Very low temperatures and their applications in nuclear orientation

In NO-experiments at very low temperatures problems arise from the finite life-time of the nuclei and the radioactive self-heating of the source. Recent developments of top loading hyperfine enhanced nuclear demagnetization cryostats of small cooling power give fast access to temperatures around 1 mK. To reach lower temperatures the bottleneck of thermal contact must be overcome in order to cool samples which are themselves the main source of heat. In this context the limitations of nuclear demagnetization cryostats are discussed with respect to their application in 'brute force'- and NQR/NMR-experiments. (Auth.)