Design Studies of an X-band Multi-beam Klystron

Accelerator Laboratory, KEK Design Studies of an X-band Multi-beam Klystron S. Fukuda KEK US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK 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 budget, we want to develop an X-band mbk. US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK 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 . US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK 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 US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK Parameters (2) US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK Sketch of whole MBK US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK Gun Simulation Bz=2.5kG, Bz/Bb=2 Focusing by 2-lenses compensation of transverse Field, less than 0.005Bz Magnetic field is a key point. Micro-perv. of a beam-let=1.25 Current of a beam-let=14A US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK Cavity simulation TM410 Mode is used. 6 cavities system US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK Electromagnet Design US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK Klystron simulation : one dimensional and Magic simulation US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK Design Difficulties and Drawback • Hot dimension of the cathode • Different expansion factors between copper and iron for magnetic lens • High perveance of 10 microperv. can lead the instability, 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 high microperv of a beam-let. US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK 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. US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK 10.3MW 10.1MW 9.8MW US High Gradient Research Collaboration Workshop

Accelerator Laboratory, KEK 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. US High Gradient Research Collaboration Workshop

Design Studies of an X-band Multi-beam Klystron