Performance of KEK-Toshiba PPM-Focused X band pulse klystrons

The R&D of PPM (periodic permanent magnet)-focused X-band (11.424GHz) pulse klystrons in Japan started in 1999, originally for Global Linear Collider (GLC) project. So far six prototype tubes (as named PPM1, ... PPM6) have been built. All these tubes were fabricated by Toshiba Electron Tubes and Devices Co. and tested at KEK. A new project named International Linear Collider started in 2004 and GLC project was terminated (and has been integrated into the worldwide research programs). The new collider is based on L-band (1.3GHz). Our recent X-band research interest lies in the development of a 50 MW-class tube which is stable enough, usable for various applications such as a compact linear accelerator. The research work in this paper includes the test of the rebuilt tubes as well as disassembling them after the test for further inspections.