Hi-pot results summary Speaker - Lab

MQXFA Electrical requirements and He BD voltages Component V_test @ warm @ 1.9 K after He Coil-Ground 3680 V 1840 V 368 V Coil-Heater 2300 V 460 V (2018-04-23) MQXFA Electrical Design Criteria: EDMS 1963398 v4/ Docdb 879 Design 10 K 75 K 150 K 300 K Polyimide BD Voltage (50 mm) 10000 V 7000 K He BD (4 mm) 11000 V 2500 V 1500 V 900 V Failure 10 K 75 K 150 K 300 K He Breakdown Voltage (0.2 mm) 300 V 350 V 270 V 200 V

MQXF coils (Test after fabrication) Coil to quench heater requirements: 3680 V (since ~04/18) 55 coils have been tested after fabrication (220 heaters) 26 coils (* in the table) have been assembled into a magnet (104 heaters) # coil 2000 V 2500 V 3000 V 3200 V 3680 V 3700 V 5000 V Short model 29 1 23 (17*) 3 MQXFA 18 2 (2*) 11 (7*) 5 MQXFB 8 4 No issues but test voltages changed over time

Coils assembled in a magnet Magnets LONG MIRROR US- HiLumi MQXFS1 MQXFS3 CERN MQXFS4 MQXFS5 MQXFA P1 MQXFAP 2 coils P1 103, 104, 3, 5 105, 106 107, 7, 8 108, 109 110, 111 203, 204 205, 206 P2, P3, P4, P5 102, 104 105, 106 # of training 52 349 100 8 50 18 29 # of thermocycle s ? 5 3 1

MQXFS3 @CERN after cold test (May 2018) Coil 105, 106, 107 5 thermal cycles 1 full disassembly ~100 quenches Coil 8 2 thermal cycles ~50 quenches 1000 - 2000 V 0 - 500 V 2000 - 3680 V > 3680 V Coil 8 ORH failed the hipot at the test facility First breakdown voltages testing up to 10000 V (200 V steps and 30 s waiting time) 105 106 107 8 OLL 9585 V 7325 V 10000 V OLH 5220 V 5694 V ORH 5887 V (?) 5020 V 6747 V 1500-3000 V ORL 6542 V 6324 V 7211 V OLL= outer left low field 105 106 107 8 OLL 7589 V 5777 V 10000 V OLH 5354 V 5396 V ORH 6869 V (?) 3570 V 136 V 859 V ORL 6609 V 5097 V 144 V

MQXFS3 Hi-pot history MQXFS3a (105, 106, 107 and 7) QH passed Hipot in air up to 3000 V before cold test (test facility) Nov 23 2016 (test facility) : failure going up to 3000 V in air after cold test. This test is done in the test facility going up to 3000 V very fast. No recording of breakdown voltage. It was probably a breakdown of the facility. (EDMS 2020286) MQXFS3c: (105, 106, 107 coil 7 substituted with coil 8) May 31st 2017 (bldg 927) coil 105, 106, 107, 7 and 8 passed the hipot tests up to 2500 V done in air in bldg 927 (coil on the table). Confirmation that the failure in Nov 2016 was due to the test facility 30th of April 2018 (test facility): first failure after cold test is observed in coil 8 going up very fast to 3000 V. Second failure going up to 1000 V. No recording of the BD voltage. It passed at 500 V. Coil 8 OHR quench heater was identified as the source of problem May 18th 2018 (test facility): Test in He gas was performed (results in slide 21) June 20th 2018 (bldg 927) : hipot tests in air with coil on the table. 200 V steps and wait 30 s each step. Coil 107 OHR QH failed at 6747 V (first failure) and coil 107 ORL QH failed at 7211 V (first failure) January 10th 2018 (Where?): hipot tests in air with coils on the table. High voltage test up 5000 Vat 1kV/min. ORH QH failed at 181 V going up to 1000 V and it was not tested up to 5000/10000 V. Burn test up to 10000 V (500 V test)

MQXFS5 @CERN after cold test 1000 - 2000 V 0 - 500 V 2000 - 3680 V > 3680 V Coil 203, 204, 205, 206 3 thermal cycles ~50 quenches Breakdown voltages testing up to 3700 V (Jan 2019) up to 10000 V 203 204 205 206 OLL 3700 V OLH 2000 V ORH ORL 206 2000 V 2500 V 5000 V 10000 V All quench heaters passed the hipot test up to 1000 V after the first cold test 106 OLH breakdown the first time at 2000 V going up to 2000 at flat top

MQXFS4a @CERN after cold test 1000 - 2000 V 0 - 500 V 2000 - 3680 V > 3680 V Coil 108, 109, 110, 111 1 thermal cycles ~9 quenches All passed breakdown voltages tests up to 1000 V in the test facility 108 109 110 111 OLL 1020 V OLH ORH ORL

Short model MQXFS1e: magnet history MQXFS1 - the first 150 mm aperture, 1.5 m long Nb3Sn quadrupole within the CERN and LARP collaboration Coils fabricated by CERN (#103 and #104) and LARP (#3 and #5) Electrical checkout after fabrication: no issues up to 2500 V Five tests performed since 2016 All QH passed the hipot test in air up to 1000 V after cold test 119 spontaneous quenches 230 provoked quenches and trips (I>1 kA) Total of 8 thermal cycles (not counting the latest one for the hi-potting tests).

Short model MQXFS1e: He gas Hi-pot tests CLIQ leads used for heater and coil connections The CLIQ lead from the magnet connected to CL2 OL heaters (8 strips) in coils 3 & 103 connected to CL3 OL heaters (8 strips) in coils 5 & 104 connected to CL1 Hi-pot tests at selected temperatures up to selected voltages (800, 1500 V) Heater to coil voltage CL1 Heater to coil Voltage CL3 1.9 K 2300 V 75 K 800 V (test 1) 1500 V 150 K 1500 V (failed at flattop) 300 K 1200 V 1360 V 970 V

Short model MQXFS1e: 300 K in air (after He gas tests) QH 3 (CL3) 103 (CL3) 5 (CL1) 104 (CL1) OL1 460 V OH2 short OH3 OL4 The shorted heater (B01) was in the group that failed 150 K and 300 K hipot in He Meet requirements at ambient T in air (after a thermocycle) 4 QH/coil: survivability of ~100% at 800V and ~94% at 1,500V at 150 K.

Short model MQXFS1e: 300 K in air (after He gas tests) QH 3 (CL3) OL1 short OH2 6000 V OH3 OL4 1840 V Heaters of coil 3 were further hi-potted in air up to 6000 V. Ramp 1kV/min

MQXFAP1, MQXFAP2, LONG MIRROR P1 coil 22 training quenches 30 QH induced quenches thermocycles MQXFAP1 P2, P3, P4, P5 coil 18 Quenches 3 thermocycles MQXFAP2 102, 104, 105, 106 coils 29 quenches 1 thermocycle Electrical check out after coil fabrication: no issues but tested all < 3680

Coil autopsy after He: coil P01 (Mirror) First breakdown voltages testing up to 2500-3700 V 500 - 2000 V 0 - 500 V 2000 - 3680 V > 3680 V QH P01 OL1 3700 V OH2 1500 V OH3 2070 V OL4 2340 V OL1 OH2 OH3 OL4 RE LE

Some history of coil P01 Fabrication: 2500 V QH P01 OL1 3700 V OH2 shorted

after test in He: coil P5 (MQXFAP1) QH to coil Hi-Pot before testing up to 3000 V P5 First Failure after warmup 2380 V @ OL-LF 2.38kV Short in heaters 1 and 2 1000 - 2000 V 0 - 1000 V 2000 - 3680 V > 3680 V First breakdown voltages testing up to 6000 V QH P05 OL1 2380 V OH2 shorted OH3 2290 V OL4 2820 V OL4 OH3 OH2 OL1

MQXFAP2 after He First breakdown voltages testing up to 1500 V 6 out of 8 heater circuits passed the test Heater circuit 3 failed at 1.4 kV (arc-fail, 116.5 μA leakage current) Heater circuit 4 failed at 1.5 kV (arc-fail, 92.3 μA leakage current) Each single heaters passed the Hi-pot test up to 460 V afterwards

Coil 108 short samples QH test after fabrication 108 coil: before He test passed hi-pot up to 6000 V QH 108 long piece OL1 6000 V OH2 OH3 OL4

LQS03 model 41 training quenches 4 trips Thermocycles: Each heater covers half length, and full width of the surface where it is applied Each coil has four heaters: 2 OL heaters (one on return end, one on lead end) 2 IL heaters (one on return end, one on lead end) Polyimide thickness: 25 µm 41 training quenches 4 trips Thermocycles:

LQS03 hi-pot results after cold test 500 - 2000 V 0 - 500 V 2000 - 3680 V > 3680 V Breakdown voltages testing up to 6000 V (OL), 2000 V (IL) COIL 18 COIL 16 COIL 19 COIL 15 Lead end, OL 2.11 kV (BD) 2.47 kV (BD) 1.92 kV (A) Return end, OL 1.61 kV (A) 1.71 kV (A) 1.55 kV (A) 3.46 kV (A) Lead end, IL 1.41 kV (A) 1.21 kV (A) 1.64 kV (A) 1.12 kV (A) Return end, IL 1.31 kV (A) 1.42 kV (A) 1.47 kV (A) All heater passed the 650 V (max coil to heater voltage seen by the magnet) Hipot test after breakdown test

First heater-coil hi-pot failure in air after cold test Hipot tests were performed on # 104 heaters Test were performed up to different max V values # 15 failures between 1.2 and 3.0 kV. # 11 failures above 5.0 kV No failure below 1200 V

Some comment on first failure plot MQXFS1: 16 heaters, one QH in coil 3 failed in He at 150 K at 1500 V, one in coil 5/104 circuit failed in He gas at 300 K at 1360 V. Coil 3 heaters were also tested in air and a second QH failed and two passed (next slides). MQXFS3a and b: coil 105 106 107 and 7. All heaters passed HV tests (very fast) up to 1000 V. There was a failure going up to 3000 V. The instrument does not register the breakdown failure value. All the QH passed the hipot in air with coil on the table at 2500 V so the failure is due to the test facility issue. MQXFS3c: coil 105 106 107 and 8. OHR heater of coil 8 passed the HV test up to 1000 V after the first cold test. A second cold test took place and the heater failed the HV tests (very fast) up to 3000 V afterwards. Then it failed the test up to 1000 V and it passed at 500 V. I assumed the first failure between 1000 and 3000 V for coil 8 OHR.

Heaters passing heater to coil hi-pot in air after cold test Hipot tests were performed on # 104 heaters Test were performed up to different max V values # 78 heaters passed the hi-pot at > 1000 V

Hipot test in He gas Hipot tests were performed on # 31 heaters Not all the heaters in MQXFS3 were tested at each temperature All the tested heaters passed the 800 V hipot at 300K in He

Some comments on Hipot test in He gas MQXFS3: Hipot tests were made at 200 V steps waiting 30 s at each step. Reported values are the ones observed before first failure. Failure of hipot could be due to the test facility itself. MQXFS1: Hipot tests were made at 1kV/min using CLIQ leads for heater and coil connections

backup

MQXFS3 @CERN tests (Jan 2019) Coil 105, 106, 107 5 thermal cycles 1 full disassembly ~100 quenches Coil 8 2 thermal cycles ~50 quenches 1000 - 2000 V 0 - 500 V 2000 - 3680 V > 3680 V Breakdown voltages testing up to 5000 V (* indicates not well insulated ext. wires) 105 106 107 8 OLL 3900 V * 5000 V OLH 2300 V* 3600 V ORH 3700 V* 4500 V* 181 V 659 V ORL 3800 V* OLL= outer left low field Breakdown voltages testing up to 10000 V OLL 10000 V 7000 V OLH 3600 V ORH 6500 V 8500 V 181 V 659 V ORL 8000 V