Abstract: It has not previously been known to measure, by means of thermoluminescent detectors, both gamma and fast neutron radiation at the same time. The present invention performs such measurements on an equal basis to produce a summed dose reading. The present invention broadly comprises the use of a thermoluminescent phosphor in hydrogenous matrix and the measurement of thermoluminescence due to electron fluence from the matrix into the phosphor for gamma ray dose and recoil proton fluence into the phosphor for fast neutron dose. The invention further embraces the manufacture of a detector and a novel die for use therein.