be brought to 5.5 TeV after this.
Sector 8-1; the RB circuit reached 5.5 TeV level and it is now fully commissioned. ElQA is proceeding on the DFBX circuits and powering of the correctors of the inner triplet has started.
C. Fernandez Robles showed the status of 7-8 and 8-1 resuming what is still left to do. It is considered useful to have a similar file with all sectors that is updated regularly. It will have however to distinguish clearly between the stages of commissioning.
ElQA status
G. D'angelo reported on the status of ElQA activities.
Sector 2-3: all DFBs are qualifyed except for DFBMB and DFBMC and Q6R2 waiting to be released by CRG
Sector 8-1: DFBAs and DFBMI are qualified. The other DFBMs are not released by CRG and the two DFBXs are currently being qualified.
Sector 6-7: The quality assurance work is almost done. A series of non conformities are still being solved. In total, 16 NC were open from which 10 were discovered at cold. Seven of them are already closed.
RQ10R6 has a problem with a voltage tap warm cable 156m long. TS/EL is solving it.
The other two NC are solved but ElQA needs to be repeated.
The high voltage test in the RB circuit (without instrumentation) failed at 1.9kV and 1.4kV. The problem was found in one current lead and traced back to the heating part in the cartridge. The problem is solved but the test has to be repeated.
Level gauges
For sector 2-3 Q4R2 and Q5R2 are released (waiting for CRG-OP). The boil-off test results for cryostat Q6L3 are being analyzed. For Q6R2, the level is oscillating and requires more time. R. Saban asked for a recurring report showing the status of all level gages in one slide. The release procedure for CRG instrumentation is still pending. It should include the global release for all CRG group activities. (Action: J. Casas Cubillos and N. Catalan Lasheras)
In sector 6-7 al the level gages are released
The cryostats Q5R8 and D2L1 are still pending and access is needed. It was proposed at the RAT meeting to give access on Monday for this purpose before emptying the cryostats.
Status of the powering proceduers
M. Modena showed the list of procedures. A lot of the sector specific documents are missing. R. Saban reminded that these documents have to be released before the powering of the sector. (Action: editors)
Matters arising
- During QPS IST tests one discharge in magnet A21L3 (MB3708) showed a problem. The heater discharge was clearly interrupted as if the circuit was open. ElQA team is investigating the integrity of the magnet and the cable. This magnet send back to the manufacturer and repaired due to bad quench performance. It will be useful to investigate the details of the repair to understand the origin of this failure (Action: M. Modena).
- A short report from the investigation of traveling waves in 7-8 was presented by M. Badnarek (sees slides). A scope was connected in the tunnel to two adjacent magnets in the two different extraction channels. A rare event was seen Were small voltage oscillations were seen without correlation with any powering. When the power converter goes to standby position, small oscillations are also seen in differential and common mode. It was noticed by R. Schmidt that the power converter is not stable at this moment and that this is not completely unexpected. No other oscillations are seen during normal powering of power abort. However waves are detected in common mode when opening the energy extraction switches. The amplitude of the oscillation grows with current. After a quench the oscillation is slightly larger and as a different period and phase. W. Venturini pointed out that this may be explained by the change in resistance and impedance of the full chain of magnets. In summary, nothing abnormal was observed and all voltage levels match the calculations. R. Schmidt suggests to make a model of the circuit.
- As no intervention in the magnets is scheduled, It is not needed to discharge the heaters in sector 7-8 for the cryogenic intervention. The equipment is safe against an accidental discharge. For the inner triplet and separation dipoles the situation is different and the heaters will be discharged. If the temperature stays bellow 10-20 K ElQA tests are not required either.
- R. Flora proposes to reduce dI/dt when starting the power converter to avoid spurious tripping of the RB detector . The nominal ramp rate of 7A/s should go to 3 A/s. The total time will increase only one minute. It implies an intervention in the converter itself. The sequencer does not have to be changed.
Issues for the next MPP meeting (in two weeks):
- Tool for unbalance observation
- Procedures for recommissioning sector 4-5.
- Investigation on the detection of symmetric quenches.
3 July 2008
Nuria Catalan Lasheras