cooling and test of large diameter mgb2 based cryocooled ... · superconducting magnets design and...

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



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



WIC and Coil Test• WIC Test

• Coil Manufacture and Test



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



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



Coil Test ArrangementTest coil

Cold conduction

Ring – 10 K

Test Cryostat

6



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.



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



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



Inside of OSU Dewar

OSU

Constructed

YBCO Busbar



Closing up cryostat



Cool-Down

Tc = 39 K

Cool down

time = 28 h

T13 is at the coil center



NZP Measurements

Longitudinal and transverse NZP

determined by time of flight of heat

propagation



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.



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



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.



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.



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



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



Coil: Preparation for

MeasurementCoil was measured above helium gas,

OSU attached Cu rods to top flange for

temperature equilibration, instrumented

coil as at right



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



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.



Appendix

E-lense Coil run

showing Temp vs

time



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



NZP Instrumentation:V-taps


V23 0

V24/V25 3.3 Both V-wires soldered at same solder bead



V30//V31 14.5 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



NZP Instrumentation:

Thermocouples


T12 0.7

T13 - 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



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)



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

cooling and test of large diameter mgb2 based cryocooled ... · superconducting magnets design and...

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