New methods for testing cyclotron carbon stripper foils

Carbon foils are used in cyclotrons and other accelerators to strip electrons from fast ions, enabling the extraction or further acceleration of those ions. Lifetimes of stripper foils (extractor foils) need to be as long as possible to maximize the efficiency of accelerator use and minimize radiation exposure of maintenance personnel. A foil's useful lifetime is determined in part by operating temperatures, manufacturing method, and mounting method. We used two methods to test foils in a simulated accelerator environment. These methods involve the heating in vacuum to temperature ranges 500–1750 and 500–4000 K. Either kind of testing can be done in a few minutes instead of the days or weeks typically needed in a cyclotron. Such tests show clearly that foils manufactured by different methods have different responses to elevated temperatures. Because of this fact, optimum mounting techniques depend on the foil type. Results to date are summarized.