Recent testing of x band PPM klystrons at the Klystron Department at SLAC

Klystrons capable of driving accelerator sections in the Next Linear Collider have been developed at SLAC during the last decade. The latest specification for these tubes, as of June 2003, is shown. In addition to fourteen 50 MW solenoid focused devices, eight Periodic Permanent Magnet focused (PPM) devices have been tested including a 50 MW klystron, two diodes, an initial 500 kV 75 MW klystron, and 4 more 75 MW tubes. Testing of the first 75 MW device was completed in 1999, attaining 80 MW with 3 μs pulses but with a very low duty cycle. Beam transmission must be excellent in such devices in order to gain predictable and stable performance, reduce radiation intensity, keep thermal issues manageable and increase lifetime. Magnet quality and fabrication tolerances have been strong issues during tube development. Knowledge of the beam transmission during testing is difficult due to noise and calibration issues. Our later experiments have included drift tubes which are thermally mapped by including thermocouples into the design.