Sadiq BIW 2012

Abstract

We performed transverse emittance measurement of medical linac at physics department of Idaho State University. Al foil with a thickness of 1 micron used to observe electron via OTR. Imaging system composed of 3 lenses of different focal length were used to improve image quality. We found the projection of electron beam does not follow Gaussian distribution. So, we fit Super-Gaussian distribution to the beam and extracted the transverse emittance.

Introduction

We used 3 lenses to collect OTR light from Al target. To improve image quality, 2 inch diameter lenses were selected. They have focal length of 100 mm, 500 mm and 50 mm, they were called collector lens, fine tune lens and main focus lens respectively. Collector lens has the middle focal length, collects most of the light from the source. Fine tune lens has the biggest focal length, act as fine tune of magnification. Main focus lens: has the smallest focal length, has biggest focusing strength, so act as main focus of light and focuses light to CCD.

Experiment Setup

Camera cage system was located below the OTR target. There are 3 lenses used to focus lights from target to the CCD camera. Target can be pushed into or taken out of the beamline by the actuator at the top.

Fig. HRRL beamline: Optical cage system to focus OTR lights on CCD camera.

Fig. HRRL beamline: Optical lenses lay out for optical cage system.

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