Speaker
Description
Gamma-ray imaging based on Compton scattering typically requires a two-component system, consisting of a scatterer and an absorber. The present work explores an alternative approach using a single, segmented high-purity germanium (HPGe) detector from the Advanced GAmma Tracking Array (AGATA) [1] collaboration for reconstructing the position of a radioactive source. A key advantage of using a single HPGe detector is its superior detection efficiency, compared to a scatterer-absorber device, as it can simultaneously capture and process gamma rays from nearly the full solid angle. The detector’s segmentation, 36 segments and a central core contact, allows pulse shape analysis (PSA) [2,3] techniques to enhance position resolution of the gamma rays interactions. Additionally, the excellent energy resolution of HPGe intrinsically reduces uncertainty in the half-opening angle of the Compton cone, enhancing the reconstructed image resolution.
The present study introduces a lightweight PSA machine learning model based on a 3D basis of waveforms, of more than 46000 points equally spaced by 2 mm along X, Y and Z axes in the HPGe crystal volume, constructed using the IPHC scanning table with the Pulse Shape Comparison Scan (PSCS) [4] method. By replacing the computationally intensive 𝜒2 comparison between recorded waveforms and a 3D database, this model improves processing speed, making it well-suited for real-time applications. These advancements highlight the potential of a single segmented HPGe detector for timeefficient and precise gamma-ray imaging.
Keywords Gamma-ray imaging, 4𝜋-detection, lightweight PSA, single-volume device
[1] S. Akkoyun et al., “AGATA—advanced GAmma tracking array,” Nucl. Instrum. Methods Phys. Res. A, vol. 668, pp.
26–58, Mar. 2012, doi: 10.1016/j.nima.2011.11.081.
[2] B. Bruyneel, B. Birkenbach, and P. Reiter, “Pulse shape analysis and position determination in segmented HPGe detectors: The AGATA detector library,” The European Physical Journal A, vol. 52, no. 3, Mar. 2016, doi: 10.1140/ epja/i2016-16070-9.
[3] R. Venturelli and D. Bazzacco, “Adaptive Grid Search as Pulse Shape Analysis Algorithm for γ-Tracking and Results.” [Online]. Available: https://www1.lnl.infn.it/~annrep/read_ar/2004/contrib_2004/pdfs/FAA122.pdf
[4] B. De Canditiis and G. Duchêne, “Simulations using the pulse shape comparison scanning technique on an AGATA segmented HPGe gamma-ray detector,” The European Physical Journal A, vol. 56, no. 10, Oct. 2020, doi: 10.1140/epja/s10050-020-00287-6.
| Workshop topics | Sensor materials, device processing & technologies |
|---|
