How to keep U.S. ports of entry safe and secure by detecting and interdicting illicit radioactive or nuclear materials? A team led by Northeastern’s Swastik Kar and Yung Joon Jung has developed a technology that could go a long way toward achieving that goal.
“Our detector could dramatically change the manner and accuracy with which we are able to detect nuclear threats at home or abroad,” says Kar, associate professor in the Department of Physics. It could also help streamline radio-medicine, including radiation therapies and scanning diagnostics, boost the effectiveness of unmanned radiation monitoring vehicles in mapping and monitoring contaminated areas following disasters, and revolutionize radiometric imaging in space exploration. Made of graphene and carbon nanotubes, the researchers’ detector far outpaces any existing one in its ultrasensitivity to charged particles, minuscule size, low-power requirements, and low cost.
All radiation, of course, is not harmful, and even the type that may be depends on dosage and length of exposure. The word “radiation” refers simply to the emission and propagation of energy in the form of waves or particles. It has many sources, including the sun, electronic devices such as microwaves and cellphones, visible light, X-rays, gamma waves, cosmic waves, and nuclear fission, which is what produces power in nuclear reactors. Most of the harmful radiations are “ionizing radiations”—they have sufficient energy to remove electrons from the orbits of surrounding atoms, causing them to become charged, or “ionized.” It is those charged particles, or ions, that the detectors pick up and quantify, revealing the intensity of the radiation. Most current detectors, however, are not only bulky, power hungry, and expensive, they also cannot pick up very low levels of ions. Kar and Yung Joon’s detector, on the other hand, is so sensitive it can pick up just a single charged particle.
“Our detectors are many orders of magnitude more sensitive in terms of how small a signal they can detect,” says Yung Joon, associate professor in the Department of Mechanical and Industrial Engineering. “Ours can detect one ion, the fundamental limit. If you can detect a single ion, then you can detect everything larger than that.”