A method and an apparatus for detecting photons are disclosed. The apparatus includes a scintillator single crystal and an avalanche photodiode coupled to the scintillator single crystal. The scintillator single crystal is at a temperature greater than about 175° C. and at a shock level in a range from about 20 Grms to about 30 Grms. The scintillator single crystal includes a praseodymium doped composition selected from (LaxY1-x)2Si2O7:Pr, ABCl3-yXy:Pr, A2(Li, Na)LaCl6-yXy:Pr, or any combinations thereof. As used herein A is cesium, rubidium, potassium, sodium, or a combination thereof, B is calcium, barium, strontium, magnesium, cadmium, zinc, or a combination thereof, and X is bromine, iodine, or a combination thereof. Further, (0