The origin of beam non-uniformity in a large Cs-seeded negative ion source

Abstract

Origin of the longitudinal beam non-uniformity, that is one of the key issues in large Cs-seeded negative ion sources for fusion application, was experimentally investigated in the JAERI 10 A negative ion source. After a sufficient caesium of ~0.3 g was seeded in the negative ion source to enhance the negative ion production, the longitudinal distribution of the beam intensity was measured. The distribution of the beam intensity was non-uniform,

Particle in Cell Simulation of Low Temperature Laboratory Plasmas

“…Recent experiments in the JAEA 10A H source show an interesting feature concerning the non-uniformity of the extracted beam [101,102]. This H beam non-uniformity strongly depends on the dominant production mechanism, i.e., either pure "volume" H production (VP) or Cs-seeded "surface" H production (Cs-SP).…”

Simultaneous measurements of work function and H‒ density including caesiation of a converter surface

“…In plasma environment, some investigations on the correlation between H -yield and work function are presented, e.g. [14][15][16][17][18]. In these studies, the work function of the converter surface is obtained by the photoelectric method using an Ar + laser and by conversion of the photoelectric currents to the quantum efficiencies, which depend on the work function and on the photon energy.…”

Temperature dependence of the work function of caesiated materials under ion source conditions

“…Some measurements of the work function of the converter surface in caesiated negative ion sources exist [8][9][10][11][12]. However, systematic and reproducible studies on parameters affecting the work function under ion source relevant conditions both in plasma and vacuum, like Cs evaporation rate, surface temperature or bias voltage, have not been performed to the author's knowledge.…”