A Negative Hydrogen-Ion Source for SNS Using a Helicon Plasma Generator

Abstract

The Spallation Neutron Source (SNS) at Oak Ridge National Labo�ratory is a world-class facility for materials research based on neutron scattering. It consists of a negative hydrogen (H-) ion source, linear accelerator, proton accumulator ring, and liquid Hg target. A power up�grade is planned for the device, which will require significant improvements in the negative ion source, including the production of H- beam currents of 70-95 mA (~2 � the present SNS source value), with a pulse length of 1 ms and duty factor of ~ 7%. No H- sources currently in existence meet these combined requirements. A proof-of-principle experiment is being constructed in which the rf inductive plasma generator in the present source is replaced by a helicon plasma generator. This is expected to produce a factor of three or better in�crease in the maximum source plasma density at a reduced rf power level, resulting in significantly increased negative ion current with reduced heat removal requirements.