27th March 2018
RTI recently completed a comprehensive study which investigated the effect of belt load variation on the performance of online PGNAA analysis.
Prompt Gamma Neutron Activation Analysis (PGNAA) has been the technology of choice for many decades for measuring chemical variation in many bulk materials transported on a belt conveyor.
PGNAA works by bombarding the material on the conveyor belt with neutrons emitted from a radioactive isotope. When neutrons collide with an element in the material, gamma rays are emitted with a specific energy unique to that element – in effect, creating chemical signature for that element. The greater the amount of an element in the material the greater the number of gamma rays emitted with the corresponding specific energy. By measuring the specific energy of the gamma rays that are emitted and the counts of gamma rays, an analysis of the chemistry of the material is generated.
To date, it has been uncertain as to the extent that variation in geometry and the amount of material on the conveyor belt affects the measured prompt gamma spectra. However, the research conducted by our design team during the development of the AllScan scientifically proved that changes in geometry and bed depth variation influenced the spectra to a greater degree than changes in elemental composition.
“The research conducted by our design team during the development of the AllScan scientifically proved that changes in geometry and bed depth variation influenced the spectra to a greater degree than changes in elemental composition – a ground breaking discovery with significant implications for Online PGNAA Analysis”.
In response to this ground-breaking discovery, RTI developed an innovative data processing, and sophisticated modelling software – which we have called Dura-G – that dramatically improves the accuracy of online elemental analysis . It does this by applying bed depth compensation prior to “de-convolution of the spectra”. The resultant spectra, after bed depth compensation has been applied, and background activation removed, provides information purely on the elemental composition of the material. This ground-breaking spectral analysis technique applies a non-linear transformation to the spectra to produce pure elemental results, free from error caused by bed depth changes.
RTI has written a technical publication which summaries the results of the research conducted. In summary the paper provides a word of caution to PGNAA users by demonstrating that an analysis based on simple linear combinations of elemental spectra is not sufficient to produce an accurate result over a wide range of compositions and sample loadings on the conveyor belt. However, the Dura-G technology developed by RTI and implemented in the AllScan Online PGNAA Analyser effectively eliminates this.
A copy of the publication can be downloaded here.