Challenge to stripper foils in the world

The author has engaged in the production of target thin films for atomic nucleus experiment, and started the production of high strength carbon films. For the acceleration of heavy ion beams, in order to heighten the acceleration efficiency of ions, it is necessary to change them to multivalent ions through a charge convertor for stripping electrons from accelerated ions. But conventional carbon stripper films break soon by beam irradiation. The development of the carbon stripper films having high reliability and long life has been desired in Japan and foreign countries. The initial basic targets were hard to break, durability and long life against the irradiation of high intensity heavy ion beams, simple manufacturing method and high yield in the film production. As the methods of production, the merits and demerits of the methods by thermal evaporation, sputtering, the growth in gaseous phase reaction and laser ablation were investigated. The life of carbon strippers is defined. Four entirely new production processes for long life carbon films have been successfully developed, namely, controlled AC-DC are discharge method, heavy ion beam sputtering method, mixed ion beam sputtering method and method of ion beam sputtering with reactive nitrogen. The results of the beam test using the beam of Tokyo Institute of Technology Van de Graaff and the H- beam of Los Alamos are reported. (K.I.)