Ad-hoc MP3 meeting 22/2/2013

1. Present: Bernhard, Gerard, Arjan, Andrzej, Mirko, Sandrine, Zinour, Per, Daniel, Rudiger RD2.R8(7 TeV=6020 A, 6.5 TeV=5590 A) RD2.R8 is a D2 separation dipole. Cold mass is HBMBRCA001-BL000001 (first of the production). MM available up to 7 kA, so it has been trained up to there. Quench during cold test: 6309 A, 6877 A, then up to 7 kA + one quench at 6309 A after thermal cycle. Quenches in 2007/8: 5816, 5788, 5856, 5854 A Quenches in Feb 2013: 5350, 5723, 5779 A Decision 18/2: perform max 1 quench more. Then perform cycle with plateau for 20 min at I_Q_max-100 A. New results: 4thquench at 5670 A Decision 19/2: Run the circuit for 8 hrs at 5.6 kA. New results: Quench on plateau after 8 min!!!! Decision 20/2: Make sure it is not the BB. If it is the magnet, then perform pyramid 5.4, 5.5, 5.6, 5.7, … with 2 hrs on each plateau, and present a.s.a.p. in TE-TM. New results: Except for the first quench, all quenches are in the BB, very close to the magnet. 21/2: Antonio presented possible cooling problem of the bus if the plug is not at the lowest point. Radios by CRYO foreseen asap. See also picture of positioning of the RD2.R8 bus. Ad-hoc MP3 meeting 22/2/2013

3. RD3.L4 (nominal 5850 A, HWC 2008: 4984 A, 5080 A, reduced to 4500 A) RD3.L4 is a D3 separation dipole. The cold mass HCMBRSA001-BL000002 is installed there. Quench during cold test: 6265, 6997, then went up to 7000. No quench after thermal cycle 3 quenches done in Feb 2013: 4660, 4751, 5112 A Decision 20/2: OK for 2 more tests. Check in which aperture quenches occur. New results: Quench 4 at 5293 A, Quench 5 at 5386 A. All 5 quenches in same aperture (U_RES_B1 positive). Decision 21/2: max 3 quenches more New results: 6th quench at 5444 A Decision: Train up to 6.6 TeV equivalent (5515 A). Then stop because this magnet was already a slow trainer at BNL with a bad memory, and we are pretty sure that the magnet will reach nominal, but we don’t want to overstress. RCBX: 550 A with low RR. Decision 18/2: 1st ask for overcooling on leads. If no improvement then reduce I_nom to 450-500 A. New: For info: Mikko gave a list of weak MCBX magnets, that could only work with Q1 magnets. Check correlation. RQ7.R4: repetitive trips during PGC, also one at stable 4.8 kA. Decision 22/2: make sure that the trips are no related to cooling problems

4. RQ6.R2 (Q at 3896, 4124, 4190 all in B1) Decision 21/2: perform max 2 quenches more New results: Q at 4251 A in B1, to be cntd RQ6.L7B1: QPS triggered when ramping down in PNO.a3. Very noisy U_RES signal. Forwarded to QPS. 0 V crossing. Check and repeat. New results: Noise induced by PC. Forward to EPC. Decision 22/2: Jens will send e-mail to EPC. Should be looked at for long term but at the moment not urgent. Closed RQTD.A23B1 (550 A): Quench at plateau. Ad-hoc decision 21/2: perform pyramid 500 (20 min), 525 (20 min), 550 (2 hr) New results: not yet done RCBXV3.L8 (550 A): Quench at plateau. Decision 22/2: PNO tests with 1 hr plateau at 500, 525 and 550 A (note overcooling restrictions)

5. RQ5.R1: 2 quenches (3910 and 4086 A) on B1 but not in B2? Sandrine and Ivan analysed and they think it is a PC problem, and not a quench. Huguesshows that the voltages on the leads correspond to the DCCT currents. It seems very likely that the quench was not detected by QPS and the heaters were not fired. Decision 19/2: Jens will check QPS boards in detail, and check in timber if boards were blocked in the past. Lock circuit. We should probably perform an ELQA test. Heaters not fired. Both boards stuck. After reset both boards came back. No signals since aug 21, 2012. Seems software issue, not a hardware problem. Scan boards + reset IPQ/IPD/IT. Decision 20/2: Issue forwarded to QPS. New results: Hot spot of first 2 quenches would have been maximum 350 K. ELQA OK. 3rd quench at 4286 A in B1. Decision 21/2: perform max 2 quenches more New results: Q at 3718 and 4071 (both in B2 with B1 at 4310 A). Decision 22/2: max 2 quenches more

6. RCBYHS5.R8B1: quenches at 64 A “Decision 19/2”: we will discuss tomorrow Decision 20/2:we will discuss tomorrow Decision 21/2:we will discuss tomorrow New results: Gerard and Bernhard looked in detail. Known poblem. Quenched 4 times at 63-64 A. Quench level getting lower wrt previous HWC. 1 hr plateau at 55 A. Trip when ramping down. Decision 22/2: Look also at other cases in the machine. Keep I_nom at 20 A. Perform PNO, but no other tests. Needs follow up with recommendation to fix/replace magnet. RCBXH3.L5: ELQA OK. Tripped in the past at 50 A Decision 22/2: QPS problem. Intervention in tunnel according to proposal Zinour. RCO.A78B2: special ELQA to be done To be looked at by somebody. Who??? PGC test, for all remaining sectors: Proposal 56: run IPD, IPQ, IT at I_nom-100 A run 600 A at I_nom-25 A For the other sectors: add a PNO test for the IPQ’s with equal currents in B1 and B2.

7. Comments from GLM: (Rudiger) RQ.A34 because int. splice resistance of 15+15 nOhm in Q7? Should circuit be tested to 6.5 TeV? Recommendation 20/2: No, and send e-mail to GL’s (Arjan). Done. 1) Resistance measurements in the LHC at about 6 kA showed for this magnet: RQF: 20+-5 nOhm and RQD 27+-5 nOhm. These resistances are stable for the 2010, 2011 and 2012 runs, so it is very likely that this magnet had the same splice resistances during the reception tests in SM18. Additional ELQA measurements showed that these resistances were not in a single splice but somewhat distributed over several splices (we are collecting the exact values). 2) This magnet passed all reception tests in SM18 successfully. However, extended powering at high current was not part of the test. 3) In 2009 a so-called 'life test' has been done in SM18 where dipole MB2303 (with an internal resistance of 50 nOhm) has been trained to 11850 A (with only one quench at 10.9 kA), cycled hundreds of times between 500 A and 11850 A, and thermally cycled. The resistance did not significantly change. 4) 6.5-7 TeV corresponds to 10-10.8 kA in the RQ, so the resistive losses, as compared to MB2303 should be at least about 50/20*(11.85/10.8)^2=3 smaller. 5) RQ.A34 has been tested during HWC in 2008 up to 9.3 kA (=6 TeV equivalent) without problems.

8. 6) The probability of having a magnet quench in RQ.A34 up to 10 kA is very small but can of course not be excluded, especially because we have no idea of the impact of 4 years of powering on the training behaviour of the quadrupoles. 7) Running RQ.A34 up to about 10-10.8 kA requires a modification of the energy extraction, because with the actual tau=9.2 sec we would risk a serious multiple quench in case a quad quenches. 8) We know that some of the quad diode leads are weak. Every quench in a quad gives a small probability of a thermal runaway in a diode lead, possibly resulting in a burn-through of the quad and an arc in the circuit. We could of course assess the quality of the leads by performing some heater induced quenches on this magnet at, for example, 6, 8 and 9 kA. 9) At higher currents (>9 kA) a magnet quench (associated with the heat in the diode) propagates through the bus towards the interconnect. We know that many interconnects are weak and can burn through if they quench at high currents. The fact that we have to increase the dump decay time constant from 9.2 s to 15-20 s makes the situation even worse. Since we are sure that this magnet reaches 6 TeV equivalent, and since we are almost 100% sure that it can safely run up to 6.5 TeV (and even 7 TeV) equivalent, and taking into account the small risk of a burn-through (with associated arcing) in case it will be tested, the MP3 recommends not to test the circuit before LS1. Do people see more arguments against or in favour?? Add histogram, get ELQA values, shift to R values from ELQA

9. Closed issues linked to excessive quenching RQX.L2closed (3 Q, 4thPNO OK) RQ5.L5: closed (4 Q, 5th PNO OK) RQ6.R5: closed (3 Q, 4th PNO OK) RQ5.R2: closed (3 Q in B1, 1 Q in B2, I_nom reduced to 4100 A, 5thPNO_red OK) RQ5.R5Closed (1 Q in B1, 2 Q in B2, 4th PNO OK) RQX.L2Closed (3 Q, 4th PNO OK) RQ6.L5:Closed (2 Q in B1, 2 Q in B2, 5th run OK) RQTL11.R5B1 closed (nominal is 550 A, expected for 7 TeV: 250 A, Q at 487, 506, 514, 543, 498, 545 A, PNO reached, reduced to 450 A) RQTL11.L6B1 closed (nominal=400 A, expected for 7 TeV: 200 A, Q at 358, 392, 376 A, reduced to 350 A) RQ5.L1 closed (3 Q, 4th PNO OK)

10. Closed issues linked to quenches on plateau RQ4.R6: Closed (Q on plateau, PNO.c4 with 2x2 hr OK) RQ7.L4: Closed (Q on plateau, PNO.c4 with 2x2 hr OK) RQ6.L2: Closed (Q on plateau, PNO.c4 with 2x2 hr OK) RQTD.A23B1: Closed (Q at plateau, PNO.c4 with 2x2 hr OK) RCD.A56B2: Closed (Q at plateau, PNO.c4 with 2x2 hr OK) RCD.A45B1: Closed (Q at plateau of 550 A, Pyramid and PNO OK) ROF.A45B2 : Closed (Q at plateau of 550 A, Pyramid and PNO OK) RQTF.A56B1: Closed (Q at 500 A, Q at plateau, Pyramid OK) RQS.A56B2: Closed (Q at 520 A, Q at plateau, Pyramid OK) RQT13.R6B1: Closed (Q at plateau, Pyramid OK) RQS.R5B1: Closed (Q at plateau, Pyramid OK)

11. Closed issues (Various) RQS.L5B2: Closed (TT893>324 K, ELQA informed) RQT13.R5B1:Closed (QPS A&B frozen) RQ4.L5:Closed (QPS A&B frozen) RSD1.A56B2: Closed (minor issue due to electrical interference) RQ6.L8: Closed (Heater induced quench at 2500 A) PGC in arc alone?: Closed (Everywhere!!!) RQS.A56B2: Closed (U_RES saturation, forwarded to QPS) RQX.R1: Closed (heater firing after PC_failure, PNO OK, Q1 and Q2 on board A the same) RCBXH2.R5: Closed (CL cooling problems) RQSX3.R5: Closed (CL cooling problem) RSBXV1.R5 : Closed (CL cooling problem)

12. New PNO values RQ5.R2: 4310 reduced to 4100 A RQTL11.R5B1 reduced to 450 A RQTL11.L6B1 reduced to 350 A