MQXF quench heaters: tests and investigation (CERN)¶ Paolo Ferracin, Arnaud Foussat, Juan Carlos Perez, Jan Petrik on behalf of the MQXF collaboration MQXF Video-meeting 03 April 2019 CERN

Outline Overall design Electrical Test after coil fabrication Electrical Test on MQXFS3 and MQXFS5 coils (after cold test) Test up to 5 kV of MQXFS3 coils (105,106,107,L8) Test up to 3.7 kV of MQXFS5 coils (203,204,205,206) Partial discharge test on MQXFS3 coils, MQXF5 coils and 207 (virgin) Breakdown test on MQXFS3 coils and 206 (limiting coil in MQXFS5) Paolo Ferracin

MQXF coil and cavity size Radius insulated cable after reaction R1: 75.000 mm R2: 93.653 mm R3: 94.313 mm R4: 112.965 mm Cable before reaction   Bare width Bare thickness in Bare thickness out Bare mid-thickness Keystone angle Insulation thickness Ins. width Ins. thickness in Ins. thickness out Ins. mid-thickness mm 18.150 1.462 1.588 1.525 0.400 0.145 18.440 1.752 1.878 1.815 Cable after reaction 1.17 % growth in width 4.5% growth in thickness 18.363 1.530 1.658 1.594 18.653 1.820 1.948 1.884 Paolo Ferracin

Impregnation – New coils (second generation) Polyimide trace (real thk. 75 µm) Impreg Design: 310 µm 3 layers S2 Glass Hexcel 4522 CERN meas @ 5 MPa: 290 µm plain CERN meas @ 1 MPa: 329 µm plain Silicone Mold Putty (removed after impregnation) Radial filler: 0.5 mm Radial filler 0.6 mm Coating on 4 sides of the fillers for 0.120 mm total 100 µm Polyimide trace (real thk. 75 µm) 250 µm G11 Impreg Design: 150 µm 1 layer S2 Glass Hexcel 4522 LARP meas @ 5 MPa: 121 µm plain LARP meas @ 1.6 MPa: 133 µm plain CERN meas @ 0 MPa (micrometer): 160 µm plain CERN mould has 40 µm additional inner radius due to Teflon coating Midplane 250 µm G11

Ground insulation Paolo Ferracin

Voltage withstand level table EDMS 1963398 v4 (2018-04-23) Paolo Ferracin

Electrical test after coil fabrication Outline Overall design Electrical test after coil fabrication Electrical Test on MQXFS3 and MQXFS5 coils (after cold test) Paolo Ferracin

Test after coil fabrication Short model Coil to quench heater: 3680 V (since ~04/18) Out of 29 coils electrically tested, no issues, but… 1 tested only up to 2000 V 23 tested only up to 2500 V 4 tested up to 3000 V 1 tested up to 5000 V Paolo Ferracin

Test after coil fabrication MQXFB prototype (to be updated) Coil to quench heater: 3680 V (since ~04/18) Out of 8 coils electrically tested, no issues, but 4 tested to 3000 V 4 (MQXFBP1) tested to 3700 V Paolo Ferracin

Test after coil fabrication MQXFA prototype (to be updated) Coil to quench heater: 3680 V (since ~04/18) Out of 15 coils electrically tested, no issues, but 2 tested to 2500 V 11 tested to 3000 V 2 tested to 3680 V Paolo Ferracin

Test after coil fabrication All (to be updated) Coil to quench heater: 3680 V (since ~04/18) Out of 52 coils electrically tested, no issues, but the test voltage ranged from 2000 V to 5000 V Paolo Ferracin

MQXFS3 Coil 105, 106, 107 Coil 8 5 thermal cycles 1 full disassembly ~100 quenches Coil 8 2 thermal cycles ~50 quenches Paolo Ferracin

MQXFS3 coil tested up to 5 kV QH Test to…. Bdv kV 105 OLL 5 3.9 External wire OLH 2.3 ORH 3.7 ORL 106 NO 3.6 4.5 3.8 107 0.1 LARP8 0.6 Paolo Ferracin

MQXFS3 coil tested up to 5 kV QH Test to…. Bdv kV 105 OLL 5 3.9 External wire OLH 2.3 ORH 3.7 ORL 106 NO 3.6 4.5 3.8 107 0.1 LARP8 0.6 Paolo Ferracin

MQXFS5 Coil 203, 204, 205, 206 3 thermal cycles ~50 quenches Paolo Ferracin

MQXFS5 coil tested up to 3.7 kV QH Test to…. Bdv kV 203 OLL 3.7 NO OLH ORH ORL 204 205 206 2.0 Paolo Ferracin

Partial discharge Occurs when high enough excitation voltage(for given insulation system) is present Represents miniature failures in insulation (bubbles, voids, discharges..) Can accumulate over time and result in failure Requirement for PD free insulation in power transformers and other expensive equipment which are subjected continuous AC excitation – not our case Very sensitive Good for relative comparison 17 Jan Petrik, 20/03/2019

PD Inception Voltage - [ACV] Overall Results Assembly Coil Side Field PD Inception Voltage - [ACV] MQXFS3 LARP 8 Right High 559 Virgin 207 Low 1000 MQXFS5 206 619 Left 1011 204 821 205 1022 106 837 107 1053 850 105 1055 853 203 1069 902 1072 922 1086 929 1096 960 1136 961 1139 976 1150 980 1218 986 1234 992 1238 1342 1349 107 Right-High – QH already shorted Jan Petrik, 20/03/2019

PD Results The Worst 10 – all are High field QH 7 out of 10 – Right side, High field QH Right side, high field is the worst QH for 8 out of 9 coils…#107 – RH QH was already busted… Virgin coil (#207) is comparable with others This would indicate (= not conclusive!!) that there is no damage during assembly and cold testing To be sure we would need to measure #207 after cold testing. 19 Jan Petrik, 20/03/2019

Breakdown voltage test Tests Break down test – ramp 1kV/min Burn mode – Step, 500V increase Capacitive discharge to do more damage 5 coils 105, 106, 107, LARP 8, 206 Paolo Ferracin

Paolo Ferracin

Breakdown voltage test Coil QH Test to…. Bdv kV 105 OLL 10 NO OLH ORH 6.5 Located ORL 106 3.6, then lower 8.5 107 0.1 8 LARP8 7 0.6 206 2 ?? 2.5 5 Paolo Ferracin

Locations Paolo Ferracin

Breakdown voltage test (above 3.7 kV) Coil QH Test to…. Bdv kV 105 OLL 10 NO OLH ORH 6.5 ORL 106 3.6, then lower 8.5 107 0.1 8 LARP8 7 0.6 206 2 ?? 2.5 5 Paolo Ferracin

Appendix Paolo Ferracin

Coil design Paolo Ferracin

Cable insulation thickness Paolo Ferracin

Change in coil size with heaters outside Removal of 0.310 mm impregnated fiberglass (3 layers) 0.100 mm trace Adding of ~0.100 mm fiberglass (11T scenario) Total 0.310 mm smaller impregnated coil 0.210 mm smaller coil including external quench heaters Paolo Ferracin

Voltage withstand level table How to obtain the test voltage levels Paolo Ferracin

Test after coil fabrication Short model Coil to quench heater: 3680 V (since ~04/18) Paolo Ferracin

Test after coil fabrication MQXFB prototype Coil to quench heater: 3680 V (since ~04/18) Paolo Ferracin

Test after coil fabrication MQXFA prototype Coil to quench heater: 3680 V (since ~04/18) Paolo Ferracin

MQXFS coil 105 Paolo Ferracin

MQXFS coil 106 Paolo Ferracin

MQXFS coil 107 Paolo Ferracin

MQXFS coil 8 Paolo Ferracin

MQXFS5 Coil 203, 204, 205, 206 3 thermal cycles ~50 quenches Paolo Ferracin

MQXFS coil 203 Paolo Ferracin

MQXFS coil 204 Paolo Ferracin

MQXFS coil 205 Paolo Ferracin

MQXFS coil 206 Paolo Ferracin

Partial Discharge AC Filter PD Detector DUT Jan Petrik, 11/01/2019

What we evaluated PD inception voltage PD vs voltage PD pattern Tricky Comparison based 43 Jan Petrik, 20/03/2019

Limits We do not have bare coil Where are the limits of used cables? QH contains Voltage taps traces Cables We measure everything together Where are the limits of used cables? Quick test with separate cable - 1689V Single test, let’s assume that above 1300V we are not sure… Distinctive PD pattern If PD activity was low, we’ve kept increasing test voltage, in 3 cases the coil DP pattern was swamped by cables Jan Petrik, 20/03/2019

PD Inception Voltage - [ACV] Results Per Coil   PD Inception Voltage - [ACV] Coil QH Count Avg Min Max STD Larp 8 4 1071.25 559 1349 304.9347266 206 3 859.66667 619 1000 170.9587345 204 937 821 986 67.60547315 106 1019.6667 837 1150 133.0321599 207 928.5 850 1011 77.10544728 107 1017 902 1096 83.19054433 205 1099 922 1234 131.9507484 203 1027.5 929 1136 80.38812101 105 1118.75 992 1342 133.2692294 Due to RH QH Virgin Coil Jan Petrik, 20/03/2019

PD Inception Voltage - [ACV] PD Inception Voltage - [ACV] Results per QH   PD Inception Voltage - [ACV] QH QH Count Avg Min Max STD All QH 33 1012.6364 559 1349 169.9536155 High Field only 16 931.3125 1342 188.4667473 Low Field Only 17 1089.1765 961 102.7431036 Left Side only 1080.8125 853 141.0528353 Right side only 948.47059 1218 169.8588056 Left & High only 8 1046.5 155.9503126 Left & Low only 1115.125 980 114.5277668 Right & High only 816.125 992 142.0655109 Right & Low only 9 1066.1111 84.55562856 And per Assembly   PD Inception Voltage - [ACV] Assembly QH Count Avg Min Max STD MQXFS3 14 1062.1429 559 1349 196.6711749 MQXFS5 15 988.86667 619 1234 145.3230272 Jan Petrik, 20/03/2019

CERN short models Magnet tests summary – updated 8.10.2018 Reception (warm, air) After LHe (warm,air/He) In LHe Test station Coil-Gnd Coil-QH EDMS 1963398 3680 V 368 V 460 V 1840 V 2300 V 3a 3700 3000 1500 2300 HFM 3b - 1000 5_1 Cluster D 5_2 3c_1 Cluster D? 3c_2 3c_3 500/1000 800 1100 4a 950 1800 4b 500 1880 Chronological order Target >> EDMS Target = EDMS Target < EDMS Target not reached

After LHe (warm,air/He) Details on MQXFS5 tests Reception (warm, air) After LHe (warm,air/He) In LHe Test station Coil-Gnd Coil-QH EDMS 1963398 3680 V 368 V 460 V 1840 V 2300 V 3a 3700 3000 1500 2300 HFM 3b - 1000 5_1 Cluster D 5_2 3c_1 HFM? 3c_2 3c_3 500/1000 800 1100 4a 950 1800 4b 500 1880 5, 1st run: tests Coil-Gnd at cold OK at 500, 1000 V. Then failed at 1500 V, but tested again at 1000 V OK 5, 2nd run: tests Coil-Gnd at cold OK at 500, 1000 V. Did not try to go beyond that Target >> EDMS Target = EDMS Target < EDMS Target not reached

Details on MQXFS3c, run 3 tests Reception (warm, air) After LHe (warm,air/He) In LHe Test station Coil-Gnd Coil-QH EDMS 1963398 3680 V 368 V 460 V 1840 V 2300 V 3a 3700 3000 1500 2300 HFM 3b - 1000 5_1 Cluster D 5_2 3c_1 HFM? 3c_2 3c_3 500/1000 800 1100 4a 950 1800 4b 500 1880 3c, 3rd run: testing up to the EDMS recommended value did not show the defective quench heater found at our own target value (1 kV). For this run we also tested the coil-QH insulation in gaseous helium at 80, 150 and 280 K. Target >> EDMS Target = EDMS Target < EDMS Target not reached

After LHe (warm,air/He) Details on MQXFS4 tests Reception (warm, air) After LHe (warm,air/He) In LHe Test station Coil-Gnd Coil-QH EDMS 1963398 3680 V 368 V 460 V 1840 V 2300 V 3a 3700 3000 1500 2300 HFM 3b - 1000 5_1 Cluster D 5_2 3c_1 HFM? 3c_2 3c_3 500/1000 800 1100 4a 950 1800 4b 500 1880 4a: tests at cold failed to reach the EDMS target value. Maximum reached was 900 V coil-ground and 1700 V coil-QH. 4b: after changing test facility and upgrading the auxiliary leads for CLIQ, the maximum voltage reached was 1140 V coil-ground and 1400 V coil-QH Breakdown in coil-QH at 1880 V happened after ~25 s of maintaining the voltage Target >> EDMS Target = EDMS Target < EDMS Target not reached

Possible test plan Additional tests to 3.7 kV MQXFAP2 coils For all the coils of MQXFS3 and for coil 206 of MQXFS5 Identify failure mode  destructive discharge test After destructive discharge test, micrograph on a cut coil We have pieces of LARP coil 7 (MQXFS3ab) already available Partial discharge tests Multiple cool-downs? Paolo Ferracin