8/6/2023 0 Comments Transverse fission meaningModifications to the RAFFLE code were necessary in order to score the Ge detector count rate. Some of the reasons for the apparent differences between the calculated and experimental results are discussed. Both experimental and calculated responses are given. The results of this initial study are given for a point source and a FPDS gas line collimator designed for PBF. Each of these measured curves have an estimated overall error of +-20% from 60 to 250 keV, +-10% from 250 to 1500 keV, and +-15% above 1500 keV. The test case for the collimated system was the PBF Fission Product Detection System (FPDS) installation viewing the gas effluent line. The two geometries included the simple case of a point source emitter located on the detector axis 15.3 cm from the detector end cap, and the more complicated case of a collimated system. The investigative approach consisted of using a modified RAFFLE code to predict the photopeak efficiency curves for two geometries for which experimental curves had been more » measured. Additionally, a RAFFLE prediction of a detector-collimator-source efficiency curve might provide important data for the design of collimator/detector systems. It is anticipated that substantial savings in time and money can be realized by using RAFFLE to generate the system photopeak efficiency curve. This report is the result of an initial investigation into the feasibility of calculating photopeak efficiency curves for any gamma-ray detection system using the photon-transport capabilities of the INEL RAFFLE Monte Carlo code. The discrepancy in the low frequency regime is understood in terms of limits on the test capabilities. The correlation is excellent at all but the lowest frequencies tested. In this current work the theoretical factor has been validated by creating the plane wave environment inside a gigahertz transverse electromagnetic (GTEM) cell instead of an anechoic chamber. Warne, et al, at Sandia have developed a theoretical correction factor and a previous attempt to more » validate it using an anechoic chamber (Higgins & Charley, Electromagnetic Radiation (EMR) Coupling into Complex Systems Aperture Coupling into Canonical Cavities in Reverberant and Anechoic Environments and Model Validation (SAND2007-7391), 2007) was not conclusive. Subsequently, a plane wave correction factor is needed to relate the plane wave and reverberation environments. This would result in an under test of the system. At the same time, a reverberation chamber averages out the directive gain of any points of entry. Sandia strongly prefers to test electromagnetic susceptibility in a reverberation chamber because a reverberant environment does not allow any potential point of entry to be shadowed. Electromagnetic threats to weapon systems are always specified in terms of an incident plane wave.
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