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Purpose: To explore the response of different thermoluminescent (TL) readers to micro‐cube and chip LiF:Mg,Ti (TLD‐100) TL dosimeters. Method and Materials: The precision of Harshaw Company TL reader models 3500 and 5500 was evaluated for LiF:Mg,Ti micro‐cube and chip dosimeters. Sets of TLD‐100 1mm × 1mm × 1mm micro‐cubes and 3mm × 3mm × 1mm chips were mounted in PMMA holders and irradiated to a dose equivalent to 1.00 Gy to water using . After irradiation, TLDs were evaluated on one of the readers. The annealing procedure between irradiations consisted of one hour at 400 °C, quick cooling to room temperature, and 24 hours at 80 °C. The ratio of the output of each TL dosimeter to the median output was tracked for three irradiations for each reader. In addition, the response of the model 5500 reader PMT to various amounts of TL output was analyzed. Sets of micro‐cubes and chips were irradiated to doses ranging from 0.10 Gy to 10.00 Gy dose to water. The light output from the PMT was analyzed for linearity with dose. Results: The mean reproducibility (1 standard deviation) of TLD‐100 micro‐cubes was 2.27% when evaluated with the model 3500 reader and 1.00% for the model 5500 reader. The mean reproducibility (1 standard deviation) of TLD‐100 chips was 1.68% for the model 3500 and 0.55% for the model 5500. In addition, the PMT of the model 5500 reader was found to have an exponential response with dose. Conclusion: The reader used to evaluate TL dosimeters affects measurements. This work concludes that the model 5500 reader is more precise for evaluation of TLD‐100 micro‐cubes and chips than is the model 3500 reader. In addition, the overresponse of the PMT to TL must be accounted for when using the model 5500 reader.

MCNP5 v1.51 and v1.60 model partial broadening when used with the MCPLIB04 data library. MCNP5 v1.60m models DB more accurately due to the form of the electron subshell data. In response to these results, Los Alamos National Laboratory has released a new photon data library, MCPLIB84, that presents the electron subshell data in cumulative distribution form. MCNP5 v1.60 should be used with this library when incoherent scattering has a significant impact on simulation results.

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Purpose: The energy spectrum of a linear accelerator used for dose calculations is determined during beam commissioning by iteratively adjusting the spectrum and comparing calculated and measured percent depth-dose curves. Direct measurement of the energy spectrum using pulse mode detectors is particularly challenging because of the high-energy, high fluence nature of these beams and limitations of the detector systems. This work implements a Compton scattering (CS) spectroscopy setup and presents detector corrections and spectral unfolding techniques to measure the spectrum of a 6 MV linear accelerator using a pulse mode detector. Methods: Spectral measurements were performed using a Varian Clinac 21EX linear accelerator and a high-purity germanium (HPGe) detector. To reduce fluence to the detector, a custom-built lead shield and a CS spectrometry setup were used. The detector was placed at CS angles of 46˚, 89˚, and 125˚. At each of these locations, a detector response function was generated to account for photon interactions within the experimental geometry. Gold's deconvolution algorithm was used to unfold the energy spectrum. The measured spectra were compared to simulated spectra, which were obtained using an experimentally benchmarked model of the Clinac 21EX in MCNP6. Results: Measurements were acquired and detector response corrections were calculated for all three CS angles. A comparison of spectra for all CS angles showed good agreement with one another. The spectra for all three angles were averaged and showed good agreement with the MCNP6 simulated spectrum, with all points above 400 keV falling within 4%, which was within the uncertainty of the measurement and statistical uncertainty. Conclusions: The measurement of the energy spectrum of a 6 MV linear accelerator using a pulse-mode detector is pre-