A study of the helium-jet recoil-transport method and its application to on-line isotope separation

The helium-jet recoil-transport method and its coupling to the isotope separator on-line have been investigated. The dependence of the transport efficiency on several equipment parameters was studied both experimentally and theoretically. First, the transport efficiency of the He-jet method itself was studied. Pure commercial-grade helium, both at room temperature and at liquid nitrogen temperature, as well as carrier-loaded helium, was used. Efficiencies obtained with pure helium at room temperature were below 1 % when transport distances longer than one meter were used. Cooling of the helium down to liquid nitrogen temperature gave efficiencies of 10 - 50 % with several-meter transport distances. High transport efficiencies were also obtained when the helium was loaded with different carrier vapors. It was shown that additives have to form clusters with diameters from 0.01 - 1.0 μm for efficient transport of radioactivities. Next, a pure helium-jet at liquid nitrogen temperature coupled to a Nielsen type ion source, and a NaCl-loaded helium-jet coupled to a hollow cathode ion source, were investigated as means of connecting a cyclotron target chamber on-line to an isotope separator. Total separation efficiencies measured under various experimental conditions for several nuclides (Cu, In, Sn, Sb, Ba, Bi) were typically between 0.01 and 1.0 %.