Researchers from Los Alamos Laboratory have created a new technique for nuclear forensics that helps conductive radioactive particle analysis. The technique uses laser-based optical tweezers that can levitate uranium and plutonium particles, allowing for the measurement of recoil during radioactive decay. The method improves radioactive particle analysis, which is a major component of nuclear forensics.

Los Alamos scientists Alexander Malyzhenkov and Alonso Castro demonstrate levitating uranium particles with laser beams. Source: Los Alamos National Laboratory

"Our idea relies on trapping a particle using 'optical tweezers,' a technique which is the subject of this year's Nobel prize in Physics," said Alonso Castro of Los Alamos's Actinide Analytical Chemistry Group. "It is only fitting that Arthur Ashkin's invention is still yielding novel science even after 30 years."

The kinetic energy of an emitted nuclear particle, or daughter particle, is found by measuring the recoil of a sample particle that is levitated with a laser-powered optical trap. The sample particle fully absorbs the recoil momentum of the daughter particle. All of this leads to oscillation in the trap.

"For applications such as nuclear forensic analysis, this technique could have significant value. Thus far, we have been able to hold uranium particles in optical traps, and we find that holding them in place, with their oscillation energy 'cooled,' gives us the opportunity to see the recoil when the daughter atom's motion causes displacement of the sample," said Castro.

"The next step would be to measure those displacements and then calculate the energy of the recoil. The impact of our approach is that it can very quickly determine the isotopic composition of the types of nanometer and micrometer-sized particles found in nuclear forensic scenarios," he said.

The paper on this research was published in the journal Physical Review A.