Electron beam bunch length characterizations using incoherent and coherent211 radiation on the APS SASE FEL project

摘要

The Advanced Photon Source (APS) injector linac has been reconfigured with a low-211u001eemittance rf thermionic gun and a photocathode (PC) rf gun to support self-211u001eamplified spontaneous emission (SASE) free-electron laser (FEL) experiments. One 211u001eof the most critical parameters for optimizing SASE performance (gain length) is 211u001ethe electron beam peak current, which requires a charge measurement and a bunch 211u001elength measurement capability. We report here initial measurements of the latter 211u001eusing both incoherent optical transition radiation (OTR) and coherent transition 211u001eradiation (CTR), A visible light Hamarnatsu C5680 synchroscan streak camera was 211u001eused to measure the thermionic rf gun beam's bunch length ((sigma) 211u001e(approximately)2 to 3ps) via OTR generated by the beam at 220 MeV and 200 mA 211u001emacropulse average current. In addition, a CTR monitor (Michelson Interferometer) 211u001ebased on a Golay cell as the far infrared (FIR) detector has been installed at 211u001ethe 40-MeV station in the beamline. Initial observation s of CTR signal strength 211u001evariation with gun a-magnet current and interferograms have been obtained. 211u001eProgress in characterizing the beam at these locations and a comparison to other 211u001ebunch length determinations will be presented.