Choose timezone
Your profile timezone:
MPP meeting
Minutes of the MMP general meeting held on 12/12/2007
General info
Powering of the arc magnets is still possible before the end of the year.
Pending activities
Ramp rates for commissioning: the subject has been investigated by Glyn and Walter and can be presented at the next meeting
High resistance in the corrector of Q5L8 (circuit RCBCHS5.L8B1 with corrector MCBCH.B5L8.B1): we still need to assess how much above nominal we can power the adjacent MCBCH in Q5L8.
Routing of the warm cables to the120 A correctors: S. Russenschuck’s team found polarity errors when including the warm cables (which is not usually done as this part of the circuit is not under the responsibility of Mr. Polarity). An update will be given by Antonio at the next meeting.
RCBYV5.R4B1: in situ reparation could be attempted during the consolidation campaign. AB PO reiterated the risk of powering with a floating PC (loss of protection against a second fault to ground).
Status of the powering tests in S 4-5.
Glyn illustrated some features of the MS tests: the evidence of a partial transition to the normal state of the coils in Q6 and Q5 (MQY) during heater discharges at 80 A;
a double bump in the half coil voltage signals and its correspondence in the second derivative of the current: this is probably due to inter layer transition of the normal front (several people are now trying to simulate this effect).
We need to elaborate and store these data and build references for future tests.
Note: the current decay curves of D4 can be held as a reference for all the superconducting separation dipoles (same coil type, only yokes are different).
Glyn pointed out that the heater wires are extremely fragile, which is an excellent reason to minimize the number of provoked quenches.
Indeed this seems to be true for all types of superconducting magnets in the LHC: the wire used to interconnect the heaters had been developed to minimize heat in-leaks through the capillary, and its mechanical properties are not suited for the inner part of the circuits, that may be exposed to vibrations in the helium flow during quenches. The wire is multifilament and failures can therefore happen in steps.
Status of the powering procedures
Most of general documents are under engineering check.
Editors are reminded to include the comments and switch the status to under approval as soon as possible.
The detailed procedures for each sector are in most cases not yet available. It is reminded that we urgently need those of sector 4-5. However, these documents cannot be finalized before ELQA at cold is completed on the relative sector.
An official template for the PAC is being discussed between MPP and HC people and will be presented in the next meeting.
Status of ELQA
Stephan reported on high voltage tests on RBA45. At 1.9 kV there was a partial discharge after 15 s. 45 QPS tripped. The weak spot was in an instrumentation wiring, and after disconnection it was OK. A short to ground was detected in a Q7 in point 2.
Another short was found in a MCS circuit in sector 3-4.
MPP CCC rotation plan in January
Andrzej presented the shift table; it appears that, according to official planning, only one week needs to be covered in this period.
Modifications requested by MPP on triplet powering
Reminder of the problem: for the time being, a water fault would trigger the firing of the heaters as there is no other mean to accelerate the current decay, and a slow power abort may damage the PC (diode).
Some proposals for improvement are presented:
PIC1 will now be done with the quench heater power supplies connected to a dummy load.
We still have a quench heater discharge during PIC2 and two discharges during P2N.
The protection of the diode is only required above 2 kA, so PO proposes to discharge the heaters only above 2 kA.
AB CO was asked to propose a solution in terms of interlock logic.
MPP reiterates that it makes little sense to fire the heaters only to protect the power converter (also in the light of what has been reminded by Glyn, see above).
MPP acknowledges the progress made, but would like to ask further AB PO to consider a solution that allowed avoiding at all the firing of heaters in case of a water fault.
Sandor F. questions the usefulness of high current provoked quenches: the protection could be validated at intermediate current, and there would be nothing to be gained by systematically quench at high current. This could be done only once to estimate the recovery time of the cryogenics. Andrzej however would have each circuit quenched once at top energy. This will be discussed again in a future meeting.
Common powering of QD/QF
Powering tests up to PLI3 will be done individually for QD and QF. From PLI3 on, both circuits will have a single test and will be powered simultaneously. It was discussed and agreed with PO that the fast power abort will be done in both circuits at the same time.
MPP related steps in MTF
A. Vergara showed the path to find the MTF structure for the circuts powering in MTF.
http://hcc.web.cern.ch/hcc/mtf_links.html HC arborescence.
After finding the proper circuit, the "Installation & Commissioning" tab contains the steps that were succesfully passed. The log of the sequencer is kept as one of the result files but more can be added by hand. The first step " MPP ok to start powering" has to be signed by MPP before any powering test. The last step "Circuit Released" will be also signed by MPP after the full analysis is done.
The real time status of the powering tests can be accessed through the HC page and the following address: http://p2n.web.cern.ch/p2n/default.php?search_psect=S45.
There are minutes attached to this event.
Show them.