Wiktionary
n. (context physics English) Any substance that glows under the action of photons or other high-energy particles
Wikipedia
A scintillator is a material that exhibits scintillation — the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, (i.e., re-emit the absorbed energy in the form of light). Sometimes, the excited state is metastable, so the relaxation back down from the excited state to lower states is delayed (necessitating anywhere from a few nanoseconds to hours depending on the material): the process then corresponds to either one of two phenomena, depending on the type of transition and hence the wavelength of the emitted optical photon: delayed fluorescence or phosphorescence, also called after-glow.
Usage examples of "scintillator".
It will make your scintillator go wild, but you can handle it with fair safety for about five minutes.
They managed to gather some fragments anyway, and when they measured them with Winsor's NaI Scintillator detector, they registered radiation levels 50 percent higher than normal.
Power conduits radiated outward, urchin-like, towards huge mass spectrometers and organic scintillators stacked into massive detector arrays.