H- Source Deveidpment at ANL
The H- source development program at ANL1-7 has produced the first operational source for direct H- injection into a proton synchrotron and is now directed toward the development of a 30 Hz H- source for booster injection into a synchroton. On October 1, 1976, direct injection of 50 MeV H- ions into the ANL Zero Gradient Synchrotron (ZGS) and stripping of the H- to obtain protons for acceleration to full energy became the normal mode of operation. With >6 mA of 50 MeV H- beam injected and ~1012 protons per mA accelerated to full energy during each cycle, new ZGS intensity records have been established.8 In the operational tandem-acceleration H source, a single-aperture source grid is followed by a multislot parallel-ribbon extraction grid. Full and fractional energy H- ions derived from H+, H+2 and H+3 are produced by electron attachment in a target gas consisting of the hydrogen outflow from the plasma source. Power dissipation in the extractor grid, and lifetime considerations, limit the repetition rate to ~1 Hz. A source which uses two or more aligned multiaperture grids to minimize grid dissipation is being developed for 30 Hz injection into the rapid-cycling booster-injector9,10 for the ZGS. A modification of this source will be combined with a recirculating supersonic sodium vapor jet charge exchange cell to obtain a greater H- yield. A sodium cell has been built and is being tested.11,12