Position resolution and energy spectra from a two-dimensional gas proportional detector in the region of the krypton K-edge

Results are presented of the position resolution and energy spectra from a two-dimensional gas proportional detector in the region of the krypton K-edge of 14.326 keV. Measurements were made with a gas mixture of Kr/10%CO2 and the position resolution was fit by a simple model based on the photoelectron and Auger electron range. In the energy region below the K-edge, X-rays interact primarily in the L-shell, yielding an energetic photoelectron that limits position resolution to no better than several hundred μm. For X-rays with energy just above the K-edge, position resolution in the range of 90 μm FWHM was achieved using the technique of escape peak gating. We found broad low-level wings forming about 31% of the total area in the position spectrum above the K-edge, indicating that the L-shell interactions are included (and inseparable) in the gating technique of photopeak events within this energy range. Furthermore, the shape of the position spectrum was well explained when the energy dependence of σ L / ( σ K + σ L ) was considered above the K-edge.