Veja a citação abaixo, e o URL. Se me permite uma sugestao, eu escreveria pra esse site perguntando exatamente de que material é o "foil";
http://www.scied.science.doe.gov/scied/Abstracts2005/ANLphys...
Development of the next generation of accelerator facilities, the Rare Isotope Accelerator (RIA), is underway. It's construction will lead to fundamental breakthroughs in the study of unstable nuclei and nuclear physics. In order achieve the goals of RIA, a method of proper cooling of integral beam strippers in necessary. Using a pendulum swinging, rotating foil wheel it may be possible to reach the required cooling rates. Several possible cam designs that can be used to cause the pendulum motion are analyzed in this paper. Mathematical models of of the cam designs have been developed and can be used to determine the most desirable configuration. The optimal design depends on several factors, including increasing smoothness of rotation and reducing friction. The disadvantages of each design are detailed, with the cylindrical cam appearing as a strong design option. Design of the foil beam strippers, while integral, is only a small part of the massive collaboration working on RIA in the drive to reach the next level of experimental nuclear physics.