Tandem surface–plasma source: A new concept for a dc negative ion source

Abstract

The newly developed tandem surface–plasma source (SPS) concept is expected to break new ground in the production of high-current, high-brightness H− ion beams. The tandem SPS consists of three successive separate stages: the multipole plasma driver; the H− ion generator with a low-voltage closed converter, and the ion extraction and beam formation system. To date the plasma driver stage has been designed, and is anticipated to produce an intense plasma stream with high efficiency (low energy-per-ion expenditure). The atomic processes in the second stage have been analyzed, the anticipated result is a dense population of H− ions with a very low temperature. The tandem SPS source is expected to produce dc beams of H− ions with currents up to 50 mA and pulsed H− beams at large duty factors with currents up to 100 mA.

A small radius hydrogen discharge: An effective source of volume produced negative ions

“…However, the rf source in its present design of a large-scale two-chamber source does not ensure efficiency high enough for volume production of the ions, and currently it is considered as a source with surface production of the ions. [2][3][4] The design of the rf sources of negative hydrogen ions is based on the experience accumulated during many years of work on the dc filament sources [5][6][7][8][9][10][11][12][13][14] starting in the 1980s, the time when the idea for the tandem type of the source arouse. The idea is for a design that ensures spatial separation in the source of two regions, respectively, of high-and low electron temperature, and it originates from the conclusion that such a design provides conditions favoring the two-step reaction of the volume production of the negative ions: excitation of the molecules to highly vibrationally excited states that requires high-energetic electrons and production of negative ions via dissociative attachment of electrons to the vibrationally excited molecules that requires low-energetic electrons.…”