Radiation Tests for a Single-GEM Loaded Gaseous Detector
  We report on the systematic study of a single-gas-electron-multiplication (GEM) loaded gaseous detector developed for precision measurements of high-energy particle beams and dose-verification measurements. In the present study, a 256-channel prototype detector with an active area of 16$\times$16 cm$^{2}$, operated in a continuous current-integration-mode signal-processing method, was manufactured and tested with x rays emitted from a 70-kV x-ray generator and 43-MeV protons provided by the MC50 proton cyclotron at the Korea Institute of Radiological and Medical Science (KIRAMS). The amplified detector response was measured for the x rays with an intensity of about 5$\times$10$^{6}$ Hz cm$^{-2}$. The linearity of the detector response to the particle flux was examined and validated by using 43-MeV proton beams. The non-uniform development of the amplification for the gas electrons in space was corrected by applying proper calibration to the channel responses of the measured beam-profile data. We concluded from the radiation tests that the detector developed in the present study will allow us to perform quality measurements of various high-energy particle beams and to apply the technology to dose verification measurements in particle therapy. 
Kyong Sei Lee, Byungsik Hong, Sang Yeol Kim, Sung Keun Park
physics.ins-det