Simulations of a Solid Graphite Target for High Intensity fast Extracted Uranium Beams for the Super-FRS

Extensive numerical simulations have been done to study, generation, propagation and decay of deviatoric stress waves induced by a high intensity uranium beam in a wheel shaped solid graphite Super–FRS production target. Maximum beam intensities that the target can tolerate using different focal spot sizes that are determined by requirements of good isotope resolution and transmission of the secondary beam through the fragment separator, have been calculated. A circular focal spot is superior to an elliptic one as the former generates minimum thermal stress in the material. The maximum spot size allowed by requirement of good isotope resolution is characterized with σ = 4 mm. Simulations have shown that the target will survive a beam intensity of 10 ions per bunch. It is also to be noted that the yield strength of graphite increases with temperature. At 2000 K it becomes 100 MPa compared to 70 MPa at the room temperature. It has therefore been suggested that the target may be preheated by a defocused beam to a higher temperature before performing the experiments in order to take advantage of this effect [1]. Simulations show that at a temperature of 2000 K, the target will survive with a higher intensity of 2.0 × 10. However, for the full intensity of the uranium beam at the Super–FRS one would require an elliptic focal spot with σX = 4 mm and σY = 11 mm.