Trends in Materials for Radiation Detection

The needs of the domestic security and medical imaging industries are driving both development of new radiation detection materials and improvements to existing materials. The ultimate goal is a material with better resolution, faster decay time, and better resistance to environment and radiation, while maintaining reasonable light yield and cost. While no one has yet discovered the ideal material and it is unlikely that such a material exists, sales of both legacy and newer materials are creating a market that is projected to grow from $1.8 billion market in 2015 to nearly $3 billion by 2022.

NanoMarkets’ latest report on radiation detection, “Radiation Detection Materials Markets – 2015-2022,” discusses market opportunities for over two dozen materials capable of gamma ray, X-ray, and/or neutron detection. We discuss which materials are especially promising replacements for legacy materials and which have not quite lived up to expectations but can’t be written off entirely.

Scintillator Materials for Gamma Ray Detection

Lanthanum bromide: This was the first scintillation material on the market with better resolution than sodium iodide. In addition to excellent resolution, it boasts a very short decay time. Lanthanum bromide is seeing increased adoption, especially for domestic security applications, but its high cost is a concern. Since Saint-Gobain Crystals owns commercial rights for this material and other companies can only supply it for research and trial purposes, the normal competition between suppliers that might drive down prices is not present. Still, it behooves Saint-Gobain to reduce costs to accelerate commercial adoption of LaBr3, so the price is likely to come down if Saint-Gobain can improve yields.

In the search for a high resolution scintillator material, lanthanum bromide is the one to beat, and a supplier that can come up with a material that matches its performance will find itself a lucrative market. Competitors like RMD, Inc. (the research arm of Dynasil) are trying. RMD was instrumental in developing CLYC and is working to improve strontium iodide and cerium bromide. The combination of RMD’s research expertise and the commercial crystal growth experience of its sister company Hilger Crystals puts it in a good position to bring newer materials to market. The real challenge for all of these materials is growing large enough crystals for commercial applications while maintaining the high performance that has made them look so promising in the laboratory, and being able to produce them at a cost the market can bear.

Strontium iodide: This is another material to watch, but one that has struggled to achieve its potential. CapeSym claims to be able to bring the price of strontium iodide down to well below that of lanthanum bromide. This might provide the company with a winning strategy, especially if it can produce crystals larger than 1-inch diameter with sufficient performance. There is a significant degree of uncertainty here, but CapeSym strikes NanoMarkets as perhaps the company most likely to make a commercial success out of strontium iodide.

Lutetium fine silicate: Some new materials might find themselves on a fast track to commercial success. Promising entrants include lutetium fine silicate (LFS), patented by Canada-based Zecotek Photonics. As this material is related to other lutetium-bearing scintillators such as LSO and LYSO, the greatest opportunities are in nuclear medicine. Indeed, Zecotek is selling LFS commercially in time-of-flight PET scanners, and its settlement agreement with Philips Healthcare over a patent dispute resulted in a strategic partnership between the two companies that puts Philips in the position of influencing uptake of the LFS scintillator material in the medical imaging industry.

Replacing 3He for Neutron Detection

The primary driver for neutron detection is to replace 3He in radiation detection portals for domestic security, but there are also opportunities for other applications such as oil well logging. The first generation of 3He replacements based on 10B and 6Li was effective at detecting neutrons but overly sensitive to gamma radiation. Better solutions appear to be on the horizon that promise excellent neutron detection even in the presence of high levels of gamma radiation.

Materials using 6Li: Combining silver-activated zinc sulfide with 6LiF produces an effective thermal neutron detection material with a decay time of several hundred nanoseconds. More importantly, the material has a gamma sensitivity that is well within the specification required for a 3He replacement, so NanoMarkets believes that it has the potential to displace 10B tubes for this purpose. At least two companies, Eljen Technology and Applied Scintillation Technologies, make sheets of 6LiF/ZnS in a form that is ready for commercial use. Symetrica is currently using 6Lif/ZnS in its radiation detectors in products ranging from handheld devices for first responders to cargo scanning portals.

Saint-Gobain has demonstrated proof of concept for a LaBr3 gamma ray detector surrounded by 6LiF, which acts as a neutron detector and can discriminate between gamma rays and neutrons. This concept still needs refining and is further away from commercialization but is worth watching.

Noble gases: Compressed noble gases – natural helium, argon, and xenon – are a low-cost option for neutron detection that can act as a drop-in replacement for 3He. Arktis Radiation Detectors Ltd has developed a detector based on these materials that is currently being tested by customs organizations in Europe to further evaluate its ability to detect special nuclear materials in cargo containers. These materials may also be of interest for neutron detection in industrial and nuclear power applications. Although this is a relatively new concept, NanoMarkets believes that the promise of accurate thermal and fast neutron detection at low cost is likely to make adoption of compressed gas-based detectors accelerate quickly, assuming positive results from trials.

CLYC: CLYC has gotten a lot of attention and may be a viable replacement for 3He in neutron detection, but it has yet to prove itself, having fallen somewhat short on its promise use as a dual function gamma ray and neutron detector. Commercial acceptance of CLYC has been slower in coming than the U.S. government might have hoped when it sunk research money into the material several years ago, probably because performance is not matching up to expectations.

Thermo Fisher recently released a high-resolution RIID for dual gamma and neutron detection that uses CLYC but also incorporates LaBr3 for gamma detection. The need to add a separate gamma detector is somewhat of a red flag for the dual detection aspect of CLYC.

New Twists on Legacy Materials

Plastic scintillators have long been the preferred low-cost, low-performance option, but should see new life in applications requiring higher performance while maintaining low cost. For example, research begun at Lawrence Livermore National Lab and successfully transferred to Eljen Technologies for commercial production has created a new PVT-based material. The new material combines PVT with a scintillating dye, using much higher concentrations of dye that were previously considered feasible, and is able to distinguish between neutrons and gamma rays. Other high-performance plastics are in development as well.

While the older generation of plastic materials is being replaced in applications where better alternatives exist, this new generation of higher performing organic scintillators may be able to take market share away from low-cost materials for use in large detectors. And if performance is high enough, they may be competitive in other applications as well.