CERN, 4th June 2008
Magnet Performance Panel
COMPARISON OF QUENCH PERFORMANCE OF MAIN
DIPOLES IN SM18 AND IN SECTOR 5-6
E. Todesco
Magnets, Cryostats and Superconductors Group
Accelerator Technology Department, CERN
This work relies on the “gold mine” of SM18 data thanks to the teams lead by A. Siemko and V. Chohan,
and on the brave work of the Hardware Commissioning Team lead by R. Saban
and of the MPP lead by A. Siemko
Thanks to P. Fessia for discussion on Noell magnets and significant help on non-Gaussian statistics
Acknowledgements: V. Chohan, L. Rossi, A. Siemko, A. Verweij
E. Todesco
FOREWORD
The training of sector 5-6 has some unexpected features
Strong difference between firms: out of 24 quenches, 22 from Noell, 2
from Ansaldo, none from Alstom
After 24 quenches we are at 11.1 kA, instead than nominal as
expected (25-30 quenches for going to 11.85 kA†)
[†P. Pugnat and A. Siemko, IEEE Trans. Appl. Supercond. 17 (2007) 1091]
First quench around 10 kA, against previous forecast† of 11 kA
Is this unexpected behavior hidden inside the SM18 data or
is there something new ?
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 2
CONTENTS
A plot for estimating the training of a string of magnets
Analysis of the training of virgin magnets
Training estimates based on
magnets tested after thermal cycle
virgin magnets plus correlation
Conclusions
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 3
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Training first 5 Alstom, virgin magnets
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
1001
1002
1003
1004
1006
10
9
8
0
5
10
15
20
Quench number
Training of the first 5 Alstom dipoles at SM18
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 4
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Training of a string made up of the first 5 Alstom, virgin magnets
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
9
8
0
10
5
15
Quench number
Training of the 5 dipole in series, assuming that quench are
monotonous
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 5
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Training of a string made up of the first 10 Alstom, virgin magnets
Current (kA)
12
8.3 T, 7 TeV
7.7 T, 6.5 TeV
11
10
9
8
0
5
10
15
20
25
30
Quench number
We double the string length – from 5 to 10 magnets
We double the scale in x: if 5 magnets need ~15 quenches to ultimate, 10 magnets
will need ~30 quenches
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 6
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Training of a string made up of the first 20 Alstom, virgin magnets
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
9
8
0
10
20
30
40
50
60
Quench number
We double the string length – from 10 to 20 magnets
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 7
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Training of a string made up of the first 40 Alstom, virgin magnets
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
9
8
0
20
40
60
80
100
120
Quench number
We double the string length – from 20 to 40 magnets
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 8
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Training of a string made up of the first 80 Alstom, virgin magnets
Current (kA)
12
8.3 T, 7 TeV
7.7 T, 6.5 TeV
11
10
9
8
0
40
80
120
160
200
240
Quench number
We double the string length – from 40 to 80 magnets
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 9
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Training of a string made up of the first 160 Alstom, virgin magnets
Current (kA)
12
8.3 T, 7 TeV
7.7 T, 6.5 TeV
11
10
9
8
0
80
160
240
320
400
480
Quench number
We double the string length – from 80 to 160 magnets
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 10
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Training of a string made up of the 416 Alstom, virgin magnets
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
9
8
0
208
416
624
832
1040
1248
Quench number
We put all Alstom magnets in the string (416)
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 11
A PLOT FOR ESTIMATING TRAINING OF A
STRING OF MAGNETS
Some remarks
Even though quench is a highly random phenomena, the quench of a
string of magnets looks very regular
For virgin Alstom, 20 magnets give main pattern of 416 magnets
Training of a string made up of the first 20 Alstom, virgin magnets
12
8.3 T, 7 TeV
11
Current (kA)
Current (kA)
12
Training of a string made up of the 416 Alstom, virgin magnets
7.7 T, 6.5 TeV
10
9
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
9
8
8
0
10
20
30
Quench number
40
50
60
0
208
416
624
832
1040
1248
Quench number
One should plot all quenches, not only the first one or the second
one
Remember to rescale the quench number with the number of
magnets
If 5 magnets need 10 quenches, 50 magnets will need 100 quenches …
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 12
CONTENTS
A plot for estimating the training of a string of magnets
Analysis of the training of virgin magnets
Training estimates based on
magnets tested after thermal cycle
virgin magnets plus correlation
Conclusions
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 13
TRAINING OF VIRGIN MAGNETS
In SM18 data one observes a difference among firms
especially at low fields
At low fields, Noell and Ansaldo quench much more than Alstom
All quenches, all LHC dipoles first training
Current (kA)
12
8.3 T, 7 TeV
7.7 T, 6.5 TeV
11
10
Alstom
Ansaldo
Noell
9
8
0
E. Todesco
400
800
Quench number
1200
1600
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 14
TRAINING OF VIRGIN MAGNETS
We rescale data to 1 magnet per firm
To get to nominal, 0.7 quench per magnet in Alstom, 1 quench per
magnet in Noell, 1.2 in Ansaldo
This is for virgin magnets - or magnets who lost totally their memory
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Alstom
Ansaldo
Noell
9
All quenches, all LHC dipoles first training normalized to one dipole per firm
8
0
E. Todesco
1
2
Quench number
3
4
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 15
TRAINING OF VIRGIN MAGNETS
We rescale to one sector with 1/3 magnets per firm
60 quenches of Ansaldo, 50 of Noell, 30 of Alstom for going to 7 TeV –
total 140 quenches
This is for virgin magnets - or magnets who lost totally their memory
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Alstom
Ansaldo
Noell
9
All quenches, all LHC dipoles first training normalized to one sector made of 1/3 per firm
8
0
E. Todesco
50
100
Quench number
150
200
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 16
TRAINING OF VIRGIN MAGNETS
We now consider the composition of sector 5-6
84 Noell, 42 Ansaldo, 28 Alstom
51 Noell take 50 quenches to 7 TeV  84 Noell will take 83 quenches
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Alstom
Ansaldo
Noell
9
All quenches, all LHC dipoles first training normalized to one sector made as 5-6
8
0
E. Todesco
50
100
Quench number
150
200
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 17
TRAINING OF VIRGIN MAGNETS
We now consider the data of the magnets in sector 5-6
Are they worse than average?
Alstom and Ansaldo are a bit better, Noell are as average
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Alstom
Ansaldo
Noell
9
All quenches, all LHC dipoles first training magnets in 5-6
8
0
E. Todesco
50
100
Quench number
150
200
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 18
TRAINING OF VIRGIN MAGNETS
If dipoles had totally lost their memory …
First quench 5-6: 8.5 kA (instead of 10 kA)
To get to 11 kA: 40 Noell quench, 12 Ansaldo, 1 Alstom = 53 total
(instead of 20 quenches)
12
Current (kA)
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Ansaldo SM18
Noell SM18
Alstom SM18
9
Ansaldo HC
Noell HC
8
0
E. Todesco
20
40
60
Quench number
80
100
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 19
TRAINING OF VIRGIN MAGNETS
Some remarks on training of virgin magnets
Firms are different especially at low fields:
Noell and Ansaldo have a worse training than Alstom at low fields
Differences disappear at high fields
Training of a virgin sector 5-6 would be completely dominated by
Noell magnets for the first 1.5 kA
Mainly because this sector has a lot of Noell
First quench level with respect to virgin magnets
+0.6 kA for Ansaldo, +1.5 kA for Noell – not all the memory is lost …
20 quenches to go to 11 kA instead of 53 - but the slope now is pretty
low …
All quenches, all LHC dipoles first training
10
Alstom
Ansaldo
Noell
9
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Alstom
Ansaldo
Noell
9
8
8.3 T, 7 TeV
Current (kA)
7.7 T, 6.5 TeV
11
12
12
8.3 T, 7 TeV
Current (kA)
Current (kA)
12
E. Todesco
400
800
Quench number
1200
1600
7.7 T, 6.5 TeV
10
Ansaldo SM18
Noell SM18
Alstom SM18
9
All quenches, all LHC dipoles first training magnets in 5-6
Ansaldo HC
Noell HC
8
8
0
11
0
50
100
Quench number
4h
150
200
0
20
40
60
Quench number
80
100
June 2008 – Comparison of quench performance in the main LHC Dipoles - 20
CONTENTS
A plot for estimating the training of a string of magnets
Analysis of the training of virgin magnets
Training estimates based on
magnets tested after thermal cycle
virgin magnets plus correlation
Conclusions
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 21
TRAINING AFTER THERMAL CYCLE
All magnets in the machine were tested virgin, and 11%
after a thermal cycle
Hypotheses of the estimate
From SM18 data, we keep only data relative to ALL test after the
thermal cycle
42 magnets from Ansaldo, 58 from Alstom, 36 from Noell
All together 136 magnets (nearly one sector)
We assume that all magnets behave as the magnets tested after
thermal cycle (the “bad” ones)
We separate magnet per Firm
We scale the number of magnets to the actual proportion in the LHC
and in sector 5-6
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 22
TRAINING AFTER THERMAL CYCLE
136 magnets tested after thermal cycle
42 magnets from Alstom, 58 from Ansaldo, 36 from Noell
These data include also some magnets which have been rejected
All quenches SM18 after thermal cycle
8.3 T, 7 TeV
Current (kA)
12
7.7 T, 6.5 TeV
11
Alstom
Ansaldo
Noell
10
9
0
10
20
30
40
50
60
Quench number
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 23
TRAINING AFTER THERMAL CYCLE
We rescale to have 1/3 per firm in the sector, otherwise the statistic
is biased
Noell and Ansaldo are worse than Alstom at low fields
For a (bad?) sector after thermal cycle: 30 (Noell) + 25 (Ansaldo) + 15
(Alstom) ~ 70 quenches to nominal
All quenches SM18 after thermal cycle rescaled to 1/3 per firm
8.3 T, 7 TeV
Current (kA)
12
7.7 T, 6.5 TeV
11
Alstom
Ansaldo
Noell
10
9
0
10
20
30
40
50
60
Quench number
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 24
TRAINING AFTER THERMAL CYCLE
We now rescale to have the proportion of 5-6
All quenches SM18 after thermal cycle rescaled to 5-6
8.3 T, 7 TeV
Current (kA)
12
7.7 T, 6.5 TeV
11
Alstom
Ansaldo
Noell
10
9
0
10
20
30
40
50
60
Quench number
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 25
TRAINING AFTER THERMAL CYCLE
We compare to HC data
General trends are there: no Alstom, few Ansaldo, a lot of Noell
First 10 quenches agree well, then the slope is lower
All quenches SM18 after thermal cycle rescaled to 5-6
8.3 T, 7 TeV
Current (kA)
12
7.7 T, 6.5 TeV
11
Alstom sm18
Ansaldo sm18
Noell sm18
10
Alstom HC
Ansaldo HC
Noell HC
9
0
10
20
30
40
50
60
Quench number
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 26
CONTENTS
A plot for estimating the training of a string of magnets
Analysis of the training of virgin magnets
Training estimates based on
magnets tested after thermal cycle
virgin magnets plus correlation
Conclusions
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 27
VIRGIN MAGNETS PLUS CORRELATION
A method based on extrapolation:
A bit such as we did for magnetic measurements
We take the first virgin quench of all magnets of 5-6 (available for all
magnets)
We sum the correlation 2nd-1st quench measured in 136 magnets,
split per firm
We take the correlations that are available, i.e. that ones of bad magnets
This correlation is affected by a random part that must be taken into
account  one needs a MonteCarlo
These correlations are the key ingredient
The statistic is low and possibly biased
The method gives only the first quench for each magnet
Up to now, all 5-6 quenches were in different magnets
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 28
VIRGIN MAGNETS PLUS CORRELATION
The increase of field between 1st and 2nd quench cannot be applied
simply as a systematic plus a random part
Example: for Ansaldo one has an average offset of +1.27kA with a stdev
of 0.82 kA – this could produce magnets going to 13 kA
We assume a linear correlation (magnets with lower first quench gain
more) plus a Gaussian random part
The sigma should decrease with larger currents – this is neglected
4
(1st quench atc - 1st virgin
quench) - linear correlation (kA)
1st quench atc - 1st virgin quench
(kA)
Subtracting the linear part the random part has 0.49 kA r.m.s
Ansaldo
3
2
1
0
y = -0.7346x + 9.2254
-1
-2
8
E. Todesco
9
10
11
1st virgin quench (kA)
12
13
4
Ansaldo
3
2
1
0
y = -9E-06x + 3E-05
-1
-2
8
9
10
11
1st virgin quench (kA)
12
13
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 29
VIRGIN MAGNETS PLUS CORRELATION
Correlation between 1st and 2nd quench in Alstom
4
(1st quench atc - 1st virgin
quench) - linear correlation (kA)
1st quench atc - 1st virgin quench
(kA)
Subtracting the linear part the random part has 0.34 kA r.m.s – very low
spread
Alstom
3
2
1
0
y = -0.5128x + 6.6608
-1
-2
8
E. Todesco
9
10
11
12
1st virgin quench (kA)
13
14
4
Alstom
3
2
1
0
y = -3E-05x - 2E-05
-1
-2
8
9
10
11
12
1st virgin quench (kA)
13
14
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 30
VIRGIN MAGNETS PLUS CORRELATION
Correlation between 1st and 2nd quench in Noell
4
(1st quench atc - 1st virgin
quench) - linear correlation (kA)
1st quench atc - 1st virgin quench
(kA)
We see that 5 magnets out of 36 have a 1st quench after thermal cycle
lower than in the virgin state
Moreover, there is a larger spread: 0.59 kA r.m.s
Moreover, the distribution looks skew …
Noell
3
2
1
0
-1
y = -0.9006x + 10.909
-2
8
E. Todesco
9
10
11
12
1st virgin quench (kA)
13
14
4
Noell
3
y = -1E-05x - 0.0002
2
1
0
-1
-2
8
9
10
11
12
1st virgin quench (kA)
13
14
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 31
VIRGIN MAGNETS PLUS CORRELATION
We take the 1st virgin quench at sm18 for dipoles in 5-6
5-6: first quench at SM18
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Alstom
Ansaldo
Noell
9
8
0
E. Todesco
20
40
First quench number
60
80
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 32
We add the linear correlation
Looks beautiful …
1st quench atc - 1st virgin quench
(kA)
VIRGIN MAGNETS PLUS CORRELATION
4
3
Alstom
Ansaldo
Noell
2
1
0
-1
-2
8
9
10
11
12
1st virgin quench (kA)
13
14
5-6: first quench extrapolation, no random part
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Alstom
Ansaldo
Noell
9
8
0
E. Todesco
20
40
First quench number
60
80
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 33
We add the random part (one seed)
Looks more real …
We now repeat a few times …
1st quench atc - 1st virgin quench
(kA)
VIRGIN MAGNETS PLUS CORRELATION
4
3
Alstom
Ansaldo
Noell
2
1
0
-1
-2
8
9
10
11
12
1st virgin quench (kA)
13
14
5-6: first quench extrapolation, with random part
Current (kA)
12
8.3 T, 7 TeV
11
7.7 T, 6.5 TeV
10
Alstom
Ansaldo
Noell
9
8
0
E. Todesco
20
40
First quench number
60
80
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 34
We make a MonteCarlo
The spread is not negligible …
This is only the first quench !!
1st quench atc - 1st virgin quench
(kA)
VIRGIN MAGNETS PLUS CORRELATION
4
3
Alstom
Ansaldo
Noell
2
1
0
-1
-2
8
9
10
11
12
1st virgin quench (kA)
13
14
5-6: first quench extrapolation, with random part - 10 cases
Current (kA)
12
11
Alstom
Ansaldo
Noell
10
9
8
0
E. Todesco
20
40
First quench number
60
80
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 35
VIRGIN MAGNETS PLUS CORRELATION
We compare with HC data
Qualitatively is fine: a lot of Noell, a few Ansaldo, no Alstom
Quantitatively is ok the beginning (first 10 Noell)
Now, after 22 Noell quenches, we are below of about 400-600 A
5-6: first quench extrapolation, with random part - 10 cases
Current (kA)
12
11
Alstom
Ansaldo
Noell
Ansaldo HC
Noell HC
10
9
8
0
E. Todesco
20
40
First quench number
60
80
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 36
CONCLUSIONS
SM18 data show that
Firms have different training at low fields, Noell and Ansaldo are worse
than Alstom as virgin magnets
Detraining at low fields is worse in Noell
Two methods have been used to guess the behavior of 5-6 sector
A simple estimate based on magnets measured after thermal cycle
A MonteCarlo based on virgin measurements and random offsets from
1st to 2nd cycle as measured in SM18
Both methods account for some of the observed behavior
Noell magnets are expected to dominate quench behavior in 5-6
First level of quench 10 kA looks consistent
Alstom are not expected to quench up to 11.5 kA
Both methods fail to justify the last 10 Noell quenches
We are ~0.5 kA below expectations
E. Todesco
4h June 2008 – Comparison of quench performance in the main LHC Dipoles - 37