Locating underground uranium deposits

Underground uranium deposits are located by placing pairs of dosimeters each about 5 to 18 mg/cm2 thick underground in a grid pattern. Each dosimeter contains a phosphor which is capable of storing the energy of alpha particles. In each pair one dosimeter is shielded from alpha particles with more than 18 mg/cm2 thick opaque material but not gamma and beta rays and the other dosimeter is shielded with less than 1 mg/cm2 thick opaque material to exclude dust. After a period underground the dosimeters are heated which releases the stored energy as light. The amount of light produced from the heavily shielded dosimeter is subtracted from the amount of light produced from the thinly shielded dosimeter to give an indication of the location and quantity of uranium underground