1. 6 th April 2010 MP3 weekly summary – issues and follow-up 0v1 M. Zerlauth for the MP3-CCC shift crew

2. Markus.zerlauth@cern.ch Summary of the events during past weeks Circuit(s) Problem Intervention in field Remarks RCO/RCD.A56B2 Tripped again 3 times during the week (total of 8 now!) Not yet done… In all 8 events RCO goes first, FGC buffer indicating an overvoltage trigger (1 st level) RQD/F in S12 and S78Total of 4 (yet unexplained) trips NOAnalysis still ongoing RQT12.R4B1Problem with output stage of power supply DONETrip due to a failure of PC. TRG OUTPUT STAGE POWER SUPPLY RB.A34 / MB.A24R3Heater Power supply discharging DONEProblem appeared on Saturday but repair postponed to Sunday RQX/RTQX2.L5Temperature sensor problemYES, but not fixed?Sensor DXEX02_03L5_TT891A faulty, no repair but only ‘touching’ cables RB.A78Broken micro-switch after opening of EE YESOpening of switches to accelerate current decay after loss of CRYO RQX R8, L8 and L1Tripped when going from stand-by to OFF NOKnown ‘feature’, could maybe be solved through procedure by EPC RQTD/FTune correction currently limited by lower QPS thresholds >= 50A QPS firmware / YESSuperimposition with B2 correction; proposal to increase 50A -> 75A Few additional issues discovered and solved by interventions done during the week Dominating issue is still with unexplained RQD/F trips in S12 and S78

3. Markus.zerlauth@cern.ch Machine Interlock Systems RCO.A56B2 /RCD.A56B2 RCO.A56B2 (and consequently RCD.A56B2) tripped another 3 times during the week, total of 8 trips now in the past 2 weeks Power supply module of RCO.A56B2 to be exchanged (indicating a trigger through over voltage (1 st level) -> Thursday?

4. Markus.zerlauth@cern.ch Summary of the RQD/F events so far Event timeSectorCircuit currentPIC historySwitch timestamps Other QPS buffers 30/03 at 08h49m45sS81Ramp with beam @1900A RQF AND RQD @ 08.49.45.949 RQF @ 947 RQD @ 947 DQAGMD @ 08.49.46.404 DQAGMD @ 08.49.46.499 30/03 at 08h51m17sS12Ramp with beam @2100A RQF @ 08.51.17.735 RQD @ 08.51.17.736 RQF @ 731 RQD @ 731 01/04 at 05h05m03sS12Flat top with beam @ 5300A RQF @ 05.05.03.176 RQD @ 05.05.03.178 by GPM RQF @ 173 RQD @ 173 01/04 at 08h43m06sS12Injection, no beam @ 750A RQF AND RQD @ 08.43.06.141 RQF @ 137 RQD @ 137 02/04 at 18h49m13sS12Standby, no beam @ 350A RQF AND RQD @ 18.49.11.362 RQF @ 357 RQD @ 358 04/04 at 02h49m48sS78Flat top with beam @ 5300A RQF @ 02.49.48.756 RQD @ 02.49.48.757 RQF @ 754 RQD @ 753 DQAGMD @ 02.49.49.290 During past days 4 yet unexplained trips on RQD/F circuits of sectors 12 and 78 were observed as shown in the summary below (completed by the two trips on Tue 30 th of March due to the SPS main power supply)

5. Markus.zerlauth@cern.ch All 4 events have an (almost identical) event sequence, ie ● PIC receives a Quench/FastPA signal from QPS (event sequence in PIC is the typical signature of an event originating within QPS) ● RQD/F trip simultaneously (but for 1 event where the GPM is ‘faster’ than the RQD quench signal) ● RQD and RQF switches open simultaneously and typically 3-5 ms BEFORE the PIC records the quench signal, ie confirming that the QPS quench loop is broken (common QPS quench loop for RQD/F circuits!) ● No indication of changes in Discharge Request Loop, thus trip must be internal to QPS (no other means of opening the switches from outside) ● No other QPS PM buffers (apart from global busbar for 2 events and nQPS buffers which are well after the initial trip and a result of switch OFF of circuits) – Trip of 2 nd QPS board? ‘Typical’ event sequence

6. Markus.zerlauth@cern.ch The RQD/F.A12 ‘hump’ ● Available data and event sequence seem to indicate triggers to origin within the QPS system, reason after loads of analysis however still unclear ● In sector 12 (where we had 3 oo 4 trips), busbar detector is showing repetitive noise patterns, some peaks up to 1.1V/550ms ● Further investigation with help of QPS experts needed as to the real origin of the trips…

7. Markus.zerlauth@cern.ch Machine Interlock Systems FIN