In recent years, wide gap semiconductor materials, such as CdTe and CdZnTe made substantial progress, which makes them competitive for high sensitivity gamma-ray detection under small volumes and without any cooling, as needed for homeland security problems. Nowadays, high resistivity large crystals become available and the earlier charge transport problems can be solved either electronically or by specific detector geometry structures. Single charge sensing detectors, either pixelized, coplanar, hemispherical structures allow to minimize the hole trapping problem and considerably improve the energy resolution for sizing of at least 1 cm³ (equivalent to approx. 5 cm³ Germanium).
The imaging systems based on these semiconductors, without the expensive and cumbersome PMT systems, can be lightweight, hand-held and operated for long periods of time.
In this presentation, focus is given to two important applications in homeland security applications, namely the identification of gamma emitters by high sensitivity spectrometers with different kind of geometries and also to the localization of hidden sources by small portable imagers.