long term behaviour and high miits test in the smc-rmc program · 2019-06-04 · logo area contents...

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Long term behaviour and high MIITs test

in the SMC-RMC program

Hugo Bajas et. al.

H. Bajas 23 May 2019

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Contents

SMC and RMC magnets introduction

Performed tests overview

Magnet performances overview

Thermal cycle effect overview

Powering cycle effect overview

Pre-stress effect overview

High quench integral (MIITs) tests

Conclusions and outlook

2H. Bajas 23 May 2019

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Contents







High quench integral tests



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Based on bladders & keys technology

Aims at :

testing performance of Nb3Sn conductor (PIT, RRP) in

racetrack configuration (block coil)

validating coil manufacturing technologies

electrical insulation (cable, central post, spacers)

impregnation methods, winding procedures

studying pre-stress’ influence on coil’s performances

Φ570 mm

4

Φ540mm

SMC & RMC magnets introduction

SMC

RMC

Racetrack Model Coil (RMC)Short Model Coil (SMC)


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Possible tests in 1DP or 2DP configuration

SMC & RMC magnets introduction


Two double pancake (2DP) configuration:

• SMC #1

• SMC #3a

• SMC #3b

• SMC #4

• SMC #5

• RMC FreSCa2

• RMC QXF

One double pancake (1DP) configuration:

• SMC 11T #1

• SMC 11T #2

• SMC 11T #3

• SMC 11T #4

• SMC 11T #5

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Magnet NameConductor

type

Stotal

(insult. cable)

[mm2]

Meas.

RRR

Bss (4.5 K)

[T]

Bss (1.9 K)

[T]

Iss (4.5 K)

[kA]

Iss (1.9 K)

[kA]

jss (4.5 K)

[A/mm2]

jss (1.9 K)

[A/mm2]

Splice

resistance

(nW)

SMC #3aPIT 288

26.375

12.7 13.4 14.0 15.2 533 579 0.910PIT 288 75

SMC #3bPIT 288

26.375

12.7 13.4 14.3 15.2 545 579 1.500PIT 288 75

SMC #4PIT 192

20.4120

13.3 14.5 11.6 12.8 568 627 0.525PIT 192 130

SMC11T #1 RRP 108/127 24.5 110 13.3 14.7 15.1 16.9 615 689 0.430

SMC11T #2 RRP 108/127 24.5 130 13.0 14.0 14.7 16.0 599 653 0.412

SMC11T #3 RRP 132/169 24.5 124 13.1 14.2 14.8 16.3 603 664 0.385

SMC11T #4 PIT 120 24.5 118 12.8 14.0 14.4 16.0 587 652 0.269

SMC11T #5 PIT 120 24.5 111 12.8 14.0 14.4 16.0 587 652 0.400

RMC_FreSCa2PIT 192

48.9180 15.1 16.8 17.2 19.2 351 392 0.164

RRP 132/169 240 15.5 16.9 17.6 19.4 360 396 0.176

RMC_QXFPIT 192

33.570

14.2 15.7 12.9 14.3 385 427 0.402PIT 192 110

Conductor type, Residual Resistivity Ratio (RRR)

and Short Sample limits (field, current, eng. current density)


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Contents










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Magnet NameTest

Station

#

cooldowns

#

Quenches

#

Pre-stress

Reached

Ultimate

85% Iss @ 1.9K

Reached

Plateau

@ 4.5 K

Reached

Plateau

@ 1.9 K

Ramp rate

dependence

Temperature

dependence

VI

meas.

AC

loss

meas.

High MIITs

SMC #3a Longue 3 83 2 Y Y Y N N N N 150

SMC #3b Longue 3 19 1 Y ? N N N N N ! (1500 K)

SMC #4 Siegtal 2 60 1 Y Y N N N Y Y 360 K

SMC 11T #1 Longue 4 96 1 Y Y N Y Y Y Y 200 K

SMC 11T #2 Longue 4 129 2 Y Y Y Y N N N 200 K

SMC 11T #3 Siegtal 8 220 4 Y Y Y Y Y N Y 200 K

SMC 11T #4 Siegtal 2 79 2 Y Y Y Y Y Y Y 200 K

SMC 11T #5 Siegtal 2 37 1 Y Y Y Y Y Y Y 400 K

RMC_FreSCa2 Longue 2 (+2) 72 1 Y Y Y Y Y N Y 100 K

RMC_QXF Siegtal 2 70 1 Y Y Y Y Y Y Y 100 K


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Contents










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RRR measurements comparison


The average RRR for:

PIT conductor: 103±32

RRP conductor: 151±52


RMC FreSca2

RRP

240

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Splices measurements comparison

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Average resistance:

Rsplice=0.543 ± 0.375 nW

Excellent results!

Rsplice < 1 nW


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Tested magnets

SMC #3a (SMC #3b)

SMC #4

SMC 11T #1

SMC 11T #2

SMC 11T #3 (SMC 11T #3 shimmed)

SMC 11T #4

SMC 11T #5

RMC FreSCa2

RMC QXF

And training curves


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One instance (SMC3a) to explain the following analysis?


92 % 92 %95 %

96 %

81 %

97 %

86 %

95 %

93 %

Main characteristics:

First quench @ 4.2 K

Quench current plateau @ 4.2 K

@ 1.9 K

Training rate

Thermal cycle effect Training memory

Re-training

Performance degradation

Powering cycle effect

Transverse Pre-stress effect 110 MPa 110 MPa 130 MPa

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Tested magnets and training curves:

SMC #3a (SMC #3b)

SMC #4

SMC 11T #1

SMC 11T #2

SMC 11T #3 (SMC 11T #3 shimmed)

SMC 11T #4

SMC 11T #5

RMC FreSCa2

RMC QXF


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Iq

/Iss (1st quench) measurements comparison

First quench (@ 4.2 K)

occuring at:

Iq

/Iss = 78.7±7.5 %


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Iq/Iss (plateau current) measurements comparison

Average Iq/Iss :

@ 4.2 K

RRP : 98%

PIT : 93%

@ 1.9 K

RRP : 94%

PIT : 95%


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Number of quenches to reach current plateau

Average number of quenches

to reach plateau @ 4.5 K:

N=13 ± 7

Average number of quenches

to reach plateau @ 1.9 K

(after 4.5 K training)

N=9 ± 4



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Training rate @ 4.5 and 1.9 K

Average training rate:

@ 4.5 K

90 ± 43 A/quench

@ 1.9 K

150 ± 59 A/quench



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Ramp rate dependence of the quench current


Core cable

No core


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Drop of current before/after thermal cycle

Average loss of performance

after thermal cycle:

DIth.cl. =740 A ± 588 A

Permanent degradation ?

Retraining...


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Drop of current before/after re-training

Average degradation after re-training:

@ 4.5 K

DIc/Iss = 2.2 ± 2.2 %

@ 1.9 K

DIc/Iss = 3.6 ± 3.4 %

Some magnets do not degrade

(SMC3#a, SMC11T#3).

Some degrade significantly (> 5%)

(SMC4, SMC11T#5, RMC_FreSCa2).


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SMC 4 (PIT)

Evidence of degradation only due to

thermal cycle.

-400 A


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Evidence of degradation after a quench at higher Lorentz force

SMC 11T # 5 (PIT)

-1500 A


Rods’

Ax. Strain vs I2

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SMC 11T # 4 & # 5 (PIT)

Exact same training behavior btw.

both magnets

-1000 A


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Effect of current plateau on quench current

(RMC QXF, PIT)

27

+ 6% increase on quench current

using plateau!


or

time

Cu

rre

nt

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Powering cycle effect overview Precursor to quench and training (RMC QXF)


Large gap (gain) of current ≡ Large precursor

Small gap (gain) of current ≡ Small precursor

Plateau current quench ≡ No precursor

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Lorentz forces cycling loading effect (SMC 4)


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Evidence of precursor (voltage spikes) vanishing from ramp to ramp

Less and less activity

at each ramp


Powering cycle effect overview Lorentz forces cycling loading effect (SMC 4)

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Quench current vs. Temperature for different level of pre-stress

SMC 11T # 3 (RRP)

Evidence of permanente degradation

going back to 180 MPa after 200 MPa.

Same degraded performance going back

to 150 MPa from 180 MPa.

Interesting change of slope for T < Tl

Superfluid stabilizing defect

-500 A


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Degradation also observed on the

Iq vs. RR plot.

-1200 A

Quench current vs. Ramp rate for different level of pre-stress

SMC 11T # 3 (RRP)


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Evidence of degradation ~200 A

from 150 to 170 MPa

No test back to 150 MPa...

Again…Change of slope for T < Tl

-200 A

Quench current vs. Temperature for different level of pre-stress

SMC 11T # 4 (PIT)


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SMC3b

36

The NbTi cable has fused.


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SMC 11T # 1 & #2

37

No degradation after any High Quench

integral tests on SMC11T

Test limited to 220 K due to the small

magnet inductance


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SMC 4

38

Using spot heater higher Hot Spot can be reached.

Thot Spot > 300 K No Clear Evidence of permanente degradation (retraining possible)

98%

92%

95%


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SMC 11T 5

39

Validation of the Hot Spot Assessment using: Fiber Optic Sensor, Votage taps and Comsol simulation

Thot Spot > 400 K No extra degradation

on top of the existing degradation (70%)


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Contents










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Conclusions and outlook Excellent splicing techniques (< 1 nW)

RRR: 120 RRP, 110 PIT

A constant in all magnets: First quench @ 80% Iss

Maximum performances

at 4.5 K 98% RRP, 93% PIT

at 1.9 K 94% RRP, 95% PIT

Degradation due to thermal cycle is observed < 4 %

Degradation due to powering cycle is observed < 2 %

Characteristic curves for degradation assessment:

Iq(ramp rate), Iq(Top), , Iq(strsv.)

Importance of the precursors and the current ramp pattern in the training behavior

High quench integral tests performed up to 400 K without clear evidence of degradation


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SMC 11T #2

After cold powering

SMC 11T #2

After impregnation

Thank you for your attention


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Literature and reference

A. Devred et al., 2006, “Overview and status of the Next European Dipole (NED) joint research activity,” Sup. Science Tech., vol. 19.

H. Felice et al., 2007, “Design and test of a subscale dipole magnet for training studies,” IEEE Trans. Applied Superconductivity, vol. 17.

P. Manil et al., 2010, “Magnetic design and code benchmarking of the SMC (Short Model Coil) dipole magnet,” IEEE Trans. Applied Sup., vol. 20.

F. Regis et al., 2010, “Mechanical design of the SMC (Short Model Coil) dipole magnet,” IEEE Trans. Applied Superconductivity, vol. 20.

M. Bajko, et al., 2012, “The Short Model Coil (SMC) Dipole: An R&D program towards Nb3Sn accelerator magnets,” IEEE Trans. Appl. Supercond., vol. 22

C. Kokkinos et al., 2012, “The SMC (Short Model Coil) Nb3Sn program: FE analysis with 3D modeling,” IEEE Trans. Appl. Supercond., vol. 22.

E. Fornassiere et. al., 2013, “Status of the Activities on the Nb3Sn Dipole SMC and of the Design of the RMC”, IEEE Trans. Appl. Sup., vol. 28.

A. Chiuchiolo et. al., 2014, “Fiber Bragg Grating Cryosensors for Superconducting Accelerator Magnets”, IEEE Photonics Journal, Vol .6.

S. Izquierdo Bermudez, H. Bajas, L. Bottura, 2015, “Quench modeling in high-field Nb3Sn accelerator magnets,” Phys. Procedia, vol 67.

J.C. Perez et al., 2015, “Performance of the Short Model Coils Wound With the CERN 11-T Nb3Sn Conductor”, IEEE Trans. Appl. Sup., vol. 25.

Bajas H et al., 2015, “Quench Analysis of High-Current-Density Nb3Sn Conductors in Racetrack Coil Configuration”, IEEE Trans. Appl. Sup., vol. 25.

A. Chiuchiolo et. al., 2016, “ Advances in Fiber Optic Sensors Technology Development for Temperature and Strain Measurements in Superconducting

Magnets and Devices” , IEEE Trans. Appl. Sup., vol. 26.

J.C. Perez et. al., 2016, “16 T Nb3Sn Racetrack Model Coil Test Result”, IEEE Trans. Appl. Sup., vol. 26.

S. I. Bermudez, L. Bottura, H. Bajas, G. Willering, 2018, “Analytical method for the prediction of quench initiation and development in accelerator

magnets”, Cryogenics, vol. 95

Bajas H et al., 2018, “Advanced Nb3Sn Conductors Tested in Racetrack Coil Configuration for the 11T Dipole Project”, IEEE Trans. Appl. Sup., vol. 28.


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Training memory

SMC3a

44

92 % 92 % 95 %

96 %

81 %

97 %

86 %

95 %

93 %


110 MPa 110 MPa 130 MPa

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Training memory

SMC3b

45

130 MPa


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Training memory

SMC 11T 1

46

78%

94%

99%

94%92%

130 MPa


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Training memory

SMC 11T 2

47

97%

76%

89%

94% 90%

81%81%

92% 91%


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Training memory

SMC 11T 3

48

150 MPa


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Training memory

SMC 11T 3

49

150 MPa 180 MPa 200 MPa 180 MPa 150 MPa


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Training memory

SMC 11T 4

50

150 MPa 170 MPa


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Training memory

SMC 11T 5

51

150 MPa 150 MPa


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Training memory

SMC 4

52

150 MPa

85%

94%

96%

93%

97%

90%

96%


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RMC FreSCa2

53

97%

95%

95%

95%

90%90%

89%

120 MPa

94%

Training memory


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Training memory

RMC QXF

54

120 MPa


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Quench velocity


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area56H. Bajas 23 May 2019

long term behaviour and high miits test in the smc-rmc program · 2019-06-04 · logo area contents...

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