IR Magnets for SuperKEKB

KEK, Norihito Ohuchi

1. IR Magnets (ES, QCS, QC1)2. Interference between Magnet-Cryosta

ts and Belle3. Summary

SuperB.WS05.Hawaii

IR Magnets - Required IR magnets from beam optics

• Compensation solenoid (SC)– ESR and ESL, canceling the Belle solenoid field

• Final focus quadrupole (SC)– QCSR and QCSL for both beams, ∫G dl QCSR= 11.99 (T/m) m, ∫G dl QCSL= 14.33

• Special Quadrupole (NC or SC)– QC1RE, QC1LE for HER beam, ∫G dl QC1RE= 9.00, ∫G dl QC1LE= 9.92

• Special Quadrupole (NC)– QC2RE, QC2LE, QC2RP and QC2LP, ∫G dl QC2RE= 7.02, ∫G dl QC2LE= 6.80, ∫G dl QC2RP= 3.40, ∫G dl QC2LP= 4.02

SuperB.WS05.Hawaii

8 mrad

22 mrad

7 mrad

e-

e+

LER

HER

IP

ESR-2

QCSRESR-1

ESL-1

ESL-2

QCSL

QC1LE

QC1REQC2LP

QC2RP

QC2RE

QC2LE

Beam-pipe axis

Belle solenoid axis

0.0 5000.0-5000.0

IR Magnets - Spatial constraint for the design of the IR magnets

• Physical aperture of beams– Determined by the beta function at the components and the beam acceptance (of which main sources are linac

beam emittance and injection error).– Improvement of the beam acceptance by the damping ring for the positron beam.

• SR envelops from QCS magnets– The intensities of the SR power are 179 kW and 64.6 kW from QCSR and QCSL, respectively.

• The interference between the IR magnets and the detector components of Belle

SuperB.WS05.Hawaii

IP

LER

QCSRI

0

50

100

150

-50

-100

[mm]

QCSR-cryostat-bore

QC1R(SC)-cryostat-bore

QCSLA

QCSLC

QCSLI

QCSL-cryostat-bore

QC1L(SC)-cryostat-bore

0

50

100

150

-50

-100

[mm]

QCSRA

QCSRCHER

Belle boundary

0.0 4000.0-4000.0

beam physical aperture

SOR from the IP or arc sides of each QCS

deviation of SOR from the central route

IR Magnets - Configuration of QCS and ES magnets (in the right side)

• Compensation solenoid, ESR– ESR is separated into two coil, ESR-1 and ESR-2.– ESR-1 is placed in front of QCS-R, and ESR-2 is ov

erlaid on the outer surface of the QCS-R.– The E.M.F. on the ESR induced by the Belle field is

2.18104N.• Final focus quadrupole, QCS-R

– The magnet consists of six layer coils.– The operation field gradient is 40.124 T/m, and th

e effective magnetic length is 0.299 m.

SuperB.WS05.Hawaii

R 239

R 50

R 69R 90

R 85

R 219

R 209

R 194

R 186

e-

e+

QCSR

ESR

QCSR

ESR-1

ESR-2

1378.3

Magnet Operation Parameters under the Belle field of 1.5 T

ESR-1 ESR-2 QCS-R

Iop, A 647.2 647.2 1186.7

Bmax, T 2.76 2.61 4.99

Iop/Ic, % 63 60 75

Length, mm 100 1000 456

O.R., mm 95.5 173.8 116.8

IR Magnets - Configuration of QCS and ES magnets (in the left side)

• Compensation solenoid, ESL-1 and ESL-2– The E.M.F. on the ESL is 3.83104N.

• Final focus quadrupole, QCS-L– The magnet cross section is the same as the QCS-

R.– The operation field gradient is 40.124 T/m, and the

effective magnetic length is 0.357 m.

SuperB.WS05.Hawaii

Magnet Operation Parameters under 1.5 T

ESL-1

QCSL

ESL-2

1036.8

R 50

R 250R 230

R 197

R 90

R 116.1

47.8

QCSL

ESL

R 72

21.2

R 69

ESL-1 ESL-2 QCS-L

Iop, A 656.2 656.2 1186.7

Bmax, T 4.33 2.93 4.77

Iop/Ic, % 80 56 74

Length, mm 166 500 514

O.R., mm 94.6 183.6 116.8

IR Magnets - QCS and ES magnets with Belle detector

SuperB.WS05.Hawaii

IR Magnets - Bz field profile along the Belle axis

• The negative peaks are -3.62 T and -1.68 T in the left and the right side with respect to the IP, respectively.

• The regions, where the field gradients are large, are closer to the IP than KEKB.

SuperB.WS05.Hawaii

-5

-4

-3

-2

-1

0

1

2

-4 -3 -2 -1 0 1 2 3 4

Bz-profile.SBWS05Bz profile of SuperKEKB, TBz profile of KEKB, T

Bz, T

z, m

-3.62 T

-1.68 T

-4.40 T

-3.20 T

IR Magnets - Bz field profile in the Belle detector

• The Bz profile in the large volume of the Belle detector is almost same as that of KEKB.• In the area near the magnets and the IP, the profile shows a large difference from that of KEKB.

– In this area, the field mapping should be performed, again.

SuperB.WS05.Hawaii

ESR-2ESR-1ESL-1ESL-2

Belle Solenoid

Belle center

Bz profile from 1.2 T to 1.6 T in the Belle detector

IR Magnets - QC1-RE and QC-1LE (Super-conducting or Normal-conducting)

• Normal-conducting type– Cu hollow conductor– Trim and backleg coils for the field correction– Unwanted multipole fields at the fringes (Ex, skew octupole)

• Super-conducting type– Nb-Ti rectangular solid cable– Corrector coils same as the QCS magnets for final alignment– Cryostat inner bore works as the function of the beam pipe.

• Careful consideration for the cryostat dislocation induced by the beam pipe.

– An additional helium refrigerator is needed.– Careful consideration for magnet quench induced by beams sin

ce is maximum at QC1s.

SuperB.WS05.Hawaii

R 78.17

SC Coil

Iron Yoke

R 59.17

R 85.17

ø570Cryostat

ø420

Normal-conducting QC1-RE

Super-conducting QC1-RE

Normal Super

G, T/m 12.0 27.67

L, m 0.75 0.328

Iop, A 3700 539.4

Turns/pole 3 130

Magnet Parameters (QC-1RE)

IR Magnets - QC1-RE and QC1-LE (Super-conducting or Normal-conducting)

SuperB.WS05.Hawaii

Normal-conducting QC1-LE

Super-conducting QC1-LE

Normal Super

G, T/m 15.54 51.34

L, m 0.64 0.195

Iop, A 1300 419.9

Turns/pole 3 100

Magnet Parameters(QC1-LE)

R 26.39

R 32.9

R 34.89

ø300.0

R 17.4

Iron Yoke

SC Coil

ø420.0

Cryostat

Interference between Magnet-Cryostats and Belle - Cryostat design of QCS and ES

Requirement from the Belle group

– Redesigning cryostat configuration to reduce the Rad. Bhabha BG

pointed by M. Sallivan in 6th HLWS, 2004 reported by O. Tajima in this meeting Introducing the heavy metal (Tungsten alloy) a

s one of the magnet structural materials.

Necessary to modify the support system of the liquid helium vessel

– Increasing the space between the detector and the cryostat for wiring the cables

ESR and ESL solenoids were calculated again, and the fronts of the cryostats were re-designed.

The created space in radial direction :25 mm for ESR38 mm for ESL

QCS-CENTER

130 85

1163.3

QCSRESR-1

ESR-2

97W-4Ni-1Cu

SuperB.WS05.Hawaii

Interference between Magnet-Cryostats and Belle - Support design of QCS and ES

• Support system– The system consists of 8 rods (titanium alloy) for one cryostat.

• Change of the cryostat weight by the heavy metal– Right : 492 kg 608 kg– Left : 451 kg 596 kg

• Heat load via 8 rods < 4 W– Requirement from the cryogenic system

SuperB.WS05.Hawaii

Liquid Heliumvessel4.7 K

Vacuum vesselroom temp.

300 K

4.7 KEMF

W

Left Right

Rod diameter, mm 7 6

Rod length, mm 65 65

Calculated stress of rod, N/mm2 306 290

Allowable stress at R.T., N/mm2 400 400

Total heat load (eight rods), W 1.92 1.44

Interference between Magnet-Cryostats and Belle - Belle end-cap, QC1 and movable table for IR magnets

• QC1– The cryostat for the SC QC1 is slightly larger than the NC QC1.

• Transfer tube from the cryostat of ES and QCS– The outer diameter of transfer tube is modified from 216.3 mm (KEKB) to

114.3 mm.

• Movable table for the IR magnets– As the material of the table, the thickness of the SUS plate is assumed to be

40 mm as same as that of KEKB.

SuperB.WS05.Hawaii

Accelerator components around the Belle end-cap iron yoke

ø42.7

ø39.4

ø114.3

ø48.6

ø45.3

ø60.5

ø8

ø76.3

ø72.1

Cryogenic transfer tube

Summary The 3-D field calculations of the QCS and ES magnets have been completed.

These magnets have sufficient operation margin for the Super-KEKB.

The field profile in the Belle was calculated for the modified model of the ES magnets. This profile around the IP and the cryostats should be checked by the Belle group.

QC1 magnets in the normal-conducting and super-conducting types are designed and compared. We should do the further study for both magnets, ex., 3-D field calculation, effect of

the field profile on the beam optics and handling in the actual operation.

For shielding the Rad. Bhabha BG, application of the heavy metal was studied as the material of the magnet components in the cryostat. The heavy metal does not have a large effect on the cryogenic design at LHe temperature.

The interference between the Belle end-cap iron yoke, cryogenic transfer tube and QC1 is manageable at present.

SuperB.WS05.Hawaii

SuperB.WS05.Hawaii

Additional end cap iron yoke For the iron yoke of 10 cm thickness in the radial direction, the EMF on the ES is reduced.

ESR: 2.18 104 N 1.00 104 N, ESL: 3.83 104 N 2.96 104 N

QC1L QC1R

ESL

ESLQCS L

670970

Additional iron yoke