NONDESTRUCTIVE DIAGNOSTICS FOR RELATIVISTIC PICOSECOND BUNCHED ELECTRON-BEAMS

The duration and form of relativistic picosecond electron bunches in t he Duke University Mark III free-electron laser have been nondestructi vely measured by monitoring the submillimeter radiation produced by th e bunches as they pass by or through a rectangular waveguide. Unlike o ther methods, our technique produces negligible electron bunch perturb ation and allows real-time beam diagnostics to be performed simultaneo usly with free-electron laser (FEL) operation. We have measured 2.1-ps full width at half maximum duration electron bunches, studied the eff ect of electron gun and FEL modifications on bunch duration, and obser ved electron bunch variations during bunch trains.