What is a scintillator?

A scintillator is a material that emits light when it interacts with ionizing radiation like X-rays, gamma rays, or charged particles. The word “scintillation” means the flash of light emitted by the material. Scintillators are used in a wide range of applications, such as medical imaging, security screening, and particle physics experiments.

Scintillators can be made of organic or inorganic materials. Organic scintillators typically consist of a solvent, such as toluene, and a fluorescent dye, such as anthracene. Inorganic scintillators are often crystals or ceramics made from compounds like sodium iodide, cesium iodide, or gadolinium oxysulfide. However, the most commonly used scintillator in scientific research is the sodium iodide crystal.

How does a scintillator work?

When a high-energy particle or photon strikes a scintillator, it deposits energy in the material by ionizing its atoms or molecules. This ionization creates excited states that can emit photons when they return to their ground state. The emitted photons are detected by a photodetector, such as a photomultiplier tube or a silicon photomultiplier, which produces an electrical signal proportional to the amount of energy deposited in the scintillator. The signal can be used to identify the type, energy, and position of the incident radiation.

The light yield, energy resolution, and timing characteristics of a scintillator depend on various factors, such as its composition, density, size, and shape. Moreover, scintillators can be combined with other materials, such as wavelength shifters, reflectors, or filters, to enhance their performance or modify their response to specific types of radiation.

Applications of scintillators

Scintillators have numerous applications in science, medicine, industry, and security. For instance, scintillation detectors can be used for:

  • Medical imaging: scintillation cameras, also known as gamma cameras, are used to detect and visualize the distribution of radiopharmaceuticals in the body. The gamma rays emitted by the radiopharmaceuticals are detected by a scintillator, which produces a 2D or 3D image of the organs or tissues being imaged.
  • Particle physics: scintillation detectors are used to measure the energy, momentum, and identity of particles produced by accelerators or cosmic rays. They can also be used in neutrino experiments to detect the faint flashes of light produced by neutrino interactions in large volumes of scintillator.
  • Security screening: scintillation detectors can be used to detect and identify illicit materials, such as explosives, drugs, or radioactive substances, in luggage, cargo, or people. The scintillator can detect the gamma rays emitted by the materials and produce an alarm signal if the radiation is above a certain threshold.

Example of scintillator technology

One example of a scintillator technology is the LUX-ZEPLIN (LZ) experiment, which aims to detect dark matter particles using a massive liquid xenon detector surrounded by scintillators. The detector is located 1.5 km underground at the Sanford Underground Research Facility in South Dakota, USA. The LZ detector consists of 10 tonnes of liquid xenon, which is sensitive to the ionization and scintillation produced by dark matter particles interacting with the xenon nuclei. The scintillation light is detected by photomultiplier tubes and other sensitive detectors, which help to distinguish the signal from the background noise. The LZ collaboration involves more than 30 institutions from around the world and is expected to start taking data in 2021.