The outstanding properties of diamond make it an ideal material for radiation detectors especially in the high temperature, high radiation and corrosion environments. For this purpose, electrical and irradiation properties of high quality CVD diamond detector were investigated at room temperature under irradiation conditions. For freestanding diamond films, dark current was in the order of 10-10 A and photocurrent was in the order of 10-8 A by 5.9 keV X-ray irradiation from a 55 Fe source with the applied voltage of 40 V. Pulse height spectrum acquired using a 241 Am alpha particle source show a full-energy peak at 820 channel which corresponded to an average charge collection efficiency of approximately 40.5%. However, a good signal-to-noise ratio and an energy resolution of 1.33% for alpha particles detecting were also obtained.
