![Page 1: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/1.jpg)
With contributions of:TE/MPE: Arjan VerweijTE/MSC-CI: N. BourceyTE/MSC-TF: M. Bajko, G. Deferne, G. Dib, M. CharrondiereTE/MSC-SCD: L. Bottura, D. Richter, G. Peiro, C. Scheuerlein, S. HeckTE/MSC-LMF: P. Fessia, K. Chaouki, R. Principe, S. TriquetEN/MME: T. Regnalia, P. PerretTE/EPC: G. Hudson, M. CerqueiraEN/ICE: A. Rijllart, D. KudryavtsevTE/CRG: V. Bendaand many more...
Thermal runaways in LHC main circuit interconnections: Experiments
Gerard Willering
1
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
![Page 2: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/2.jpg)
Experiments to the effects of defected and consolidated LHC main bus splices are conducted in three phases
1. Thermal runaways in interconnections with defectsAugust 2009 – Februari 20105 quadrupole busbar samples in test station FRESCAGoal: Validation of model → safe operating current before consolidation
2. Proof of principle of the consolidation with shuntsMarch 2010 – June 20104 quadrupole busbar samples in test station FRESCAGoal: Validation of model → Proof of principle of the consolidation proposal
3. Final validation of the consolidation with shunts in a realistic test setupMarch 2010 – October 20102 dipole busbar samples inbetween two special SSS magnetsGoal: Validation of model and final validation of the shunts
2
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Contents
![Page 3: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/3.jpg)
3
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Sample Defects LNSC
(MM)RADD (T = 300 K)(ΜΩ)
RADD (T = 10 K)(ΜΩ)
RRRCable
RRR Busbar
1 Single-sided 47 63 0.37 170 ~3002A Double-sided 35+27 43+32 0.43+0.24 100-130 ~2702B Single-sided 35 42 0.26 ~170 ~2903A Double-sided 39 + 30 51+39 0.31+0.28 140-170 ~1903B Single-sided 21 27 0.22 120 ~160
Definition of a defect:1. Stabilizer discontinuity2. Non-stabilized cable with a specified length
1
1
Gamma-ray image of sample 1, indicating the single-sided defect.
2
Important parametersRcable = 1.3 µΩ/mmRquad-busbar = 0.1 µΩ/mmRadd = Rmeasured - R8cm
RRRbus
RRRcable
30 mm non-stabilized cable
Guaranteed by Kapton tape
Preparation of the defect.
Defect preparation
![Page 4: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/4.jpg)
4
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Sample 2ASingle-sided defect
Sample 2BDouble-sided defect
Test layout with normal LHC pieces and geometry and with lots of instrumentation (RQ circuit)
DiscontinuityDiscontinuity
Heater
Sample preparation
![Page 5: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/5.jpg)
5
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Test station FRESCA
- In the FRESCA teststation the sample length is limited to 1.7 m, which gives 0.8 meter of busbar on each side of the interconnection. -24 Voltage taps- 10 Thermocouples- 5 heaters- The ends of the busbars are thermalized (a lot of copper in direct contact with helium).- Measurements are performed with constant current.
- Due to limitations of the test station (Helium volume, length of sample, vincinity of the current leads) the quadrupole interconnections are chosen to test.
![Page 6: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/6.jpg)
6
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Voltage innon-stabilized cable
Temperature innon-stabilized cable
Temperature in busbar
Typical measurement data
Thermal Runaway7 kA, 43+32 µΩ defect
Fingerprint of a local thermal runaway:- Relatively low busbar temperature.- Accelerated voltage increase in the non-stabilized cable.Main characteristic: Thermal runaway time trun
![Page 7: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/7.jpg)
7
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Thermal runaway time
- Except for sample 3B, all samples would melt within 1 second with a current of 12 kA.- The MIITs (kA^2/s) for an exponentially decaying current with timeconstant τ is reached by a constant current in t = 0.5*τ. - For the quadrupole circuit with τ = 20 s, we can correlate the safe currents for the sample conditions with a cross-section at trun = 10 s.
- Although there is a correlation, safe currents can not be drawn from the measurements.
Sample Defects LNSC
(MM)1 Single-sided 472A Double-sided 35+272B Single-sided 353A Double-sided 39 + 303B Single-sided 21
![Page 8: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/8.jpg)
8
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0.0 2.0 4.0 6.0 8.0 10.0 12.0
Ra
dd
bigg
est d
efec
t at
10 K
(µ
Ω)
I at trun=10s (kA)
The current at trun versus the additional resistance R add shows a good correlation.The allowed power at 10 K is between 16 and 27 W.
Since we varied the applied field on the sample, the effective Radd varied giving us a wider range in measurements. Therefore more than 5 points (number of samples) are shown.
16 W
27 W
Measurement characterization
![Page 9: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/9.jpg)
9
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Melt-down of a non-stabilized cable
To perform multiple thermal runaway measurements, the current is cut-off when the maximum temperature reaches in between 100 and 300 K. Out of 175 run-aways we did, we choose the smallest defect of 20 mm at 9 kA to demonstrate that the incident can be reproduced. In fact, each of the 175 measurements would lead to a melt-down.
![Page 10: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/10.jpg)
10
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Melt-down of a non-stabilized cable
With an increased protection cut-off voltage the thermal runaway was conducted until the cable melted over the full width over a length of 1.5 to 3 mm.- The temperature was at least 1360 K to melt the copper in the cable.- Remarkably, at the moment of melt-down, the thermocouple in the busbar 15 mm from the hotspot only measured 50 K.
Sample 3BLNSBC = 21 mmRadd = 27 μΩI = 9 kAtrun = 13 s
![Page 11: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/11.jpg)
Experiments to the effects of defected and consolidated LHC main bus splices are conducted in three phases
1. Thermal runaways in interconnections with defectsAugust 2009 – Februari 20105 quadrupole busbar samples in test station FRESCAGoal: Validation of model → safe operating current before consolidation
2. Proof of principle of consolidation with shuntsMarch 2010 – June 20104 quadrupole busbar samples in test station FRESCAGoal: Validation of model → Proof of principle of the consolidation proposal
3. Final validation of the consolidation with shunts in a realistic test setupMarch 2010 – October 20102 dipole busbar samples inbetween two special SSS magnetsGoal: Validation of model → safe operating current before consolidation
11
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Content
![Page 12: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/12.jpg)
12
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
First try: Discontinuity of the copper was not guaranteed due to solder creep in the voids.
Second try: Discontinuity guaranteed by cutting away part of the stabilizer
Important parameters for shunts:- Thickness of the shunt- Non-soldered shunt length (see with white arrows).
Shunt preparation
![Page 13: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/13.jpg)
13
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Sample 4 3 mm thick shunts
11 m
m5
mm
7 m
m0
mm
Sample LNSS (MM)
SHUNT THICKNESS(MM)
Radd before shunt
(T=300 K)(ΜΩ)
RADD SHUNTED
(T=300 K)(ΜΩ)
4A-3mm 7 & 5 3 51 & 39 3.9 & 3.14A-1.5mm 7 & 5 1.5 51 & 39 6.4 & 5.44B-3mm 11 & 0 3 27 & 0 2.8 & -0.54B-1.5mm 11 & 0 1.5 27 & 0 5.1 & -0.1
Shunts reduced to 1.5 mm thickness
Sample 4 without shunt
Sample 4 with shunt
Shunt preparation
![Page 14: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/14.jpg)
14
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
0
10
20
30
40
50
6 8 10 12 14 16 18 20 22
Ru
naw
ay ti
me
(s)
Current (kA)
1 3A
2A
3B2B
100
1000
10000
6 8 10 12 14 16 18 20
MII
Ts
unt
il ru
naw
ay (1
06
A2 s
)
Current (kA)
1
3A
2A
3B
2B
-Runaway time for the shunted samples much higher than for non-shunted samples.
- All the shunted samples can carry 13 kA for more than 24 seconds.
- The same data, but the MIITs are calculated (kA2*s) - The shunted samples with 1.5 and 3 mm thick shunts can handle the MIITs of 15.5 kA with τ = 20 s.- These samples do not have the worst case parameters and not the worst case conditions. Therefore no direct conclusions for LHC conditions.
Result on measurements with shunts
![Page 15: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/15.jpg)
Experiments to the effects of defected and consolidated LHC main bus splices are conducted in three phases
1. Thermal runaways in interconnections with defectsAugust 2009 – Februari 20105 quadrupole busbar samples in test station FRESCAGoal: Validation of model → safe operating current before consolidation
2. Proof of principle of consolidation with shuntsMarch 2010 – June 20104 quadrupole busbar samples in test station FRESCAGoal: Validation of model → Proof of principle of the consolidation proposal
3. Final validation of the consolidation with shunts in a realistic test setupMarch 2010 – October 20102 dipole busbar samples inbetween two special SSS magnetsGoal: Validation of model → safe operating current before consolidation
15
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Content
![Page 16: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/16.jpg)
Goal: Test in realistic conditions of a worst case scenario, with a non-soldered shunt length of 8 mm and low RRR values.- 2 Special SSS spare magnets are connected to the testbench in SM18.- In total 35 meter of RQ busbar and 35 meter of RB busbar. - Two instrumented RB (M3) interconnections.- No magnets in the test-circuit
16
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Quadrupole lines
Dipole lines
Que
nch
stop
per
Quadrupole lines
Dipole lines2 interconnections
2 interconnections
Preparation of final validation test
![Page 17: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/17.jpg)
Test conditions are rather special:
- First time 2 magnets in serie on the test-bench -> Test bench elongation- The quench needs to be stopped between M3 and M1 line.
- Additional copper strips (Lyra) for cooling- Large, 30 liter reservoir for helium
- Instrumentation wire feed-through-box - Heating power of more than 300 W for long time with significant loads on cryogenic system
17
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Preparation of final validation test
![Page 18: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/18.jpg)
U-profile/wedge
High precision measurements on resistance are important for the validation of shunt and model.- In the test the U-profile/wedge have a low RRR- In the tests the shunts have a much lower RRR than foreseen for the LHC conditions since they are not annealed
18
Technology Department
type RRR Typical LHC valueU-profile RQ 174, 176, -, - > 200U-profile RB 182, - > 200Shunt RB 156, 156, 160, 160 > 300Busbar RQ 252, 264, - , - > 200 (lab tests)Busbar RB 258, 303, - > 200 (lab tests)
shunt shunt
Gerard Willering – Splice review – 18 October 2010 - CERN
RRR measurements
![Page 19: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/19.jpg)
Thermal runaway measurements on the interconnection with the largest non-soldered length (8 mm).
19
Technology Department
10000
11000
12000
13000
14000
15000
16000
17000
18000
0 2 4 6 8 10 12
Safe
curr
ent [
A]
lwc = Distance between contact [mm]
Safe operating current for a shunted RB joint, assuming an infinitely long non-stabilized cable on both sides of the joint; tau=100 s, RRR_shunt=100
16 mm2, RRR_bus=100
16 mm2, RRR_bus=160
32 mm2, RRR_bus=100
32 mm2, RRR_bus=160
Arjan Verweij, 18/1/2010
type Calculations chamonix SM-18 sampleRRR shunt 100 160RRR busbar 160 > 250Shunt cross-section 32 mm2 45 mm2
Cooling Adiabatic Superfluid helium
What to expect in the test conditions?I > 16 kA @ τ = 100 s
Gerard Willering – Splice review – 18 October 2010 - CERN
Expected results
Figure from A.Verweij (chamonix 2010 workshop and first splice review)
![Page 20: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/20.jpg)
Current cycles for thermal runaway measurements at 1.9 K.
20
Technology Department
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 50 100 150 200 250 300
Curr
ent (
kA)
time (s)
LHC 7TeV
LHC design
SM-18 test
SM-18 limit
LHC cycle: 13 kA, tau = 100 s Very quick recovery of the normal zone
Gerard Willering – Splice review – 18 October 2010 - CERN
Current cycles for test
Test cycle: 14 kA, τ = 100 sTest cycle: 14 kA, τ = 140 sTest cycle: 14 kA for 22 s, then τ = 140 s. Still no signs of thermal runaway in the most critical shunt!!
Therefore we went to constant currents of 13 and 14 kA (power supply limit).
![Page 21: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/21.jpg)
21
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Q9 Q8
Quench behavior at a constant current of 13 kA
- No significant heating of the interconnection in 180 s.- No significant heating in the busbar Q9-1 in 180 s.- Normal zone does not enter the Q8 busbars.
- Very stable conditions at 13 kA in busbar and interconnection!!!
Q9-busbar have an RRR ≈ 250 → R9.4meter ≈ 2.3 µΩ at 10 KQ8-busbars have an RRR ≈ 300 → R16.5meter ≈ 3.5 µΩ at 10 K
![Page 22: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/22.jpg)
22
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Q9 Q8
Quench behavior at a constant current of 14 kA
- Small temperature increase in the interconnection in 85 s.- The full 35 meter of busbar between the quench-stoppers become normal- Accelerated heating effect in busbars Q8 and Q9-2.
- Limitation factor is not the shunted interconnection, but the busbar.
Q9-busbar have an RRR ≈ 250 → R9.4meter ≈ 2.3 µΩ at 10 KQ8-busbars have an RRR ≈ 300 → R16.5meter ≈ 3.5 µΩ at 10 K
- In the straight section the busbars are encapsulated in a G10 casing and close to each other. - In the region closer to the interconnection superfluid helium is available for cooling.
![Page 23: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/23.jpg)
23
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Temperature profiles in the shunts at 13 and 14 kA
- Additional proof of thermally stable conditions with measurements by two thermocouples in the shunts of Interconnection 1.
Interconnection 1
Interconnection 2
T3 T4
I = 13 kA I = 14 kA
![Page 24: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/24.jpg)
Quench propagation velocity – dipole busbar
24
Technology Department
- No propagation below 12 kA (with the busbar cooled by superfluid helium).
- Arjan’s calculation (RRR = 200) is a bit more optimistic than the measurements (RRR 250 - 300).
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Prop
agati
on s
peed
(m/s
)
I (kA)
Dipole busbar propagation velocity
dipole RRR 100 (calc)
dipole RRR 200 (calc)
V15-V18 (dipole)
V25-V27 (dipole, lyra)
Gerard Willering – Splice review – 18 October 2010 - CERN
Quench propagation velocity
![Page 25: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/25.jpg)
Quench propagation velocity – quadrupole busbar
25
Technology Department
- No propagation below about 9 kA (with the busbar cooled by superfluid helium)
- At higher currents the measured velocity might be overestimated since the temperature and therefore the resistance can be increased.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2 Quadrupole busbar propagation velocity
quad RRR 100 (calc)quad RRR 200 (calc)V32-V31 (quad)V5-V29 (quad, lyra)
I (kA)
Prop
agati
on sp
eed
(m/s
)
Gerard Willering – Splice review – 18 October 2010 - CERN
Quench propagation velocity
![Page 26: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/26.jpg)
26
Technology Department
MIITs >> 30000 kA2s at 13 kA (no sign of thermal runaway) MIITs > 18000 kA2s at 14 kA (Start of thermal runaway in busbars)(LHC 13 kA, 100 s – MIITs = 8500 kA2sLHC 11.8 kA, 100 s – MIITs = 6800 kA2s)
Gerard Willering – Splice review – 18 October 2010 - CERN
Simple and short conclusion: The proposed shunts work!
![Page 27: Thermal runaways in LHC main circuit interconnections: Experiments Gerard Willering](https://reader035.vdocuments.mx/reader035/viewer/2022062422/5681377d550346895d9f18b1/html5/thumbnails/27.jpg)
27
Technology Department
Gerard Willering – Splice review – 18 October 2010 - CERN
Summary and Conclusion
Thermal runaways in interconnections with defects- Clear proof of the damage a defect can have with the melted sample.- Measurements provided largely sufficient experimental data for model validation (by A. Verweij).- Conclusions on safe current/energy cannot be drawn directly from this measurements, since test conditions are different from machine conditions.
Proof of principle of consolidation with shunts- Clear improvement of the thermo-electric stability by applying shunts on the samples with defects.- Boundary conditions of the test-station prohibit direct conclusions on the stability of the consolidated interconnection, but indicates that the principle good.- Sufficient experimental data for model validation (by A. Verweij).
Final validation of the consolidation with shunts in a realistic test setup- A consolidated interconnection with a copper shunt having a cross-section of 45 mm^2, a double defect in the interconnection, a non-soldered lenght of 8 mm and an RRR of 160 is more stable than the busbar itself in the straight section. - In the condition a quench starts in the interconnection itself a continuous current of 13 kA does not show any sign of a thermal runaway in the first 180 seconds.- At a continuous current of 14 kA provokes an excellerated temperature increase in the encapsulated part of the busbars, with a temperature of about 40 K after 85 s.- In terms of thermo-electrical stability the shunt is overdesigned.