(Tuesday, 7/16/2019) 7:30 AM - 9:30 AM
Room: 221AB
Purpose: Literature and previous research have provided many physics-based models for the energy response function (R) of photon counting detector (PCD). For a given conductive material, most of the model parameters can be determined based on x-ray and semiconductor physics. However, the readout electronics of an experimental PCD system are vendor- or even model-specific; the latest incorporation of propriety anti-charge sharing (ACS) logic in PCD further confounds the modeling of R. The purpose of this work was to develop a practical approach that helps linking a physics-based R model to a specific experimental PCD system.
Methods: The proposed model leveraged a serial+parallel cascaded systems analysis framework to include all major x-ray interaction processes and charge carrier transport processes in the photoconductor. The hidden ACS logic and other component of the readout circuit were converted into an effective reduction in the charge cloud radius (r_effective) and fluorescent photon travel distance (L_effective). Except these two parameters, all other parameters used in the model were determined based on physics, facilitating the remaining two parameters (r_effective and L_effective) to be determined through an Am-241 isotope-based calibration procedure. The proposed method was used to determine R of a CdTe-based PCD (XCounter, Sweden) for an arbitrary polychromatic spectrum, and the result was compared with the corresponding experimental curve measured with the same polychromatic spectrum.
Results: From the experimental PCD operated under the ACS mode used in this work, r_effective was determined to be 2.2 um and L_effective was determined to be 15 um. For 85% of the data points, differences between the probability density of the predicted measured spectrum and the experimental ones were within ±0.003 keV^{-1}.
Conclusion: A practical method was developed to enable a physics-based R model to be adapted to each specific PCD system that contains components that cannot be determined by physics.
Funding Support, Disclosures, and Conflict of Interest: The work is partially supported by an NIH grant R01EB020521 and a DOD Breakthrough Award W81XWH-16-1-0031.
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