2009/3/3 US High Gradient Research Collaboration Workshop

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Design Studies of an X-band Multi-beam Klystron

S. Fukuda

KEK

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Motivation to develop x-band MBK

X-band compact linac are desired for the medical use and non-destructive inspection; ex. Cyber-knife machine, handy X-ray inspection for chemical plant.

We have developed the compact linac of 900keV collaborating between KEK and Tokyo university. RF source was a commercial magnetron.

It is desired to develop a mbk for the next stage. If we are succeeded in obtaining the competitive budg

et, we want to develop an X-band mbk.

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Achieving goal of MBK design

Lower applied voltage not to use the insulation oil or to use a small insulation oil cup.

Output Power (1) Output power of 2 MW. (2) Output power of a10 MW or more. Two approach:

(1) usual multi-gun assemblies for MBK and (2) magnetic compression gun for MBK (more high power version).

Designs were performed by Russians of BINP: Dr. Vladimir Teryaev and Dr. Alexsander Larionov at KEK .

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Project and Parameters (1)

Required parameters:

• Vbeam =50kV• Prf out =2MW• P rf in < 50W• Loading of the cathode should be no more than 7A/cm2

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Parameters (2)Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Sketch of whole MBKAccelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Gun Simulation

Micro-perv. of a beam-let=1.25Current of a beam-let=14A

Bz=2.5kG, Bz/Bb=2

Focusing by 2-lenses　　 compensation of transverse Field, less than 0.005Bz

Magnetic field is a key point.

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Cavity simulation

TM410 Mode is used.6 cavities system

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Electromagnet Design

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Klystron simulation : one dimensional and Magic simulationAccelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Design Difficulties and Drawback

Hot dimension of the cathode Different expansion factors between copper an

d iron for magnetic lens High perveance of 10 microperv. can lead the i

nstability, and beam tester is required. Collector is also possible source of instability

and model test is required. Drawback: low efficiency of 40% due to a hig

h microperv of a beam-let.

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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More high power version: Larionov’s approachMagnetically compression for MBK

More larger cathodes are possibly used.( more beam intensity)

Number of the cathodes (i.e. beamlets) are possibly used.

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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10.3MW

10.1MW

9.8MW

Accelerator Laboratory, KEK

2009/3/3 US High Gradient Research Collaboration Workshop

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Summary

X-band mbk is desired for an application of a compact linac such as medical use and non-destructive inspection use.

Design attempts of X-band mbk in KEK are shown. Features of low applied voltage to the klystron around

50-60kV are achieving goal of these designs.

Accelerator Laboratory, KEK