In the last few years we have been working on feasibility studies of future instruments in the gamma-ray range, from
several keV up to a few MeV. The innovative concept of focusing gamma-ray telescopes in this energy range, should
allow reaching unprecedented sensitivities and angular resolution, thanks to the decoupling of collecting area and
detector volume. High sensitivities are essential to perform detailed studies of cosmic explosions and cosmic
accelerators, e.g., Supernovae, Classical Novae, Supernova Remnants (SNRs), Gamma-Ray Bursts (GRBs), Pulsars,
Active Galactic Nuclei (AGN). In order to achieve the needed performance, a gamma-ray imaging detector with mm
spatial resolution and large enough efficiency is required.
In order to fulfill the combined requirement of high detection efficiency with good spatial and energy resolution, an
initial prototype of a gamma-ray imaging detector based on CdTe pixel detectors is being developed. It consists of a
stack of several layers of CdTe detectors with increasing thickness, in order to enhance the gamma-ray absorption in the
Compton regime. A CdTe module detector lies in a 11 x 11 pixel detector with a pixel pitch of 1mm attached to the
readout chip. Each pixel is bump bonded to a fan-out board made of alumina (Al2O3) substrate and routed to the
corresponding input channel of the readout ASIC to measure pixel position and pulse height for each incident gamma-ray
We will report the main features of the gamma-ray imaging detector performance such as the energy resolution for a set
of radiation sources at different operating temperatures.