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Simulation of Oscillations in High Power Klystrons

Technical Report ·
DOI:https://doi.org/10.2172/815264· OSTI ID:815264
Spurious oscillations can seriously limit a klystron's performance from reaching its design specifications. These are modes with frequencies different from the drive frequency, and have been found to be localized in various regions of the tube. If left unsuppressed, such oscillations can be driven to large amplitudes by the beam. As a result, the main output signal may suffer from amplitude and phase instabilities which lead to pulse shortening or reduction in power generation efficiency, as observed during the testing of the first 150MW S-band klystron, which was designed and built at SLAC as a part of an international collaboration with DESY. We present efficient methods to identify suspicious modes and then test their possibility of oscillation. In difference to [3], where each beam-loaded quality-factor Qbl was calculated by time-consuming PIC simulations, now only tracking-simulations with much reduced cpu-time and less sensitivity against noise are applied. This enables the determination of Qbl for larger resonant structures and weaker coupled modes. Results are presented for a typical cavity and the gun-region of the klystron mentioned above.
Research Organization:
Stanford Linear Accelerator Center, Menlo Park, CA (US)
Sponsoring Organization:
USDOE Office of Science (US)
DOE Contract Number:
AC03-76SF00515
OSTI ID:
815264
Report Number(s):
SLAC-PUB-10121
Country of Publication:
United States
Language:
English