Estimating the longevity of carbon stripper foils of cyclotron accelerators

Accelerators of negative hydrogen ions and deuterons are widely used, for example, in the field of medicine. The particle beam is removed from the accelerators by recharging ions as they pass through a thin carbon foil. The paper presents the results of a study of the longevity of stripper foils. Carbon foils with a thickness of 1 – 4 μm obtained on a glass substrate by vacuum arc sputtering of graphite rods were studied. During the experiments, a laboratory setup was used that simulates the effect of a beam of negative hydrogen ions (energy 18 MeV) using an electron beam (energy 10 keV). The samples were irradiated with a stream of electrons, while each sample retained its integrity. Before and after irradiation, the foil surfaces were analyzed using atomic force microscopy. It was found that irradiation changes the morphology of the surface (roughness parameters deteriorate). The method of electrostatic force microscopy revealed a noticeable difference between the irradiated and non-irradiated parts of the foil not only in thickness, but also in electrical conductivity. The obtained results and the developed research method can be used for prompt changes to the foil forming technology to increase their service life.