Scientists at EPFL and their collaborators have developed a simple and low-cost perovskite-based device that detects neutrons. The perovskite materials used in the study are based on lead and bromine. Both contain single crystals of a compound called methylammonium lead tri-bromide.
The team first placed these crystals in the path of a neutron source. The neutrons, hitting the crystals, penetrate the nucleus of the atoms within the crystal, exciting them into a higher energy state. When they relax and decay, gamma rays are created. These gamma photons charge the perovskite, delivering a tiny current that can be estimated.
However, this current is extremely tiny and something more is needed to make a practical neutron detector. Hence, the scientists used a thin foil of gadolinium metal, which is much better at absorbing neutrons than the perovskite crystal alone.
When neutrons interact with the Gadolinium’s atoms, they are excited into a higher energetic state and then emit gamma radiation. Compared to perovskites, Gadolinium can efficiently create gamma photons. Putting the two together proved to be simple and very effective.
The team added a carbon electrode, and the resulting electrons produced in the perovskite were easy to measure.
Later, the scientists grew the perovskite crystal around the foil to further improve this perovskite neutron detector. The detector can also measure the direction of the neutron flow and the size of the flow.
Márton Kollár from EPFL said: “The property of this material is such that it can engulf anything, from a fly to a crocodile to Gadolinium. So it grows around the object, and even when it grows around, it stays crystalline. So this is a fabulous feature of this material.”
EPFL's László Forró said: “It’s simple, it’s cheap, and it’s cost-effective. This is proof of principle that it works. And now we can think about configuration for a very efficient detector.”