A Von Ardenne‐type ion source and lens system has been developed for use as a preinjector to the 18‐Mev strong‐focusing linear accelerator. Proton beams of 120 ma at an ion production efficiency of 83% have been obtained. A magnetic beam‐confining system has been built, and a beam of 85 ma has been transported 82 in. The beam energy was 370 kev, and its emittance was 100 mrad‐mm. The beam diameter was 1 cm. This is within the linear accelerator's calculated acceptance of 179 mrad‐mm.