Transcript Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras Overview of all superconducting splices in the LHC machine N.

Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Overview of all superconducting splices in
the LHC machine
N. Catalan Lasheras
Chamonix 2010 LHC Performance Workshop
25 January 2010
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Outline
 Splices Inventory. Numbers and circuit criticality
– Stored Energy
– MIITs and hot spot temperature
 600 A corrector circuits
– Brief description
– Line M and N. US welding
– PCS measurements during HW Commissioning
– Existing NC
 Inner triplet 13 kA splices
 Future
– MCI
– Missing studies
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Superconducting splices. How many?
Line
Magnet
Splices
Interconnection
splices
Current rating
M3
9856
3372
13 kA
RQF/RQD
M1, M2
3940
6744
13 kA
Spool Pieces
M1, M2
30860
33920
600 A
Correctors
N
27006
16000
600 A
Individually
powered magnets
N’
1644
532
6 kA
Inner triplet quads
N’
80
112
13 kA
Inner triplet
correctors
N’
704
480
600 A
RB
 More than 100000 (105) splices!!
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Energy Stored in the magnets
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Criticality of a SC circuit
protection
10000
70
1000
– Cold diodes
100
– Energy Extraction
60
x2
10
50
1
x 104
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0.1
MIITs [A2s]
Hot spot Temperature [K]
Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
 Main circuits incorporate more
80
30
0.01
20
0.001
10
0
0.001
0.0001
0.01
0.1
1
10
100
1000
0.00001
10000
– Larger bus-bar cross-section
 MIITs and hot spot temperature
estimated in the bus-bar
according to real decay data and
bus-bar section
– Not a factor 104 but a factor 2
– Always safe as in nominal
conditions
Energy stored [GJ]
 What about failures
Quench of the bus-bar in adiabatic conditions.
Thanks to G. Kirby
– In the quench detection?
– In the EE switches opening?
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Splice types in the LHC.
 Splices vary in length, copper
to SC ratio, insulation,
mechanical fixation
 You will hear in the following
talks about 13 kA and 6 kA
Key to corrector busses:
Corrector bus to DFBX (purple)
Corrector bus from Q3 (orange)
4.00 inch bellows
I.D.
3.50 inch OD x
1/16 inch wall
tube
Key to lead busses:
5 KA busses from Q3 (red)
5 KA busses to DFBX (pink)
8 KA busses from Q3 (grey)
8 KA busses to DFBX (tan)
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Corrector circuits 600 A. Lines M and N
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Line M interconnection
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Line N Interconnection
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Line N Interconnection
Ultrasonic welding
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Problems with ultrasonic welding in sector 7-8. Line N.
Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
 Reported by D. Tommasini to
MARIC on November 2006 after the
inspection of the first installed sector
– Presence of insulation between
wires
– Bad alignment with reduction of
contact surface
 Cryolab measurements showed 4 to
19 nOhms
 US welding machines put in
conformity
 Suspected interconnections re-done
during following warm-up
 Test proposed during powering to
spot catastrophic cases
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
PCS splice verification
 Test systematically done during powering tests
for all 600 A circuits
 Current plateau at minimum current (200 A).
Resistance deduced from QPS voltage
measurements.
 Repeated at nominal current. Data stored in MTF
 Assumed resolution < 1mOhm
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Results from the last powering campaign
Resistance at nominal current measured during Powering
1.8E-05
1600
RCO
1400
1.6E-05
1.2E-05
1.0E-05
8.0E-06
1000
800
600
6.0E-06
400
# of splices in the circuit
1200
1.4E-05
Resistance [Ohms]
Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
2.0E-05
4.0E-06
2.0E-06
0.0E+00
200
0
 Resistance is indeed proportional to the number of splices but noise
is very high.
 Noise depends on the circuit type. Cable length, number of magnets
and inductance.
 RCO circuit is a 120 A circuit and test is done at 100 A.
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Results from last hardware commissioning campaign
16.0
1600
14.0
1400
12.0
1200
10.0
1000
8.0
800
6.0
RQ6
600
RCO
4.0
400
2.0
200
0.0
0
# of splices in the circuit
Average resistance [nOhms]
Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Average resistance per splice
 Expected value is between 4 and 6 nOhms
 RQ6 (6xMQTL) has a higher average splice value.
– Systematic. May be due to internal splices in the magnet
 RCO splices are nominally higher than others
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First circuits to verify and re-measure
Resistance at nominal current measured during Powering
1600
9.0E-06
1400
Resistance [Ohms]
1200
7.0E-06
1000
6.0E-06
5.0E-06
800
4.0E-06
600
3.0E-06
400
# of splices in the circuit
8.0E-06
2.0E-06
200
1.0E-06
0.0E+00
0
16.0
1600
14.0
1400
12.0
1200
10.0
1000
8.0
800
6.0
600
4.0
400
2.0
200
0.0
0
# of splices in the circuit
Average resistance per splice
Average resistance [nOhms]
Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
1.0E-05
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Existing NC in 600 A circuits
Sketch of the RCO.A81.B2 circuit - External aperture
Circuit found open, at 1.9K, on 23/03/2009
between B12.L1 and B11.L1
CL 4
Position:
Magnet name:
C12L1
B12L1
A12L1
Q11L1
MBB_3094
MBA_3174
MBB_1144
SSS_524
CC
MBA_1158
MBB_1103
26171.6225
26187.2825
26202.9425
26218.6025
26226.3475
26240.0642
26255.7242
Q10L1
SSS_641
26271.3842
B10L1
MBA_1160
26279.1292
B11L1
A11L1
CL 3
B12.L1
A12.L1
Q11.L1
CC
B11.L1
A11.L1
Q10.L1
Upstream position:
B10.L1
?
D20-C3 EE841
D20-C3 EE841
52,8 m
D20-C3 EE841
39 m
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Inner triplet 13 kA splices
Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
 Two double bus-bars
Cu/SC
– 5 kA and 8 kA
– Brazed similarly to the
6kA flat cable
 All splices protected
together with the magnets
at a 100mV threshold
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Inner Triplet splices during interconnection
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
NC 948545 on a 120 A octupole corrector
 As for the spool, high resistance was seen during the ElQA tests
(>mOhm)
 Need to open the cryostat to locate and repair the fault
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Chamonix 2010 LHC Performance Workshop 25 January 2010. N. Catalan Lasheras
Conclusions
 What is the maximum credible incident (MCI) affecting each of these
circuit types
– Quench detection failing? Non propagating quench
– Arcing in a spool piece next to M1, M2 line
– ...?
 Work ahead of us:
– Investigation of excessive resistance in 600 A circuits
– Verify the splice parameters (mainly for US magnets)
– Evaluate heating of the bus-bar under accidental conditions
– …
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