Developing high brightness and high current beams for HIF injectors

Abstract

The US Heavy Ion Fusion Virtual National Laboratory is continuing research into ion sources and injectors that simultaneously provide high current (0.5-1.0 Amps) and high brightness (normalized emittance better than 1.0 π-mm-mr). The central issue of focus is whether to continue pursuing the traditional approach of large surface ionization sources or to adopt a multiaperture approach that transports many smaller "beamlets" separately at low energies before allowing them to merge. For the large surface source concept, the recent commissioning of the 2-MeV injector for the High Current eXperiment has increased our understanding of the beam quality limitations for these sources. We have also improved our techniques for fabricating large diameter aluminosilicate sources to improve lifetime and emission uniformity. For the multiaperture approach, we are continuing to study the feasibility of small surface sources and a RF induced plasma source in preparation for beamlet merging experiments, while continuing to run computer simulations for better understanding of this alternate concept. Experiments into both architectures will be performed on a newly commissioned ion source test stand at LLNL called STS-500. This stand test provides a platform for testing a variety of ion sources and accelerating structures with 500 kV, 17-microsecond pulses. Recent progress in these areas will be discussed as well as plans for future experiments.

Beam Energy Scaling of Ion-Induced Electron Yield From K+ Ions Impact on Stainless Steel Surfaces

“…In order to test the physical mechanism model of ioninduced electrons production we have measured the electron yield by placing the Gas-Electron Source Diagnostics experiment (GESD) [3] at the end of a 500 kilovolt ion source test stand (STS-500) [4], which can generate a 17 microsecond duration, up to 500 KeV and 1A pulse every few seconds. The GESD, which is shown in Fig.…”

Characterization of an RF-driven plasma ion source for heavy ion fusion

“…The second has increased diagnostics and 100 kV. The third larger system is capable of 500 kV with a 20 µsec pulse [3].…”