survey

Paper	Title	Other Keywords	Page
WEPPH048	XPS Studies of Cs2Te Photocathodes	cathode, electron, photon, laser	457
	H. A. Duerr, R. Ovsyannikov, M. Sperling, A. Vollmer BESSY GmbH, Berlin J. H. Han, S. Schreiber, S. Lederer DESY, Hamburg P. Michelato, L. Monaco, C. Pagani, D. Sertore INFN/LASA, Segrate (MI) F. Stephan DESY Zeuthen, Zeuthen
	Cesium Telluride (Cs2Te) photocathodes are used as sources for electron beams because of their high quantum efficiency (QE) and their ability to release high peak current electron bunches in a high gradient RF-gun. Starting from a high QE level of about 10% the quantum efficiency of these cathodes decreases during operation in a photo-injector to below 0.5%. To understand this behaviour, XPS investigations on the chemical composition were performed at BESSY. In this contribution we compare two fresh cathodes from INFN with one used under normal operation at FLASH and one used at PITZ at a higher than usual RF-gradient of 60 MV/m.
THBAU04	Millimeter Waves Sensing Behind Walls - Feasibility Study with FEL Radiation	radiation, polarization, controls, coupling	501
	M. Einat, M. Kanter, B. Litvak, A. Yahalom, B. Yu. Kapilevich CJS, Ariel A. Gover University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
	The existing through-wall imaging (TWI) systems operate in 1 – 10 GHz, basically, in order to reduce an attenuation caused by building material. However, the spatial resolution is drastically degraded when the operating frequency is relatively low. On the other hand, a majority of building materials demonstrate increased losses as the frequency increases. As a result, higher RF power from the source is required. The Israeli mm-wave FEL provides unique opportunity to solve the above TWI problem permitting to deliver output power 100-1000W at 85-105 GHz. Design of TWI system operating on mm-waves needs comprehensive study of constitutive parameters of different building materials. This paper describes systematic measurements of effective attenuation constant of typical building materials such as concrete bricks, wood, tiles, sand, gypsum, etc. on mm-waves using powerful FEL radiation. Since the Rayleigh criterion for surface roughness cannot be satisfied for some of measured materials, scattering and depolarization effects lead to increasing measured attenuation in comparison with bulky material. Additional experiments were performed to estimate a contribution of these effects into the measured attenuation.
	Slides