The ISOCS (In Situ Object Counting System) Calibration Software brings a new level of capabilities to gamma sample assay by eliminating the need for traditional calibration sources during the efficiency calibration process. By combining the detector characterization produced by the MCNP modeling code, mathematical geometry templates, and a few physical sample parameters, the ISOCS Calibration Software gives you the ability to produce accurate qualitative and quantitative gamma assays of most any sample type and size (Figure 1).
In addition to saving money by eliminating the need to purchase, track, and dispose of many calibration sources, ISOCS calibration also saves time in the field. Instead of hours spent in traditional source preparation and long calibration counts, an ISOCS calibration for a new geometry requires only a few seconds of computer calculations. With the ISOCS software you have the flexibility to design your setup, define your geometries, and analyze data in the office; reducing actual time in the field to the system setup and sampling time, no matter how many different geometries you're measuring. And now this capability is available for LaBr3 and NaI scintillators too.
The secret to this capability is twofold:
- The energy/efficiency/spatial response profile of the detector has been characterized by Mirion with the well-known MCNP Monte Carlo modeling code.
- Mathematical templates have been created for most of the sample geometries that will be encountered – planar surfaces, rectangular boxes, barrels, pipes, beakers, etc.
To a basic geometry template, add the specifics for a given sample – its size, density, distance from the detector, etc. – and at the click of a button the ISOCS Calibration Software generates a custom efficiency calibration specifically tailored for that detector, sample, and geometry. The remainder of this document will describe how this is done and how the various standard geometry templates are used.