HPGe detectors for low-temperature nuclear orientation

Using the low-temperature nuclear orientation (LTNO) technique one can study various interesting properties of atomic nuclei and nuclear decay which can be deduced from the measurements of the angular distributions of charged particles emitted during the decay. However, the use of particle detectors working in conditions of LTNO devices (which are generally not available commercially) is a necessary precondition for the realization of these experiments. Planar HPGe detectors for detection of charged particles at "liquid helium" temperatures were developed and produced at NPI Rez. Relatively simple technology using vacuum evaporation and diffusion was employed. The performance of detectors at low temperatures was tested and their characteristics measured in a testing cryostat before using them in real experiments. The HPGe detectors were extensively used in a whole range of LTNO experiments with various physical objectives - in offline (IKS Leuven) as well as online (CERN-ISOLDE, Louvain-la- Neuve - LISOL) experiments. In the framework of the project "Meson-Exchange Enhancement of First-Forbidden $\beta$-Transitions in the Lead Region", the measurements of angular distribution of emitted $\beta$-particles allowed to determine experimentally the "meson-exchange currents" contribution to the $\beta$-decay. In the project "Isospin Mixing in N~Z nuclei", the isospin-forbidden $\beta$-transitions of the nuclei in region (A = 50-100) were studied in order to obtain information on the isospin structure of the nuclear states. A new project looking for the possible presence of the tensor currents contribution to the $\beta$-decay is being prepared for the CERN-ISOLDE facility.