That among several other fluorescent materials is the emitter for a scintillometer, The detector was a Photo multiplier tube, an extremely sensitive photon amplifier, designed it the 1930's and widely manufactured in the 50's through the 90's when the tubes became scarce. Elektor ran a complete Photodiode particle detector recently and there have been at least 3 follow-up articles from other sources since...
The device I mentioned makes no use of a photo-multiplier tube or diode, it requires no power at all. Simple and easy detection of radioactive materials;
"Way back in 1903, Sir William Crookes was experimenting with the most expensive material on Earth at the time... Radium Bromide.
Working in total darkness, he accidentally spilled a small quantity on a thin layer of a special type of activated Zinc Sulfide (ZnS). To make sure he recovered all of the expensive Radium Bromide, he used a magnifying lens to locate every single speck of it. To his amazement, he noticed flashes of light occurring around each tiny grain of the radioactive material. It was found that the flashes of light were caused by the individual Alpha particles emitted from the Radium compound, striking the activated Zinc Sulfide. The flashes of light were individual photons emitted from splitting atoms. "
I know that you weren't saying this was scintillator, but I wanted to clarify for those less familiar with the subject. :) Indeed one can still purchase scintllator detectors, which can be much more sensitive than traditional geiger counters.