1. 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

2. 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

3. MQXF coil and cavity size
Radius insulated cable after reaction
R1: mm
R2: mm
R3: mm
R4: 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

4. Impregnation – New coils (second generation)
Polyimide trace
(real thk. 75 µm)
Impreg Design: 310 µm
3 layers S2 Glass Hexcel 4522
CERN 5 MPa: 290 µm plain
CERN 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 mm total
100 µm
Polyimide trace
(real thk. 75 µm)
250 µm G11
Impreg Design: 150 µm
1 layer S2 Glass Hexcel 4522 LARP 5 MPa: 121 µm plain
LARP 1.6 MPa: 133 µm plain
CERN 0 MPa (micrometer): 160 µm plain
CERN mould has 40 µm additional inner radius due to Teflon coating
Midplane
250 µm G11

5. Ground insulation
Paolo Ferracin

6. Voltage withstand level table
EDMS v4 ( )
Paolo Ferracin

7. 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

8. 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

9. 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

10. 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

11. 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

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

13. MQXFS3 coil tested up to 5 kVQH
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

14. MQXFS3 coil tested up to 5 kVQH
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

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

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

17. 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

18. 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

19. 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

20. 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

21. Paolo Ferracin

22. 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

23. Locations
Paolo Ferracin

24. 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

25. Appendix
Paolo Ferracin

26. Coil design
Paolo Ferracin

27. Cable insulation thickness
Paolo Ferracin

28. 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

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

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

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

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

33. MQXFS coil 105
Paolo Ferracin

34. MQXFS coil 106
Paolo Ferracin

35. MQXFS coil 107
Paolo Ferracin

36. MQXFS coil 8
Paolo Ferracin

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

38. MQXFS coil 203
Paolo Ferracin

39. MQXFS coil 204
Paolo Ferracin

40. MQXFS coil 205
Paolo Ferracin

41. MQXFS coil 206
Paolo Ferracin

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

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

44. 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 V
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

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

46. 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
559
1349
High Field only 16
1342
Low Field Only 17
961
Left Side only
853
Right side only
1218
Left & High only 8
1046.5
Left & Low only
980
Right & High only
992
Right & Low only 9
And per Assembly
PD Inception Voltage - [ACV]
Assembly
QH Count
Avg
Min
Max
STD
MQXFS3 14
559
1349
MQXFS5 15
619
1234
Jan Petrik, 20/03/2019

47. 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
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

48. 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
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

49. Details on MQXFS3c, run 3 tests
Reception (warm, air)
After LHe (warm,air/He)
In LHe
Test station
Coil-Gnd
Coil-QH
EDMS
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

50. 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
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

51. 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