Studies of uranium carbide targets of a high density

Production of Cs and Fr isotopes from uranium carbide targets of a high density has been investigated at IRIS (Investigation Radioactive Isotopes at Synchrocyclotron), Gatchina. The UC target material with a density of 12 g/cm(3) was prepared in a form of pellets. Two targets were tested on-line Under the same temperature conditions: (a) a reference small target with a thickness of 4.5g/cm(2); (b) a heavier (so called intermediate) target with a thickness of 91 g/cm(2). Yields and release efficiencies of nuclides with half-lives from some Minutes to some milliseconds produced by 1 GeV protons in these targets Lire presented. It is remarkable that yields, even those of very short-lived isotopes such as Fr-214 (T-1/2 = 5 ms) and Fr-219 (T-1/2 = 20 ms), increase proportionally to the target thickness. A one month off-line heating test of the 91 mg/cm(2) target at a temperature of 2000 degrees C has been carried out successfully. The yields and release efficiencies of Cs and Fr measured on-line before and after the heating test coincided within the limits of measurement errors, thereby demonstrating the conservation of the target unit parameters. Based on these very promising results, it heavier target with a mass about 0.7 kg is prepared presently at IRIS. (C) 2008 Elsevier B.V. All rights reserved.