Download - CERN Fast Cycled Magnet demonstrator: test station, instrumentation and measurement campaign
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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
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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
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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
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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
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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
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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
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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
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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)
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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
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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
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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
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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
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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
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Quench propagation velocity
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5
10
15
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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.
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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 !
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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 !
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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
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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
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-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
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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
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Mechanics
8 Tie rods, equipped with strain gauges
8 strain gauges measuring the bending
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Mechanical measurements
Magnet supported by 8 tie-rods. Strain between 20 and 150 μm/m.Stable over the 20k cycles.
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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
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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
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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?
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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
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Backup slides
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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
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Magnet parameters