This paper presents three–dimensional numerical simulations of thermodynamic and hydrodynamic response of a wheel shaped solid graphite production target for the super conducting fragment separator (Super–FRS) that is irradiated with a fast extracted high intensity uranium beam. These fragment separator experiments will be carried out at the future Facility for Antiprotons and Ion Research (FAIR), at Darmstadt. Previously, we reported simulation results that were carried out using two–dimensional computer codes which showed that one can use a solid graphite target for the Super-FRS for the highest intensity (5 × 1011 ions per spill) of the fast extracted uranium beam. Present results, however, have shown that due to three–dimensional effects the maximum intensity that can be used with such a target is 3 × 1011 ions per spill. A detailed comparison between two–dimensional and three–dimensional results is presented in this paper.

Extensive numerical simulations have been carried out to design a viable solid graphite wheel shaped production target for the super conducting fragment separator experiments (Super-FRS) at the future Facility for Antiprotons and Ion Research (FAIR) using an intense uranium beam. In this study, generation, propagation and decay of deviatoric stress waves induced by the beam in the target, have been investigated. 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. It has been reported elsewhere that the tensile strength of graphite significantly increases with temperature. To take advantage of this effect, calculations have also been done in which the target is preheated to a higher temperature, that in practice can be achieved, for example, by irradiating the target with a defocused ion beam before the experiments are performed. We report results of a few examples using an initial temperature of 2000 K. This study has shown that employing such a configuration, one may use a solid graphite production target even for the maximum intensity of the uranium beam (5 × 1011 ion per bunch) at the Super-FRS.

Survival of the production target in successive experiments (with a repetition rate of 1 Hz) over an extended period of time is one of the key problems encountered in designing the Super-FRS (Superconducting Fragment Separator) at the future Facility forAntiprotons and Ion Research (FAIR). Because of the difficulties involved in construction of a liquid jet metal target, it is highly desirable to employ a solid production target at the Super-FRS. However, with the high beam intensities that will be available at the FAIR, the production target may be destroyed in a single experiment due to high specific energy deposition by the beam in the target material. The level of specific energy deposition can be reduced to an acceptable value by increasing the beam focal spot area. However, the spot size is limited by requirements of achieving good isotope resolution and sufficient transmission of the secondary beam through the system. The resolving power of the fragment separator is inversely proportional to the X-dimension of the focal spot whereas the transmission depends on Y-dimension only. It has been previously shown [Tahir et al., 2005c] that an elliptic focal spot with appropriate dimensions, will fulfill the above two conditions simultaneously and will also have a large enough area to reduce the specific energy deposition to an acceptable level for certain beam intensities of interest. In this paper we present numerical simulations of thermodynamic and hydrodynamic behavior of a solid graphite target that is irradiated by 1 GeV/u uranium beam in the intensity range of 1010 –1011 ions per bunch with a bunch length = 50 ns. These simulations have been carried out using a three-dimensional computer code, PIC3D, that includes elastic-plastic effects. This theoretical work has shown that up to a beam intensity of 1011 ions/bunch, one can employ a solid target while for higher intensities the target will be destroyed due to thermal stresses induced by the beam. It has also been found that a circular focal spot leads to minimum thermal stresses as it generates minimum pressure gradients compared to an elliptic focal spot, for the same specific energy deposition. Moreover, the stress level increases with an increase in the ellipticity of the focal spot. It is therefore recommended that one should use a circular focal spot for lower intensities provided that the criteria for isotope resolution and transmission are fulfilled.

This paper presents numerical simulations of thermodynamic and hydrodynamic response for solid targets that are irradiated with strongly bunched, highly focused, intense beams of energetic uranium ions. The main purpose of this work is to study the behavior of thermal stress waves induced in such targets by the incident ion beam. These theoretical studies will complement the experimental investigations that will be carried out in the near future at the Gesellschaft für Schwerionenforschung (GSI) plasma physics experimental area. These experiments will be performed using the existing heavy ion synchrotron, SIS18, which delivers 4 × 109 uranium ions in a single bunch with a length of about 125 ns. Other time structures, for example, a pulse that consists of a series of bunches, are also possible. The particle energy is on the order of 400 MeV/u and the beam can be focused to sub millimeter radius. This information concerning material response under intense beam loading will have important implications on designing a viable production target for the superconducting fragment separator, Super-FRS, which is going to be constructed at the future facility for antiproton and ion research (FAIR), Darmstadt, Germany, for the production and separation of exotic nuclei.

The new international facility for antiproton and ion research (FAIR), at Darmstadt, Germany, will accelerate beams of all stable isotopes from protons up to uranium with unprecedented intensities (of the order of 1012 ions per spill). Planned future experiments include production of exotic nuclei by fragmentation/fission of projectile ions of different species with energies up to 1.5 GeV/u at the proposed super conducting fragment separator, Super-FRS. In such experiments, the production target must survive multiple irradiations over an extended period of time, which in case of such beam intensities is highly questionable. Previous work showed that with full intensity of the uranium beam, a solid graphite target will be destroyed after being irradiated once, unless the beam focal spot is made very large that will result in extremely poor transmission and resolution of the secondary isotopes. An alternative to a solid target could be a windowless liquid jet target. We have carried out three-dimensional numerical simulations to study the problem of target heating and propagation of pressure in a liquid Li target. These first calculations have shown that a liquid lithium target may survive the full uranium beam intensity for a reasonable size focal spot.