Assessment of Technology for Testing and Demonstration of Gamma-Ray Measurement Systems without the Use of Nuclear Materials

Calibration and testing of radiation measurement systems can be very difficult and expensive, especially so if large amounts of radioactive materials are required. An electronic surrogate that can simulate a pulse train from a detector for arbitrary amounts and configurations of materials and shielding would be valuable for testing, debugging, authenticating and calibrating gamma-ray detection hardware and software. This technology could greatly reduce, or eliminate, the need for nuclear material sources in testing and training (in, e.g. international safeguard regimes). We discuss results of an assessment of the performance of such a surrogate. Given a target pulse-height spectrum the pulser generates a random series of pulses that reproduce the target spectrum. We have performed blind testing of the gamma-ray pulser system: material attributes were chosen to create input to the pulser and the attributes inferred from the output of the pulser were compared to the inputs. The tests proceeded through several steps. First a container and Pu isotopic composition were chosen and for a particular detector system, the corresponding pulse height distribution was predicted. This predicted pulse height distribution was loaded into the pulser. An operator who did not know the composition acquired pulse height analyzer data from the pulser and measurement electronics to produce a measured pulse height distribution (MPHD). The MPHD was analyzed to infer an isotopic composition. The inferred and original compositions were then compared. A calculation procedure and pulser that have been proven to accurately test a measurement system can be used as a surrogate for any amount of Pu of any isotopic composition in any sort of container. Using a pulser for testing or training, making the use of actual Pu unnecessary, can save a great deal of time and resources.