Breakthrough in Radioactive Material Detection

Context:

On March 31, 2025, The Hindu reported a significant scientific advancement by U.S. physicists who developed a novel technique using carbon-dioxide lasers to detect radioactive materials from a distance. This innovation, rooted in avalanche breakdown, holds immense potential for enhancing national security and emergency response capabilities, making it a critical topic for understanding modern technological progress.

Key Information in Points:

• Innovative Technique: A team of U.S. physicists demonstrated a new method to detect radioactive materials remotely using carbon-dioxide (CO2) lasers.
• Core Mechanism: The technique leverages "avalanche breakdown," where charged particles from radioactive decay ionize air, creating plasma that scatters laser light.
• Detection Process: By analyzing the profile of backscattered laser light, researchers can identify the presence of radioactive materials.
• Test Case: The method was tested with a 3.6-mCi polonium-210 alpha particle source, detected at a 10-meter standoff distance—far exceeding previous capabilities.
• Range Potential: Scaling up laser optics could enable detection of gamma-ray sources, like caesium-137, up to 100 meters away.
• Limitations: Extending the range to 1 kilometer or more requires larger optics and higher laser energy due to weaker signals and interference from background radiation and atmospheric conditions.
• Applications: This technology is vital for national defense and emergency response, allowing rapid and safe identification of radioactive threats.
• Previous Efforts: Earlier experiments used mid-infrared lasers in 2019 and gyrotron sources in 2017, with the latter achieving only a 1-meter range.
• Expert Validation: EunMi Choi from South Korea’s Ulsan National Institute praised the 10-meter detection as "highly impressive."
• Challenges: CO2 lasers are bulky, posing deployment issues, though mounting them for long-range use is a potential solution.
• Future Goals: Researchers aim to refine the technique to distinguish between radioactive source types entirely remotely.
• Fluorescence Imaging: A CMOS camera captured visible plasma emissions, likened to “balls of plasma,” aiding calibration but impractical for field use due to close-range requirements.
• Scalability Issues: Longer focal lengths for extended detection demand larger apertures, complicating practical application.
• Significance: The method surpasses current detection limits, offering a safer, more efficient approach to managing radioactive risks.

Key Terms:

• Carbon-Dioxide Laser: A laser using CO2 gas to emit infrared light for cutting, sensing, or detection.
• Avalanche Breakdown: A rapid increase in charged particles triggered by ionization, amplifying a detectable signal.
• Radioactive Materials: Substances emitting radiation due to unstable atomic nuclei, like polonium-210 or caesium-137.
• Plasma: A state of matter with ionized particles, here created by radioactive decay in air.
• Backscattered Light: Laser light reflected back after hitting a target, used to detect materials.
• Gamma Rays: High-energy radiation emitted by some radioactive substances, capable of traveling far in air.
• Standoff Distance: The safe distance from which detection occurs, critical for hazardous material handling.

Link To The Original Article – https://www.thehindu.com/sci-tech/science/laser-allows-long-range-detection-of-radioactive-materials/article69396261.ece