- A new neutron detector made of a layered, lithium-enriched semiconductor material can fit in your hand.
- Neutron detectors are important in many industries, including space exploration and analysis.
- Lithium is extremely reactive, and layering it between other materials isolates and protects it.
Scientists at Northwestern University and Argonne National Laboratory have shrunk room-sized neutron detector technology into a portable, handheld device powered by lithium semiconductors. Existing detectors “use helium gas or flashes of light,” which means the lithium technology makes a third family of detectors.
Lithium is a wild overachiever. It’s the lightest metal and the only non-gas (the other elements are hydrogen and helium) that dates back to the beginning of the universe. Lithium salts are used to treat a variety of mental illnesses, and it’s hard to imagine life in 2020 without lithium-ion battery technology. The pure element itself is white, crumbly, and volatile, carefully stored in liquid like explosive feta cheese.
And it’s a powerful neutron attractor, which is the quality scientists have sought to isolate for years in order to make a new kind of neutron detector. In combination, the lithium attracts neutrons and the semiconductive activity allows an electrical “alert” to occur. The obstacle, for a long time, was to find a semiconductor that also contained lithium.
Mercouri Kanatzidis, who works for both Northwestern and Argonne, is leading the team that developed the new detector. He says researchers understood the idea of a lithium neutron detector but couldn’t quite find the right material to close the loop. “You can find good semiconductors, but they don’t have lithium. Or you can find stable lithium compounds that are not good semiconductors,” he said in a press release.
Kanatzidis’s team combined lithium, indium, phosphorous, and selenium in a layered array of crystals. Lithium turns to dust when exposed to water, so the lithium is sealed within the crystal structure and protected from the elements.
“We anticipate that these results will spark interest in this field and enable the replacement of [helium-powered] counters by semiconductor-based neutron detectors,” the team concludes in its paper.
The new detector doesn’t just have lithium—it has a lot of lithium, giving it a density of detection ability that means it can be effective at pocket size. Having such a portable option is a huge benefit for neutron detectors, which “are critical in many sectors, including national security, medicine, crystallography and astronomy,” the team writes. Crystallography is the study of crystals, and identifying neutrons can help scientists in turn identify what crystals are and how they form and work. Neutron detectors also help scientists measure the nuclear power and radiation output from reactors.
A much smaller detector could cost a lot less, require less infrastructure and installation, and be discreet for use by safety inspectors or security personnel. Kanatzidis says the variety of technologies itself is also important, because a detector the size of a truck is still useful for, well, trucks, the same way you don’t want to vacuum your whole house with a Dust Buster. But having a neutron Dust Buster in your toolkit is a great option across a variety of research and commercial settings.
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