The present invention provides a radiation detection system for detecting X-ray and gamma rays featuring Cd1-xMgxTe in solid solution as a crystal semiconductor and electrical connection means. The crystal has a composition in the range of Cd0.99Mg0.01Te to Cd0.71Mg0.29Te and may be doped with indium or another Group III element, which may be suitable for use at room temperature as well as controlled temperatures. The present invention further provides a method for detecting X- or gamma ray radiation by (a) providing a solid solution Cd1-xMgxTe crystal in the composition range of Cd0.99Mg0.01Te to Cd0.71Mg0.29Te; (b) providing an electrical contact means for connecting the Cd1-xMgxTe crystal to an amplification, measurement, identification or imaging means; and (c) detecting the presence of the X- or gamma ray radiation.