High-spatial resolution measurements with a GaAs:Cr sensor using the charge integrating MÖNCH detector with a pixel pitch of 25 μm

Abstract

The aim of this project is to determine the imaging capabilities of a 25 μm pixel pitch GaAs:Cr sensor of 500 μm thickness bump-bonded to the charge integrating MÖNCH 03 readout chip (also called GaAs-MÖNCH assembly) and to assess the possibility to improve the spatial resolution by applying a position interpolation algorithm developed at PSI. Measurements were performed at the TOMCAT beamline of the Swiss Light Source (SLS) using photon beams in the energy range of 10–30 keV. The imaging experiments indicate the possibility to enhance the spatial resolution of the detector beyond its actual physical pixel pitch. We have quantified the spatial resolution of a GaAs-MÖNCH assembly by means of the modulation transfer function (MTF), achieving 10 μm at 10 keV and 12 μm at 20 keV photon energies. By applying a modified interpolation algorithm, a spatial resolution of ∼5 μm was obtained for 16 keV when binning to 2.5 μm virtual pixels, while with the silicon-MÖNCH assembly, we achieved a spatial resolution of 3.5 μm, which serves as gold standard. The results are promising because they open new possibilities to perform imaging measurements using the GaAs-MÖNCH assembly at photon energies above 15 keV, where silicon sensors suffer from a diminishing quantum efficiency.

Resolving soft X-ray photons with a high-rate hybrid pixel detector

“…Additionally, the charge integrating architecture means charge sharing between neighboring pixels can be utilized to perform position interpolation, improving the spatial resolution of the detector beyond the pixel size. With the 25 µm pitch MÖNCH chip, for instance, spatial resolution in the micron range has been demonstrated in the hard X-ray domain [27,34]. Based on these results, we note that an iLGAD hybrid detector based on the MÖNCH chip or an adapted version of JUNGFRAU with smaller pitch in one dimension would open further possibilities for spectroscopic techniques such as RIXS, soft X-ray spectro-ptychography, and soft or tender X-ray full field imaging techniques that rely on high spatial resolution.…”