Neutral beam injection for fusion reactors: technological constraints versus functional requirements

Abstract

In this paper we look at the technological constraints of neutral beam injection (NBI) systems and compare them with the functional requirements that NBI has in the various envisaged plasma scenarios for tokamak fusion reactors of the DEMO and fusion power plant (FPP) class. We show in particular that there is an intermediate beam energy range in which beamlines are unattractive because of size. Furthermore, for scenarios that consider NBI only for ion heating during the ramp-up and heat-to-burn phase we show that the use of beam energies in the range of 100 to 200 keV, which could be produced from positive ion beams with a much simpler system, could be an attractive option that should be further investigated.

Charged Particle Beam Injection into Magnetically Confined Plasmas

“…The high currents and efficient production of positive ions saves on power losses at the source relative to the negative ion beams used for neutral beam injection [13]. The inefficiencies and beam energy limitations associated with neutralization and neutral beam injection introduce approximately a factor of 2 loss in absolute power efficiency [14].…”

Langmuir-probe measurement through the plasma grid aperture of hydrogen negative ion source

“…A negative hydrogen-ion-based Neutral Beam Injector (N-NBI) is a powerful heating and current drive device for future tokamak-based fusion reactors such as ITER and DEMO [1][2][3]. The N-NBI can provide a toroidal current drive, which is necessary to sustain the tokamak configuration.…”

New Method to Evaluate Negative-Ion Density Using Conventional Langmuir Probe

“…A negative-ion based Neutral Beam Injector (N-NBI) is an essential heating device for ITER, DEMO, and future fusion reactors [1][2][3] to obtain high energy beams. The negative-ion source is the key component of N-NBI.…”