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With the increasing energies and intensities of heavy-ion accelerator facilities, the problem of an excessive activation of the accelerator components caused by beam losses becomes more and more important. Numerical experiments using Monte Carlo transport codes are performed in order to assess the levels of activation. The heavy-ion versions of the codes were released approximately a decade ago, therefore the verification is needed to be sure that they give reasonable results. Present work is focused on obtaining the experimental data on activation of the targets by heavy-ion beams. Several experiments were performed at GSI Helmholtzzentrum für Schwerionenforschung. The interaction of nitrogen, argon and uranium beams with aluminum targets, as well as interaction of nitrogen and argon beams with copper targets was studied. After the irradiation of the targets by different ion beams from the SIS18 synchrotron at GSI, the γ-spectroscopy analysis was done: the γ-spectra of the residual activity were measured, the radioactive nuclides were identified, their amount and depth distribution were detected. The obtained experimental results were compared with the results of the Monte Carlo simulations using FLUKA, MARS and SHIELD. The discrepancies and agreements between experiment and simulations are pointed out. The origin of discrepancies is discussed. Obtained results allow for a better verification of the Monte Carlo transport codes, and also provide information for their further development. The necessity of the activation studies for accelerator applications is discussed. The limits of applicability of the heavy-ion beam-loss criteria were studied using the FLUKA code. FLUKA-simulations were done to determine the most preferable from the radiation protection point of view materials for use in accelerator components.
Design and optimization of the lattice of the superconducting synchrotron SIS300 for slow extraction
(2011)
The superconducting synchrotron SIS300 is planned to be built at the new Facility for Antiproton and Ion Research (FAIR), at GSI-Darmstadt [1]. SIS300 will be a versatile machine, which by means of a low-energy stretcher-mode or a high-energy ramped-mode will provide slowly extracted heavy ion beams towards the experimental areas. To reach the required maximum field of 4.5 T, cos(θ) magnets are necessary. Thus, SIS300 will become the first superconducting synchrotron worldwide with cos(θ) magnets providing resonant slow extraction.
Since SIS300 will be installed in the same tunnel as the SIS100 synchrotron, the dipole layout of SIS300 cannot be freely chosen. Thus, a standard lattice cannot be applied. A redesign of the SIS300 lattice accepting compromises concerning the positions and phase advances between the optical elements has been proposed. Using the analytical model of the slow extraction, firstly proposed by Kobayashi, and the analytical description of the resonance driving modes, a multiobjective optimization algorithm has been developed for the optimization of the lattice under the given boundary conditions. The final goal of the lattice optimization is a higher efficiency of the slow extraction. The results are evaluated by means of tracking simulations performed with the code Elegant.
The field quality in superconducting cos(θ) magnets is determined by the positions of the superconducting cable and the static and time-dependent effects of the current in the cable. Furthermore, the fast ramp rates of 1 T/s in the dipoles, which are fifty times faster than in any other superconducting cos(θ) magnet, together with the fact that the aperture is smaller than in conventional accelerator magnets, makes it extremely difficult to obtain a high-quality magnetic field. The unavoidable field errors affect the beam dynamics and worsen the slow extraction efficiency. Therefore, the field errors in the SIS300 dipoles have been estimated, and their effects have been taken into account in the optimization algorithm. As a result a compensation scheme has been proposed, in which time-dependent gradients in the sextupoles counteract the decay of the sextupole field errors in the dipole magnets during the slow extraction. For the limits where the compensation was no longer possible, tolerances to the magnet field errors have been determined.