For plasma heating and stabilization in open magnetic traps, the high-power neutral beam injector with tunable beam energy was developed at Budker Institute of Nuclear Physics. The initial energy of the beam particles is 15 keV, and it can be subsequently increased to 40 keV. In this case, the neutral beam power increases from 1.7 to 3.5 MW. A distinctive feature of this injector is the fact that, as the accelerating voltage considerably changes, the ion beam current remains constant. The injectors based on the ion sources with tunable energy are used in experiments at the C-2W open trap (USA).

A diagnostic neutral beam injector DINA-KI60 has been developed and produced for upgraded T-15 tokamak (Kurchatov Institute, Moscow). The system will be primarily used for measurement of the ion temperature by charge exchange recombination spectroscopy (CXRS), for magnetic field measurements via motional Stark effect (MSE) and investigation of plasma turbulence by Beam emission spectroscopy (BES). The ion source provides 60 keV, 6 A hydrogen beam with low angular divergence less than 10 lima Ions are extracted from a plasma created by an are-discharge source with cold cathode and, after accelerating and focusing, are neutralized in a gas target. The extracted beam has about 86% of full energy specie. The grids of ion optical system in.. spherically curved providing geometric focusing of the beam at a distance 4 in. Diagnostic neutral beam has been successfully tested at Budker Institute of Nuclear Physics at 2 seconds pulse duration with modulation of the beam (duty ratio from 1:1 to 1:3).

Within this report we summarize the technical and experimental effort made on high power neutral beam injector system (NBI) and diagnostics neutral beam injector (DINA-5M which was installed at Gas Dynamic Trap device (GDT) last year. Basic components of NBI-systems and DINA are reviewed. Recent experimental results support the concept of the neutron source based on the gas dynamic trap.

The injector ion source is based on an arcdischarge plasma box. The plasma emitter is produced by a 1 kA arc discharge in deuterium. A multipole magnetic field produced with permanent magnets at the periphery of the plasma box is used to increase its efficiency and improve homogeneity of the plasma emitter. The ion beam is extracted by a 4-electrodes ion optical system (IOS). Initial beam diameter is 200 mm. The grids of the IOS have a spherical curvature for geometrical focusing of the beam. The optimal IOS geometry and grid potentials were found by means of numerical simulation to provide precise beam formation. The measured angular divergence of the beam is 0.025 rad, which corresponds to a 4.7 cm Gaussian radius of the beam profile measured at focal point.