Lumpkin, A. H.

Paper	Title	Page
TUPPH011	Near-Field Optical Diffraction Radiation Measurements at CEBAF	254
	P. Evtushenko, A. Freyberger JLAB, Newport News, Virginia C. Liu CASA, newport news A. H. Lumpkin Fermilab, Batavia, Illinois
	Optical diffraction radiation (ODR) is a promising technique, which could be used for non interceptive beam size measurements at future light sources. An ODR diagnostic station was designed and installed on a CEBAF transfer beam line. The purpose of the setup is to evaluate experimentally the applicability range for an ODR based non interceptive beam size monitor an to collect data to benchmark numerical modeling of the ODR. An extensive set of measurements were made at the electron beam energy of 4.5 GeV. The ODR measurements were made for both pulsed and CW electron beam of up to 80 μA. The wavelength dependence and polarization components of the ODR were studied using a set of insertable bandpass filters and polarizers. The typical transverse beam size during the measurements was ~150 microns. Complete ODR data, wavelength and polarization, were recorded for different beam sizes and intensities. The beam size was also measured with an optical transition radiation (OTR) as well as wire scanner located next to the ODR station. In this contribution we describe the experimental setup and present first results of the measurements with the comparison to the numerical simulations.
THBAU05	COTR and SASE Generated by Compressed Electron Beams	501
	A. H. Lumpkin Fermilab, Batavia, Illinois R. J. Dejus, N. Sereno ANL, Argonne, Illinois
	Observations of strongly enhanced optical transition radiation (OTR) following significant bunch compression by a chicane of photoinjector beams have been reported during the commissioning of the Linac Coherent Light Source (LCLS) accelerator and at the Advanced Photon Source (APS) linac. These localized transverse spatial features involve signal enhancements of nearly a factor of ten in the APS case at the 150-MeV and 375-MeV OTR stations. They are consistent with a coherent process seeded by noise and may be evidence of a longitudinal microbunching instability which leads to coherent OTR (COTR) emissions. Additionally, we suggest that localized transverse structure in the previous self-amplified spontaneous emission (SASE) free-electron laser (FEL) data at APS in the visible-UV regime as reported at FEL02 may be attributed to such beam structure entering the FEL undulators and seeding the SASE. In one specific case, the SASE process enhanced separate beam structures 120 microns apart in x and 2.9 nm apart in wavelength. The details of these observations and operational parameters will be presented.
	Slides