A Novel X-ray Detector System

T. E. Hansen1, A. Ferber2, N. Ahmed1, O. Løvhaugen2, J. Østby3, G. Bouquet2, F. Tyholdt4,

M. Hjelstuen5, O. Paulsen6

1 MiNaLab, SINTEF ICT, P.O. Box 124, Blindern, N-0314, Oslo, Norway, thor-erik.hansen@sintef.no

2 Dept. of Optical Measurement Systems, SINTEF ICT, P.O. Box 124, Blindern, N-0314, Oslo, Norway

3 Dept. of Communication, SINTEF ICT, P.O. Box 124, Blindern, N-0314, Oslo, Norway

4 Dept. of Energy Conv. and Materials, SINTEF MC, P.O. Box 124, Blindern, N-0314, Oslo, Norway

5 Dept. of Instrumentation, SINTEF ICT, P.O. Box 124, Blindern, N-0314, Oslo, Norway

6 Dept. of Energy conversion and Materials, SINTEF MC, N-7465 Trondheim, Norway

ABSTRACT

The paper describes an interdepartmental effort at SINTEF, Norway to develop a novel x-ray detection system based on photon counting to open new applications in medicine, security and industry. The system is centred round a silicon sensor chip in the edge-on configuration which theoretically allows detection at x-ray energies ? 200 keV. The concept is already demonstrated to 100 keV with an existing chip fabricated by SINTEF combined with a non-optimal front-end readout chip. In order to extend the sensitivity at low energies to ? 5 keV, a new sensor chip with active edge is being fabricated for the system. This requires 3-dimensional wafer processing, but will make the sensor sensitive almost to the chip edge with a very narrow dead region. X-ray optics are developed in the form of collimators and band pass filters to adapt the radiation from the x-ray point source to the multi element line sensor, and to restrict the bandwidth to the interesting energy ranges.

A low noise front end electronic chip is developed for the readout of the multi element silicon sensor. The purpose of the front-end electronics is to collect the charge generated in the sensor by the x-ray photons, amplify and quantify this charge, and then identify the energy interval where the photon belongs. The front-end circuitry will also detect and eliminate “faulty” hits that may reduce the quality of the data. The front end is designed for an average hit rate up to 5Mhits/s. 16-bit counters is used to find the number of hits within each energy interval. The front end electronic is designed with a high level of flexibility in order to permit adaptation to applications with highly different specifications regarding acquisition speed and energy resolution, which are two highly competitive features.

Keywords X-ray detection system, photon counting, edge-on silicon sensor, active-edge, capillary x-ray optics, multilayer x-ray filters