2009/3/3US High Gradient Research Collaboration Workshop 1 Design Studies of an X-band Multi- beam Klystron S. Fukuda KEK Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 2 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. Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 3 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

2009/3/3US High Gradient Research Collaboration Workshop 4 Project and Parameters (1) Required parameters: V beam =50kV P rf out =2MW P rf in < 50W Loading of the cathode should be no more than 7A/cm 2 Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 5 Parameters (2) Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 6 Sketch of whole MBK Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 7 Gun Simulation Micro-perv. of a beam-let=1.25 Current 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

2009/3/3US High Gradient Research Collaboration Workshop 8 Cavity simulation TM410 Mode is used. 6 cavities system Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 9 Electromagnet Design Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 10 Klystron simulation : one dimensional and Magic simulation Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 11 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. Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 12 More high power version: Larionov ’ s approach Magnetically 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

2009/3/3US High Gradient Research Collaboration Workshop 13 Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop MW 10.1MW 9.8MW Accelerator Laboratory, KEK

2009/3/3US High Gradient Research Collaboration Workshop 15 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