Solid scintillation detectors

Solid scintillation refers to the process by which certain organic and inorganic compounds emit light photons when they absorb energy resulting from ionizing radiation like X-rays, gamma rays, alpha particles, and beta particles. Non-ionizing radiation like that from neutrons can also generate an indirect scintillation effect in some solid scintillators. These can be used to detect and measure neutrons.

The (n,p) or (n, α) nuclear reactions that occur within the scintillator compound cause scintillation and ionization, which are both responsible for the effect that neutrons have on solid scintillators. Even non-ionizing neutrinos, which are known to have a negligible amount of rest mass, can bring about detectable reactions in scintillators.

When radiation energy interacts with certain organic solvents, that energy is transferred to the organic fluors at a molecular level. These molecules, which are originally at a ground energy state, are subsequently elevated to an excited state. When they return to their original ground state, the absorbed energy is emitted as visible radiation in the form of photons.

The high-penetrating power of electromagnetic radiation makes the analysis and detection of X-rays, gamma rays, and other forms of ionizing radiation inefficient. This can be attributed to the low atomic number of the organic compounds, as well as their low density – two factors that both diminish the scintillators’ “stopping power.”

The ideal solid scintillator needs to have the following properties:

• Chemical resistance and stability even when subjected to mechanical and thermal shock
• Excellent energy and spatial resolution
• High atomic number and density for optimum stopping power and detection efficiency
• Low manufacturing cost as far as the growth of the solids and their respective shapes and sizes go
• Low refraction index for light to photodetector transmission

Solid scintillation has a wide variety of applications, including nuclear security and plant safety, environmental and personnel monitoring for radioactive contamination, hand-held radiation survey devices, among others.