Low-background NaI Scintillator
Inorganic crystalline scintillators are single crystals that emit optical radiation upon exposure to X-ray, gamma-ray or neutron radiation. Scintillators composed of alkali, alkaline earth and rare earth halide crystals generally have an activator dopant uniformly dispersed throughout the crystal lattice. The most common scintillator crystal in use today is thallium-doped, low-background NaI.
RMD’s thallium-doped, high purity, low-background sodium iodide scintillators are grown using the Bridgman-Stockbarger method and can be produced in the required size and configuration for dark matter and other high energy physics studies.
The instruments used in this research require detectors fabricated of high sensitivity, ultra-low radioactivity materials to record these rare events and to minimize the possibility of false counts. To construct these specialized detectors, RMD has developed and perfected the manufacturing process to produce extremely pure, high quality, low-background sodium iodide scintillator crystals, and to package them with an appropriate photomultiplier tube (PMT).
- Unprecedented low levels of potassium, <5 ppb in finished crystals.
- Crystal now being measured in SABRE underground lab with liquid scintillator veto at LNGS
- Production of 8 kg boules for finished pieces, ~ 5 kg now underway at RMD.
Thallium-doped, low-background NaI scintillators are best suited to study dark matter and other high energy physics that require the development and use of special experimental techniques to detect the signal that dark matter particles emit when they interact with ordinary matter. Because of the extremely low probability of an interaction, these events are exceptionally rare and can only be observed if the numbers of events resulting from other possible origins are minimized. For this reason, dark matter studies are carried out deep in underground laboratories, such as the Gran Sasso in Italy, where the shielding effect of the mountain overlooking the laboratory (1,500 meters of rock) absorbs the majority of the cosmic rays striking the earth’s surface.