High efficiency CsI(Tl)/HgI2 gamma ray spectrometers

Y. J. Wang, B. E. Patt, J. S. Iwanczyk, S. R. Cherry, Y. Shao

Research output: Chapter in Book/Report/Conference proceedingConference contribution


CsI(Tl)/HgI2 gamma-ray spectrometers have been constructed using 0.5' diameter detectors which show excellent energy resolution: 4.58% FWHM for 662 keV 137Cs gamma-ray photons [1]. Further efforts have been focused on optimization of larger size (≥1' diameter) detector structures and improvement of low noise electronics. In order to take full advantage of scintillation detectors for high energy gamma-rays, larger scintillators are always preferred for their higher detection efficiencies. However, the FWHM resolutions of larger PDs may be higher as a result of larger capacitances and dark currents. For very large volume scintillators, it may necessary to employ a PD with a sensitive area smaller than the cross-section of the scintillator. Monte Carlo simulations of the light collection for various tapered scintillator/PD configuration were performed in order to find those geometries which resulted in the best light collection. According to the simulation results, scintillators with the most favorable geometry, the conical frustum, have been fabricated and evaluated. The response of a large conical frustum (top-2', bottom-1', 2' high) CsI(Tl) scintillator coupled with a 1' HgI2 PD was measured. The energy resolution of the 662 keV peak was 5.57%. The spectrum shows much higher detection efficiency than those from smaller scintillators, i.e., much higher peak-to-Compton ratio in the spectrum.

Original languageEnglish (US)
Title of host publicationIEEE Nuclear Science Symposium & Medical Imaging Conference
Editors Anon
Number of pages5
StatePublished - Dec 1 1994
EventProceedings of the 1994 Nuclear Science Symposium and Medical Imaging Conference. Part 1 (of 4) - Norfolk, VA, USA
Duration: Oct 30 1994Nov 5 1994


OtherProceedings of the 1994 Nuclear Science Symposium and Medical Imaging Conference. Part 1 (of 4)
CityNorfolk, VA, USA

ASJC Scopus subject areas

  • General Engineering


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