Characterization of CsI(Tl) and LYSO(Ce) scintillator detectors by measurements and Monte Carlo simulations.

In this study, we investigated the performance of two cuboid scintillation detectors: thallium-activated cesium iodide [CsI(Tl)] and cerium-doped lutetium yttrium orthosilicate [LYSO(Ce)]. The CsI and LYSO crystals were 5 mm thick with an active area of 10 mm × 10 mm. The LYSO scintillator is characterized by its high stopping power and non-hygroscopicity (neither packaging nor light guide are required). Nevertheless, the main disadvantages of LYSO detectors are a lower light output (32 photons/keV) and an intrinsic radioactivity caused by the ß- decay of 176Lu (half-life 3.78 × 1010 years). In contrast, CsI crystals present a relatively high light output (54 photons/keV) allowing better energy resolution; however, the drawback of a CsI detector is low detection efficiency. First, we measured the photon detection efficiency of each scintillator in the photon energy range of 60-1332 keV using radioactive sources. Second, we computed detector efficiencies using the Monte Carlo codes MCNP and Geant4. A comparison between simulated and measured efficiencies showed a good agreement. This comparison confirmed the validity of the mathematical models developed for the two scintillation detectors CsI(Tl) and LYSO(Ce) under investigation.

Dead layer thickness characterization of an HPGe detector by measurements and Monte Carlo simulations.

To fully characterize the front dead layer (DL) of an HPGe detector at low photon energy range, its intrinsic efficiency curve was measured using a (241)Am radioactive source in 10-60 keV energy range. A comparison between experimental efficiency and MCNPX results showed that the DL value of 0.4 µm initially quoted by the manufacturer has to be changed to 7.5 µm to reproduce measurements.

Experimental characterization and Monte Carlo simulation of Si(Li) detector efficiency by radioactive sources and PIXE.

This work relates to the study and characterization of the response function of an X-ray spectrometry system. The intrinsic efficiency of a Si(Li) detector has been simulated with the Monte Carlo codes MCNP and GEANT4 in the photon energy range of 2.6-59.5keV. After finding it necessary to take a radiograph of the detector inside its cryostat to learn the correct dimensions, agreement within 10% between the simulations and experimental measurements with several point-like sources and PIXE results was obtained.