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Department of Materials
Science and Engineering
Cooling and Test of Large Diameter MgB2-
based Cryocooled Coils for MRI and
Nuclear Physics Applications
M.D. Sumption, M. Majoros, Y Yang, M. Susner, C.
Myers, C. Kovacs, E.W. Collings
Center for Superconducting and Magnetic Materials, MSE, The
Ohio State University
M. A. Rindfleisch, X. Peng, M. J. Tomsic, C. J. Thong, D. Doll,
HyperTech Research
Funded by a the state of
Ohio, NIH, commercial
sources, and a DOE SBIR
Department of Materials
Science and Engineering
Outline of Present Work
1. Wire-In-channel Development and NZP
Estimation – MgB2
2. 100 m length of MgB2 instrumented
(MRI-like Coil Winding, but one layer)
for Thermal, Ic, and NZP measurement
3. Developments in persistent joints
4. E-lenz Coil, HTR, BNL
Department of Materials
Science and Engineering
WIC and Coil Test• WIC Test
• Coil Manufacture and Test
Department of Materials
Science and Engineering
WIC NZP and Quench (gas cool)
25
30
35
40
45
50
55
60
65
0
5
10
15
0 20 40 60 80 100 120
WIC-20
T_1 (K)T_2 (K)T_3 (K)T_4 (K)T_5 (K)
Heater power (W)
T (
K)
Hea
ter p
ow
er (W
)
Time (s)
I = 175 A
Deposited energy = 210/2 Joule
I/Ic = 0.515
20
40
60
80
100
120
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70
WIC-29
T_1 (K)T_2 (K)T_3 (K)T_4 (K)T_5 (K)
Heater power (W)
T (
K)
Hea
ter p
ow
er (W
)
Time (s)
I = 275 A
Deposited energy = 44.8/2 Joule
I/Ic = 0.809
QUENCH
NZP: 0.5-1 cm/s
Department of Materials
Science and Engineering
MgB2 Coil, 100 m of WIC MgB2 Conductor
HTR: MgB2
strand, Wire-in-
channel
Conductor
HTR: Coil wound,
coil epoxy
impregnated by
HTR
OSU: Coil
Instrumented
with 30+ voltage
taps, 18+
thermocouples, ,
other sensors
OSU: Cool down
and Test
Department of Materials
Science and Engineering
Coil Test ArrangementTest coil
Cold conduction
Ring – 10 K
Test Cryostat
6
Department of Materials
Science and Engineering
V-Tap wires run along coil
turns, then twisted off as
V-tap pair to minimize
inductive signal
InstrumentationV-tap wires: (MWS) 30HPN-155, insulated
copper wire.
Thermocouples: (Omega) 5LRTC-KK-E-24-48,
Type-E.
Heaters: (Birk) BK3542, Kapton-insulated
Nichrome heater. The heater active areas
were double the width of the WIC so they
were folded over.
Department of Materials
Science and Engineering
NZP Instrumentation: V-taps, T, Heaters
V1 V2/V3 V4/V5 V6/V7 V8/V9 V10/V11 V12/V13 V14/V15 V16/V17 V18/V19 V20/V21 V22
T1 T2 T3 T4 T5T6 T7 T8 T9 T10 T11
Located between V11 & V12
T12
T13
T14
T15 T16 T17 T18 T19 T20 T21 T22 T23 T24
T25
T26
V23 V24/25 V26/27 V28/29 V30/31 V32/33 V34/35 V36/37 V38/39 V40/41 V42/43 V44
A1 A2
A3 A4
A5 A6
A7 A8
H1 H2
A1-8 V-taps & T13,14,25,26 TCs
are on the nearest neighbor
turns to witness possibility of
transverse NZP
V23 is 47.272
meters from the
edge of CT1 going
towards the
winding
CT2CT1
CT2CT1
Department of Materials
Science and Engineering
Test Bed
Xfrm
(2 kA)
Cryostat
2ft x 4 ft
Coil
63 KVA
PS
OSU Coil Test Bed – Test of Coil
• Cryocooled Test Bed
capable of cooling coil
4’ OD by 2’ high to 4 K
• Two Sumitomo
Cryocoolers
• 700 A Current lead DC
• Labview controlled DC
or AC
• Coil being tested with active protection circuits on 10 segments
• Possible to use voltage control
Department of Materials
Science and Engineering
Inside of OSU Dewar
OSU
Constructed
YBCO Busbar
Department of Materials
Science and Engineering
Closing up cryostat
Department of Materials
Science and Engineering
Cool-Down
Tc = 39 K
Cool down
time = 28 h
T13 is at the coil center
Department of Materials
Science and Engineering
NZP Measurements
Longitudinal and transverse NZP
determined by time of flight of heat
propagation
Department of Materials
Science and Engineering
Measured and Estimated
Longitudinal NZPAdiabatic Model
Vnzp = normal zone
propagation velocity, here
along the conductor
Jm, ρm, κm = current
density, resistivity, and
thermal conductivity in the
channel/stabilizer,
respectively
Tcs = T current sharing
Top = T operation
Ccd = specific heat of the
total composite
Measurements-Theory agree
well for conduction cooled
coil
Theory > measurement for
helium gas flow cooled WIC
Y. Iwasa, Case Studies in
Superconducting Magnets Design
and Operational Issues, Second
Edition, Springer,2009.
Department of Materials
Science and Engineering
Measured and Estimated
Transverse NZPAdiabatic Model
VT-T,nzp = normal zone
propagation velocity, here
turn-to-turn
VL,nzp = normal zone
propagation velocity, along
conductor
δcd = length of composite
path (conductor width)
δI = insulation path (2 x
insulation thickness)
κi, κm = thermal conductivity
in the insulation and
channel/stabilizer,
respectively
Theory ≈ 1/2 x Measured value
Vt-t,NZP about an order of magnitude slower than along the conductor
Department of Materials
Science and Engineering
Measured and Estimated MQE
For our conditions,
MPZ = 15 cm
This leads to MQE =
0.5 J
CCA WIC = 3.45 mm2,
CCA strand = 0.75 mm2
sharing energy evenly
MQEstrand = 0.22MQEWIC
MQEstrand = 200 mJ
• Theory ≈ 1/2 x Measured value for
conduction cooled coil
• Value for WIC much higher because
of flowing He gas coolingVan Weeren, Magnesium Diboride
Superconductors for Magnet Applications,
PhD Thesis, the University of Twente, 2007.
Department of Materials
Science and Engineering
Time to reach RT(assuming
current is kept on)
Acd= cross sectional area
comp
Am=cross sectional area WIC
Ccd = specific heat, comp
Jcm=current in the WIC
Iop=Operating current
Ti = initial T
Tf = final T
ρm = matrix resistivity
Y. Iwasa, Case Studies in
Superconducting Magnets Design
and Operational Issues, Second
Edition, Springer,2009.
Department of Materials
Science and Engineering
Development of Persistent JointsTwo styles of joints
1. Superconducting
solder type
2. Direct MgB2-MgB2
In both cases, used
already reacted wire
Preliminary testing
to date using direct
I-V, R < 10-10 Ω
Decay Testing rig
and samples in
preparation for
increased R
sensitivity and decay
test
Working now to improve performance
and measure to high sensitivity
Superconducting
Solder Type 4 K
MgB2-MgB2Type 4 K
Department of Materials
Science and Engineering
MgB2 based Coil Development for
E-Lenz, Hyper Tech and BNL
From R. Gupta
BNL
Transition from Cu to MgB2 saves
space, power
Would operate at 20 K, He gas
Target field 0.7 – 1 T
Department of Materials
Science and Engineering
Coil: Preparation for
MeasurementCoil was measured above helium gas,
OSU attached Cu rods to top flange for
temperature equilibration, instrumented
coil as at right
Department of Materials
Science and Engineering
ResultsI
c(20 K) = 86 A
Bmax
= 0.7 T
∆T (top-bottom) = 0.01 K
Coil has n-type transition
Inner, high field portion dictates transition
Department of Materials
Science and Engineering
Summary• An MgB2 based wire-in-channel (WIC) has been developed,
and quench properties have been evaluated
• A single layer coil has been wound with React and Wind
MgB2 WIC conductor
• The Coil has been cooled in conducting mode to 10K
• NZP and MQE have been measured at 20 K, compared to
the WIC, and to model/theory [MQE 0.5J, long nzp = 5
cm,/s, turn-to-turn 0.3 cm/s]
• Initial Results on Persistent joints shown
• An MgB2 based Wind and React Solenoid coil for E-lens
application has been made and tested at 20 K in helium
gas -- hit targets (Bmax = 0.7 T/20 K), had an Ic = 86 A, and
had an n-like transition in the high field region.
Department of Materials
Science and Engineering
Appendix
E-lense Coil run
showing Temp vs
time
Department of Materials
Science and Engineering
NZP Instrumentation: Heaters
Name Distance from V23 (cm) Description
H1 0.7 Measured from center of active area
H2 38.1 Measured from center of active area
CT2CT1T12
T13
T14
T15 T16 T17 T18 T19 T20 T21 T22 T23 T24
T25
T26
V23 V24/25 V26/27 V28/29 V30/31 V32/33 V34/35 V36/37 V38/39 V40/41 V42/43 V44
A1 A2
A3 A4
A5 A6
A7 A8
H1 H2
V23 is 47.272 meters from the
edge of CT1 going towards the
winding
6mm
6mm
Folded in half 3mm
6mm
Making Kapton-insulated nichrome heater correct width
= Active Area
Note: the closest distance
of the active areas of the
heaters H1 to H2 is 36.8cm.
The “true” active width (the nichrome wire) was 4.49mm and ~2.3mm after folding
Department of Materials
Science and Engineering
NZP Instrumentation:V-taps
Name Distance from V23 (cm) Description
V23 0
V24/V25 3.3 Both V-wires soldered at same solder bead
V26/V27 8.5 Both V-wires soldered at same solder bead
V28/V29 9.5 Both V-wires soldered at same solder bead
V30//V31 14.5 Both V-wires soldered at same solder bead
V32//V33 15.3 Both V-wires soldered at same solder bead
V34/V35 25.1 Both V-wires soldered at same solder bead
V36//V37 26.1 Both V-wires soldered at same solder bead
V38//V39 30.5 Both V-wires soldered at same solder bead
V40//V41 31.5 Both V-wires soldered at same solder bead
V42//V43 37.5 Both V-wires soldered at same solder bead
V44 41.2
CT2CT1
Note: V23 & V24 are a
voltage tap pair (shown
by twisted wires). V24/25
only refers to the fact that
both of these wires are
soldered to the sample at
the same location
T12
T13
T14
T15 T16 T17 T18 T19 T20 T21 T22 T23 T24
T25
T26
V23 V24/25 V26/27 V28/29 V30/31 V32/33 V34/35 V36/37 V38/39 V40/41 V42/43 V44
A1 A2
A3 A4
A5 A6
A7 A8
H1 H2
Note: A1-8 voltage taps are
shown in another NZP
instrumentation diagram
V23 is 47.272 meters from the
edge of CT1 going towards the
winding
Department of Materials
Science and Engineering
NZP Instrumentation:
Thermocouples
Name Distance from V23 (cm) Description
T12 0.7
T13 - Shown in other diagram
T14 - Shown in other diagram
T15 5.9 Shorted to sample (unusable)
T16 9
T17 12
T18 14.9
T19 20.2
T20 25.6
T21 28.3
T22 31
T23 34.5
T24 38.1
T25 - Shown in other diagram
T26 - Shown in other diagram
CT2CT1T12
T13
T14
T15 T16 T17 T18 T19 T20 T21 T22 T23 T24
T25
T26
V23 V24/25 V26/27 V28/29 V30/31 V32/33 V34/35 V36/37 V38/39 V40/41 V42/43 V44
A1 A2
A3 A4
A5 A6
A7 A8
H1 H2
Note: T13,14,25,26
thermocouples are shown
in another NZP
instrumentation diagram
TC-bead
(uninsulated)
Gently scraped
away WIC
insulation
GE-varnish and
thin cigarette
paper insulation
(1.27 µm thick)
Department of Materials
Science and Engineering
NZP Instrumentation: Neighboring
Strands
CT2CT1
T12
T13
T14
T15 T16 T17 T18 T19 T20 T21 T22 T23 T24
T25
T26
V23 V24/25 V26/27 V28/29 V30/31 V32/33 V34/35 V36/37 V38/39 V40/41 V42/43 V44
A1 A2
A3 A4
A5 A6
A7 A8
H1 H2
Name Longitudinal Distance
from V23 (cm)
Description
A1 -3.05
A2 4.45
A3 -3.05
A4 4.45
A5 34.35
A6 41.85
A7 34.35
A8 41.85
T13 0.7
T14 0.7
T25 38.1
T26 38.1
Transverse distance of the
neighboring taps/TCs to the
center of the main strand is
~2.4mm