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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 stand based on a magnetron, circulator, parallel-coupled accelerating structure, electron gun, diagnostic equipment, and modulator has been being created at the Budker Institute of Nuclear Physics (BINP) for testing the accelerator and injection part of a compact linear accelerator. The installation operates in the S-band with a pulsed power of 3–3.5 MW and average magnetron power up to 3 kW. This work contains descriptions and results of preliminary launching of the stand.

Concept of photon neutralizer for large ITER like NBI system has been proposed. The use of proposed concept allows beam neutralization with significantly lower requirements concerning optical radiation quality in comparison with resonance schemes, also there is no need for complicated stabilization and tuning system.Concept of photon neutralizer for large ITER like NBI system has been proposed. The use of proposed concept allows beam neutralization with significantly lower requirements concerning optical radiation quality in comparison with resonance schemes, also there is no need for complicated stabilization and tuning system.

The paper presents the results of experiments on quasi-stationary photoneutralization H− and D− beams. Studies were carried out using non-resonance adiabatic photons accumulate.

Experimental results on neutralization of negative ion beams in a photon stripping target are presented. For the energy of beams used in these studies (6–10 keV), the maximum neutralization efficiency is 95%. In contrast with gas or plasma neutralizers, the generation of positive ions from the negative ion beam was negligible. A non-resonance photon trap with highly reflecting mirrors of special shape was used as a stripping target. Due to a special mirror shape, in the process of photons reflections and propagation inside the trap there are some adiabatically conserved invariants that limits the volume accessible for photon motion even if the mirror surface is not closed. This approach makes it possible to overcome limitations typical for the Fabry–Perot cells, which require high radiation quality, high quality of the optical elements, and very high mechanical stability of the cell. The trap was pumped by commercially available fiber laser (λ = 1070 nm, Δλ = 7 nm, P = 2.1 kW) through a small hole in the mirror. The experiments were carried out with H- and D-beams. The observed neutralization efficiency depended mainly on the reflectivity of the mirrors, on defects on their surface, and on the laser pumping power.