Speaker
Description
The most common sensor material for detectors at synchrotron sources and free electron lasers is silicon due to its outstanding material quality in terms of homogeneity and charge carrier transport properties. However, silicon (Z = 14) based sensors suffer from relatively low absorption efficiency at energies above 20 keV. Sensors manufactured from high atomic number material, so-called high-Z sensors, provide absorption efficiencies that are significantly higher but typically suffer from downsides in comparison to silicon, including crystal inhomogeneities, fluorescence emission, dislocation lines and charge-trapping. The usability and progress of different high-Z sensor materials (GaAs, CdTe, CZT) at synchrotron sources has been evaluated using the JUNGFRAU readout chip as a possibility to widen the usable energy range of the detector systems. JUNGFRAU is a low noise, charge-integrating pixel detector with a pixel pitch of 75 x 75 µm$^2$ and 256 x 256 pixels per single chip.
Charge-integrating detectors provide a suitable environment to reveal the properties of sensors as each pixel provides a direct measure of the charge collected in a defined area. In addition, each pixel is sensitive to temporal as well as spatial sensor effects, which affect the charge collection and help to understand those aforementioned shortcomings of high-Z sensors.
We will evaluate and present an overview of the typical sensor material characteristics like charge transport properties (µτ), resistivity (ρ) and I-V characteristics including temperature dependency studies for various high-Z materials. Moreover, system characteristics like stability, noise and spectroscopy performance (FWHM) will be shown. The findings will be interpreted in the context of the actual sensor performance and usability to highlight key variables and potential improvements for the future. Furthermore, first imaging results with a CdTe quad sensor (active area: 3.92 x 3.92 cm$^2$) will be presented.