Environmental monitoring is one of modern day drivers of microsystems technology. For example, radiation sensors can be potentially used to detect the presence of radioactive contamination either from an accident of from a terrorist attack involving a “dirty” bomb (conventional explosive devices used to disperse radioactive material). Since only a few radioactive materials emit X-rays, X-ray detectors have only limited applicability. The best way to detect most radioactive materials is through their emission of beta particles. There is a wide variety of beta emitting isotopes, and thus a considerable range of emitted beta energy. Solid-state detectors for beta particles exist, but they are relatively large, with sizes on the order of 1 cm3. They typically require cryogenic cooling to distinguish radiation type and energy, and are particularly susceptible to radiation damage. Gas-based Geiger counters remain the preferred sensors for detecting beta radiation. They are reliable, simple, temperature insensitive, and measure over a much wider range of radiation species and energies. However, they are typically toaster-size devices, and cannot discriminate between different radiative species, e.g. between medical waste and reactor by-products, or between benign and lethal isotopes.
Researchers at the University of Michigan have developed the D-microGeiger, a device presently ranging from 9 to 64 mm2 in area and 2.5 mm thick (about the size of a coin), which works at room temperature and measures beta radiation. Beta particles interact with the background gas in two independent cavities. This differential measurement allows energy spectroscopy, thus providing the user with real time information on radiation composition - this real time aspect is currently unavailable in a conventional Geiger counter.
Applications and Advantages
- Detection and analysis of beta radiation
- Small size
- Ability to differentiate between the isotopes
- Real time information on radiation analysis.