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Intense, Neutralized-Ion Beam: A Potential Game Changer for Fusion-Plasma Heating and Current Drive

Intense, Neutralized-Ion Beam: A Potential Game Changer for Fusion-Plasma Heating and Current Drive

Contemporary fusion reactor designs utilize high-power microwave systems and neutral-particle beams for plasma heating, current drive, and fueling. However, these systems, despite their potential, have their challenges in efficiency, cost, and implementation. An alternative, the Neutralized-Ion Beam (NIB), offers intense plasma flows with energies between 100 to 1,000 keV. Compact, scalable, and efficient, NIBs are a promising supplement to existing technologies.

Figure 1 offers a schematic of a NIB source. Ions are produced and shot into a magnetically-insulated high-voltage space. A high-voltage pulse is introduced, and the transverse-magnetic field ensures efficient operation. The beam produced is remarkably intense, often hundreds of times greater than the Child-Langmuir Limit. This results in a plasma that’s both charge- and current-neutralized.

Initially, NIBs were developed for ion-beam-inertial fusion but have been adapted for magnetically-confined plasmas, proving essential for very high plasma temperatures in magnetic fields up to tens of Tesla. As the NIB interacts with the plasma, it generates electric fields that sustain its motion. Shorting by the transversely-magnetized plasma is possible but can be prevented with optimal NIB design.

Several key metrics illustrate NIB’s capabilities and potential. The parameters include average-beam current, power, ion energy, energy density, pulse duration, and repetition rate. Furthermore, various techniques exist for NIB focusing and transportation.

When it comes to burning plasma environments, detailed NIB performance specifications are still under development. Past commercial settings have showcased its continuous-operation feasibility. There's room for advancement using modern high-voltage, pulsed-power technologies, indicating a promising future for the NIB approach.

Drivers and Key Metrics

Fusion-power plants derive efficiency from the ratio of power components for fusion, heating, and losses. Neutralized-ion beams (NIBs) have shown to have a significant edge in efficiency over their neutral-particle beam counterparts. Moreover, NIBs are more compact and versatile than neutral particle beam systems, capable of being integrated directly with fusion power plants.

Extensive NIB experimentation has proven their relevance for fusion reactor applications. Their ability to deliver mass, charge, and heat flow directly into a confined plasma makes them invaluable.

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