CERN Fast Cycled Magnet demonstrator:test station, instrumentation and measurement campaign

 G. Willering1, M. Bajko1, F. Borgnolutti2, L. Bottura1,

V. Datskov1, G. Deferne1, J. Feuvrier1, L. Fiscarelli1,

C. Giloux1, M. Guinchard1, V. Roger1

1CERN, 2LBL

18-07-2013MT-23, Boston, MA4OrCB-05

Contents Introduction

FCM magnet project Test station Instrumentation Test conditions

Measurements Magnet powering Current Cycling Training quenches Quenches at Short Sample limit Temperature and losses Mechanical measurements

FCM magnet project

- Injector upgrade scenario includes a new PS2 (Proton-Synchrotron)

- Ramp time 1.1 s, flattop 0.1 s.- Required dipole field 1.8 T- Energy consumption can be reduce by

a factor of 2 compared to a normal conducting option

- The FCM project aims to demonstrate the feasibility of reliable, low-loss superconducting technology.

The PS at CERN, operating since 1959

Magnet concept

Warm iron yoke70 mm gap

Cryostat

Central gap

Yoke length 0.821 mMagnetic length 0.710 m

Cross-section

2 coils of 10 windings

Conductor

Conductor specificationsType Nuclotron cableID 4 mmOD 7.7strands 32 Nb-TiMatrix mixed Cu/Cu-MnMechanics Ni-Cr wrap

Magnetic fieldCentral magnetic field 1.8 TMaximum conductor field 0.7 T

CryogenicsForced flow cooling though central tube by supercritical helium at 3 B, 3 g/s at 4.5 K.

Demountable joints

Cable soldered in Cu shoeTwo Cu parts clamped with In-foil

New test station at CERN

Supercritical helium at 4.5 K, 3 Bar, mixed with warm He-gas

Temperature reach between 4.5 and 80 K forced flow

Designed for FCM and SC Link

FCM – Summer 2012

The superconducting link aims at connecting the LHC magnet circuits to the power converters over a distance of 600 meter, cooled by He gas

Magnet cooling schematics

Cooling control:1. Mixing supercritical Lhe of 4.5 K with Ghe of 300 K2. For each coil a heater can increase the temperature

MixingChamber

4.5 K, 2-3 B

300K

Temperature probes

CCS temperature sensor on the cable (V. Datskov, session 1PoAP-01)

12 CCS (Carbon Ceramic) temperature sensors.

Good contact with the cable & temperature stabilized

In hind-sight the main error in enthalpy determination came from high uncertainty in pressure measurements (±0.1 Bar)

Cryogenics- Long (~ 18 m) small diameter (4 mm) tube- Large pressure drop over the magnet resulting in a big

change in density at 3 bar at a point where the heat capacity is at its maximum. Calorimetric measurement has a very low resolution at this condition.

- Temperature control for low flow-rate of GHe was stable to 0.2 K

Calorimetric measurements

0

5

10

15

20

25

4.6

4.7

4.8

4.9

5

5.1

5.2

5.3

5.4

5.5

0 100 200 300 400

Hea

t (W

)

Tem

pera

ture

(K)

Time (s)

T1 : Output coil 1

T2 : Input coil 1

Heater1

Stepwise increase of heating power resulted in:1. Stepwise increase in temperature2. Decrease in helium flow due to

density change.

Major issues:- Stable supply of helium

temperature, flow and pressure.- Operation in the phase transition

region of Helium: Large expansion in a long thin tube.

0

0.5

1

1.5

2

2.5

3

3.5

2

2.5

3

3.5

4

4.5

5

0 100 200 300 400

Pres

sure

(B)

Hel

ium

flow

(g/s

)

Time (s)

Helium flow coil1

Pressure output coil1

Pressure input coil1&2

Powering summary

First powering to 6 kA, August 10th, 2012

1 quench to Inominal = 6 kA

3 quenches to Imax = 7.5 kA

Possible detraining

(6.6 K) from Imax = 7.5 kA

Cycling

One quadrant power supply: Ramp down speed limited by L/R of the circuit

at 3 kA/s Ramp up at nominal 6 kA/s

Cycling tests were performed in trains of 10 minutes at about 4.8 K, 3 g/s, 3 Bar supercritical helium cooled

Test cycle duration 3.5 s versus a nominal cycle duration of 2.4 s

First test cycle trains, August 16th, 2012

Longest series: 5h - 4650 cycles (3.9 s/cycle aver.)

In total 20000 cycles performed

Measurement of Tcs

Set stable temperature at the inlet (e.g. 7 K)

Current ramp (e.g. 1 kA/s)

Quench (e.g. 6 kA)Hot helium expulsion

Dump ( t ≈ 0.2 s, Vmax ≈ 60 V)

≈ 0

.2 K

Quench propagation velocity

0

5

10

15

20

25

30

35

40

45

0 2000 4000 6000 8000

Que

nch

prop

agati

on v

eloc

ity (m

/s)

Quench current (A)

coil 2coil 1

plug connection 2

- Rough estimates from measurements of vnzp

- Length of normal zone at detection 0.1 to 0.2 m- Quench position unknown during these training

quenches

Magnetic field profile along the conductor

0

5

10

15

20

25

30

35

40

45

0 2000 4000 6000 8000

Que

nch

prop

agati

on v

eloc

ity (m

/s)

Quench current (A)

Frescaat 1 Tnot impregnated

Quench propagation velocity well in between adiabatic calculations and cable test in FReSCa.

Tcs resultsData from FRESCA

cable tests

Quenches outside the

magnet coils

Overall excellent agreement to short sample !

• Error in temperature 0.2 K

• The behavior of the two coils is very similar !

Ramp-rate dependence

Data from Tcs measurement at different ramp-rate was reduced to a reference temperature of 7 K (Iq ~ 6200 A) applying an average temperature correction of 2300 A/K

Most of the scatter can be explained by the uncertainty on

temperature (±0.2 K in Tcs

equals± 500 A in Iquench)

6200

±0.2 K

±0.2 K

No ramp-rate dependence can be

observed in the resulting data-set !

Pushing the limitWorking

point

Stable cycling at 0.5 K from the expected cable critical current!(2600 cycles)

T inlet

T outlet coil 1

T outlet coil 2

AC loss estimate

Tinlet (K) 6.62

pinlet (bar) 1.90±0.05

Toulet (K) 6.29

poutlet (bar) 1.20±0.05

Low density (10 kg/m3), high speed (13 m/s) flowThe large JT expansion causes temperature drop

System oscillations (cryoplant) do not allow a precise evaluation of the loss by calorimetry. Error bound ± 1 W/coil

The measured AC loss for the magnet is smaller than 2 ± 2 W

Expected AC loss (based on cable measurements and field map) is 0.15 W/coil, compatible with above estimate

-0.01

-0.005

0

0.005

0.01

0.015

0.02

0.025

0 2 4 6 8

Volta

ge (V

)

Current (kA)

Coil2 - 300 A/s

Coil2 - 1000 A/s

Coil2 - 3000 A/s

Coil2 - 6000 A/s

Coil1 - 300 A/s

Coil1 - 1000 A/s

Coil1 - 3000 A/s

Coil1 - 6000 A/s

Pick-up coils efficiencyChallengeMeasure resistive voltage of a coilSolutionCo-wind the voltage tap wire with the coil to eliminate Vinductive

ResultMax 25 mV at 6 kA/sPickup coil voltage only 0.2 % of coil voltageSaturation effect above 3 kA visibleNon-uniform field on magnet coil and pick-up coil results in a different response

-0.2%

0.0%

0.2%

0.4%

0.6%

0.8%

1.0%

1.2%

1.4%

1.6%

0 1 2 3 4 5 6

Perc

enta

ge o

f the

com

pens

ated

sig

nal

com

pare

d fu

ll si

gnal

(%)

Current (kA)

coil 1 - 300 A/s

Coil 2 - 300 A/s

Coil 1 - 1000 A/s

Coil 2 - 1000 A/s

Coil 1 - 3000 A/s

Coil 2 - 3000 A/s

Coil 1 - 6000 A/s

Coil 2 - 6000 A/s

Magnetic performance

MSC/MM Measurement Note 2012-02, by Lucio Fiscarelli

Measured field (700 mm probe)

Reconstructed field

Measured field corresponds with calculations.

Multipole b3 is specifically high -> Magnet is not yet optimized for field quality.

load line 3000 A (units @ 17 mm)

n bn an

2 1.47 0.103 7.56 -0.024 0.00 0.005 0.03 0.006 0.00 0.007 0.00 0.008 0.00 0.009 0.00 0.00

Magnetic field profile along the conductor

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 250 500 750B

3D(0

,0,z

)/B

2D(0

,0)

z (mm)

simulationmeasurements

Mechanics

8 Tie rods, equipped with strain gauges

8 strain gauges measuring the bending

Mechanical measurements

Magnet supported by 8 tie-rods. Strain between 20 and 150 μm/m.Stable over the 20k cycles.

Mechanical measurements

Courtesy: Sergio dos Santos, Michael Guinchard, Giuseppe FoffanoEDMS 1173289

- Calculated deflection up to 0.8 mm at 6 kA- Measured strain on bending parts 70 μm/m- Strain about linear to I2

- Mechanics well-understood and far from its limits.

Calculated st

rain

75 – 105 μm/m

Conclusions and perspectives (1)

To the extent that we could probe the FCM magnet performance, the concept is suitable for a fast cycled injector magnet ! No issue of performance (we had 1 quench to nominal

field, and we think we understand why) Very stable operation beyond the performance envelope

(in 3 quenches, up to 50 % Lorentz force in excess of the design value, estimated > 0.5 mm coil movement)

20 kCycles close to nominal operation conditions, no spurious quenches, no observed degradation

Losses in the coil below measurable level of 4 W/m of magnet

Conclusions and perspectives (2)

The magnet is not yet optimized for magnetic field quality and the multipole b3 error is still too high.

The mechanics of the magnet are as designed.

Nb-TiNuclotron

Invited talk 2OrBB-01by D.C. van der Laan, High-temperature superconducting Conductor on Round Core magnet cables operated at high current ramp rates in background fields of up to 19 T

ReBCOCORC

HTS may be feasible?

Thank you! Project follow-up

F. Borgnolutti (LBNL), L. Bottura

Concept and design B. Auchmann, G. Foffano, M. Karppinen, G. Kirby, R. Maccaferri, C.

Maglioni, V. Maire, V. Parma, T. Renaglia, G. de Rijk, L. Rossi, T. Salmi (LBNL), W. Scandale, D. Tommasini

Procurement and manufacturing A. Bonasia, M. Bruyas, S. Clement, W. Gaertner (BNG), R. Gauthier,

J.M Gomes de Faria, C. Lopez, L. Oberli, G. Sikler (BNG), the CERN Central Workshop

Instrumentation and tests M. Bajko, V. Datskov, G. Deferne, L. Fiscarelli, M. Gateau, M.

Guinchard, S. le Naour, G. Peiro, V. Roger, D. Richter, G. Willering

Backup slides

Strand and cablemixed matrix

Cu/CuMn/NbTi wire (ALSTOM)

Cu-Ni pipe Nb-Ti strands Ni-Cr wrap Glass-tape

CACC: Cable-around-conduit conductor (BNG-Zeitz)

Diameter (mm) 0.6

Twist pitch (mm) 10

Cu:CuMn:NbTi (-) 2.39:0.47:1

RRR (-) 110

Jc(5 T, 4.2 K) (A/mm2) 1875-2015

N-index (-) 10-25

Strands (-) 32

Twist pitch (mm) 86

ID (mm) 4

OD (mm) 7.74

Supercritical helium force-flow cooling

Magnet parameters