Polaris (Helion 7th generation)

Overview

Polaris is Helion's seventh-generation fusion energy prototype, located at the company's facility in Everett, Washington. It is designed to be the first fusion device to demonstrate net electricity generation. Polaris operates on the principles of a Field-Reversed Configuration (FRC), a type of compact toroid plasma, and utilizes a pulsed, non-ignition approach. The machine aims to achieve fusion conditions by magnetically accelerating two FRC plasmoids to high velocity (~1.6 x 10^6 km/h), colliding and compressing them to fusion-relevant temperatures and densities. A key feature of the Helion architecture is its intended use of a deuterium-helium-3 (D-³He) fuel cycle, which produces primarily charged particles (protons and alpha particles) rather than high-energy neutrons. This aneutronic characteristic is central to the system's design, which employs direct energy conversion to recapture the plasma's expansion energy as electricity, bypassing the need for a conventional thermal cycle with steam turbines.

Physics / Mechanism

Polaris employs a pulsed magnetic confinement scheme based on the Field-Reversed Configuration. An FRC is a mass of plasma confined by closed magnetic field lines within a cylindrical conductor, but with a near-zero magnetic field at the plasma's core. This high-beta (β ≈ 1) configuration, where plasma pressure is comparable to the magnetic pressure, allows for a compact and potentially efficient confinement system.

The operational sequence of Polaris involves several distinct stages:

Formation: Two FRC plasmoids are formed at opposite ends of the 12-meter-long machine. This is achieved by discharging high-voltage capacitor banks into formation coils, ionizing a deuterium gas puff and creating the initial closed-field-line structures.
Acceleration: The two plasmoids are accelerated towards each other down tapered magnetic guide fields, acting as a magnetic peristaltic pump. This process heats the plasmoids through adiabatic compression.
Merging and Compression: The plasmoids collide and merge at the center of the device in a compression chamber. A powerful, rapidly rising external magnetic field (up to 12 T) is applied, compressing the merged plasmoid to fusion conditions. Helion's sixth-generation device, Trenta, demonstrated ion temperatures exceeding 10 keV (over 100 million °C) using this method.
Fusion Burn: During the brief period of maximum compression (lasting microseconds), D-D and D-³He fusion reactions occur. While the ultimate goal is D-³He, initial operation and physics studies rely on D-D reactions, which have a higher cross-section at these temperatures.
Expansion and Direct Energy Conversion: After the fusion pulse, the magnetic compression field is relaxed. The plasma, containing thermal energy and high-energy fusion products, expands axially. As the plasma's magnetic flux expands, it pushes back against the magnetic field coils, inducing a current. This process directly converts the plasma's kinetic and thermal energy back into electrical energy, which is used to recharge the capacitors for the next pulse. Helion has reported energy recovery efficiencies exceeding 95% in sub-scale experiments.

The system is designed to operate at a repetition rate of approximately 1 Hz, enabling a quasi-steady power output from a series of discrete pulses.

Historical Development

The development of Polaris is the culmination of over two decades of research and six preceding generations of FRC prototypes built by Helion, founded in 2013, and its predecessor, MSNW. The company's approach is based on the early FRC work at institutions like Los Alamos National Laboratory and the University of Washington.

Key milestones leading to Polaris include:

Early Prototypes (1-4): These machines established the basic principles of FRC formation, acceleration, and merging. They demonstrated the stability and scalability of the concept.
The Grande (5th Gen): This device achieved significant improvements in plasma parameters and stability, validating the magnetic compression scheme.
Trenta (6th Gen): Commissioned in 2020, Trenta was a pivotal machine. In 2021, Helion announced that Trenta had achieved ion temperatures exceeding 100 million °C (over 8.6 keV), a critical threshold for D-³He fusion. It also demonstrated sustained operation for over 16 months, firing more than 10,000 high-power pulses. Trenta's results provided the physics basis and engineering confidence to proceed with Polaris.
Polaris Construction: Construction of Polaris began in 2021 at a new 3,000-square-meter facility in Everett. The project represents a significant scale-up in size, magnetic field strength, and power handling capabilities compared to Trenta.

In 2021, Helion announced a power purchase agreement with Microsoft to supply 50 MWe of fusion-generated electricity starting in 2028, a commitment that hinges on the success of Polaris and its successor. This agreement marked a significant commercial milestone in the fusion industry.

Current Status

As of early 2026, Polaris is in the final stages of construction and the initial phases of commissioning. The device was mechanically complete by late 2023, and the focus since has been on integrating the massive pulsed power systems, diagnostic suites, and control systems. The commissioning process involves systematically testing each subsystem, from the vacuum vessel and gas injection to the multi-MJ capacitor banks and magnetic coils.

Initial plasma operations are expected to commence in 2026. These first experiments will focus on replicating and surpassing the performance of Trenta, validating the scaling laws for FRC compression and heating. The primary goal is to achieve a plasma temperature and density-confinement time product sufficient for significant fusion energy gain. The company aims to demonstrate net electricity generation with Polaris by the end of its operational campaign, which would be a world-first for any fusion device.

Notable Implementations

Polaris is a singular device and the sole focus of its operator, /companies/helion. It represents the most advanced implementation of the staged, colliding FRC concept globally. While other research groups explore FRCs, such as those at TAE Technologies and Princeton Plasma Physics Laboratory, Helion's approach of high-speed collision, magnetic compression, and direct energy conversion is unique.

Key technological systems implemented in Polaris include:

Pulsed Power System: A network of high-voltage, high-current capacitor banks and solid-state switches capable of delivering hundreds of megajoules of energy in microseconds.
High-Field Magnets: Advanced pulsed magnets designed to withstand the immense forces generated by the 12 T compression field.
Advanced Diagnostics: A comprehensive suite of tools to measure plasma parameters, including Thomson scattering for temperature and density, interferometry for density profiles, neutron and proton detectors for fusion reaction rates, and magnetic probes.
Direct Energy Conversion Circuitry: High-efficiency power electronics designed to capture the energy from the expanding plasma and recycle it for the next pulse.

Open Challenges

Despite the progress made with previous generations, Polaris faces significant scientific and engineering challenges to achieve its goal of net electricity generation.

Plasma Stability and Confinement: While FRCs are kinetically stable, they can be susceptible to magnetohydrodynamic (MHD) instabilities, particularly the tilt instability, during the compression and burn phases. Maintaining plasma stability and achieving sufficient energy confinement time (τ_E) at fusion conditions in this larger, more powerful device is a primary challenge. The required confinement must be sufficient to exceed the Lawson criterion for energy breakeven.
Energy Gain (Q): Polaris must demonstrate a Q_engineering > 1, where the electrical energy produced exceeds the total electrical energy consumed by the plant's systems (capacitors, cryogenics, vacuum pumps, etc.). This requires not only high fusion power but also extremely high efficiency in the direct energy conversion and pulsed power systems.
Helium-3 Sourcing: The D-³He fuel cycle is attractive for its low neutronicity, but ³He is extremely rare on Earth. Helion's strategy is to breed its own ³He fuel from D-D fusion reactions (D + D → T + p, followed by tritium beta decay to ³He). Polaris must demonstrate this breeding process at a rate sufficient to create a self-sustaining fuel cycle for future power plants. The required tritium breeding ratio for ³He is effectively 1, but achieved through a different pathway than conventional D-T reactors.
Component Lifetime and Rep-Rate Operation: Operating at 1 Hz subjects all components—magnets, insulators, capacitors, and plasma-facing surfaces—to extreme cyclical thermal and mechanical stresses. Ensuring the durability and reliability of these components for commercially relevant operational periods is a major engineering hurdle.
Neutron Management: While D-³He is aneutronic, side D-D reactions produce a non-trivial flux of 2.45 MeV neutrons. These neutrons activate surrounding materials and can damage components over time. Polaris must demonstrate effective shielding and materials strategies to manage this neutron flux.

Outlook

The credible 5- to 15-year trajectory for the Polaris program and its successors is aggressive, driven by commercial commitments. The primary near-term goal (1-3 years) is for Polaris to successfully demonstrate net electricity generation. This would be a landmark achievement for the entire fusion field, validating both the FRC approach and the economic potential of direct energy conversion.

If Polaris succeeds, the next step (3-7 years) would be the design and construction of a pilot power plant. This successor machine would need to operate at a higher repetition rate, produce tens of megawatts of net electricity continuously, and demonstrate a closed, self-sustaining fuel cycle. This is the device envisioned to fulfill the power purchase agreement with Microsoft by 2028.

Looking further out (7-15 years), the focus would shift to commercialization. This involves refining the power plant design for cost-effectiveness, reliability, and ease of maintenance. Establishing a robust supply chain and navigating the regulatory landscape for licensing and deploying fusion power plants will be critical. The success of Polaris is the linchpin for this entire trajectory; its results over the next few years will determine whether Helion's approach can transition from experimental physics to a commercially viable energy source.

References

High-Performance Field-Reversed Configuration Plasmas in the Trenta Device — APS Division of Plasma Physics Meeting Abstracts (2021)
Helion to build first fusion power plant, with funding from CEO of OpenAI — Ars Technica (2021)
Microsoft makes a bet on fusion energy — The Verge (2023)
Staged Magnetic Compression of a Field-Reversed Configuration to Kiloelectronvolt Temperatures — Physics of Plasmas (2012)
Fusion Energy Base Technology — U.S. Department of Energy
Helion’s Polaris is mechanically complete, commissioning underway — Helion Blog (2023)
The Helion Fusion Energy Prototype — Helion
FRC-Based Fusion-Space Propulsion — NASA Technical Reports Server (2011)