ChrysosTM PhotonAssay provides a unique, chemistry-free approach to material analysis. It hits samples with high-energy X-rays, causing short-lived excitation of atomic nuclei of targeted elements. These excited nuclei then give off a characteristic signature that can be detected and used to calculate metal grade.
The high-energy X-rays are produced using a device called an electron accelerator. Similar accelerators are commonly used in hospital radiotherapy units, and for industrial sterilisation of products such as medical supplies.
Both the X-ray beam used to excite the samples and the resulting elemental signature gamma-rays are very penetrating, meaning that large samples can be measured. A true bulk reading is returned, independent of the chemical or physical form of the sample. A single rock or section of core can be measured just as easily as a powdered or crushed sample, and solutions or slurries can also be directly analysed.
Samples are sealed inside plastic jars before analysis, and remain in the jar throughout. The analysis is completely non-destructive, and all samples can be retained for further analysis or testing if required. Jars are labelled with a unique identifier, providing an unambiguous reference for the future.
The basic physics principles of the PhotonAssay method, also known to scientists as gamma activation analysis, stem back to the 1960s. Indeed, as early as the 1970s a commercial laboratory was established in the former Soviet Union for gold analysis. However, the sensitivity and accuracy of these early implementations, particularly for samples containing less than 1 gram per tonne of gold, limited their more widespread application.
Over the past 15 years, the CSIRO has developed and patented methods that significantly improve both absolute accuracy and sensitivity to very low concentrations. These improvements form the basis of ChrysosTM PhotonAssay technology.
Using experience built up through more than 40 years of designing and building cutting-edge analysis instruments for the mining industry, the core ChrysosTM PhotonAssay technology has been developed into a robust platform suitable for 24/7 use in demanding environments.