Abstract
The performance of prototype active-edge VTT sensors bump-bonded to the Timepix ASIC is presented. Non-irradiated sensors of thicknesses 100–200μm and pixel-to-edge distances of 50μm and 100μm were probed with a beam of charged hadrons with sub-pixel precision using the Timepix telescope assembled at the SPS at CERN. The sensors are shown to be highly efficient up to a few micrometers from the physical edge of the sensor. The distortion of the electric field lines at the edge of the sensors is studied by reconstructing the streamlines of the electric field using two-pixel clusters. These results are supported by TCAD simulations. The reconstructed streamlines are used to study the field distortion as a function of the bias voltage and to apply corrections to the cluster positions at the edge.
Highlights
Silicon pixel detectors are chosen in experiments where radiation hardness and high precision tracking are demanded
The smaller residuals are a result of setting the telescope planes in their optimum angle in contrast to the device under test (DUT) which is set perpendicular to the beam
To measure the efficiency the following procedure is used: charge calibration correction with the formula xCOG 1⁄4 x0 þ PPNi Ni1⁄41⁄400xqiqi i charged particles edge implant pixel pitch 55 m pixel pixel
Summary
Silicon pixel detectors are chosen in experiments where radiation hardness and high precision tracking are demanded. Conventional sensors use guard ring electrodes to gradually reduce the electric field towards the edge and in this way isolate the pixel matrix from edge effects. This results in an area with reduced sensitivity at the edge of the sensor up to a few hundred microns. Novel types of sensors with a smaller inactive area at the edge have been developed. These so-called edgeless sensors are divided into two sub-categories, slim-edge and active-edge. In this paper the performance at the edge of a series of non-irradiated active-edge sensors manufactured by VTT2 is studied
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