Dosimetric Aspects of tie Electron Microbeam irradiation System for Use in Low-Dose Radiation Effect Study

Abstract

Microbeam experiment studies up to now have been performed with alpha and proton beams in major and with soft x-rays in minor. In this paper, the electron microbeam irradiation system under development in Korea is introduced with a focus on dosimetric aspects. The system consists of an electron gun, an electron transport chamber having the beam collimation of 5 urn in diameter and a biology stage automatically controlled. Dose distributions for the target layer in a cell dish have been investigated by Monte Carlo simulation for 25, 50, 75 and 100 keV electron source beams on the basis of the preliminary design specifications of the vacuum window, the cell dish bottom and the air gap in between. At the beam center, the average dose to the liquid water target layer in a cell dish was 0.078, 0.157, 0.179 and 0.194 cGy per single electron emission through a 5 um-dia. collimator with 25, 50, 75 and 100 keV electron source beam, respectively. With 25 keV electron beam, dose was reduced to 66.5, 28.7 and 2.10 percents at a 3, 5 and 10 jim distance, repectively, from the beam center. With 100 keV electron beam, on the other hand, the corresponding values were 46.1, 2.30 and 0.764 percent.