High power microwave generation at high repetition rates
Generation of microwaves at high power has progressed largely with single shot devices. Yet applications require repetitive operation at substantial repetition rates, implying high average power. This requires operation in a new domain for microwave devices. The technical challenge is to achieve very high electric fields in the source on a repetitive basis. We describe experiments on CLIA, a Compact Linear Induction Accelerator, generating 750 kV, 10 kA using magnetic switching to produce 60 ns pulses. We describe experiments with relativistic magnetrons and klystrons in the 1 GW, 100 Hz domain. As a first application we used CLIA to drive a water-cooled L-band magnetron at repetition rates as high as 250 Hz with no breakdown or pulse shortening. This gave 6.3 kW average power. A short burst at 1 kHz operated at ≈25 kW. In this regime operation is not limited by gas build-up, electrode erosion or microwhisker depletion. We are now operating on CLIA with relativistic klystrons of both the high current and low current varieties. Beams with modulated current powers of ≈ 1 GW have been generated at 200 Hz for bursts as long as 1000 pulses.
Operation of an L-band relativistic magnetron at 100 hz
Until the present work, experience with repetitive relativistic magnetrons was sparse, consisting of $OM 1 Hz cooled devices and $OM 100 Hz bursts in uncooled resonators. The highest average power reported is approximately 500 W. The authors have modified an existing magnetron to include water cooling for repetitive operation. The system is designed for five second bursts at 200 Hz. Earlier single shot operation produces rf energies exceeding 50 Joules per micropulse. The authors have achieved 40 Joules per micropulse at a repetition rate of 100 Herz, or an average power of 4 kW for 0.5 seconds. The authors discuss issues in interfacing magnetrons with repetitive pulsed power and the operating characteristics during a burst of pulses.
Space-charge waves on a relativistic, unneutralized electron beam and collective ion acceleration
The space‐charge‐wave dispersion characteristics of a thin, hollow, relativistic electron beam is calculated for beam currents near the space‐charge limit for propagation of the beam.