Ar beam induced desorption from different materials at TSL O.B. Malyshev a, * , B. Zajec b, c , A. Haase b, d , L. Westerberg b , M. Leandersson e, f , M. Bender g , A. Krämer g , H. Kollmus g , H. Reich-Sprenger g a ASTeC, STFC Daresbury Laboratory, Daresbury, Warrington WA4 4AD, UK b Department of Physics and Astronomy, Box 516, SE-75120 Uppsala, Sweden c “Jo zef Stefan” Institute, Jamova 39, SI 1000 Ljubljana, Slovenia d Department of Physics, Freie Universität Berlin, Germany e Materials Physics, Royal Institute of Technology KTH-ICT, Electrum 229, SE-16440 KISTA, Stockholm, Sweden f MAX-lab, Lund University, Box 118, SE-22100, Lund, Sweden g GSI, Darmstadt, Germany article info Article history: Received 19 February 2010 Received in revised form 23 June 2010 Accepted 9 July 2010 Keywords: Heavy ions Gas desorption Desorption yield Vacuum system Secondary particles abstract This paper describes new experiments on the heavy ion desorption yield measurements with 5 MeV/u Ar 8þ and summarizes all results of experiments with 5 MeV/u Ar 8þ performed at The Svedberg Labo- ratory in Uppsala (Sweden). These results are important for the update and design of the FAIR facility at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt (Germany) where the required increase in beam intensity is limited by ion induced pressure instability. It was shown that lowest desorption yields can be achieved with gold coatings, whereas grazing incident loss increases the desorption yield by roughly an order of magnitude compared to perpendicular loss. The desorption yield of saturated NEG samples was measured to be higher compared to any non pumping samples. The desorption yield of copper can be lower and higher compared to stainless steel depending on cleaning procedure and sample history. Additionally the secondary electron and ion yield was measured to be a few tens of electrons and ions emitted per projectile impact in backward direction. Their influence on the desorption yield due to secondary effects was less than 5% compared to the primary desorption by the high energetic projectile. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The existing SIS18 synchrotron at GSI will serve as injector for the future Facility for Anti-proton and Ion Research (FAIR) [1]. Previous machine experiments have shown that the beam lifetime decreased with increasing number of injected particles [2]. The phenomenon limiting the beam lifetime is called heavy ion induced pressure instability [3]. To model and predict the effect of heavy ion induced desorption and design a vacuum system that guarantees no heavy ion induced pressure instability one needs to know the heavy ion induced desorption yields for different materials and different ions and ion energies, angle of incidence and other vari- able parameters. The heavy ion induced desorption and corre- sponding desorption yields are currently investigated in a few research centres where heavy ion accelerators are in operation or design. As such, several studies of desorption yields caused by heavy ion bombardment in particle accelerators have been published [4e16, and references therein], but several data are still missing to have a complete understanding. As a part of this study a few series of experiments were performed at The Svedberg Laboratory (TSL) in Uppsala, Sweden. Heavy ion induced desorption yields were measured from different materials bombarded with 5 MeV/u Ar 8þ , 9.7 MeV/u Ar 9þ and 17.7 MeV/u Ar 12þ Ar ions in Run 1 and 5 MeV/u Ar 8þ in Run 2 and were published in Ref. [17]. In this paper, we report on new results obtained with 5 MeV/u Ar 8þ in Run 3 and compare these with results from the previous two runs. 2. The experimental setup The experiments were performed in the K-beamline at TSL in Uppsala, Sweden. A detailed description of the beamline from the TSL cyclotron and the experimental installation for ion induced desorption measurements can be found in Ref. [18]. For the study described in this paper, the ending part of the experimental installation has been extended to allow measurements at grazing incidence angle, as shown in Fig. 1 . A long tubular sample has been installed in place of the previous Faraday Cup [18]. This sample was * Corresponding author. Tel.: þ44 1925 603948; fax: þ44 1925 603192. E-mail address: oleg.malyshev@stfc.ac.uk (O.B. Malyshev). Contents lists available at ScienceDirect Vacuum journal homepage: www.elsevier.com/locate/vacuum 0042-207X/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2010.07.007 Vacuum 85 (2010) 338e343