Radiation Detection and Measurement Studies

Alonzo, Jolina

Student Work

Radiation Detection and Measurement Studies

Público Deposited

The characterization of the WELL3 detector, a well-type detector, at Pacific Northwest National Laboratory (PNNL) is an important and necessary capability for performing high-precision, low-intensity radio-isotope measurements. The characterization of the WELL3 detector provided the Advanced Radio-Emission Spectroscopy (ARES) team with another detector to analyze and obtain data for weak radioactive isotopes. A benchmarked calibrated and characterized model of the WELL3 detector was created using the CERN C++ particle simulation framework GEANT4 with a PNNL developed utility, the Geant4-Cascade Summing Correction tool. This benchmark was constructed by conducting quantitative intercomparison of the modeled and measured detector response to a National Institute of Standards & Technology (NIST) traceable mixed gamma standard mix 7503 from Eckert & Zeigler and a medical isotope standard of Molybdenum-99 (Mo-99) from the National Physical Laboratory. The mixed gamma standard, NIST traceable measured detection efficiency, was used to optimize the model parameters before conducting an independent validation using the Mo-99 standard. A comparison of peak ratios was performed between the measured and simulated spectra of Mo-99 to analyze the accuracy of the decay cascade summing probabilities predicted by the model. From the counted Mo-99 sample the half-life (T1/2) was obtained for each relevant gamma ray energy lines and compared against the Evaluated Nuclear Structure Data Files (ENSDF) available from the National Nuclear Data Center. The analysis of the true-coincidence summing (TCS) corrections of the Mo-99 response from the benchmarked model show large corrections were made to simulate the spectrum from Mo-99 on WELL3. The future work will encompass further optimization of the calibrated detector model on GEANT4 with G4CSC. The current characterization of the WELL3 detector shows promise for the counting of Tb-161, an important nuclide in medical physics. Overall, the characterization of the WELL3 detector at PNNL now provides the ARES team a new capability for the high-efficiency detection of weak samples.

This report represents the work of one or more WPI undergraduate students submitted to the faculty as evidence of completion of a degree requirement. WPI routinely publishes these reports on its website without editorial or peer review.

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