To problem about construction of cyclotron target for bombardment of metal zinc and cadmium targets on exterior beams of the accelerator U-120

Full text: Industrial intrusion of diffusion-and-thermal methods of radionuclides separation it is impossible at use of traditional targets representing a Cu or Ag substrate, on which the starting isotopic enriched material is marked. For embodying these technologies it is necessary to modify a target so that completely to eliminate an opportunity of a physicochemical interaction (diffusion, alloy building) labilized material and target radionuclide with a substrate in requirements of heightened temperatures. One of the possible solutions of this problem - manufacture of substrates of cyclotron targets from high-melting inert materials. For the bombardment of metal Zn or Cd metal targets (production of 67Ga and 111In, basic medical radionuclides) on the on exterior beam of the accelerators U-120 designed the cyclotron target, where as a bottom for drawing a isotopic enriched materials will be utilized a tantalic substrate by a diameter of 28 mm and depth 750 microns. At centre of a substrate are made a dimple by a diameter 16 mm, where (from a melt) are superimposed metal Zn or Cd. For heat removal during bombardment: a) on the part of a tantalic substrate the target is washed by water, b) for refrigerating a obverse surface of a target the gaseous He will be utilized. The evaluation calculations are carried out: a) of the basic characteristics of a helium heat exchanger (for dissecting away of irradiated target from volume of the accelerator the titanium metal foil by depth 50 μm will be utilized), b) of strength of a Ta substrate (will be utilized at pressure of 'frigorific' water 0.5 MPa), c) of operating temperatures of a substrate and targets (Zn or Cd) at the bombardment by their of beams of deuterons (energy - 13/0 Me V, peak current of beam - 20 μA). Is ro tined, that the optimum interval of values of pressures of helium compounds 25-32 mm Hg; the build-up of pressure of helium gives in linear magnification of voltages and down stroke of ultimate strength owing to magnification of temperature of a metal foil. Are calculated a voltage and sag of a Ta substrate in a dependence of pressure of 'frigorific' water and thermal loading (i.e. current of a beams of charged particles) of cyclotron target. Is ro tined, that all section of a substrate works in requirements of small compression stresses (-14-45 MPa), that is most favourable mode and ensures operational stability of metal during 100 and more than clocks at currents of a beam up to 20 μA. On a procedure for a longitudinal flow of a radiopaque plate the values of thermal heat transfer coefficients of a tantalum to water in limits 98000-67200 W·m-2·K-1 (down stroke in a direction from centre) are received. Is ro tined, that at a medial thermal gradient on boundary 'metal- water' 18.6 K (at medial temperature of 'tantalic wall' - 311.6 K) maximal temperature inside an irradiated stratum (Zn or Cd) does not exceed 363 K. The investigations are supported by Rbr (project No. 03-02-17391)