1. Hi-pot results summary
Speaker - Lab

2. 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
( )
MQXFA Electrical Design Criteria: EDMS 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

3. 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

4. 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, , 7, 8
108, , 111
203, , 206
P2, P3, P4, P5
102, , 106
# of training 52
349
100 8 50 18 29
# of thermocycle s ? 5 3 1

5. 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 V V V
> 3680 V
Coil 8 ORH failed the hipot at the test facility
First breakdown voltages testing up to 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 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

6. 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 (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 )
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 V (500 V test)

7. MQXFS5 @CERN after cold testV V V
> 3680 V
Coil 203, 204, 205, 206
3 thermal cycles
~50 quenches
Breakdown voltages testing up to 3700 V (Jan 2019)
up to 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

8. MQXFS4a @CERN after cold testV V 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

9. 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).

10. 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

11. 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.

12. 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

13. 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

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

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

16. after test in He: coil P5 (MQXFAP1)
QH to coil Hi-Pot before testing up to 3000 V
P5 First Failure after warmup V @ OL-LF 2.38kV
Short in heaters 1 and 2 V V 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

17. 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, 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

18. 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

19. 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:

20. LQS03 hi-pot results after cold testV V 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

21. 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 kV.
# 11 failures above 5.0 kV
No failure below 1200 V

22. 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 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 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.

23. 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

24. 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

25. 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

26. backup

27. MQXFS3 @CERN tests (Jan 2019)
Coil 105, 106, 107
5 thermal cycles
1 full disassembly
~100 quenches
Coil 8
2 thermal cycles
~50 quenches V V 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 V
OLL
10000 V
7000 V
OLH
3600 V
ORH
6500 V
8500 V
181 V
659 V
ORL
8000 V