NIST Unveils Cryogenic Decay Energy Spectrometry to Accurately Measure Radioactivity in Microscopic Samples

USA: NIST Introduces Cryogenic Decay Energy Spectrometry for Precise Radioactivity Measurement

On July 8, 2025, researchers at the National Institute of Standards and Technology announced a new technique—cryogenic decay energy spectrometry (DES)—that can identify and quantify radionuclides in samples weighing less than one‑millionth of a gram. The method, detailed in the journal *Metrologia*, leverages a transition‑edge sensor (TES) to capture the energy released by individual radioactive decays, offering both compositional and activity data from a single analysis.

How the Transition‑Edge Sensor Works

The TES operates at temperatures near absolute zero, where a minute change in electrical resistance signals the absorption of decay energy. According to NIST physicist Ryan Fitzgerald, this resistance shift provides a high‑resolution energy fingerprint that distinguishes one radionuclide from another, unlike conventional Geiger counters that only register the presence of radiation.

Advantages Over Traditional Techniques

Prior approaches typically required separate procedures to measure total activity and to identify specific isotopes, often involving chemical tracers or multiple instruments. DES consolidates these steps, delivering a complete radioactivity profile in “just a few days” instead of the months sometimes needed for conventional analyses.

Inkjet Gravimetry Enables Microscopic Samples

The research team employed a specialized inkjet device to deposit droplets smaller than 1 µg onto gold foils patterned with nanometer‑scale pores. By precisely weighing the dispensed mass and subsequently measuring the decay energy on the dried sample, the scientists calculated the massic activity with unprecedented accuracy.

The TrueBq Initiative

DES forms the first phase of the True Becquerel (TrueBq) project, which aims to integrate TES technology with a precision mass‑balance system for a comprehensive measurement platform. The initiative seeks to streamline workflows, reduce uncertainties, and eventually support a broader range of radioactive materials, including complex mixtures.

Potential Applications and Future Directions

Stakeholders anticipate that the technology could improve quality control for radiopharmaceuticals used in cancer therapy, accelerate characterization of reprocessed nuclear fuel, and enhance environmental monitoring during waste remediation. Long‑term goals include developing portable versions of the system for field deployment in medical, environmental, and security contexts.

This report is based on information from NIST, licensed under Public Domain (U.S. Government Work). Source: Official U.S. Government release.