Abstract: Methods for constructing radiation sensitive detectors are described. In one method, distinct layers of optical cement and plastics material are disposed between a semiconductor photodiode and a layer of rare earth phosphor in order to permit the phosphor and the plastics material to be peeled from the optical cement without damaging the photodiode in the event of a problem arising with the deposition of the phosphor layer. The phosphor layer may be loaded with heavy metal such as lead or tin. In the event that an array of semiconductive photodiodes is used, with stopper channels between adjacent diodes, the plastics material is preferably provided with markings overlying the stopper channels so as to reduce optical cross-talk between adjacent detectors.