2003/5/16 nufact-J 1

FFAG RF for muon

C. Ohmori

KEK

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Contents

• FFAG RF for 10-20 GeV muon– Parameters– Air-core system– Multi-feed scheme by Iwashita

• FFAG RF for PRISM

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FFAG RF for 10-20 GeV muon -RF parameters-

• Kinetic Energy : 10 => 20 GeV• Radius : 120 m (Circumference 754 m)• Longitudinal Emittance : 5 eVs• RF freqeucney : 18 or 24 MHz (Fixed Frequency)• Bucket Height : 10 GeV• : 0.003(Lattce 1), 0.002(Lattice 2)• Field Gradient 0.55-0.75 MV/m(average)• Cavity Length 1.6 m • Number of Cavity 120 (1 cavity/cell)• Gap Voltage : 1.8-2.43 MV• Beam Pipe : 360

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Lattice1 Lattice 2

T 18.2 21.2

0.003 0.002

frequency 24 MHz 18 MHz 24 MHz 18 MHz

H 60 45 60 45

Total Voltage 5.6 GV 4.2 GV 4.1 GV 3.1 GV

Average Field Gradient

0.75 MV/m

0.56 MV/m

0.55 MV/m

0.41 MV/m

# of turns 20 27?

RF Voltage for 2 X 5.4 GeV Bucket HeightHigh T is better for RF Voltage! But slow rotation.

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Design of High Gradient Cavity 1

-Air-core cavity-• Length 1.6 m /gap

• Outer Diameter : 2m

• Type of Cavity : Air –core

• Driven by a 150 kW class tetrode

• Driving Method: Loop Coupling

• Feeding : Direct or Co-axial line

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SUPERFISH Calculation(24MHz)

• Frequency : 24.03 MHz• Shunt Impedance: 3.53 M 2.2M/m• Q: 26400• Max. E field: 7.4MV/m 1.06Kilp. at 1 MV/

m• Lattice 1 (Low T)

– Max. E field : 12MV/m 1.7 Kilp. at 1.5 MV/m

• Lattice 2 (High T)– Max. E field : 8.3MV/m 1.2 Kilp. at 1.1 MV/m

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Design of Amplifier(24 MHz)• Load : • Vgap: 2.43 MV• 1 AMP per Cavity• Driven by 150 kW tube• Anode Voltage : 30kV• Peak Cathode Current: 120A (Max. 140 A) • RF Output Power: 0.84MW (duty < 0.16%)

• Operation : Class B• Cathode DC Current: 38 A (pea

k)

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Operation Line of Tube

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SUPERFISH Calculation(18MHz)

• Frequency : 18.16 MHz

• Shunt Impedance: 2.43 M 1.52 M/m

• Q: 23500• Max. E field: 10.6MV/m 1.65Kilp. at 1 MV/m• Lattice 1 (Low T)

– Max. E field : 12MV/m 1.85 Kilp. at 1.12 MV/m

• Lattice 2 (High T)– Max. E field : 8.7MV/m 1.35 Kilp. at 0.82 MV/m

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Design of Amplifier(18 MHz)• Load : • Vgap: 1.8 MV• 1 AMP per Cavity• Driven by 150 kW tube• Anode Voltage : 30kV (Max. 40kV)• Peak Cathode Current: 100A (Max. 140 A)• RF Output Power: 0.67MW (duty < 0.16%)

• Operation : Class B• Cathode DC Current: 30 A (pea

k)

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Air-core cavity • Superfish calculation seems OK (18 and 24

MHz systems), about 1.2 Kilp.

• Vacuum tube can deliver enough power.

• Many engineering issues – Large cavity (2m )– Driving method, loop coupling at low frequenc

y– Lifetime of tube: few 10000 hours => 15 tubes

(12%) will die in 6 months=> OK

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Design of High Gradient Cavity 2

-ferrite cavity-• Iwashita proposes a new approach, Multi-

Feed by Switching Devices.

• Type of Cavity : Ferrite cavity

• Driven by FET switch

• Driving Method: Loop Coupling

• Feeding : Multi-Feed

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PRISM RF

• MA (Magnetic Alloy) Cavity for high field gradient (-300kV/m) at 5MHz

• High Power operation of small vacuum tubes– 1 MW by 150 kW tubes

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MA 　 Cavity• Will be used for JKJ synchrotron RF cavities• Characteristics of Magnetic Alloy

– Thin Tape , 18 m– High Field Gradient

• Voltage limit: Brf <Bsat. (1T) and Voltage per layer < 5 V

– High Curie Temperature– Large core, Rectangular Shape, (<4mX1.7m)– Large permeability(about 2000 at 5MHz)– Original Q value is small(0.6).– High Q is possible by cut core configuration– Thickness -35mm (50mm in future)

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High Gradient Cavity

1.00E+09

1.00E+10

1.00E+11

1 10 100 1000 10000

Brf[Gauss]

up'Q

fSY2

N5C

4M2-302

FT-small

FT-large

Magnetic Alloys

Ferrites

B=V/S=25kV/2pX5MHzX5cmX40cm=400GaussVlayer=25kV/(0.4mX0.7/18mm)=1.6V<5V(limit)

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MA Cavities

PoP FFAG CavityJKJ RF Cavity: 1.7m, 60kV, Cut CoreWater cooling, driven by 600kW tubes

KEK-PS MA Cavity: 90cm, 30kV, Cut CoreFluorinate Cooling

Himac Cavity: 50cm, 20kV, water cooling driven by 150kW tubes

5kV, CW, driven by 30kW tubes.

Barrier Bucket Cavity: 2.6m, 40kV, 6% duty, air cooling, driven by 30kW tubes installed in BNL AGS.

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Parameters of MA CavityPRISM

Power tube EIMAC 4CW150K

DC35-40kV900-kW(peak)

Field gradient 62.5- kV/cavity

250- kV/m

Gaps/cavity 1 gaps, 31.25-kV/gap, 25cm

Impedance 1k /gap 　以上

# of cores 4 cores /gap （ 2.5- ３ｃｍコア）

Cooling Air cooling

Barrier Cavity

EIMAC 4CW30K

~200kW(peak)

40 kV/cavity

15.3 kV/m

4 gaps, 10kV/gap

1k /gap

12 cores /gap

Air cooling(6%)

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MA core

MA core for 150MeV FFAG

1.7m X 0.985m X 30mm

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Summary• Conceptual Design for 10-20 GeV FFAG

RF system• Air-Core Cavity

• Ferrite Cavity using multi-feed

• High T is good for system design (-35% less voltage) but slow acceleration(35 % slower).

• Need a prototype system.

• System Design for PRISM RF is undergoing.