Ion sources at the Novosibirsk Institute of Nuclear Physics (invited)

Abstract

A review of investigations in the physics and technology of ion sources, developed in the Institute of Nuclear Physics in Novosibirsk is presented. Distinctive features of physical processes and technical characteristics of plasma sources of gaseous ions, negative ion surface-plasma sources, electrohydrodynamic (liquid metal) ion sources are considered. In original design plasma sources, ion beams with a current of up to 90 A and energies 1–30 keV are formed by four-electrode multislit extraction systems from highly ionized, high brightness plasma flux, generated by an high-current arc discharge with a cold cathode in a small cross-section diaphragmed channel, and directed with a magnetic field of a special configuration. Plasma jet expansion for a very low ion temperature (0.1 eV) production is used. In surface plasma sources, the fluxes of negative ions are produced when electrons are captured from the electrode surface at the electron affinity level of sputtered and reflected particles. A discharge of a special type in a gas-cesium mixture with in a thin plasma layer between the negative ion emitter and emission holes is used. A number of versions of SPS with different types of discharges are considered: SPS which operate in pulse mode with H− beam current up to 11 A, with current 0.1 A, and high brightness for accelerators, for continuous mode operation. Specific features of physical processes in electrohydrodynamic (EHD) ion emitters are studied and the technology of production of different ions is worked out. The production of ion beams with high brightness from the dielectric melt in the EHD-emission regime is developed. The dynamics of spontaneous oscillation excitation with a quasidiscrete spectrum in the frequency range of up to 108 Hz, transient processes occurring at the emission disturbances, emission stability at low current, a physical model for calculating the emission surface dimensions, and the evolution of the ion momentum distribution function for the ion motion are studied. The utilization of the designed EHD sources in the ion microscope, in submicromachining and in high voltage accelerators are discussed.

Perspective for development of a source of highly polarized 3He- ions

“…Using the arc discharge source (from BINP as used in OPPIS [5,6,9]) one can extract up to I+~2 А of Не + at 6-12 keV energy with good emittance and up to ~0.1 А of Не -can be obtained A schematic of an experiment using BNL equipment to measure He-beam production is shown in Fig. 4.…”

“…Being one of the 24 equally populated hyperfine states, a polarized 3 He -beam has ~4% intensity of all 3 He -beam, which in turn can have up to 5% of a 3 He + beam intensity. The high-brightness arc-discharge ion source with geometrical focusing and low gas consumption developed in BINP and used for BNL OPPIS upgrading [5,6,9] can be used for production of 3 He -beams with ~1mA current and ~90% polarization.…”

“…-beam is separated from the intense He + and He 0 beams by the bending magnet (5). The beam pipes must be cooled below 150 K to prevent He -stripping by the black body radiation.…”

“…With 2A of 3 He + beam current, up to 0.1 A of 3 He -beam can be produced by charge exchange in an alkali vapor target and up to 2 mA of highly polarized 3 He -ions can be produced [5,7]. With a pulsed gas valve [10] it is possible to have a low gas consumption, which is important, because 3 He gas is very expensive.…”

“…For polarized 3 He ++ production, one can use also the same high-current arc-discharge source (developed in BINP [5] and used in the BNL OPPIS upgrading [6]) with pulsed injection of nuclear polarized 3 He 0 ↑ atoms (polarized by optical pumping) into an arc-discharge plasma source [7]. For protection of the nuclear polarization during step-by-step ionization a strong magnetic field can be used.…”