Velocity Modulation System for Enhancement of 50 Picosecond Radiation Pulse

Radiation pulses 50 ps in duration have been attained at the EG&G/AEC electron linear accelerator by isolation of individual microstructure groups of electrons which normally occur at the fundamental accelerating frequency. Pulse compression by means of velocity modulation techniques has been used to increase the intensity of these pulses from 0.02 nC to 1.5 nC per pulse, or 30 A for the 50-ps pulse length. The injector pulse is synchronized to the RF acceleration frequency with a precision of 30 ps, which results in pulse-to-pulse reproducibility to within a few percent, permitting recurring pulse measurements to be made with sampling oscilloscopes. These intense short bursts of radiation allow the study of radiation detectors, scintillators, and chemical systems in the subnanosecond time domain. Neutron time-of-flight measurements with a total resolution of 400-500 ps have also been demonstrated. The calculated charge enhancement resulting from velocity-modulation bunching is compared to measured performance, and the system is described in detail.