IR Magnets for Super KEKB
Norihito Ohuchi, Masafumi Tawada, Kiyosumi Tsuchiya,
Norio Higashi, Zong Zhanguo

2010/2/15

15th KEKB Accelerator Review Commitee1

Contents
1. Configuration of IR magnet system
2. Design of IR magnets– SC magnets [QC1, QC2, correctors]– Permanent magnets [QC2]– SC compensation solenoids

3. R&D and progress
4. Construction schedule of IR magnets

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15th KEKB Accelerator Review Commitee2

Configuration of IR magnet system

HER
LER

5 SC main qadrupoles (QC1RP, QC1RE, QC2RP, QC1LP, QC1LE)
3 permanent quadrupoles (QC2RE, QC2LP, QC2LE)
2 SC compensation solenoids
32 SC correction coils
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15th KEKB Accelerator Review Commitee

3IR magnets
QC1LP(Superconducting)
QC2LP(Permanent)

QC1RE(Superconducting)

QC2RE(Permanent)

QC1RP(Superconducting)

BPM & V.P.

BPM & V.P.

QC2LE(Permanent)

QC1LE(Superconducting)
QC2RP(Superconducting)Integral field gradient, (T/m)・m

Position from IP, mm

Magnet type

QC2RE

12.91

2925.0

Permanent

QC2RP

10.92

1936.1

S.C.

QC1RE

26.22

1376.0

S.C.

QC1RP

22.43

908.1

S.C.

QC1LP

22.91

‐922.1

S.C.

QC1LE

26.03

‐1461.0

S.C.

QC2LP

10.96

‐1977.1

Permanent

QC2LE

14.13

‐2900.0

Permanent

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Design of IR SC magnets (QC1P)

e‐e+Magnet design (QC1RP and QC1LP)
Same design of the cross section for QC1RP and QC1LP
2 layer coils [double pancake type]
Designed SC cable [under development]
Cable size : 2.5 mm in height, and 0.93 mm in width

SC cancel correctors against the leak field from QC1Pb3, b2, b1 from the inside

Beam pipe : warm tube , inner radius=10 mm

SC strand cable : φ 0.5 mm, 10 wires in the cable

SC correctors inside of the magnet boreb4, a2, b1, a1 from the inside
Single layer coilBeam pipe : warm tube, inner radius=10 mm
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Design parameters of QC1RP and QC1LP
QC1RP

QC1LP

Coil inner radius, mm

22.00

Coil outer radius, mm

27.55

Turns in one pole

11 (1st layer), 12 (2nd layer)

Spec. of integral field, T

22.43

22.91

Field gradient, T/m

75.61

62.00

Effective magnetic length, m0.2967

0.3695Magnet current, A

1510.71232.3Current density of the cable (SC area), A/mm2

1615.81326.2Magnetic field by Belle and comp. sol., T

1.2

3.0

Max. field in the coil without solenoid field, T

2.24

1.84

Max. field in the coil with solenoid field, T

2.70

3.98

Operating point with respect to Bc at 4.4 K

66%

80%

Error field at 1 cm (2D calculation)b6 = ‐1.04 × 10‐4
b10 = ‐1.60 × 10‐4
b14 = 4.31 × 10‐6

2010/2/15

15th KEKB Accelerator Review Commitee6SC correctors on the inner bores of the QC1RP and QC1LPb4a2

b1a1

Coil inner radius, mm

19.2

19.8

20.4

21.0

Coil outer radius, mm

19.8

20.4

21.0

21.6

Turns on one pole

71430

30

Design current, A50505050

6438 T/m3

2.298 T/m

0.048 T

0.047 T

Bias magnetic field by all magnets for QC1RP, T

2.20

2.29

2.34

2.39

Operating point with respect to Jc at 4.4 K< 30 %< 30 %< 30 %< 30 %

NA± 15.3 mrad

± 0.64 mm± 0.62 mm

Magnetic field at R=1cm

Capacity for magnetic alignment for QC1RP at R= 1 cmOperating points ofSC correctors

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Cancel correctors for the leak field of QC1RP and QC1LPThe SC quadrupoles are designed not to have iron yokes since they are installed in the Belle solenoid field.
The leak magnetic fields of the main quadrupoles on the opposite beams are canceled with the SC correctors ofb1, b2 and b3.

••

Profile of the leak field of QC1RP on the e‐ beam line••

The magnetic fields at r=1cm of the e‐beam line are expanded by Fouriertransformation, and the leak fieldcomponents are studied.
The main components are B1, B2 and B3,and the leak field of QC1RP can becancelled with these correctors under thelevel of 10 gauss.

Position of Z=0 corresponds to the center of QC1RP.

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8Design of the cancel correctors
Typical coil shape of the correctors

Coil design••••

The wire positions in the coil ends aredesigned to have the field profile of theleak field of the quadrupoles.
2 layer coils [double pancake type]
No SC wire connection between the coils
Designed superconductor [wire]
Wire size : φ 0.4mm (bare)
φ 0.46mm (with insulation)
Cu ratio : 1.1

The field profiles of the By component of the leakfield and the dipole component by the corrector.
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9Design parameters of the correctors in the cross section for QC1RPb3

b2

b1

Coil inner radius, mm

19.5

20.5

21.5

Coil outer radius, mm

20.5

21.5

22.5

Turns on one pole

2234

72

Design current, A

50

5050

273.3 T/m2

5.10 T/m

0.108 T

1.2

1.2

1.2

< 30 %< 30 %< 30 %Magnetic field at R=1cm
Bias magnetic field by Belle and compensation
solenoids, T
Operating point with respect to Jc at 4.4 K

The quadrupole field by the b2 corrector can cancel this component in the leak field.
• This quadrupole field can be used as the defocusing field for the e‐ beam in the rightside of IP.
• In the left side, it can work as the focusing field.
• Integral field of B2 in the leak field = 0.98 (T/m)• m– Sum of the B2 fields in the leak field and by the corrector corresponds to 7.6% of
the field by QC1RE.

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10Design of QC1E

Magnet design (QC1RE and QC1LE)
Same design of the cross section for QC1RP and QC1LP
2 layer coils [double pancake type]
Designed SC cable : same as the QC1P
SC correctors inside of the magnet bore

SC cancel correctors against the leak field from QC1E
b3, b2, b1 from the inside
2 layer coils [double pancake type]

Beam pipe : warm tube , inner radius=15 mm

b4, a2, b1, a1 from the inside
2 layer coils [double pancake type]

Beam pipe : warm tube, inner radius=15 mm
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11Design parameters of QC1RE and QC1LEQC1RE

QC1LE

Coil inner radius, mm

28.25

Coil outer radius, mm

33.80

Turns in one pole

14 (1st layer), 15 (2nd layer)

Spec. of integral field, T

26.22

26.03

Field gradient, T/m

72.91

72.38

Effective magnetic length, m0.3596

0.3596

Magnet current, A

1814.61801.4Current density of the cable (SC area), A/mm2

1940.7

1926.6

Magnetic field by Belle and comp. sol., T

1.2

1.0

Max. field in the coil without solenoid field, T

2.89

2.87

Max. field in the coil with solenoid field, T

3.28

3.15

Operating point with respect to Bc at 4.4 K

76%

75%

Error field at 1 cm (2D calculation)b6 = 1.15 × 10‐4
b10 = ‐0.27 × 10‐4
b14 = 0.23 × 10‐6

2010/2/15

Load lines of QC1RE and QC1LE

15th KEKB Accelerator Review Commitee

12Design of IR permanent magnets(QC2RE, QC2LP, QC2LE)

QC2RE

QC2LP
QC2LE•
2010/2/15

QC2RE, QC2LP and QC2LE locate out of the inner area of Belle detector.
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13Magnet parameters of QC2RE, QC2LP and QC2LE
Int. field gradient,(T/m)m

Magnet length,mRequired fieldgradient, T/m

Beam pipe
outer radius, mField at coil inner radius,
T

QC2RE

12.91

0.6

21.52

0.04

0.86

QC2LP

10.96

0.45

24.36

0.035

0.85

QC2LE

14.13

1.0

14.13

0.04

0.57

•

Requirement of installation of BPMs and vacuum pumps as close to IP aspossible.
– BPMs and vacuum pump can be installed out of the cryostats.

•Small disturbance on the field profile of the solenoid fringe field••

Permanent magnet for QC2RE, QC2LP and QC2LE is considered.
The remnant field of Samarium‐cobalt (SmCo) is 1.04~1.12 T.
– This material is available for these permanent magnets.
– The corrector coils for these permanent magnets will be installed in case of insufficientfield stability due to temperature and radiation, and the necessity of the field change atenergy scan.

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Compensation solenoids, ESR and ESL•

Design of compensation solenoids––•The axes of the compensation solenoids consist with the Belle solenoid axis.
The solenoids encircle the QC1RP, QC1RE, QC1LP, a part of QC2RP and correctors.

From the recent beam simulation, the fringe fields by the compensation solenoids
increase the beam emittance.

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Proposed new compensation solenoids•

Design of compensation solenoids
–––

•
•

The solenoids are designed to be segmented into small coil pieces.
The coil pieces have decreased turns gradually along the distance from IP.
The electro‐magnetic forces on the ESR and ESL are 31.2 kN and ‐26.2 kN, respectively.

The field changes of the solenoid field are managed to be a half of the previous design.
The field profile will be included in the beam simulation and studied soon.
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R&D and progress
1. Small cross section SC cable for QC1
2. QC1RP R&D magnet
3. Permanent quadrupole development
4. Multi‐current leads for correctors–

One set of assembly of eight conductors for 4 correctors is designed andmanufactured. The cold test will be performed in April.

5. Power supply for IR magnets–––

2010/2/15

The power supply for the QC1 is now being constructed.
The target stability of the transport current is less than 20 ppm/24 hours.
The performance of the power supply with QC1RP R&D magnet will bemeasured in Dec. 2010.

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Small cross section SC cable for QC1•

STEP‐1– Construction of dummy cable with Cu strand [Flat Cable] : completed.
••

Strand dia.=0.5mm, cable size=2.5mm × 0.93mm, strand number=10, cable length=10m

STEP‐2a– R&D of SC cable with NbTi strand[Flat Cable] : now under development up to March 2010.
•••

Strand dia.=0.5mm, cable size=2.5mm × 0.93m, strand number=10, cable length=10m × 2Cu/SC ratio=2.0, Ic=125A at 6T and 4.2K, Insulation ①12.5μm(T) × 3mm(W) , ② 25.0μm(T) × 3mm(W)

STEP‐2b– R&D of SC cable with NbTi strand [keystoned cable] : R&D will start from April 2010.

•STEP‐3– Construction of the SC cable for QC1RP magnet : scheduled date of completion is September
2010.
•2010/2/15

Strand dia.=0.5mm, Cu/SC ratio=1.1, cable size=2.5mm × 0.93m, strand number=10, cable length=200m
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R&D of QC1RP
QC1RP R&D magnet construction drawings•••

The design of tools for the QC1RP R&D magnet is now completed.
Manufacturing the tools of the magnet will be completed in March 2010.
The SC corrector coils for QC1RP will be developed in the September 2010.
––2010/2/15

The superconducting wire for correctors has been already manufactured.
The cable diameter is 0.4 mm, and the Cu/SC ratio is 2.0.
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19Permanent magnet developmentMagnetic field, T

R=10mm

R=5mm

Azimuthal direction, degree•

The permanent R&D magnet was constructed.
––••

The material was SmCo [R26HS: Shin‐Etsu Chemical Co., Ltd.].
The magnetic field of the R&D magnet was measured.
––•The magnet was designed for QC1.
The length of the magnet is 50 mm.

The measured field gradient was 63.7 T/m.
The remnant field of the material was calculated to be 1.019 T at the coil inner radius of 16 mm.

The precise field measurement system of the harmonic coil and the position tuning
machine of the pieces of the permanent magnet will be prepared until this summer.
–
2010/2/15

Error field of this permanent magnet will be measured and improved by the system.
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Construction schedule of IR magnets

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