One of the most important security tasks for entry points into the U.S. is the detection of radiation that might indicate an attempt to smuggle radioactive materials or weapons into the U.S. A research team from Northwestern University and the Argonne National Laboratory has developed a new material that could be used to make radiation detectors that are much less expensive than the current generation of commercial detectors.
The new material can be used in a device that can detect gamma rays given off by radioactive materials. It can also easily identify specific radioactive isotopes. Potential uses of the new material beyond hand-held radiation detectors includes applications in spectroscopy, astronomy and biological imaging.
Northwestern's Mercouri G. Kanatzidis is a Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences and the corresponding author of the paper. He said, “Governments of the world want a quick, low-cost way to detect gamma rays and nuclear radiation to fight terrorist activities, such as smuggling and dirty bombs, and the proliferation of nuclear materials. This has been a very difficult problem for scientists to solve. Now we have an exciting new semiconductor device that is inexpensive to make and works well at room temperature.”
In 2013, Argonne published a paper that discussed the potential of using cesium lead bromide in the form of perovskite crystals for the detection of high-energy radiation. Since then, the labs at Northwestern and Argonne have been working on purifying and improving the material.
Yihui He is a graduate student in Kanatzidis’ group and the first author of the new paper on the group’s research. He made the major breakthrough when he redesigned the semiconductor device at the heart of the radiation detector. Instead of using the exact same material for the electrodes on either side of the perovskite crystal, He used two different compositions of electrodes. In this configuration, the device only conducts electricity if are gamma rays present. When the new device was compared to a conventional cadmium zinc telluride (CZT) radiation detector, it performed just as well as the more expensive CZT in detecting cobalt-57.
If and when radiation is detected, it is important to be able to say exactly which radioactive isotope triggered the detector. Some isotopes are legal, and some are not. The detector with the new material was able to successfully identify americium-241, cobalt-57, cesium-137 and sodium-22 in tests. The researchers also produced larger crystals than they needed for their tests to prove that the production of the new material was very inexpensive.
With the grave concerns about smugglers trying to bring radioactive materials into the U.S., an inexpensive handheld gamma ray detector and isotope identifier could be distributed to every manned border crossing into the U.S. The border patrol could also carry these new devices as they patrol the border between manned crossing points. Customs officials for international travelers could scan checked luggage and carry-on bags at airports and ports of entry. This new device could give U.S. citizens more confidence that smuggling of nuclear materials into the U.S. will be prevented.
