Depth profiling of the residual activity induced in carbon-based materials by heavy ions

We present new results of the experimental study of the residual activity induced by high-energy heavy ions in carbon-based materials: graphite and carbon composite. The graphite target was irradiated by 500 MeV/u tantalum ions and the carbon composite target was irradiated by 500 MeV/u uranium ions. The targets were assembled from a stack of thin plates and after irradiation were investigated using gamma-ray spectroscopy. Main tasks of the experimental study were: 1) to identify induced radioactive isotopes in the gamma spectra of the measured samples, 2) to estimate residual activity of the identified isotopes and 3) to determine depth profiles of the residual activity of individual isotopes. Depth profiling of the residual activity of all identified isotopes was performed by measurements of individual target plates. According to the depth profiles, the identified isotopes can be classified into two main groups: target-nuclei fragments and projectile fragments. In the measured gamma spectra of the carbon-based materials irradiated by heavy ions only one target-nuclei fragment, 7 Be, was identified. All the rest of the isotopes detected using gamma-ray spectroscopy, are the projectile fragments of various masses. The experimental data were compared with Monte Carlo simulations performed by FLUKA code in order to verify validity of physical models and data libraries implemented in the code. A satisfactory agreement between the experiment and the simulations was observed

Radiation damage studies of soft magnetic metallic glasses irradiated with high-energy heavy ions

Some soft magnetic metallic glasses are considered for use in magnetic cores of accelerator radio frequency cavities. Due to losses of the circulating ion beam, they may be exposed to irradiation by different ions at different energies. This paper presents data and review results of irradiation experiments concerning the influence of high-energy heavy ions on magnetic susceptibility of VITROPERM®-type metallic glasses. Samples of the VITROPERM® magnetic ribbons were irradiated by Au, Xe and U ions at 11.1 MeV/A (per nucleon) and 5.9 MeV/A, respectively. Irradiation fluences from 1 x 1011 up to 1 x 1013 ions/cm2 were applied. In case of the Au and U ions, the total fluence was accumulated in one beamtime, whereas two separate beamtimes were used to accumulate the final fluence in case of the Xe ions. Relative change in the samples' magnetic susceptibility after and before irradiation was evaluated as a function of the irradiation fluence. The irradiation experiments were performed with the UNILAC accelerator at GSI Helmholtzzentrum für Schwerionenforschung GmbH. They were simulated in SRIM2010 in order to obtain ionization densities (electronic stopping, dE/dx) and dpa (displacements per atom) caused by the ion beams in the sample material. This paper focuses mainly on the results collected in experiments with the Xe ions and compares them with data obtained in earlier experiments using Au and U ions. Radiation hardness of VITROPERM® is compared with radiation hardness of VITROVAC® that was studied in previous experiments. The VITROPERM® samples showed less drop in magnetic susceptibility in comparison with the VITROVAC® ones, and this drop occurred at higher fluences. This indicates higher radiation hardness of VITROPERM® compared with VITROVAC®. In addition, heavier ions cause bigger change in magnetic susceptibility than the lighter ones. The effect can be roughly scaled with electronic stopping, which suggests that the main mechanism of radiation damage is associated with swift electrons generated in the material via ionization by primary heavy ions

Overview of EuCARD Accelerator and Material Research at GSI

EuCARD is a joined accelerator R&D initiative funded by the EU. Within this program, GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt is performing R&D on materials for accelerators and collimators in workpackage 8 (ColMat). GSI covers prototyping and testing of a cryogenic ion catcher for FAIR’s main synchrotron SIS100, simulations and studies on activation of accelerator components e.g. halo collimatiors as well as irradiation experiments on materials foreseen to be used in FAIR accelerators and the LHC upgrade program. Carbon-carbon composites, silicon carbide and copper-diamond composite samples have been irradiated with heavy ions at various GSI beamlines and their radiation induced property changes were characterized. Numerical simulations on the possible damage by LHC and SPS beams to different targets have been performed. Simulations and modelling of activation and long term radiation induced damage to accelerator components have started. A prototype ion catcher has been built and first experiments have been performed in 2011. New collaborations with other institutes and industry participating in the EuCARD framework have been established and findings of the joined R&D effort influence decisions in the FAIR project and LHC upgrade. This work offers an overview and points out highlights of the GSI’s ColMat activities which are not separately presented within other contributions to this proceedings