ABSTRACT
In previous chapters we have seen how fusion products were studied using mechanical devices like rotating wheels and cylinders. In all of them the fusion products are stopped and transported to detectors. That takes time. The fastest method was the Russian cylinder which could measure half-lives down into the range of milliseconds but was sensitive only for fission fragments. For the measurement of -decay one must place the detectors further away from the target because the energy of -particles is about 10 times smaller than the energies of fission fragments, so more sensitive detectors must be used. These, however, would suffer from too high a radiation background near the target. To overcome this problem, tape devices were developed which moved the activity a few metres away. Gas transport systems (helium jets) transported the activity in a gas stream (usually helium) through a thin capillary several metres long. With these methods, the detectors could be placed far away from the target in a well-shielded area, although the transport time increased to several seconds so that all nuclei with half-lives from microseconds to seconds would be lost. A completely new separation technique had to be developed and this became possible with kinematic separators.
