Production of Cs and Fr isotopes from a high-density UC targets with different grain dimensions

A UC target material of 11.3±0.5 g/cm^3 uranium density with the grain size of 20 and 5μm manufactured in a form of pills by the method of powder metallurgy has been tested on-line within the temperature range of 1800-2100 ^° C . The mass of uranium exposed to the beam was 4-7g. The yields and release rates of Cs and Fr isotopes produced by fission and spallation reactions of ²³⁸U by 1GeV protons have been measured. The yields of Cs and Fr isotopes obtained from the tested target materials have been compared, including yields of very short-lived Fr isotopes with half-lives down to 1ms. Temperature-resistant materials (porous graphite and tantalum foil) have been used for the internal-container construction, which holds the UC target pills inside a tungsten external container heated by the resistant heating. The fastest release and the highest efficiency for short-lived isotopes have been obtained for the targets with the internal container manufactured from the tantalum foil. Results of on-line tests of a big mass target (730g of 5μm grain UC target material) have been discussed.