Two-dimension position sensitive Transition Radiation Detector in beam- tests using new Fast Analog Signal Processor (FASP)

The new two-dimension position sensitive TRD prototype architecture for CBM experiment developed by us is based on diagonally split rectangular pads of the read-out electrode [1]. The choice of triangular-pad geometry allows for position determination in both coordinates: across and along the pads, respectively. The TRD prototype used in the present tests has a readout electrode of 25 μm thickness kapton foil having on both sides evaporated Al/Cr layers with the mentioned pad structure. The first version of the prototype was built with an anode-cathode distance of 3 mm (DSTRD-V1) and a readout electrode with a double sided pad structure [2] [3] similar with small size double sided TRD prototype which showed that such a geometry preserves the performance up to 2x10 part.·cm−2·s−1 counting rate. In order to improve the charge sharing between the pads for position reconstruction, the second version was built with a 4 mm anodecatode distance (DSTRD-V2). Both detectors were tested with the 5.9 keV X-ray Fe source using both the anode and pad signal, respectively. 80% Ar + 20% CO2 gas mixture was flushed trough the counter. For pad signal processing we used the new FEE Fast Analog signal Processor (FASP) [4] developed in our group. It has 8 input/output channels and can provide two type of outputs: a fast output with a semi-Gaussian shape (Fig. 1-blue line) and a flat top output (Fig. 1-red line) [5].