Alexander Zlobin US Magnet Development Program

Fermi National Accelerator Laboratory

Assembly and First Test of the US-MDP

Nb3Sn Dipole Demonstrator (MDPCT1)

June 27, 2019

Acknowledgment

FNAL: I. Novitski, E. Barzi, J. Carmichael, G. Chlachidze, J. DiMarco, V.V.

Kashikhin, S. Krave, C. Orozco, S. Stoynev, T. Strauss, M. Tartaglia, D. Turrioni,

G. Velev, A. Rusy, S. Jonhson, J. Karambis, J. McQueary, L. Ruiz, E. Garcia

LBNL: S. Caspi, M. Juchno, M. Martchevskii

CERN: D. Schoerling, D. Tommasini

FEAC/UPATRAS: C. Kokkinos

US-MDP: G6 and TAC

This work was supported by Fermi Research Alliance, LLC, under contract No.

DE-AC02-07CH11359 with the U.S. Department of Energy and the US-MDP.

2

Program goals

• Demonstration of 15 T field level

o Record Nb3Sn dipole magnets:

• D20 (LBNL, 1997): Bmax=13.5 T @1.9K, 12.8 T @4.4K

• HD2 (LBNL, 2008): Bmax=13.8 T @4.5K

• FRESCA2 (CERN, 2018): Bmax=14.6 T @1.9K, 13.9 T @4.5K

• Study and optimization of

o magnet quench performance and mechanics

o quench protection

o field quality

• The development and test of the 15 T dipole demonstrator

is a key milestone of the US Magnet Development Program

o coordinated with EuroCirCol program and supported by CERN

3

15 T Dipole design

4

Innovative mechanical

structure (I. Novitski et al.): • Thin StSt coil-yoke spacer

• Vertically split iron laminations

• Aluminum I-clamps

• 12-mm thick StSt skin

• Thick end plates and StSt rods

• Cold mass OD<610 mm

Cable (E. Barzi et al.): • L1-L2: 28 strands, 1 mm RRP150/169

• L3-L4: 40 strands, 0.7 mm RRP108/127

• 0.025 mm x 11 mm SS core

• Insulation: E-glass tape

RRP-108/127

0.7 mm

RRP-150/169

1 mm

26

18

33 32

Coil (V.V. Kashikhin et al.):

• 60-mm aperture, 4-layer graded coil

• Wsc = 68 kg/m/aperture

Magnet conductor limit

5

15.0

15.5

16.0

16.5

17.0

17.5

18.0

2500 2750 3000 3250 3500 3750 4000

Bo

re f

ield

(T

)

Jc(12T, 4.2K) (A/mm2)

4.2 K

1.9 K

10% margin

Jc(12T,4.5K)~2600 A /mm2

Magnet conductor limit for the wire Jc(12T,4.2K)~2.65 kA/mm2

• Bap=15.3T @4.5K

• Bap=16.7T @1.9K

Courtesy V.V. Kashikhin

Magnet mechanical limit

• Magnet design limit is determined by the coil

maximum stress and the pole turn separation

from poles

o independent FNAL and FEAC analysis

Mechanical limit for this design is 15 T!

6

300K

Seqv=133 MPa

Limit 150 MPa

4K

Seqv=176 Mpa

Limit 200 MPa

4K+15T

Seqv=168 Mpa

Limit 200 MPa

Courtesy I. Novitski

TAC recommendations

TAC members:

• Andy Lankford (UCI, Chair), Giorgio Apollinari (Fermilab), Joe Minervini (MIT),

Mark Palmer (BNL), Davide Tommasini (CERN), Akira Yamamoto (KEK & CERN)

Report of the Technical Advisory Committee for the U.S. Magnet

Development Program

February 22, 2019

Recommendations:

• Maintain as the priority for the cos-theta approach using the clamped

mechanical structural design to realize a field of about 14 T, with special

attention to mechanical stress management and control.

• Continue with demonstration of 15 T cos-theta performance only after the

review of the 14 T magnet test results and feedback from the international

workshop.

7

Target coil prestress for the first assembly

8

4K+14T

Seqv=138MPa

300K

Seqv=68MPa

4K+13T

Inner Pole at 13T

Gap=0.003mm

Seqv=117MPa Seqv=143MPa

Inner Pole at 14T

Gap=0.037mm

Conservative pre-stress:

• Smax at all steps <150 MPa

Courtesy I. Novitski

9

Coil winding and

curing using ceramic

binder

Coil lead splicing and

epoxy impregnation

Coil reaction Coil instrumentation

Coil fabrication process Coil fabrication, measurements and

instrumentation

Coil size control,

accuracy ~10 microns

• Coil fabrication, measurement and instrumentation

time ~3 months • IL spare coil was wound, reacted and impregnated

• OL spare coil – the cable and coil parts are available

Witness sample data

10

• HT cycle optimized for the 28-starnd and 40-strand cable

• Witness sample data are close to the target Ic

• Good reproducibility of witness sample data for IL and OL coils

• Magnet short sample limit: 15.16 T @4.5K and 16.84 T @1.9K

Average = 601 A

Average = 583 A Average =

584 A

100

200

300

400

500

600

700

0 2 4 6 8 10 12 14 16

Cu

rre

nt,

A

Test number

Ic @ 15 T

CL1_002

CL1_003

CL1_004

IL coils

Average = 266 A

Average = 256 A

Average= 258 A

100

120

140

160

180

200

220

240

260

280

300

0 2 4 6 8 10 12 14 16 18 20 22 24

Cu

rre

nt,

A

Test number

Ic @ 15 T

CL2_002

CL2_004

CL2_005

OL coils

Courtesy E. Barzi and D. Turrioni

Coil interfaces analysis and optimization

11

HFM-CL1-002 230mm from RE

HFM-CL1-003 230mm from RE

Coil SS 230

L2 OD by 80

mic smaller

L2 OD by

96 mic

smaller HFM-CL2-004 201mm from RE

HFM-CL2-005 218mm from RE

L3 ID by 88

mic smaller

L4 OD by

80 mic

smaller

L4 OD by 187

mic smaller

Coil assembly and preload scheme

12

Yoke-Skin

Rad

interference

d Skin

Clamp-Yoke

interference

Mid-Plane shims

Shell-Yoke Rad

interference

Clamp-Skin Rad

interference

Coil-Coil Rad

interference

Yoke-Yoke

gap taper

Filler-Yoke

interference

Coil assembly, yoking and skinning

13

Magnet transportation and test preparation

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Instrumentation

• Voltage taps on all coil layers

o one dead and one inactive (both by-passed

by using longer segments)

• Strain Gauges

o skin gauges: OK

o bullet gauges: two (on different bullets) dead

o pole gauges: layer 3 and 4 all gone or

inactive, layer 1 are OK

o coil gauges: one switched off (problems

during ramp up), another off for technical

reasons (could be recovered if needed)

• Quench antennas

o only sensitive to quenches in Layer 1 (didn’t

happen yet)

• Acoustic sensors

o not useful data (very noisy signal)

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Magnet training

• Only 2 quenches in IL coil 2

• No quenches in coil 3

• OL quenches are equally distributed between coil 4 and coil 5

• Quenches are in both layers 3 and 4 mostly in the LE

• Highest achieved quench current 9758 A at 4.5 K

• Magnet quenching was stopped to avoid coil damage

16

Courtesy S. Stoynev

Magnetic field measurements

17

1.40

1.42

1.44

1.46

1.48

1.50

-0.3 -0.2 -0.1 0 0.1 0.2 0.3

TF

(9kA

) (T

/kA

)

Z (m)

1.460

1.462

1.464

1.466

1.468

1.470

1.472

1.474

1.476

-0.3 -0.2 -0.1 0 0.1 0.2 0.3

TF

(9kA

) (T

/kA

)

Z (m)

130 mm probe

26 mm probe

0

2

4

6

8

10

12

14

16

0 2000 4000 6000 8000 10000

B0 (

T)

Magnet current (A)

130 mm probe

26 mm probe

Courtesy J. DiMarco and T. Strauss

1.40

1.50

1.60

1.70

1.80

1.90

0 2000 4000 6000 8000 10000

TF

(T

/kA

)

Magnet current (A)

Low-order field harmonics

• Good correlation of measurements

with theoretical predictions

18

-60

-40

-20

0

20

40

60

80

0 2000 4000 6000 8000 10000

b3 (

un

its)

Magnet current (A)

-10

-5

0

5

10

15

20

0 2000 4000 6000 8000 10000

b5 (

un

its)

Magnet current (A)

-50

-40

-30

-20

-10

0

10

0 2 4 6 8 10 12 14 16b

n (

10

-4)

Bore field (T)

b3

b5

V.V. Kashikhin and A.V. Zlobin, NAPAC2016

TF analysis

• 2D analysis has been updated based

on the actual yoke material properties

and the final magnet geometry

• 3D calculations are in progress

• Measurements have been verified

with NMR probes (provided by GMW)

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Courtesy I. Novitski Courtesy V.V. Kashikhin

Courtesy M. Tartaglia

Maximum field achieved

• First quenches above 11 T

• Maximum bore field at 4.5 K

o measured 14.10±0.04 T

o calculated (COMSOL, V.V. Kashikhin) 14.112 T

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Summary and next steps

• 15 T cos-theta dipole is a challenging and important MDP milestone to

understand limits of Nb3Sn accelerator magnet technology

• integrated international effort with EuroCirCol

• 1-m long 15 T dipole model (MDPCT1) has been developed, fabricated

and first tested at Fermilab (June 2019)

• The goals of the first test have been achieved

o Bmax = 14.10±0.04 T at 1.9 and 4.5 K – record field at 4.5 K for accelerator

magnets!

o graded 4-layer coil design, innovative support structure and magnet

fabricated procedure tested

• Next steps

o Magnet re-assembly

• coil pre-load increase to the level sufficient to achieve the goal of 15 T

• improve instrumentation

o Magnet second test in the fall of 2019

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