High power test of the first C-band (5712 MHz) 50 MW PPM klystron

Hot isostatic pressing (HIP) technique has been applied to fabricate a magnetic circuit in a PPM klystron. Simply stacking disks of the magnetic stainless-steel (Mag-SUS) and oxygen-free-copper (OFC) alternatively, and processing in a HIP vessel filled with pressurised Ar gas at 1200-kgf/cm² and temperature of 800°C for 2 hours, they were bonded in one block with diffusion bonding. No brazing-alloys were used in this process. After machining the rf-cavities and beam drift-tube on the bonded PPM stack, they were assembled together in one body by means of a conventional brazing method. The C-band PPM klystron based on this technique was fabricated in the course of the Linear Collider R&D. An output power of 37 MW was generated with 2.5-μsec pulse width and 50 pps repetition rate