Invention of CLYC Scintillation Crystals for Radiation Detection

Personal Radiation Detectors (PRDs) and Spectroscopic Personal Radiation Detectors (SPRDs) are used by police and fire departments, hazardous materials teams, customs inspectors, border patrol agents, the military and the U.S. Coast Guard to detect the presence of radioactive materials.

Helium-3 was a critical component of radiation detectors, as it allows the detection of neutron radiation, giving first responders the ability to not only identify the presence of a nuclear source, but also to identify the type of source. Unfortunately, Helium-3 is scarce and as the supply dwindled, the U.S. Department of Energy rationed Helium-3. To help alleviate the shortage, the Domestic Nuclear Detection Office (DNDO), an arm of the Department of Homeland Security, supported the development of alternative neutron detection technologies.

RMD’s excellence in material science helps overcome a critical supply issue

Because of RMD‘s world-renowned reputation in material science and specifically in scintillation crystal development, it was a crucial player in DNDO’s project. RMD set to work developing a new scintillator detector (a material that gives off light when exposed to radiation) consisting of the elements cesium, lithium, yttrium, and chlorine, doped with cerium and with the lithium enriched in 6 Li. It has the chemical formula of: Cs2 6 LiYCl6:Ce, named CLYC.

With CLYC, when the 6 Li absorbs a neutron the resulting light pulse is brighter and longer than the pulse from a gamma-ray.  This makes it easier for signal-processing electronics to analyze and count neutron radiation with less contamination from gamma rays. One CLYC scintillation crystal mounted into a detector can be used to detect both gamma and neutron radiation instead of needing two separate detectors. Because only one detector is needed, CLYC enables the smallest and lightest personal monitoring devices available on the market today.

Why detecting neutron and gamma radiation is important for security

PRDs are very limited in their ability to tell the operator the nature of the material that has been discovered because they only detect gamma radiation. So spectroscopic PRDs (SPRDs) and neutron detecting PRDs were invented. These devices detect both gamma and neutron radiation, allowing responders wearing them to detect both types of radiation. This is important for two reasons:

  1. Plutonium containing sources can be identified, which would indicate the presence of a nuclear device rather than just radioactive material
  2. Gamma rays can be easily shielded by lead or other heavy metals. Neutrons are not absorbed by those materials, so plutonium shielded with lead can still be detected by its neutron emission.

RMD Invents CLYC – a Smaller, Lighter and Safer Neutron and Gamma Scintillator

Given RMD’s tremendous depth of knowledge in scintillators, they started working to solve the Helium-3 problem and invented the CLYC formula and manufacturing process. RMD then collaborated with Thermo Scientific to put CLYC in their RadEye SPRD in 2013 and their RadEye GN+ in 2015. Additionally, a new RIID (radiation isotope identifier detector), completely based upon 2” x 2” CLYC crystals, is being readied for release by Target in Germany.

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