Technique for the removal of electrons from an extracted, pulsed, H− ion beam

A small, permanent‐magnet insert structure for the removal of electrons from pulsed, extracted, negative ion beams has been developed at Lawrence Berkeley National Laboratory. The device was computer modeled and designed for an extraction field strength of 3 kV/mm. The testing was carried out with a rf driven multicusp ion source optimized for the production of H− ions and pulsed at a few Hz with pulse widths of several hundreds of μs. It is demonstrated that the insert structure together with a collar can remove over 98% of electrons from the extracted H− ion beam without any significant deterioration of the H− ion output. Application to other negative ion beams can be expected from this magnetic collar insert.