TY  - THES
AB  - The intention of this work is to analyze the detector response and the participating processes of a X- and γ-ray detector consisting of a single Silicon Drift Detector (SDD) cell coupled to a CsI(Tl) or LaBr3(Ce) scintillator and a SDD array or pn-Charged Coupled Device (pnCCD) coupled to a CsI(Tl) scintillator in order to define limitations of the detector performance and possibilities to improve it. For the system, SDD / pnCCD + CsI(Tl) or LaBr3(Ce) scintillator, the relevant contributions to the energy and spatial resolution are investigated and their values are determined from results of measurements, calculations and simulations, which have not been presented in literature yet. Results indicate, that the main contribution to the energy resolution for a single SDD cell coupled to CsI(Tl) or LaBr3(Ce) originates from the so called scintillator non-proportionality. Simulations show that the light and charge collection efficiency inside the system generate only a minor contribution to the energy resolution, if CsI(Tl) is used as scintillator. These and the remaining contributions are presented for incident γ-rays in the range from 6 keV to 662 keV. A γ-camera consisting of a SDD array with 77 hexagonal cells and an active area of 29 x 26 mm2, which is coupled to a 5 mm thick CsI(Tl) scintillator, has been investigated with respect to the spatial and energy resolution for γ-rays with an energy of 60 keV and 122 keV. These detectors have been developed for medical applications, e.g. emission tomography for small animals, with a sub millimeter spatial resolution in the energy range of interest. The spatial resolution reaches values of 1.1 mm for 60 keV and 0.5 mm for 122 keV photons. The relative energy resolution has a value of about 0.37. Results from simulation reproduce these results and indicate that the main contributions to the energy resolution originate from a high data acquisition threshold, due to the increased electronic noise and the dependence of the number of signal electrons on the generation depth of the scintillation photons inside the scintillator. A reduction of the scintillator thickness and especially the decrease of the electronic noise, which enables a lowering of the data acquisition threshold, improves the spatial and energy resolution. The combination of a pnCCD with a pixel size of 75 x 300 μm2 or 300 x 300 μm2 and a CsI(Tl) scintillator of 0.7 mm or 1 mm thickness respectively were investigated by simulations for their suitability as a γ-camera in the energy range of 1 keV - 150 keV. In particular the application as a detector for X and γ-ray diffraction pattern analysis with sufficient spatial and energy resolution was of interest. By coupling a scintillator onto the pnCCD a higher quantum efficiency of the system is reached. The coupled system will be irradiated from the pnCCD side to utilize the good performance of the pnCCD in the low X-ray energy range up to several 10 keV. The pnCCD is almost transparent for hard X- and γ-ray photons, which generate scintillation photons inside the scintillator. Results from simulations indicate that the detector, pnCCD + CsI(Tl), is suitable to detect diffraction patterns in the energy range 1 keV - 150 keV, if detector parameters are chosen and set properly.
AU  - Schlosser, Dieter Michael
DA  - 2014
KW  - Cäsiumiodid
KW  - Silizium Drift Detektor
KW  - Photodetektor
KW  - CsI(Tl)
KW  - LaBr3(Ce)
KW  - Simulation
KW  - silicon drift detector
KW  - photodetector
KW  - simulation
LA  - eng
PY  - 2014
TI  - Response of high resolution silicon photodetectors coupled to CsI(Tl) or LaBr3(Ce)
UR  - https://nbn-resolving.org/urn:nbn:de:hbz:467-8281
Y2  - 2024-11-22T09:04:16
ER  -