Characteristic of a PDP-based radiation detector in Xe-He mixture gas

In this study, we have investigated a 2-dimensional gas detector based on plasma display technology as a candidate for the flat-panel radiation detector. Using the Geant4 and Garfield codes, that simulate the passage of particles through matter, we examined the dependence of X-ray absorption and multiplication factors on the Xe-He gas mixture. Prototype detectors, with four different gas mixtures, were designed and fabricated based on the results from the simulations. The performance of four detectors was evaluated by measuring the collected charge density, dark current density and sensitivity. The maximum collected charge occurred when the Xe 80%-He 20% gas mixture was 1.216 μC/cm² at -1800 V. The dark current of this detector varied between 0.124 and 0.321 nA/cm² in the bias range of -300 to -1800 V, which is approximately one-third of the dark current density of an a-Se based detector, in this range. The sensitivity of Xe 80%-He 20% detector was 0.246 nC/mRcm² at 0.61 V/μm. It is about a tenth lower than that of an a-Se based detector at 10 V/μm.