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MPP meeting
General Information
The temperature of the magnets in sector 4-5 is approaching 4 T after the refrigerator was switched on last week. The powering tests will start next week as planned.Following of actions: the ramping rates for main magnets and correctors will be presented in the next meeting.
Status of the powering procedures and approval process in EDMS (M. Modena)
Four out of seven specifications have passed the engineering check. The editors need to include the modifications and corrections suggested in the comment in the following week. Michele requested that the last version from the Word document from Gosia is taken for the modifications. A. Siemko asked for the deadline for the final release of the documents. Simultaneous powering of circuits (PAC) procedures need to be included in the list. The procedures for the correctors inside the inner triplet need to be treated as 600 A circuits.
MPP CCC rotation plan (A. Siemko)
A. Siemko presented the rotation plan for the MPP CCC expert team. Two people will be present in the CCC every week. Tel: 162266. The plan will be added to the web page. B. Bellesia asked is MPP plans on having people during the weekend between weeks 50 and 51 as for the rest of HC. A. Siemko replied that this was not officially requested and that will be discussed in the HC meeting tomorrow. Also the plan applies to normal working hours but extended hours could be discussed. The presence of only one of the MPP experts in the CCC is acceptable for sector 4-5 but needs to be revised for the next sectors next year as it may not be sufficient when commissioning several sectors and fronts. Meetings have started already this week at 8:30 and 16:30 in the CCC. MPP will assist to the meetings as from next week. Modification of PIC for common powering of QD/QF (M. Pojer, T. Tortschanoff)
The question was raised during the presentation of QF/QD powering procedures if both circuits need to be always powered simultaneously. This is in general the case during machine operation. The commissioning procedure plans for separate powering up to 2000 A and simultaneous powering of both circuits above 2000A. It is stated that during manufacture and testing, the quadrupole magnets were always tested with both apertures in series. This should avoid de-training, and mechanical stresses. A. Siemko added that the magnetic state of one aperture could be also affected by the powering of the other. This kind of unbalanced powering will be produced in the case of a powering failure and a slow power abort.
Two solutions could solve this. 1. A modification of the sequencer that sends a SPA also to the other power supply. 2. A modification of PIC that currently soes not couple the circuits. Both solutions imply only software modifications.
R. Schmidt pointed out during past discussions that nothing prevents one convertor to go up to nominal current while the other stays at low current. Solving this may require a hardware modification like a differential current reader.
T. Tortschanoff informed that, by design, the mechanical forces are taken by the collars. No stress is expected between apertures if only one aperture is powered. As for the magnetic state, the magnetic flux of a single aperture powered is limited to the iron yoke. The filaments in the non-powered aperture will not be magnetized. The contribution of the yoke to the magnetic field is only 10-15% so that this is not very critical.
The magnetic history of both apertures in the same magnet will be however different after a slow power abort and that may affect the magnetic quality and the beam. Warming up the magnet will remove this problem in the particular case of hardware commissioning of 4-5 but in routine operation this is not possible. The effect of pre-cycling the magnets is not known yet and may not be sufficient. As hardware commissioning should be as close to operation as possible MPP recommends to modify the coupling of QD/QF circuits above 2000 A for the future. AB/CO should use the solution they consider more reliable.
Priority list for 600 A and 4-6 KA circuits in sector 4-5 (W. Venturini Delsolaro, N. Catalan Lasheras)
A list of priorities for the 600A circuits was given where circuits are grouped by type. Trim quadrupoles should be commissioned first, followed by sextupole spool pieces. Then tuning and skew quadrupoles and last, chromaticity sextupoles. All those circuits have priority one as they are needed for running the machine. R. Denz pointed out that f the required ramp rates for some of the correctors cannot be reached the by the QPS system. Thresholds may need to be reconsidered. This will be discussed in the next meeting.
For individually powered quadrupoles and dipoles, there is no priority for what concerns the machine as all the magnets are needed for any kind of beam operation. For the point of view of hardware commissioning, priority should be given to the circuits:
- not tested previously in 7-8 as the magnets in the dispersion suppressor (Q8-Q10),
- powered through the superconducting link.
AOB
M. Modena suggested that the presentation of the MPP logbook should take place as soon as possible as powering will start next week.R. Wolf asked how the training between experts was going to be organised. Mutual training between the two members of MPP in CCC should be part of it.
W. Venturini Delsolaro inquired about the status of the automatic analysis. The analysis for the 60 A and 80 A circuits is underway and the specifications are being compiled for the 600 A circuits. The activity will continue.
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