The RF H⁻ ion source project at RAL

A project to design and construct an RF-driven long-lifetime volume production ion source producing 30 mA of H⁻ with 50 Hz repetition rate and 1.5% duty factor at 35 keV energy for the ISIS Neutron and Muon Source has been started at Rutherford Appleton Laboratory. The development of the new ion source aims at replacing the caesiated Penning-type surface plasma ion source that has served the ISIS facility since 1980s. The design of the ion source is based on recent developments at CERN demonstrating 30 mA H⁻ in volume mode with less than 50 kW of RF-power but at lower repetition rate of 0.8 Hz. This paper describes the physics design of the ion source and the status of the project. The magnetic field, extraction optics, RF system and preferred plasma ignition scheme are discussed in detail.