High Reliability, Long Lifetime H-Ion Source

Existing high current negative ion sources have unacceptably short lifetimes. In this Phase II project, a long lifetime, high reliability H- ion source capable of delivering current greater than 10 mA will be constructed, built, and tested. Feasibility was proven and preliminary designs were completed during Phase I. The immediate DoE need for this technology is a H- ion source to serve as an injector to proposed Intensity Frontier accelerators at Fermi National Laboratory. There are several other science, medical, energy, and industrial applications for which this technology will enhance capabilities. Existing H- ion sources embed the H- production in a plasma environment. Inevitability, these H- production processes lead to transport and extraction complications. Disadvantages of existing H- sources are power and gas inefficiencies, leading to low duty factor operation, and large vacuum facilities to maintain injector pressure. Larger duty factor and H- sources have comparatively short lifetimes before ion source refurbishment is required. An ion source generating hyperthermal hydrogen atoms via the interaction of molecular hydrogen ions with electrons generated in a 2.45 GHz microwave source (MWS) will be constructed. These atoms will be converted to H- ions via surface and volume conversion mechanisms. Recent advances in positive ion sources using the resonant interaction of 2.45 GHz microwaves in hydrogen gas with an 875 Gauss magnetic field have led to intense DC positive ion beams. Twenty five percent efficiency in converting hydrogen gas into positive ions using 1 kW of microwave power has been routinely observed. MWSs are becoming increasingly common in commercial use due their inherent DC operating capability. The Phase I study showed that these positive ion sources can be modified to be good sources of atomic hydrogen and negative ion beams. Phase II will construct of source construction and extensive testing with a suite of diagnostics. Though H- ion sources enjoy several advantages over positive ion sources, their commercial use has been limited by their short lifetime. In this work, a modified 2.45 GHz microwave proton source will be used as a source of neutral hydrogen atoms that will be surface-converted to H- ions and extracted into a high current, low emittance ion beam. The anticipated result will be a prototype of an extremely reliable DC H- ion source capable of producing greater than 10 mA of beam, which will enable a wide range of DoE and commercial applications including isotope production and separation, semiconductor manufacturing applications, cyclotron injectors, and ion injectors for magnetic confinement fusion energy.