MP3 recommendations from June 2013-Feb 2014 Arjan Verweij on behalf of the MP A. Verweij, LSC meeting 7/2/2014 One of the tasks of the MP3 is to make recommendations concerning the SC circuits in the LHC, in order to resolve NC’s or improve future operation. Since June 2013 we issued 12 recommendations. MP3 website: Recommendations on:

Issue: Short in RCS.A56B2 (NC ), likely due to sharp edge inside HCM-LCM module Recommendation EDMS (June 2013): Protect the inside of a tube in 12 HCM-LCM interconnects with a G10 foil. Ensure that sound electrical insulation is present in the N-line of 11 HCM- SHM interconnects. (PS: already presented to the LSC on 21/6/2013) Follow-up (as of 21/1/2014): Insulation of faulty wire repaired HCM-LCM interconnects  all 12 have been opened.  11 are already consolidated.  The last one (DFBAK) will be consolidated in the coming weeks. Line N in SHM-HCM interconnections  5 DFBAs are OK according to existing pictures.  3 are OK according to recently made X-rays  2 will be checked  1 is open (DFBAO) 1 A. Verweij, LSC meeting 7/2/2014

Issue: Unusual wiring of a spool piece due to a short in RCS.A78B1, NC Recommendation EDMS (sept 2013): Disconnect spool 9 from 10 in QQBI.B33L8 Follow-up: Done. Validated by ELQA. NC closed. ELQA test result still needs to be added to NC. NC still needs to be attached to the 2 IC’s. 2 A. Verweij, LSC meeting 7/2/2014

Issue: Quenching at low current of RCO.A78B2 (NC ) Recommendation EDMS (Sept 2013): Bypass two MCO magnets using a spare busbar. Follow-up: Bypass made. Validated by ELQA. QPS is OK. EPC to be checked. NC not yet closed. Layout DB still to be updated. NC still needs to be attached to the 2 IC’s. 3 A. Verweij, LSC meeting 7/2/2014

Issue: Circuit RCO.A81B2 highly resistive and sometimes open (NC955048) Recommendation EDMS (Sept 2013): Bypass two MCO magnets using a spare busbar. Follow-up: Bypass made. QPS is OK. EPC to be checked. Layout DB still to be updated. NC not yet closed. NC still needs to be attached to the 2 IC’s. 4 A. Verweij, LSC meeting 7/2/2014

Issue: Short-to-ground in RSS.A34B1 inside the SC link (NC ) Recommendation EDMS (Oct 2013): Bypass from DFBLC to DFBAF using a spare bus Follow-up: Procedure under definition. Connection foreseen between DFBLC extremity and QDQI.7R3. Work in progress. 5 A. Verweij, LSC meeting 7/2/2014

Issue: Short to ground in RQTF.A81B1 (NC ) Recommendation EDMS (Oct 2013): Bypass 4 MQT magnets Follow-up: Done. Validated by ELQA. NC not yet closed. Electrical DB still needs to be updated. QPS and EPC still have to implement some modifications. NC not yet attached to the modified IC. 6 A. Verweij, LSC meeting 7/2/2014

Issue: Decay time constant of the RB and RQ magnets Recommendation EDMS (Nov 2013): Modify the EE resistances so that  RB =100 s and  RQ =30 s. Follow-up: In progress. Resistances modified in almost all points. 7 A. Verweij, LSC meeting 7/2/2014

Issue: Sparking in 98 Fischer connectors of the RCO, RCBCH/V and RCBYH/V circuits during ELQA testing at nominal voltage (NC ) Recommendation EDMS (Jan 2014): Improve insulation around 36 Fischer connectors Follow-up: Pending decision required by MSC-SCD section from the TE-TM before they start the work. 8 A. Verweij, LSC meeting 7/2/2014

Issue: Possible tripping of the QPS due to very low threshold of 0.5 mV on the 13 kA busbar segments of the RB and RQD/F circuits. Recommendation EDMS (Jan 2014): Increase threshold from 0.5 to 2 mV. Follow-up: In progress by MPE-EP (QPS team). Awaiting new firmware. 9 ADC moving average filter f s =5 Hz t filter = 10 s U thres comparator A. Verweij, LSC meeting 7/2/2014

Issue: Short circuit between RCD.A78B1 and RCO.A78B1 in an SSS (NC ). In this SSS both circuits do not contain any magnet. Recommendation EDMS (Jan 2014): Bypass both faulty segments using spare bus bars. Follow-up: Done. Validated by ELQA. NC closed. NC not yet attached to the 2 IC’s. 10 A. Verweij, LSC meeting 7/2/2014

Issue: Quench back in 600 A circuits after a FPA. Recommendation EDMS (Jan 2014): Change EE resistance from 0.7 to 0.4  in all (8) RQTL9 circuits. Follow-up: In progress by MPE-EE. Expected to be finished in June. 11 A. Verweij, LSC meeting 7/2/2014

Issue: Limited number of spare EE systems for 600 A circuits (only 4, i.e. 2% of total) and spare circuit breakers (6.6% of total). Same type of circuit breakers cannot be procured anymore. Recommendation EDMS (Feb 2014): 8 RQS and 16 RSS circuits can run without EE. DC contactors should be bought. No change during LS1. Reconsider spare policy by end Follow-up: Price offer for DC contactors made. 12 A. Verweij, LSC meeting 7/2/2014

Conclusion Since June 2013 the MP3 issued 12 recommendations, in order to:  Resolve NC’s: 8  Improve future performance: 4 11 recommendations are being followed, and will be finished in time to start IST and HWC. 1 recommendation is pending, and it is probably too late now to be implemented. A. Verweij, LSC meeting 7/2/2014