Tri Alpha Energy's experimental program has demonstrated reliable field-reversed configuration (FRC) formation and sustainment, driven by fast ions via high-power neutral-beam (NB) injection. The world's largest compact-toroid device, C-2U, was upgraded from C-2 with the following key system upgrades: increased total NB input power from ~4 MW (20 keV hydrogen) to 10+ MW (15 keV hydrogen) with tilted injection angle; enhanced edge-biasing capability inside of each end divertor for boundary/stability control. C-2U experiments with those upgraded systems have successfully demonstrated dramatic improvements in FRC performance and achieved sustainment of advanced beam-driven FRCs with a macroscopically stable and hot plasma state for up to 5+ ms. Plasma diamagnetism in the best discharges has reached record lifetimes of over 11 ms, timescales twice as long as C-2. The C-2U plasma performance, including the sustainment feature, has a strong correlation with NB pulse duration, with the diamagnetism persisting even several milliseconds after NB termination due to the accumulated fast-ion population by NB injection. Power balance analysis shows substantial improvements in equilibrium and transport parameters, whereby electron energy confinement time strongly correlates with electron temperature; i.e. the confinement time in C-2U scales strongly with a positive power of T e .

TAE Technologies' research is devoted to producing high temperature, stable, long-lived field-reversed configuration (FRC) plasmas by neutral-beam injection (NBI) and edge biasing/control. The newly constructed C-2W experimental device (also called "Norman") is the world's largest compact-toroid (CT) device, which has several key upgrades from the preceding C-2U device such as higher input power and longer pulse duration of the NBI system as well as installation of inner divertors with upgraded electrode biasing systems. Initial C-2W experiments have successfully demonstrated a robust FRC formation as well as its translation into the confinement vessel through the newly installed inner divertor with adequate guide magnetic field. They also produced dramatically improved initial FRC parameters with higher plasma temperatures (Te up to 300 eV; total electron and ion temperature >1.5 keV) and more trapped flux (up to ~15 mWb, based on rigid-rotor model) inside the FRC immediately after the merger of collided two CTs in the confinement section. As for effective edge biasing/control on FRC stabilization, a number of edge biasing schemes have been tried via open-fieldlines, in which concentric electrodes located in both inner and outer divertors as well as end-on plasma guns are electrically biased independently. As a result of effective outer-divertor electrode biasing alone, FRC plasma diamagnetism duration has reached up to ~9 ms which is equivalent to C-2U plasma duration. Magnetic field flaring/expansion in both inner and outer divertors plays an important role in creating a thermal insulation on open-field-lines to reduce a loss rate of electrons, which leads to improvement of the edge as well as core FRC confinement properties.

TAE Technologies, Inc. (TAE) is pursuing an alternative approach to magnetically confined fusion, which relies on field-reversed configuration (FRC) plasmas composed of mostly energetic and well-confined particles by means of a state-of-the-art tunable energy neutral-beam (NB) injector system. TAE’s current experimental device, C-2W (also called ‘Norman’), is the world’s largest compact-toroid device and has made significant progress in FRC performance, producing record breaking, high temperature (electron temperature, T e > 500 eV; total electron and ion temperature, T tot > 3 keV) advanced beam-driven FRC plasmas, dominated by injected fast particles and sustained in steady-state for up to 30 ms, which is limited by NB pulse duration. C-2W produces significantly better FRC performance than the preceding C-2U experiment, in part due to Google’s machine-learning framework for experimental optimization, which has contributed to the discovery of a new operational regime where novel settings for the formation section and the confinement region yield consistently reproducible, hot, and stable plasmas. An active plasma control system has been developed and utilized in C-2W to produce consistent FRC performance as well as for reliable machine operations using magnets, electrodes, gas injection, and tunable NBs. The active control system has demonstrated stabilization of FRC axial instability. Overall FRC performance is well correlated with NBs and edge-biasing system, where higher total plasma energy is obtained by increasing both NB injection power and applied-voltage on biasing electrodes. C-2W divertors have demonstrated a good electron heat confinement on open-field-lines using strong magnetic mirror fields as well as expanding the magnetic field in the divertors (expansion ratio > 30); the energy lost per electron ion pair, η e ∼ 6–8, is achieved, which is close to the ideal theoretical minimum.

A repetitively driven compact toroid (CT) injector has been developed for the large fieldreversed configuration (FRC) facility of the C-2/C-2U, primarily for particle refueling. A CT is formed and injected by a magnetized coaxial plasma gun (MCPG) exclusively developed for the C-2/C-2U FRC. To refuel the particles of long-lived FRCs, multiple CT injections are required. Thus, a multi-stage discharge circuit was developed for a multi-pulsed CT injection. The drive frequency of this system can be adjusted up to 1 kHz and the number of CT shots per injector is two; the system can be further upgraded for a larger number of injection pulses. The developed MCPG can achieve a supersonic ejection velocity in the range of ~100 km s −1 . The key plasma parameters of electron density, electron temperature and the number of particles are ~5 × 10 21 m −3 , ~30 eV and 0.5-1.0 × 10 19 , respectively. In this project, singleand double-pulsed counter CT injection fueling were conducted on the C-2/C-2U facility by two CT injectors. The CT injectors were mounted 1 m apart in the vicinity of the mid-plane. To avoid disruptive perturbation on the FRC, the CT injectors were operated at the lower limit of the particle inventory. The experiments demonstrated successful refueling with a significant density build-up of 20-30% of the FRC particle inventory per single CT injection without any deleterious effects on the C-2/C-2U FRC.

Proton-boron (p11B) fusion is an attractive potential energy source but technically challenging to implement. Developing techniques to realize its potential requires first developing the experimental capability to produce p11B fusion in the magnetically-confined, thermonuclear plasma environment. Here we report clear experimental measurements supported by simulation of p11B fusion with high-energy neutral beams and boron powder injection in a high-temperature fusion plasma (the Large Helical Device) that have resulted in diagnostically significant levels of alpha particle emission. The injection of boron powder into the plasma edge results in boron accumulation in the core. Three 2 MW, 160 kV hydrogen neutral beam injectors create a large population of well-confined, high -energy protons to react with the boron plasma. The fusion products, MeV alpha particles, are measured with a custom designed particle detector which gives a fusion rate in very good relative agreement with calculations of the global rate. This is the first such realization of p11B fusion in a magnetically confined plasma.