Spectroscopic response of a CdTe microstrip detector when irradiated at various impinging angles

A study of the spectroscopic response of a CdTe detector, 10 mm×3 mm×3 mm in size, equipped with a 10 mm×3 mm full cathode and a 10 mm×0.3 mm central strip anode placed between two parallel focusing strips spaced of about 0.050 mm from the collecting anode, was carried out. This configuration increases the intensity of the weighing field surrounding the anode strip, thus improving the collection of the electrons. The detector was irradiated through the cathode by a narrow photon beam (57Co source) at various impinging angles θ in the range 0–87° , θ being the angle between the photon beam axis and the normal to the cathode surface, aiming at obtaining better spectroscopic performance. The measurements were carried out with the long side of the beam spot (0.90 mm×0.18 mm) oriented both transversal and parallel to the central strip anode. In this last case, significant improvements for some spectroscopic parameters were obtained; e.g. the peak-to-valley ratio of the 122-keV peak changes from 13.5 at 0° to 25.8 at 82°, i.e. an almost two times better value.