2. Magnet Circuit performance at 6
Magnet Circuit performance at 6.5 TeV… and beyond Arjan Verweij, TE-MPE-PE on behalf of the MP3 (cern.ch/MP3) acknowledgments to everybody involved in magnet reception tests, powering tests, and operation and analysis of the magnet circuits
Mera peak, 6.5 km high
Kun, 7 km high
Arjan Verweij, LHC Performance Workshop, Jan 2016

3. Outline
Overview of the magnet circuits from an operational point of view, with focus on quenches, excluding issues presented by Felix (shorts, ELQA, ...), Reiner (QPS), and Bernhard (beam-induced quenches w.r.t. BLM thresholds).
Feasibility of operation at 7 TeV, based on training behaviour of previous HWC campaigns.
I will not discuss the origin/understanding of quenches, de-training, memory, etc; see website of QBT (Quench Behaviour Team).
Useful links:
cern.ch/MP3/SummaryIssues List of all issues
cern.ch/MP3/QuenchDatabase Database of all training quenches
Arjan Verweij, LHC Performance Workshop, Jan 2016

4. Initial HWC. Target: 7 TeV (12 kA)
Date
Description
2007/8
Initial HWC. Target: 7 TeV (12 kA)
Sept 2008
Accident in S34
Repair
nQPS installed. Warm-up of S12, S34, S45, S56, S67 to 300 K. Warm-up of S23, S78 and S81 to 80 K. tRB reduced to 51 s, tRQ reduced to 9 s.
2009
HWC to 3.5 TeV (6 kA)
Begin 2011
HWC after Xmas to 3.5 TeV
Begin 2012
HWC after Xmas to 4 TeV (6.85 kA)
Feb 2013
Powering tests to 7 TeV (except mains)
LS1. Warm-up of all sectors to 300 K. tRB back to 102 s, tRQ back to 30 s
9/2014-3/2015
HWC to 6.5 TeV (11.1 kA)
Mar 2016
HWC after Xmas to 6.5 TeV
Run1
Run 2
Arjan Verweij, LHC Performance Workshop, Jan 2016

5. Global view of training quenches
Nr. of magnets
2008
2009
Feb 2013
2014/5
60 A
752 2 3 23 A
1476 37 38 4
120 A triplet 40 1
600 A
6518
140 77
154
600 A triplet 56 26 14
IPD 18 13 10
IPQ
220 49 68 31
IT mains 32 RQ
794 RB
1232 (twin aperture) 30
(S56 to 11.2 kA)
175
(all sectors to 11.1 kA)
Important: some commissioning currents and test sequences have been changed during the years, so the number of quenches cannot always be directly compared among HWC campaigns.
Arjan Verweij, LHC Performance Workshop, Jan 2016

6. 60 A circuits Nr. of magnets 2008 2009 Feb 2013 2014/5 60 A 752 2 3 2323
5 quenches in 5 different magnets
Possibly not all quenches registered
23 quenches in 21 different magnets
2 quenches on flat-top (60 A)
Other issues: 2 circuits condemned
Small number of quenches considering large number of magnets, and all quenches well above the operational currents.
Arjan Verweij, LHC Performance Workshop, Jan 2016

7. 80-120 A circuits Nr. of magnets 2008 2009 Feb 2013 2014/5 80-120 A
1476 37 38 4 22
120 A triplet 40 1
RCO
16x77=1232
Some retraining after thermal cycling.
3 out of 4 triplet quenches due to additional 5 A margin.
Other issues:
nominal current of 4 circuits reduced to A
4 triplet circuits condemned
Small number of quenches considering large number of magnets.
Arjan Verweij, LHC Performance Workshop, Jan 2016

8. 600 A circuits
Circuit
# of magnets
Magnet
2008
2009
Feb 2013
2014/5
RCD
16x77=1232
MCD 40 3 16
RCS
16x154=2464
MCS 15
8+1
ROD/F
332 MO 2
6+1
RQ6 48
MQTLH 5
RQS 64
MQS 6
8+2
RQT12/13
MQT 20 7
5+2
RQTD/F
32x8=256 21 35
39+13
RQTL7-11 72
MQTLI 29 17
23+4
RSD/F
688 MS 4
9+1
RSS
MSS 1 RU MU 8
Significant retraining after LS1, especially for RQTD/F and RQTL circuits.
Other issues: RSS.A34B1, RCS.A78B2 condemned. 9 circuits with less magnets. 35 circuits with reduced nominal current.
Arjan Verweij, LHC Performance Workshop, Jan 2016

9. 600 A circuits - triplets Significant retraining after LS1.
# of magnets
Magnet
2008
2009
Feb 2013
2014/5
RQSX3 8
MQSX 1
16+2
RCBX * 48
MCBX 25 4 14 19
*: not including the quenches due to combined powering
Significant retraining after LS1.
Other issues:
Combined MCBX H-V powering imposes some constraints
600 A circuits:
Many circuits to be closely watched in upcoming HWC campaigns.
Arjan Verweij, LHC Performance Workshop, Jan 2016

10. IPD circuits Nr. of magnets 2008 2009 Feb 2013 2014/5 IPD 18 13 10 410 4
Nr. of magnets
2008
Feb 2013
2014/5
RD1
4 x MBX (1.9 K)
5800 A: 0
5450 A: 0
RD2
4 x MBRC (4.5 K)
4400 A: 0
4150 A: 0
6000 A: 7
6000 A: 0
5650 A: 0
RD3
4 x MBRS (4.5 K)
5860 A: 6
5860 A: 9
5550 A: 2
RD4
2 x MBRB (4.5 K)
6150 A: 0
6150 A: 1
5850 A: 2
RD4.L4 and RD4.R4 quenched once in 2014/5, within 100 A of nominal.
Other issues:
RD1.R8 operates with one quench heater.
Arjan Verweij, LHC Performance Workshop, Jan 2016

11. RD3.L4
Worrying in 2013 but trained quickly in 2014/5 (up to a reduced current of 5550 A).
Arjan Verweij, LHC Performance Workshop, Jan 2016

12. IPQ circuits Other issues:
# of magnets
Magnet
Temp
[K]
I_tr
[A]
2008
Feb 2013
2014/5
RQ4 28
MQY
4.5
3610 9 7
3450
RQ5 16 1 8
RQ6 4 2
MQM
4310 17 23
4100 14 24 15 25
RQ7 36
1.9
5390
5250 3
RQ8
5100
RQ9 48
RQ10
Other issues:
RQ9 and RQ10 frequently trip due to thunderstorms and other external pick-ups
RQ8, RQ9, and RQ10 trip when the MB in positions A8, B8, A9, B9, A10 or B10 quenches.
Arjan Verweij, LHC Performance Workshop, Jan 2016

13. Quench behaviour is closely monitored over time, see MP3 meeting dd 14/10/2015 (S. Le Naour).
Arjan Verweij, LHC Performance Workshop, Jan 2016

14. IT-mains circuits Nr. of magnets 2008 2009 Feb 2013 2014/5 IT mains 324 2
3 x RQX.L2 (Q1)
1 x RQX.R2 (Q2)
1 x RQX.L8 (Q3)
1 x RQX.L5 (Q3)
Other issues:
One training quench during operation in RQX.L2 (Q1) at 6760 A
Arjan Verweij, LHC Performance Workshop, Jan 2016

15. RQ circuits Nr. of magnets 2008 2009 Feb 2013 2014/5 RQ 794 2
10899 A (28R4)
11280 A (14R5)
10550 A (26L5)
10363 A (15L1)
No training quenches during operation
Arjan Verweij, LHC Performance Workshop, Jan 2016

16. RB circuits: Outline Reception acceptance tests in SM-18 (2002-2007)
1st cool-down
2nd cool-down
HWC 2008: training of S56 to 11.2 kA
HWC 2014/5: training of all sectors to 11.1 kA (6.5 TeV equiv.)
Forecast for 7 TeV as presented by E. Todesco in MSC-TM (7 Jan 2016) and LMC (20 Jan 2016).
Other issues:
In 3 dipoles, a high-field quench heater is replaced by a low- field one.
Arjan Verweij, LHC Performance Workshop, Jan 2016

17. Reception test (2002-2007) – 1st cool-down
Cumulative plot of all quenches per firm, sorted by quench current
Firm-1
Firm-3
Firm-2
Firm-1
Firm-2
Firm-3
All
# magnets
400
420
412
1232
#Q to A
321
593
450
1364
#Q to A 47
183
413
Arjan Verweij, LHC Performance Workshop, Jan 2016

18. Reception test (2002-2007), 2nd cool-down
Firm-1
Firm-2
Firm-3
All
# magnets 33 55 28
116
#Q to A
1st cool-down 73
140 77
290
2nd cool-down 11 34 15 60
#Q to A 54
119 67
240 6 21 10 37
#Q to A 4 30 68 1 3 8
4.8 x
faster
6.5 x
faster
8.5 x
faster
Magnets from all 3 firms show a good “memory” when tested a few weeks later, after a thermal cycle.
Based on these data, the nr. of quenches to reach 7 TeV in the LHC was estimated to be about 160 (P. Xydi, A. Siemko, 2009).
Arjan Verweij, LHC Performance Workshop, Jan 2016

19. HWC 2008 – S56 to 11.2 kA
30 quenches in 29 different magnets (2x Firm-2, 27x Firm-3).
19 out of 27 quench values are lower than the first quench during reception.
One detraining quench.
Firm-3 magnets clearly behave differently as compared to Firm-1 and Firm-2, and w.r.t. to expectations based on “memory” observed during 2nd cooldown of the reception tests.
Based on a simple exponential fit, and weighting for large percentage of Firm-3 magnets in S56 (55%), reaching kA (6.5 TeV) in 8 sectors was expected to require 84 training quenches, and about 30 more when adding a margin of 100 A.
“…. one should expect about 1000 quenches to reach 7 TeV. This number is however very approximate and a better estimate can only be made after at least one sector has trained to 7 TeV.” (A. Verweij, Chamonix 2009)
Arjan Verweij, LHC Performance Workshop, Jan 2016

20. LHC – 8 sectors (2015) 175 training quenches,
quite a bit more than expected.
Arjan Verweij, LHC Performance Workshop, Jan 2016

21. LHC – 8 sectors (2015)
Cumulative plot of all quenches per firm, sorted by quench current
About 8x faster (as expected)
Only 1.3x faster
6.5 TeV + margin
Extrapolation to 7 TeV (12 kA) very tricky
Arjan Verweij, LHC Performance Workshop, Jan 2016

22. Some interesting observations
S56: (containing 28 x Firm-1, 42 x Firm 2, 84 x Firm-3)
2008: 24 quenches to reach A (2 x Firm-2, 22 x Firm-3). 15 out of 22 quenched below the 1st quench during reception. 30 quenches to reach 11.2 kA.
2014/5: 16 quenches to reach A (all in Firm-3). 10 out of 16 quenched below the 1st quench during reception.
24 of the 27 Firm-3 magnets that quenched in 2008, did not quench again in 2014/5.
All sectors:
Nr of quenches
Nr of different magnets that quenched at least once
Cases for which the 1st quench during HWC is lower than the 1st quench during reception
Firm-1 5
4 (80%)
Firm-2 27
17 (63%)
Firm-3
143
132
97 (73%)
No clear correlation between training during reception and in the LHC.
The average quench value of the “2nd and 3rd quenches” is A.
Arjan Verweij, LHC Performance Workshop, Jan 2016

23. Conclusions on the observed training as presented by E
Conclusions on the observed training as presented by E. Todesco (LMC, 20/1/2016)
Differences in quench behaviour of the Firm-3 magnets along the production are statistically significant. (See also G. Willering, LMC, 8/4/2015)
Quench data are compatible with a scenario where at each warm-up we start in the same condition as at the beginning of the previous training.
Quench data of Firm-3 are compatible with a partial but small preservation of memory.
Quench results in S56 (comparison 2008 with 2015/5) are compatible with magnets belonging to the same production (no bad or good magnets). No evidence of magnets to be removed in LS2.
A good fraction of HWC data are compatible with Gaussian distribution for the first quench.
Arjan Verweij, LHC Performance Workshop, Jan 2016

24. Required training to reach 7 TeV as presented by E
Required training to reach 7 TeV as presented by E. Todesco (LMC, 20/1/2016)
The upper bound for the number of “2nd quenches” is 150.
Possible strategy: push S12 and S45 to 7 TeV before LS2.
S12: to see the behaviour of the Firm-1 and Firm-2 magnets
S45: to see possible “2nd quenches” in the Firm-3 magnets.
These two sectors require the lower number of quenches, so maximising information while minimising risk.
Arjan Verweij, LHC Performance Workshop, Jan 2016

25. Training quenches during operation in 2015
5 training quenches occurred at A, all in Firm-2 magnets (14/5, 11/6, 9/7, 19/9, 3/11)
1 May 2015
15 Dec 2015
Arjan Verweij, LHC Performance Workshop, Jan 2016

26. Conclusions (operation at 6.5 TeV)
HWC 2014/5: Reaching 6.5 TeV required a significant number of training quenches, mainly in some 600 A circuits, some MQM magnets, and in the RB circuits. Some magnets/circuits train slower than in previous campaigns. The QBT should look into these cases to assess the long-term behaviour.
Operation 2015: Only a few training quenches were observed, showing that the additional current margins during HWC are correct.
Powering tests March 2016: We will ramp all magnet circuits to the same values as during the campaign of 2014/5. We expect some quenches but this should not impact the planned duration of the tests.
Some QPS thresholds will be reduced to be better protected in case of almost symmetric quenches in the high current circuits.
The RB circuits will be cycled to A with a plateau of at least 4 hrs. Depending on the number of training quenches during operation, we might recommend to repeat such a test at regular intervals (e.g. before each TS).
Operation 2016: We expect smooth operation of the magnet circuits.
Arjan Verweij, LHC Performance Workshop, Jan 2016

27. Conclusions (towards 7.0 TeV)
There is no indication that one or more high-current circuits could not be operated at 7 TeV, even though some magnets/circuits seem to train slower than in the past.
Commissioning time to 7 TeV would be dominated by the MB training. Estimates by E. Todesco show that another 270 training quenches are needed plus an unknown number of second quenches for which an upper bound of 150 is given, plus an additional 170 if the training is preceded by a thermal cycle. A proper number for the entire machine can be given by training S12 and S45 to 7 TeV, which would require about 2 weeks.
Training of all 8 sectors can be performed in parallel, with a rate of about quenches per week. Possibilities to speed up the time for commissioning should be looked at (see also presentation R. Schmidt).
Each quench implies a certain risk (heater failure, inter-turn short, short-to- ground, pressure-related damage, etc), and a proper risk analysis should be performed before starting such a long training campaign.
Arjan Verweij, LHC Performance Workshop, Jan 2016

28. Annex
Arjan Verweij, LHC Performance Workshop, Jan 2016

29. Firm-3 quench behaviour along production
Arjan Verweij, LHC Performance Workshop, Jan 2016

30. Statistics on the LHC main dipole quench heater firing for 2014-2015
Since October 2014 (QPS-IST included):
2533 full charge firings in total
about 1660 firings at zero current
Since April 2015 (1st beam in the machine):
247 full charge firings in total
about 175 firings at zero current
B15R8
C14R8
A15R8
A21L5
B14L6
B8L4
A8L7
A10L7
A8L2
Arjan Verweij, LHC Performance Workshop, Jan 2016