Beam size reduction of a several hundred-keV compact ion microbeam system by improving the extraction condition in an ion source

Ishii, Yasuyuki; Okubo, Takeru; Kamiya, Tomihiro; Saito, Yuichi

A hundreds-keV compact ion microbeam system with a three-stage acceleration lens is under development to form an ion beam of several micrometers in diameter. A proton beam of 17m in diameter was formed in the previous study and the smaller beam size could be expected at the lower pressure. In this study, the vacuum system at the extraction space was improved and the relation between the beam size and vacuum pressure was examined by forming hydrogen ion beams at 130 keV. As a result, the beam size of 5.8 m which almost satisfied our present goal was obtained at the achievably lowest pressure (510 Pa).