Burst mode FEL with the ETA-III induction linac

Pulses of 140 GHz microwaves have been produced at a 2 kHz rate using the ETA-III induction linac and IMP wiggler. The accelerator was run in bursts of up to 50 pulses at 6 MeV and greater than 2 kA peak current. A feedback timing control system was used to synchronize acceleration voltage pulses with the electron beam, resulting in sufficient reduction of the corkscrew and energy sweep for efficient FEL operation. Peak microwave power for short bursts was in the range 0.5-1.1 GW, which is comparable to the single-pulse peak power of 0.75-2 GW. FEL bursts of more than 25 pulses were obtained.<
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