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

摘要

Summary form only given. A novel source of transform-limitedpulses of coherent electromagnetic radiation relying on the synchrotronradiation process in a fast wave guiding structure is investigated. Anultrashort electron bunch transversally accelerated by a periodicexternal field is considered. At grazing, where the bunch and groupvelocities are matched, the duration of the resulting ultrawidebandchirped pulse is governed by group velocity dispersion instead ofslippage. Because of the intimate connection between the rate ofchirping and the bandwidth, the corresponding pulse duration is shown tobe very close to the Fourier transform limit. In addition, thepropagation of such chirped pulses through a guiding structure withnegative group velocity dispersion is investigated both theoreticallyand computationally. The spectral and temporal characteristics of thechirped and compressed pulses are derived analytically. Detailedcomputer calculations complement this theoretical analysis. In addition,a detailed description of our X-band photoinjector facility (currentlyunder construction), capable of producing trains of 100, 1 nC,subpicosecond photoelectron bunches at a micropulse repetition rate of2.142 GHz and with a normalized emittance of 0.75 π mm-mrad (at 0.1nC) will be given