Laser allows long-range detection of radioactive materials

In a new breakthrough, a team of physicists from the U.S. has successfully demonstrated a new way to detect radioactive materials using carbon-dioxide lasers — from a distance. The researchers used a carbon-dioxide laser emitting long wave infrared radiation at a wavelength of 9.2 micrometres to accelerate the electrons, and were able to detect alpha particles from a radioactive source located 10 m away. The advance sets the stage to potentially expand avalanche-based laser detection techniques to identify gamma-ray radiation sources at greater stand-off distances. Using longer focal lengths to reach distances of around 1 km or more would require even larger optics and higher laser energies due to diminishing signal strengths. At such extended distances, the laser backscatter method — the primary approach tested here — is limited because the signal could become saturated by background radiation and atmospheric interference.