TIME-RESOLVED MEASUREMENT OF ELECTRON-BEAM EMITTANCE AND ENERGY SPREAD WITH OPTICAL-TRANSITION RADIATION

In order to analyze the effect of the transient beam quality on the fr ee-electron laser operation, we have measured the time-varying emittan ce and energy spread with optical transition radiation (OTR) on the ba sis of submacropulse. The emittance and energy spread were identified by measuring the beam size on the OTR screen with different quadrupole field. The OTR images having the information of beam size were observ ed by a gated, intensified charge-coupled device (ICCD) camera. The be am sizes were measured with time step of 100-300 ns by controlling gat e time of the ICCD camera; We have observed that the emittance was cha nged from 0.2 to 0.35 pi mm mrad and the fractional energy spread was varied from 0.2 x 10(-4) to 7 x 10(-4) during the macropulse of 3 mu s . (C) 1998 Elsevier Science B.V. All rights reserved.