Permanent magnet small-size quadrupole lenses for ion linear accelerators

Rare-earth quadrupole lenses for the focusing channel of ion linear accelerators (linacs) are presented. The authors have developed an inorganic lens concept and a fabrication technique which allows one to produce high-fidelity lenses for various applications. These lenses have a comparatively higher level of permissible integral radiation exposure and they can be placed in a high vacuum volume. The focusing channel with vacuum-opened drift tubes for the first and the second tanks of the linac ISTRA has been created at the ITEP (Institute of Theoretical and Experimental Physics) in the USSR using the inorganic lens technique. The first tank with a proton energy of 10 MeV was put into operation two years ago. Experience shows that vacuum-opened drift tubes with inorganic quadrupoles operate in the same manner as vacuum-sealed tubes