HQ test at CERN:

overview and protection studies

H. Bajas

02/09/2012 H. BAJAS | Hi-Lumi special session on HQ test results

I. Training curve at 4.2 K and 1.9 K

II. Ramp rate study

III. Final test main results

OUTLINE

I. Training curve at 4.2 K and 1.9 K

II. Ramp rate study

III. Final test main results

OUTLINE

I. Training curve at 4.2 K and 1.9 K Short sample limitT [K] 4.2 1.9

Ic [kA] 17.3 19G [T/m] 196 215

0 10 20 30 40 50 60 7013000

13500

14000

14500

15000

15500

16000

16500

17000

Quench number [-]

Iq [

A]

1st & 2nd cooldown 3rd cooldown

4

16,216 kA184 T/m

14,681 kA

Nominal current14900 A

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0 10 20 30 40 50 60 7070

72

74

76

78

80

82

84

86

88

4.2 K | 20 A/s LBNL) 4.2 K | 20 A/s (CERN)1.9 K | 13 A/s 1.9 K | 50->20 A/s1.9 K | 50->20->5 A/s 1.9 K | 50-20-5 | 10 min plt.1.9 K | 50-20-5 | 2 min plt. 4.2 K | 50-20-5 | 2 min plt.

Quench number [-]

Iq/I

ss[%

]II. Training curve at 4.2 K and 1.9 K

1st & 2nd cooldown 3rd cooldown

Normalisation to short sample limitHQ01e performance: 85 % Iss

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0 10 20 30 40 50 60 7070

72

74

76

78

80

82

84

86

88

4.2 K | 20 A/s LBNL) 4.2 K | 20 A/s (CERN)1.9 K | 13 A/s 1.9 K | 50->20 A/s1.9 K | 50->20->5 A/s 1.9 K | 50-20-5 | 10 min plt.1.9 K | 50-20-5 | 2 min plt. 4.2 K | 50-20-5 | 2 min plt.

Quench number [-]

Iq/I

ss[%

]II. Training curve at 4.2 K and 1.9 K

1st & 2nd cooldown 3rd cooldown

Importance of the way one goes to quench current: need plateau.

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II. Training curve at 4.2 K and 1.9 K

0 10 20 30 40 50 60 7070

72

74

76

78

80

82

84

86

88

4.2 K | 20 A/s LBNL) 4.2 K | 20 A/s (CERN)1.9 K | 13 A/s 1.9 K | 50->20 A/s1.9 K | 50->20->5 A/s 1.9 K | 50-20-5 | 10 min plt.1.9 K | 50-20-5 | 2 min plt. 4.2 K | 50-20-5 | 2 min plt.

Quench number [-]

Iq/I

ss[%

]

1st & 2nd cooldown 3rd cooldown

17 Miits

No inner PHs12.2 Miits

18.3 Miits

16,216 kA

13.2 Miits

14,681 kA

14,050 kA

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0 10 20 30 40 50 60 7070

72

74

76

78

80

82

84

86

88

4.2 K | 20 A/s LBNL) 4.2 K | 20 A/s (CERN)1.9 K | 13 A/s 1.9 K | 50->20 A/s1.9 K | 50->20->5 A/s 1.9 K | 50-20-5 | 10 min plt.1.9 K | 50-20-5 | 2 min plt. 4.2 K | 50-20-5 | 2 min plt.

Quench number [-]

Iq/I

ss[%

]II. Training curve at 4.2 K and 1.9 K

?

7

7

7

9

89 9

5

99

7

7

7

7

8

9 95

78

8

7

7

7

5

7

7

7

7 9 8 ?

77

8 8

7

88

8 8

8

7

8

87

7

57

7

7

77

7

02/09/2012

Quench initiating in the 4 coils.Coil 7 and 8 are basically limiting.

I. Training curve at 4.2 K and 1.9 K

II. Ramp rate study

III. Final test main results

OUTLINE

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III. Ramp rate study

-400 -300 -200 -100 0 100 200 300 4000

2000

4000

6000

8000

10000

12000

14000

16000

18000 CERN measurement @ 4.4K

LBNL measurement @ 4.4K

CERN measurement @ 1.9 K

Ramp rate [A/s]

Cri

tica

l cu

rren

t [A

]

No quench

zone

02/09/2012

I. Training curve at 4.2 K and 1.9 K

II. Ramp rate study

III. Final test main results

OUTLINE

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III. Final test main results

• Fast current discharge in the dump resistor for various currents :

02/09/2012

Goal: does the discharge cause quench back?

– @ 5 kA – @ 10 kA – @ 13 kA– @ 15 kA – @ 15 kA (with PHs firing)

(without firing the PHs)

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III. Final test main results

At 5 kA and 10 kA, magnet does not quenchAt 13 kA, magnet partially quenchesAt 15 kA, strong evidence that a relevant fraction of the magnet is quenched

Computation based on the instantaneous time constant of the exponential current decay:

exp (-)

02/09/2012

• Magnet resistance increase during fast ramp down ≡ quench

• Comparison of the magnet total resistance

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III. Final test main results

• Comparison of the current discharge @ 15 kA

0

2

4

6

8

10

12

14

16

0.00 0.10 0.20 0.30 0.40 0.50

Cur

rent

(kA

)

Time (s)

Discharge with QH

Discharge w/o QH

Training quench

Negligible difference of the current decay when the PHs are used or not.

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III. Final test main results

02/09/2012

• High Miits quenches without dump resistor:

Goal: can the HQ survive with all energy deposited in the helium bath?

– Iq = 15,448 A with PHs firing

– Iq = 15,917 A without inner layer PHs

Goal: What is the final temperature of the magnet for high Miits?

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III. Final test main results

• Comparison of the current decay with and without dump

Strong increase of the Miits when no dump is used, a lot of He loss.

02/09/2012

18.3 Miits

13.2 Miits

16.9 Miits

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III. Final test main results

• Magnet resistance increase

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III. Final test main results

• Attempt to compute magnet resistance from adiabatic model.

02/09/2012

• The HQ01e has undergone 3 warm-up/cool-down, and more than 70 quenches during 8 weeks of test.

• Maximum magnet current: 14,681 A @ 4.2K & 16,216 A (184 T/m) @ 1.9K i.e. 85% of the short sample limit and greater than nominal current 14.9 kA

• Regular training quenches can be obtained with pauses during the ramp and decrease of the ramp rate.Using the same ramp rate all the way has proved to limit the performance due to early quench in COIL 7. Coil 7 and 8 are statistically the limiting coils.

• The final test tends to show that when one has a fast dump on the resistor at 15 kA, the magnet quenches:• PHs have no significant impact when a dump resistor is used

• Without dump resistor current discharge is in agreement with a 20 ms delay of heaters• 16.6 MITTS at 16 kA, so hot spot below 300 K.

conclusion

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