Comparative Characterization Study of a LaBr3(Ce) Scintillation Crystal in Two Surface Wrapping Scenarios: Absorptive and Reflective

Abstract

The properties of a 50 mm × 50 mm × 30 mm monolithic LaBr3:Ce scintillator crystal coupled to a position-sensitive multi-anode photomultiplier (PMT, Hamamatsu H9500), representing the absorbing detector of a Compton camera under study for online ion (proton) beam range verification in hadron therapy, was evaluated in combination with either absorptive or reflective crystal surface coating. This study covered an assessment of the energy and position-dependent energy resolution, exhibiting a factor of 2.5–3.5 improvement for the reflectively wrapped crystal at 662 keV. The spatial dependency was investigated using a collimated 137Cs source, showing a steep degradation of the energy resolution at the edges and corners of the absorptively wrapped crystal. Furthermore, the time resolution was determined to be 273 ps (FWHM) and 536 ps (FWHM) with reflective and absorptive coating, respectively, using a 60Co source. In contrast, the light spread function (LSF) of the light amplitude distribution on the PMT segments improved for the absorptively wrapped detector. Both wrapping modalities showed almost no differences in the energy-dependent photopeak detection efficiency.

Sub-millimeter precise photon interaction position determination in large monolithic scintillators via convolutional neural network algorithms

“…Two monolithic scintillation crystals with dimensions of 50.8 mm × 50.8 mm × 30 mm were examined as potential candidates for the absorber component: LaBr 3 :Ce and CeBr 3 . The crystals were wrapped in a reflective material which, despite a more inhomogeneous spatial response of the detector compared to an absorbing coating, has a significantly better energy and time resolution and thus a better over all performance (Aldawood et al 2015). Both crystals show hygroscopic properties and were therefore protected from humidity within an aluminum housing.…”

A New Method to Reconstruct in 3D the Emission Position of the Prompt Gamma Rays following Proton Beam Irradiation

“…The Geant4 Toolkit has been employed to simulate the spectrometer and a clinical 180 MeV proton pencil beam impinging a homogeneous 4 × 4 × 30 cm 3 water ( G4Water ) phantom. For the LaBr 3 (Ce) detectors, an energy resolution of 3% FWHM 58 and a time resolution of 280 ps 59 have been chosen. For the spectrometer, to subtend a high solid angle with respect to the PG-ray emitted in proximity of the Bragg peak and to obtain meaningful results within a reasonable computational time, the internal radius was set to 8 cm.…”

Sub-3mm spatial resolution from a large monolithic LaBr3 (Ce) scintillator

“…The system consists of a large (50x50x30 mm 3 ) monolithic LaBr 3 (Ce) scintillation crystal as absorber component to detect the multi-MeV Compton scattered photons, together with a stack of 6 double-sided silicon strip detectors (DSSSD) acting as scatterer component. Key ingredient of the -source reconstruction is the determination of the -ray interaction position in the scintillator, which is read out by a 256-fold segmented multi-anode photomultiplier tube (PMT).…”

“…These characteristics resulted in an excellent time resolution (<300 ps) and a very good energy resolution (E/E~3.8%) [3], which is favourable for an optimized reconstruction of the prompt  origin and efficient background discrimination. The crystal was coupled to a 256-fold segmented multianode photosensor (Hamamatsu H9500 PMT, 16x16 segments, each 3x3 mm 2 ), which operated at a bias voltage of -1000V (in Fig.2 a photo of the detector is shown).…”