X-band PPM klystron development for JLC

In this paper, we summarize the status of X-band PPM klystron development for the Japan Linear Collider (JLC) project. The periodic permanent magnet (PPM) klystrons are under development in the two-stage/two-year project with Toshiba. The goal is to produce 50 MW output power with efficiency >50% at 1.5 μs pulse length at the first klystron and then to advance to 75 MW with efficiency =55% at the second one. The first PPM klystron has been tested, and it achieved 56 MW power with 50% efficiency at the standard 1.5 μs pulse length. Neither oscillation of the parasitic mode nor gun oscillations were observed. The particle transmission was found to be 100% when no RF signal is applied. The second PPM klystron is currently under high-power testing. It has improved water cooling system of a PPM circuit and the output cavity for 150 Hz operation. The RF system was also revised for a higher efficiency. To date (June 6, 2001), the PPM-2 klystron produced 73.2 MW at 1.4 μs pulse length and 70 MW at 1.5 μs pulse length with the efficiency of 54.5%. The maximum efficiency reached 56% at the specified cathode voltage. The high-power testing will be continued to attain a 75 MW output power with a standard 1.5 μs pulse. Details of these developments and measurement results are presented