Transform-limited coherent synchrotron radiation wavepackets in a photoinjector-driven chirped pulse free-electron laser

Abstract

Summary form only given. A novel source of transform-limited pulses of coherent electromagnetic radiation relying on the synchrotron radiation process in a fast wave guiding structure is investigated. An ultrashort electron bunch transversally accelerated by a periodic external field is considered. At grazing, where the bunch and group velocities are matched, the duration of the resulting ultrawideband chirped pulse is governed by group velocity dispersion instead of slippage. Because of the intimate connection between the rate of chirping and the bandwidth, the corresponding pulse duration is shown to be very close to the Fourier transform limit. In addition, the propagation of such chirped pulses through a guiding structure with negative group velocity dispersion is investigated both theoretically and computationally. The spectral and temporal characteristics of the chirped and compressed pulses are derived analytically. Detailed computer calculations complement this theoretical analysis. In addition, a detailed description of our X-band photoinjector facility (currently under construction), capable of producing trains of 100, 1 nC, subpicosecond photoelectron bunches at a micropulse repetition rate of 2.142 GHz and with a normalized emittance of 0.75 /spl pi/ mm-mrad (at 0.1 nC) will be given.