Mercuric iodide detector systems for identifying substances by X-ray energy dispersive diffraction

The use of mercuric iodide arrays for energy-dispersive X-ray diffraction (EDXRD) spectroscopy is now being investigated by us for inspection of specific crystalline powders in substances ranging from explosives to illicit drugs. Mercuric iodide has been identified as the leading candidate for replacing the Ge detectors previously employed in the development of this technique because HgI₂ detectors: operate at or near room temperature; without the bulky apparatus associated with cryogenic cooling; and offer excellent spectroscopy performance with extremely high efficiency. Furthermore, they provide the practicality of constructing optimal array geometries necessary for these measurements. Proof of principle experiments have been performed using a single-HgI₂ detector spectrometer. An energy resolution of 655 eV (FWHM) has been obtained for 60 keV gamma line from an ²⁴¹ Am source. The EDXRD signatures of various crystalline powdered compounds have been measured and the spectra obtained show the excellent potential of mercuric iodide for this application