Activation of accelerator construction materials by heavy ions P. Katrík a,⇑ , E. Mustaﬁn a , D.H.H. Hoffmann b , M. Pavlovic ˇ c , I. Strašík a a GSI Darmstadt, Planckstrasse 1, D-64291, Germany b TU Darmstadt, Schlossgartenstraße 9, D-64289, Germany c FEI STU Bratislava, Ilkovic ˇova 3, SK-81219, Slovakia article info Article history: Received 28 May 2015 Received in revised form 5 August 2015 Accepted 6 September 2015 Available online 16 September 2015 Keywords: Residual activity Heavy-ion fragmentation Gamma-ray spectroscopy FLUKA code abstract Activation data for an aluminum target irradiated by 200 MeV/u 238 U ion beam are presented in the paper. The target was irradiated in the stacked-foil geometry and analyzed using gamma-ray spec- troscopy. The purpose of the experiment was to study the role of primary particles, projectile fragments, and target fragments in the activation process using the depth proﬁling of residual activity. The study brought information on which particles contribute dominantly to the target activation. The experimental data were compared with the Monte Carlo simulations by the FLUKA 2011.2c.0 code. This study is a part of a research program devoted to activation of accelerator construction materials by high-energy (P200 MeV/u) heavy ions at GSI Darmstadt. The experimental data are needed to validate the computer codes used for simulation of interaction of swift heavy ions with matter. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Accelerators and their components may get activated due to beam losses during machine operation. Activation becomes an important issue especially for high-power hadron facilities. Activa- tion studies of accelerator construction materials started in 2007 in the framework of preparation of the FAIR project (Facility for Antiproton and Ion Research) [1–5]. Copper, aluminum, and stain- less steel targets were irradiated by different heavy-ion beams at different energies. The aim of these experimental studies was to identify the nuclides induced in the most common accelerator con- struction materials, to measure their residual activity (relevant for the hands-on maintenance and radiation protection issues) and to determine the depth proﬁles of the residual activity. The latter is relevant for validation of the physical models and data libraries implemented in the corresponding simulation codes like FLUKA and SHIELD [6]. In this paper, the latest results for aluminum tar- get, 200 MeV/u 238 U beam and the FLUKA 2011.2c.0 code [7] are presented. 2. Experiment and methods The aluminum target was irradiated in the stacked-foil geome- try with 200 MeV/u 238 U beam. There were altogether 70 target foils used for depth-proﬁling of the residual activity. In order to achieve reasonable depth resolution, the target foils were 0.1 mm thick. The aluminum foils had diameter 10 cm, purity 99.9% and density 2.7 g/cm 3 at 20 °C. The 200 MeV/u 238 U 73+ beam was deliv- ered by the SIS-18 heavy-ion synchrotron at GSI Darmstadt [8]. The target was irradiated in the air. The beam-line was terminated by a vacuum window made of stainless steel, 100 lm thick. The air–gap between the vacuum window and the target was 61 cm. In total, 2.8  10 12 ions were delivered to the target. The target foils were analyzed by gamma-ray spectroscopy. The gamma-ray spectra were measured either individually or in groups of 5 foils in a low-background container by a high-purity germa- nium (HPGe) detector. Two series of measurements were per- formed: (a) 6–20 days, and (b) 130–180 days after the end of irradiation. The experimental data were compared with the Monte Carlo simulations by the FLUKA 2011.2c.0 code [7]. The measured residual activities were extrapolated backwards in time to the end of irradiation and normalized per one incident ion. 3. Results and discussion The nuclides induced in the target can be classiﬁed into two groups: (a) target-nuclei fragments and (b) projectile fragments. The different characteristic shape of depth-proﬁle of these two groups is clearly distinguishable. The target-nuclei fragments are present starting from the 1 st target foil and extend even well beyond the range of the primary projectiles. The latter indicates that the target activation is caused not only directly by the primary projectiles, but also by lighter secondary particles that have range http://dx.doi.org/10.1016/j.nimb.2015.09.022 0168-583X/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +49 61 5971 1545. E-mail addresses: p.katrik@gsi.de, peter.katrik@gmail.com (P. Katrík). Nuclear Instruments and Methods in Physics Research B 365 (2015) 525–528 Contents lists available at ScienceDirect Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb