Superconducting Solenoidsfor COMET

KEK Cryogenics Center, Osaka Univ. Kuno-san’s

Team,J-PARC MLF Muon Group

Layout of Beam Line Magnets

• Pion Capture– High Field– High Radiation

• Transport & Decay – Medium Field– Curved solenoid

• Experiment– Low Field– Large volume– Curved solenoid

Pion Capture Solenoid

Requirement• High Field

– More pion to capture– More (better) conductor– Larger stored energy

• High Radiation – High Power Beam– Heat Load– Radiation Damage

Big SC Solenoids in Real World

Heat Load~1WCost~1M$

Heat Load~10kWCost~100M$

MRI MagnetsField: 1~4TCooling: He Free?

Detector SolenoidsField: 1~4T (NbTi)Cooling: IndirectAl Stabilized CableWith Cooling pipes

Fusion (ITER CS model)Field: ~13T (Nb3Sn)Cooling: DirectCable in Conduit

Heat Load~100WCost~10M$

Technology ChoiceConductor Material

1. NbTi (~5T) choice for now 1. Well established2. Not Expensive

2. Nb3Sn or Nb3Al (~12T)1. Established for solenoids2. Expensive (x5:conductor, x2:assebly to NbTi)

3. High Tc (~20T??)1. Not established for high field magnets2. Very expensive

Technology ChoiceHeat Load

• 50GeV x 15A – Beam: 750kW– Coil: ~100W– Cable in Conduit?

• 8GeV x 7A

– Beam: 56kW– Coil: ~10W– Detector Solenoid

Mostly Common Feature

•Aluminum stabilized cable

•quench stability•quench protection•transparency

•Indirect cooling with cooling pipe

•2 phase forced flow•Thermo siphon

•Technology well established

•Many solenoids are in use•Familiar to people in high energy physics

•Good for field up to ~5T•4T already achieved

•Good Solution for near future plan

•With modest budget

Detector Solenoids

ATLAS MEC MEC

B0 [T] 2 5 6

Bpeak [T] 2.3 5.3 6.4

I [A] 7730 11100 6800

Coil Layer 1 2 4

Rinn [mm] 1250 500 500

Length [mm] 5300 1400 1400

Support-Cyl [mm] 12 10 10

Conductor Width [mm] 4.25 (4.5) 4.7 (5) 4.7 (5)

Hight [mm] 30 30 30

Jcond [A/mm2] 61 80 49

Strand Diameter [mm] 1.28 1.28

Number 32 32

Total CrossSection

41.1 41.1

NbTi/Cu/Al 1/1.1/5.0 1/1.1/5.0

JNbTi [A/mm2] 566 347

LoadLineRatio 0.63 0.71

Bc [T] 8.4 9.1

Jc [A/mm2] 889 476

General M [ton] 0.988 1.94

E [MJ] 12.26 19.3

E/M [kJ/kg] 12.5 9.9

σh [MPa] 93.8 83.2

σeq [MPa] 113 97.8

σeq/σ0.2 　 0.77 0.67

Capture Solenoid Design

5mm

30mm

Load Line (5-30-2Layers)

0

500

1000

1500

2000

2500

3000

0 1 2 3 4 5 6 7 8 9 10

B [T]

Jc [A/mm

2]

4.2K

5.0K

6.0K7.0K

6.08K

5.41K

Jc = -591*B+5854

Temperature Margin

Indirect cooling

Cooling path from conductor to cooling pipei.e. Temp. gradient

We choose 5T versionMore temp margin2 < 4 layer (transparency)Lower peak field

Quench Protection

0

5

10

15

0.1 1 10 100 1000 104

WASABESS

CMD-2

D0

ZEUS

VENUS

TOPAZ

CLEO-IIBABAR

CDF

BELLEDELPHI

ALEPHH1

SDC-proto

ATLAS-CS (2 T)

CMS (4 T)under construction

BessP-Proto

Stored energy (MJ)

BessP (1 .05T)

M-E conversion

QuenchStored energypartly extractedpartly into coil

To protect coilspread heat evenly

Still there are limitParameter to lookStored Energy toCoil Mass Ratio

Yield Strength VS RRR

0

50

100

150

200

0 500 1000 1500 2000

Residual Resistivity Ratio

Ni 20000-ppm

Zn 200-ppm

Ni 1000-ppm

(20%)

(20%)

(20%)

(0 %)

(0 %) (0 %)

(+)

Cu

Good RRR: for quench stability and protection

High Yield Strength: for high EM force

High Yield Strength Al stabilized Conductor R&D

• For High Energy Physics– Higher Field ：　 > 5 Tesla– Larger Size ：　 Diameter 〜 10m

• Combination of Various Technology

– ATLAS Al Ni Alloy• Ni-0.5 ~ 1 %

– CMS-Hybrid Support • A6058 -->> A7020

Y.S.(0.2%) = 400 MPaRRR = ~ 400

13

An R&D Work using ATLAS-CS Conductor + A6061-T6

• T.S. is > 50 % reinforced with A6061using Electron Beam, and Laser Beam Welding

• LBW may be a potential technology EBW, LBW

Laser Beam Welding

Refrigerator

• Cryocoolers (GM or pulse tube) may not be strong enough

• Maybe Helium refrigerator plant needed

Guideline for magnet design

• Optimize the magnetic field design below 6 T – As base-line, using NbTi superconductor

• (with a future option for > 10 T Nb3Sn, Nb3Al magnet for the pion capture solenoid)

• Apply “thin solenoid” design concept with Al-stabilized superconductor and indirect-cooling to– Minimize radiation heating, – Refer technology established at,

• ATLAS, BESS, and CMS Solenoid

Toward Higher Field

• Al-stabilized Nb3Sn/Nb3Al Solenoid beyond 10 T

• An R&D may be proposed in cooperation with NIFS.

Toward Higher Beam Power

• Cable in conduit– Removal of large heat load– ITER CSExperiencedby modelNb3Sn ready

Up to 13 T

Can be idealIf affordable…ITER CS: 170M€

Capture SolenoidSummary & Issues

• For Pion Capture Solenoid for J-PARC– Detector Solenoid Technologies can be good solution

• Field ~5T, Heat Load ~10W (Beam Power ~56kW)

– More advanced technologies are also available• with some more money…

• Issues– High Radiation Doze

• Insulation material: Organic < 107 Gy

– High Neutron Fluence• Al and Cu: Resistivity change• Superconductor: Jc change

What about others

• Pion Capture– High Field– High Radiation

• Transport & Decay – Medium Field– Curved solenoid

• Experiment– Low Field– Large volume– Curved solenoid

Transport solenoid• COMET is not the only project

needing muon transport solenoid• Even in J-PARC there is a similar

curved solenoid needed– J-PARC MLF muon beam line– Lot of similarity in spec– Joint R&D

• Osaka Univ• KEK muon group• KEK cryogenics center

J-PARC Muon Beam Line

• Field; ~2T• Aparture; ~0.4 m

• Limited Access to shielded area– Refrigerator must be

outside of shield– Limited Space for the

refrigerators– Long distance to cold

head to coil front– Conduction Cooling with

Higher Temperature

Trial Winding of Curved Section with MgB2 conductor

• Purchase two kinds of MgB2 conductor from Columbus SC– 1 is the 1.13 mm diameter round wire

• Will be wound by a company

– 2 is the 1.5 * 2.5 mm square wire• Will be wound by Nakahara and Adachi at KEK

• They will be wound this winter and Tested in next spring

R&D Coil made at KEK in houseNbTiAlready woundTest just started

R&D on Transport SCSolenoid Coil by company

will be wound till Mar.

R&D on trim dipole coil

Trial Winding of Curved Section with MgB2 conductor

• Purchase two kinds of MgB2 conductor from Columbus SC– 1 is the 1.13 mm diameter round wire

• Will be wound by a company

– 2 is the 1.5 * 2.5 mm square wire• Will be wound by Nakahara and Adachi at KEK

• They will be wound this winter and Tested in next spring

MgB2 conductor actually purchasing

Monel 400 sheathed

Diameter: 1.13mmComposition MgB2 (Vol %) 14.6Fe (Vol %) 10.8Cu (Vol %) 13.8Ni (Vol %) 15.8Monel 400 (Vol %) 45.0

Monel 400 sheathed

Diameter: 1.13mmComposition MgB2 (Vol %) 14.6Fe (Vol %) 10.8Cu (Vol %) 13.8Ni (Vol %) 15.8Monel 400 (Vol %) 45.0

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8

0

50

100

150

200

250

300

350

400

Crit

ical

cur

rent

(A

)

Magnetic field (T)

16 K 20 K 24 K 30 K

Cost: 3€/m There is also 1.5 mm * 2.5 mm conductor

Themal Conductivity and Specific Heat of Cu and Al

89

100

2

3

4

5

6

789

1000

2

3

4

5

6

7

Thermal Conductivity (J/m2/K)

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100T (K)

103

104

105

106

Specific Heat Capacity (J/K/m3)

Cu (RRR:50) Cu (RRR:100) Cu (RRR:200) Al (RRR:200) Al (RRR:500) Al (RRR:1000) Cu Al

NbTi MgB2

Thermal Conductivity: ~ 3 times betterCp: about 10 times larger

Refrigerator Performance

• Refrigerator Efficiency– Improve significantly at higher

temperature

7.2 kW

Transport SolenoidSummary

• MgB2 can be a good candidate– Operation Temperature 10~20 K– Better Refrigerator Performance– Best Thermal Conductivity– Better Specific Heat– Good Cost saving solution