Observation of Self-Amplified Spontaneous-Emission-Induced Electron-Beam Microbunching Using Coherent Transition Radiation
نویسندگان
چکیده
We report the measurement of electron-beam microbunching at the exit of a self-amplified spontaneous-emission free-electron laser (SASE FEL), by observation of coherent transition radiation (CTR). The CTR was found to have an angular spectrum much narrower than spontaneous transition radiation and a narrow-band frequency spectrum. The central frequency of the fundamental CTR spectrum is found to differ slightly from that of the SASE, a finding in disagreement with previously invoked CTR theory. The CTR measurement establishes the uniformity of microbunching in the transverse dimension, indicating the SASE FEL operates in a dominant transverse mode. [S0031-9007(98)08027-2]
منابع مشابه
Fundamental and harmonic microbunching in a high-gain self-amplified spontaneous-emission free-electron laser.
Electron beam microbunching in both the fundamental and second harmonic in a high-gain self-amplified spontaneous emission free-electron laser (SASE FEL) was experimentally characterized using coherent transition radiation. The microbunching factors for both modes (b(1) and b(2)) approach unity, an indication of FEL saturation. These measurements are compared to the predictions of FEL simulatio...
متن کاملFundamental and Harmonic Microbunching Measurements in a High-Gain, Self-amplified, Spontaneous Emission Free-Electron Laser
The self-amplified, spontaneous emission free-electron laser (SASE FEL) gain process is a collective instability which induces microbunching in the electron beam. Microbunching approaching unity at the fundamental FEL wavelength (845 nm), and its second harmonic, have been measured at the VISA FEL, at or near saturation. These measurements, which use the beam's coherent transition radiation (CT...
متن کاملInvestigations of Electron-beam Microbunching and Beam Coalignment Using Ctr in a High-gain Sase Fel*
We recently extended our experiments on z-dependent electron-beam microbunching using coherent transition radiation (CTR) into the high-gain, self-amplified spontaneous emission free-electron laser (FEL) regime. The UV-visible FEL at the Advanced Photon Source was operated at 530 nm and 385 nm using the bunchcompressed photocathode gun electron beam, linac, and 21.6 m of undulator length. The l...
متن کاملComparison of the coherent radiation-induced microbunching instability in a free-electron laser and a magnetic chicane
040702-1 A self-amplified spontaneous emission free-electron laser (SASE FEL) is a device which is based on the creation of a very intense, relativistic electron beam which has very little temperature in all three phase planes. The beam in this system is described as having ‘‘high brightness,’’ and when it is bent repetitively in a magnetic undulator, undergoes a radiation-mediated microbunchin...
متن کاملObservation and Characterization of Coherent Optical Radiation and Microbunching Instability in the Slac next Linear Collider Test Accelerator∗
The NLC Test Accelerator (NLCTA) at SLAC is currently configured for a proof-of-principle echo-enabled harmonic generation (EEHG) experiment using an 120 MeV beam. During commissioning, unexpected coherent optical undulator radiation (CUR) and coherent optical transition radiation (COTR) was observed when beam is accelerated off-crest and compressed after the chicanes. The CUR and COTR is likel...
متن کامل