High-Power High-Efficiency L-band Multiple-Beam Klystron Development at CPI
Communications and Power Industries, Inc., has designed and manufactured two versions of a 10-MW-peak high-efficiency multiple-beam klystron (MBK) operating at 1300 MHz. This type of klystron is favored for large particle accelerator projects such as the European X-ray Free-Electron Laser at the Deutsches Elektronen Synchrotron (DESY). Two klystrons have been made for DESY. The first-generation MBK was a vertically oriented prototype using a six-cavity design with higher order mode input and output cavities and conventional intermediate cavities. For cost and performance reasons, the second-generation MBK, designated VKL-8301B, utilized seven coaxial fundamental-mode cavities and is an “industrialized” horizontally oriented klystron. The klystron was designed and optimized using state-of-the-art multidimensional design codes to ensure that all performance requirements are exceeded. Agreement between the simulated and measured performances is good. The VKL-8301B prototype achieved a peak saturated RF output power of 10.4 MW and 67.8% efficiency. The data were measured at the full 1.5% duty and with 1.5-ms pulse width. The klystron satisfied all required operating conditions, including stable operation into an output mismatch of 1.2:1 voltage standing wave ratio at various phases. The prototype has been shipped to DESY and has been successfully tested by a customer.
Design and status of the XFEL RF system
The RF system of the European XFEL under construction at present at DESY in Hamburg,Germany,consists of 27 RE stations. At a later point of time the number might be increased to 31. The RF system provides RF power at 1.3 GHz for the superconducting cavities of the main linear accelerator,the cavities of the injector and the RF gun. Each station consists of a 10 MW multiple beam klystron,a HV pulse modulator,HV pulse cables,a pulse transformer,an interlock system,a low level RF system,a waveguide distribution system and a number of auxiliary power supplies. This paper describes the layout of the RF system and summarizes the design and status of the main high power components.
Development of Toshiba L-Band Multi-Beam Klystron for European XFEL Project
A 10MW L-band Multi-Beam Klystron (MBK) is under development at Toshiba, Japan for the European XFEL and a future linear collider projects. The design goals are to have 10MW peak power with 65% efficiency at 1.5 ms pulse length at 10Hz repetition rates. The Toshiba MBK has six low-perveance beams operated at low voltage of 115kV (for 10MW) to enable a higher efficiency than a single-beam klystron for a similar power. The prototype-0 has been built and is now under testing. At the first step, it was tested without RF and operates stably at the cathode voltage of 115KV at 1.7ms pulse length at 10Hz repetition rate with beam transmission of better than 99%. No spurious oscillation was observed. The testing is now progressed with RF on. Up to date, the output power of 10.3MW has been demonstrated at the beam voltage of 115kV with efficiency of 68.4% at the RF pulse length of 1ms at 10Hz. The testing is under way to increase the RF pulse length to the goal value of 1.5ms. This paper summarizes the design and the testing results.