The LHC Beam Interlock System

1
M. Zerlauth for the MP3-CCC shift crew
0v1
2
Summary of the events during past weeks

• 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

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 (1st level)
RQD/F in S12 and S78 Total of 4 (yet unexplained) trips NO Analysis still ongoing
RQT12.R4B1 Problem with output stage of power supply DONE Trip due to a failure of PC. TRG OUTPUT STAGE POWER SUPPLY
RB.A34 / MB.A24R3 Heater Power supply discharging DONE Problem appeared on Saturday but repair postponed to Sunday
RQX/RTQX2.L5 Temperature sensor problem YES, but not fixed? Sensor DXEX02_03L5_TT891A faulty, no repair but only touching cables
RB.A78 Broken micro-switch after opening of EE YES Opening of switches to accelerate current decay after loss of CRYO
RQX R8, L8 and L1 Tripped when going from stand-by to OFF NO Known feature, could maybe be solved through procedure by EPC
RQTD/F Tune correction currently limited by lower QPS thresholds gt 50A QPS firmware / YES Superimposition with B2 correction proposal to increase 50A -gt 75A
3
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 (1st
  level) -gt Thursday?

4
Summary of the RQD/F events so far

• 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 30th of March due to the SPS main
  power supply)

Event time Sector Circuit current PIC history Switch timestamps Other QPS buffers
30/03 at 08h49m45s S81 Ramp with beam _at_1900A RQF AND RQD _at_ 08.49.45.949 RQF _at_ 947 RQD _at_ 947 DQAGMD _at_ 08.49.46.404 DQAGMD _at_ 08.49.46.499
30/03 at 08h51m17s S12 Ramp with beam _at_2100A RQF _at_ 08.51.17.735 RQD _at_ 08.51.17.736 RQF _at_ 731 RQD _at_ 731
01/04 at 05h05m03s S12 Flat top with beam _at_ 5300A RQF _at_ 05.05.03.176 RQD _at_ 05.05.03.178 by GPM RQF _at_ 173 RQD _at_ 173
01/04 at 08h43m06s S12 Injection, no beam _at_ 750A RQF AND RQD _at_ 08.43.06.141 RQF _at_ 137 RQD _at_ 137
02/04 at 18h49m13s S12 Standby, no beam _at_ 350A RQF AND RQD _at_ 18.49.11.362 RQF _at_ 357 RQD _at_ 358
04/04 at 02h49m48s S78 Flat top with beam _at_ 5300A RQF _at_ 02.49.48.756 RQD _at_ 02.49.48.757 RQF _at_ 754 RQD _at_ 753 DQAGMD _at_ 02.49.49.290 DQAGMD _at_ 02.49.49.290
5
Typical event sequence

• 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 2nd QPS board?

6
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

• FIN

Machine Interlock Systems