Development of CLYC Scintillators for Radiation Detection

RMD’s Material Science Expertise Provides First Responders with Next Generation Nuclear Detection Tools

Personal Radiation Detectors (PRDs) and Spectroscopic Personal Radiation Detectors (SPRDs) are essential instruments used by first responders to search for gamma-ray and neutron signatures of dangerous radioactive isotopes such as uranium and plutonium.

Gamma-ray spectroscopy enables the detection and identification of specific isotopes.  Unfortunately, the use of dense, high atomic number (Z) shielding such as lead cloth or bricks can be employed to mask gamma-ray signatures.  Neutrons, on the other hand, readily penetrate dense, high Z materials.  When detected, neutrons are a direct indication that fissionable nuclear materials are present.  Combining gamma-ray spectroscopy and neutron detection in a single instrument ensures the greatest probability that dangerous nuclear materials are uncovered.

In 2008 one of the key materials used to detect neutrons, Helium-3, became very difficult to obtain.  Due to this shortage, the U.S. government initiated programs to develop next generation materials to not only replace Helium-3 to detect neutrons, but also detect gamma-rays; all in a single detector.  This material had to have high efficiency, excellent energy resolution, and the ability to differentiate between gamma and neutron events.  The ultimate goal was to develop more capable instruments, while reducing the complexity and cost, thereby enabling wider deployment.

RMD responded to the government’s needs by enhancing the capability of the CLYC (Cs2LiYCl6) scintillator.  CLYC is a crystalline scintillation material that emits photons when struck by ionizing radiation.  RMD’s version of CLYC has the ability to detect and discriminate both gamma-rays and neutrons.  Additionally, it is capable of high resolution gamma-ray spectroscopy, which provides very accurate identification of the radiation source.

CLYC is coupled to a photomultiplier tube (PMT) or a solid state photodetector (SiPM), and electronics to analyze the emitted signal and assembled into a finished instrument.  Aimed at first responders, law enforcement, and other national security agencies these PRDs and SPRDs are very sensitive, portable instruments that detects both gamma-rays and neutrons.  This enables first responders to quickly locate and identify a wide range of radioactive materials utilizing a single device.

Partnering with Government Funding Agencies to Fast Track Development

RMD’s research on CLYC began through the DOE SBIR program, originally funded by the office of Nuclear Physics followed up by funding from DTRA.  With the onset of the Helium-3 crisis in late 2008, DNDO (Now CWMD) accelerated development of the most promising Helium-3 replacement technologies including CLYC.  DNDO supported low rate production (LRP) of CLYC scintillator crystals including sampling of these crystals to selected users and integration into prototype performance test units through DNDO-funded programs. In 2013 an SBIR Phase II project from DOE was funded by the Office of Nuclear Energy.  This DOE SBIR effort focused on developing and optimizing algorithms for CLYC crystals for discriminating between gamma rays and neutrons at high event rates based on pulse height discrimination (PHD), as well as more powerful pulse shape discrimination (PSD).  Thereafter, DTRA funded work to scale-up crystal production sizes (up to 3” diameter) in a cost-effective manner in order to provide higher efficiency detectors.

Commercialization into an SPRD

RMD’s CLYC detector has been integrated into the Thermo Scientific RadEye SPRD-GN, a handheld gamma and neutron spectroscopic radiation detector, used by law enforcement, military, first responders, industrial and nuclear power plants for radiation measurement and identification applications worldwide.  CLYC is in high demand by government agencies and defense contractors, and additional future customers will likely include hospitals and the recycling industry.

The Next Generation

Development is underway on a new scintillation material for the next generation of dual-mode gamma ray and neutron detectors. RMD discovered by replacing the Y in CLYC with La, and by adding some Br to the Cl site, a new crystal, CLLBC, is created.  CLLBC emits more than two times the light of CLYC. This significantly improves the energy resolution, which is a critical parameter for the fast, accurate identification of radioactive isotopes. The discovery was patented by RMD and work was funded by DOE, the Office of Defense Nuclear Nonproliferation, as well as CWMD and DTRA. Prototype detectors are currently available using 1” and 1.5” diameter crystals, and larger versions based on 2” and 3” diameter crystals will be launched this year.

 

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