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Characterization of HPGe detectors using Computed Tomography

A. Hedman ; J. B. Gogani ; M. Granstrom ; L. Johansson ; J. S. Andersson ; Henrik Ramebäck (Institutionen för kemi och kemiteknik, Kärnkemi)
Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment (0168-9002). Vol. 785 (2015), p. 21-25.
[Artikel, refereegranskad vetenskaplig]

Computed Tomography (CT) high resolution imaging have been used to investigate if there is a significant change in the crystal-to-window distance, i.e. the air gap thickness, in a small n-type detector cooled to 77 K, and in a medium sized p-type HPGe detector when cooled to 100 K. The findings were compared to detector dimension data made available by the manufacturer. The air gap thickness increased by (0.38 +/- 0.07) mm for the n-type detector and by (0.40 +/- 0.15) mm for the p-type detector when the detectors were cooled to 77 resp. 100 K compared to at room temperature. Monte Carlo calculations indicate that these differences have a significant impact on the efficiency in close geometries (< 5 cm). In the energy range of 40-700 keV with a source placed directly on endcap, the change in detector efficiency with temperature is 1.9-2.9% for the n-type detector and 0.3-2.1% for the p-type detector. The measured air gap thickness when cooling the detector was 1.1 mm thicker than manufacturer data for the n-type detector and 0.2 mm thicker for the p-type detector. In the energy range of 40-700 keV and with a source on endcap, this result in a change in detector efficiency of 5.2-7.1% for the n-type detector and 0.2-1.0% for the p-type detector, Le the detector efficiency is overestimated using data available by the manufacturer.

Nyckelord: Gamma spectrometry, HPGe, Computed Tomography, Monte Carlo modelling, Gespecor, Semi-empirical calibration



Denna post skapades 2015-05-11.
CPL Pubid: 216935

 

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Institutioner (Chalmers)

Institutionen för kemi och kemiteknik, Kärnkemi

Ämnesområden

Kärnfysik

Chalmers infrastruktur