A high-voltage negative ion based neutral beam injector is under construction at the Budker Institute of Nuclear Physics. It consists of a negative ion source, a Low Energy Beam Transport section (LEBT), which purifies the beam before acceleration, a multi-electrode single-aperture beam accelerator, a negative ion neutralizer and a magnetic separator with beam energy recuperators. The test stand to study the main injector components, consisting of the negative ion source and LEBT, the high voltage platform and the accelerator with beam transport section was launched in 2019. The initial experiments on the negative ion beam production, acceleration and 180 keV transport were tested. The power load to the acceleration tube electrodes and the data on the transported beam parameters, measured at the several positions and at the beam dump calorimeter are presented. The beam transport efficiency as a function of various ion source and LEBT parameters are presented and discussed.

A prototype of a powerful high-voltage neutral beam injector, based on acceleration of negative hydrogen ions and their neutralization, is under development at Budker Institute of Nuclear Physics (BINP). The design of the BINP high-voltage injector includes several innovative components, important for injector operation stability and overall efficiency. It includes a multi-aperture long-pulse surface-plasma negative ion source with thermostabilized grid, ithe magnetic system with concaved field lines in the ion-optic system (IOS) and the distributed cesium deposition system. The injector scheme incorporates a wide-aperture low-energy beam transport (LEBT) section, plasma target for negative ionneutralization, and recuperators of non-neutralized ions. Several test stands were constructed at BINP for injector component studies. This paper describes the results of experiments on negative ion beam production, transport through LEBT, ion acceleration to energy up to 240 keV and transport through the high voltage beam transport (HEBT) section to the distance ∼10 m from the source. The parameters of the transported beam, which were measured at several points along the beam line and at the beam dump calorimeter, are presented. The beam transport efficiency as a function of various ion source, LEBT and HEBT parameters is measured and compared with the calculated values. The results dof plasma neutralization target study are presented as well.

The long-pulse surface-plasma source prototype is developed at Budker Institute of Nuclear Physics for negative-ion based neutral beam injector use. The essential source features are (1) an active temperature control of the ion-optical system electrodes by circulation of hot thermal fluid through the channels, drilled in the electrode bodies, (2) the concaved transverse magnetic field in the extraction and acceleration gaps, preventing the electrons trapping and avalanching, and (3) the directed cesium deposition via distribution tubes adjacent to the plasma grid periphery. The long term effect of cesium was obtained just with the single cesium deposition. The high voltage strength of ion-optical system electrodes was improved with actively heated electrodes. A stable H(-) beam with a current ∼1 A and energy 90 keV was routinely extracted and accelerated.

The experiments on negative hydrogen ion beam production in a multi-aperture long-pulse surface-plasma source are described. H-ions are produced on the surface of a plasma grid covered by cesium and illuminated by fast plasma particles. The source uses a radio-frequency driver to generate plasma. A composite magnet system made of external permanent magnets confines and filters electrons in the plasma region, and deflects them in the extraction area. A multiaperture, multi-electrode ion optical system is used for beam formation. The electrode heating and cooling during long pulses is accomplished by circulating a heat transfer fluid through channels drilled in the electrodes bodies. H-ions extraction through a single aperture and 21 apertures was performed and studied. A stable H- beam with the current up to 0.7 A, energy up to 74 kV, and pulse duration up to 7 s was routinely obtained

Multi-slit triode ion-optical systems with spherical electrodes are of interest for formation of intense focused neutral beams for plasma heating. At present, two versions of focusing multi-slit triode ion optical system are developed. The first ion optical system forms the proton beam with 15 keV energy, 140 A current, and 30 ms duration. The second ion optical system is intended for heating neutral beam injector of Tokamak Configuration Variable (TCV). The injector produces focused deuterium neutral beam with 35 keV energy, 1 MW power, and 2 s duration. In the later case, the angular beam divergence of the neutral beam is 20-22 mrad in the direction across the slits of the ion optical system and 12 mrad in the direction along the slits.

The ion source with the Penning geometry of electrodes producing continuous-wave beam of H(-) ions with current up to 25 mA was developed. Several improvements were introduced to increase source intensity, reliability, and lifetime. The collar around the emission aperture increases the electrons filtering. The apertures' diameters of the ion-optical system electrodes were increased to generate the beam with higher intensity. An optimization of electrodes' temperature was performed.

Two neutral beam injectors have been developed for plasma heating on COMPASS-D tokamak (Institute of Plasma Physics, Prague). The 4-electrodes multihole ion-optical system with beam focusing was chosen to provide the low divergence 300 kW power in both deuterium and hydrogen atoms. The accelerating voltage is 40 kV at extracted ion current up to 15 A. The power supply system provides the continuous and modulated mode of the beam injection at a maximal pulse length 300 ms. The optimal arrangement of the cryopanels and the beam duct elements provides sufficiently short-length beamline which reduces the beam losses. The evolution of the impurities and molecular fraction content is studied in the process of the high voltage conditioning of the newly made ion sources. Two injectors of the same type have been successfully tested and are ready for operation at tokamak in IPP, Prague.