Speaker
Description
Carbon foils are widely used in particle accelerators to produce ion beams with high charge states. These stripper foils are primarily deposited on a soluble substrate, (e.g., NaCl, betaine-sucrose), that is subsequently dissolved to provide a free-standing foil. For use in accelerators, the free-standing foils need then to be mounted on a metallic frame, a delicate and time consuming operation. In this paper, we propose an alternative fabrication process, where the foils are deposited directly onto a metallic supporting frame. The process involves the surface preparation of plain copper plates, in-situ Ar-H2 plasma treatment to enhance adhesion, deposition of the carbon film by magnetron sputtering, and removal of the copper from the central part of the supporting plate by chemical etching, to create an aperture for the passing ion beam. We describe the different fabrication steps, the used quality control approach to assess the carbon areal density, the thermal outgassing rate, and the porosity of the foils. The first test results of CERN-produced carbon stripper foils, obtained with Pb54+ ion beams at 4.2 MeV/u at LINAC 3, are presented.
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