GIGA Fusion Power Plant

• GIGA Fusion Power Plant is a stellarator-based design featuring a fixed-boundary plasma approach to generate 3 GW of fusion power.
• It employs multi-objective optimization with modified VMEC and STELLOPT codes to meet strict reactor-scale performance targets including low bootstrap current and high alpha confinement.
• The design framework directly links plasma configuration with engineering systems such as neutronics, coil design, and tritium blanket integration.

GIGA Fusion Power Plant denotes a one Gigawatt electric stellarator power plant being developed by Gauss Fusion GmbH. Its current physics design basis is a fixed boundary stellarator equilibrium capable of producing 3 GW of fusion power, and it is framed as a steady-state, transient free, low recirculating power approach to a fusion power plant that builds on 50 years of progress in plasma physics (Lazerson et al., 10 Jul 2026). In the published design basis, the plasma boundary is treated as the central design variable because stellarator performance, including stability and transport, is primarily a function of plasma shape rather than active control. The resulting program is therefore organized around fixed-boundary equilibrium definition, multi-objective optimization, and post-optimization validation of confinement, stability, transport, and engineering interface conditions (Lazerson et al., 10 Jul 2026).

1. Configuration and design concept

The GIGA design basis is explicitly stellarator-based. The seed configuration is a modified Wendelstein 7-X high iota/high mirror configuration, adapted to 4 field periods and scaled to GIGA size (Lazerson et al., 10 Jul 2026). The design philosophy treats plasma boundary optimization as the main route to reactor-relevant performance, with the boundary and pressure profiles adjusted to match power and shape constraints.

The fixed-boundary formulation is important because it provides a stable reference geometry for integrated plant work. The source states that fixed plasma volume and boundary enables direct integration with neutronics, tritium blanket, coil design, and system engineering (Lazerson et al., 10 Jul 2026). This distinguishes the fixed-boundary equilibrium from a purely plasma-physics exercise: it is presented as the physics basis for subsequent engineering realization.

A common misunderstanding is to treat “GIGA” as a generic label for any gigawatt-class fusion plant. In the Gauss Fusion usage documented here, the design basis is a stellarator equilibrium, not a tokamak equilibrium (Lazerson et al., 10 Jul 2026). Comparative tokamak studies do discuss gigawatt-class plant design spaces and optimization strategies, but they analyze positive and negative triangularity tokamaks rather than redefining the Gauss Fusion stellarator basis (Slendebroek et al., 25 Jul 2025).

2. Quantitative requirements and reactor-scale targets

The published design basis derives a set of fixed-boundary equilibrium requirements through application of 0.5 D modeling, previous reactor studies, and scaling laws including ISS04 (Lazerson et al., 10 Jul 2026). These requirements combine plasma-performance targets with geometry and exhaust constraints.

Parameter	Target
Fusion Power	3 GW
Electric Power	1 GW
Alpha Power Confinement	>85%
Plasma Volume	1500 m³
On-axis B field	6 T
Major radius	20 m
Minor radius	~1.95 m
Effective helical ripple	$\epsilon_{\text{eff}}^{3/2} < 0.01$
Bootstrap current	< 50 kA
Maximum surface heat flux	< 600 kW/m²
Core ion temperature	> 10 keV
Core electron density	> $2 \times 10^{20}$ m$^{-3}$
Edge rotational transform	$\iota_{\text{edge}} < 1.0$
Core radial electric field	$E_r > 0$

Additional constraints include compatibility with an island divertor, 4 field periods $(N_{fp}=4)$, and avoidance of low-order rational surfaces (Lazerson et al., 10 Jul 2026). The positive core radial electric field target is used to encourage CERC, identified in the source as core electron root (Lazerson et al., 10 Jul 2026).

The ISS04 confinement scaling is given as

$$\tau_{ISS04} = 0.134\, f_{\text{ren}}\, a^{2.28} R^{0.64} P^{-0.61} \bar{n}_e^{0.54} B^{0.84} \iota_{2/3}^{0.41}.$$

This places the GIGA equilibrium in the lineage of reactor-oriented stellarator extrapolations rather than purely device-specific optimization (Lazerson et al., 10 Jul 2026). A plausible implication is that the equilibrium requirements were chosen to remain interpretable both in stellarator optimization space and in system-level reactor scaling space.

3. Optimization framework and code modifications

Two codes are central to the GIGA equilibrium design: VMEC and STELLOPT (Lazerson et al., 10 Jul 2026). VMEC solves 3D ideal MHD equilibria for given pressure and current profiles. For GIGA, VMEC was modified so the plasma boundary harmonics are renormalized at each step to fix the plasma volume at the target of $1500\,\mathrm{m}^3$ (Lazerson et al., 10 Jul 2026). This was done so that fusion power and associated performance targets remain directly comparable across optimization steps.

STELLOPT was used to optimize plasma boundary shapes through Garabedian harmonics $\Delta_{mn}$ with a chi-squared cost functional,

$$\chi^2(\vec{x}) = \sum_k \frac{\left(f_k(\vec{x}) - f_k^{\text{target}}\right)^2}{\sigma_k^2}.$$

For the GIGA project, STELLOPT was modified in several ways: addition of a DKES-based bootstrap current proxy due to underestimation by BOOTSJ in low collisionality regimes; direct coupling of PENTA into the optimizer to target core radial electric field $2 \times 10^{20}$0; capability to fix the on-axis vacuum magnetic field at 6 T during optimization; and the ability to fix plasma volume via the modified VMEC coupling (Lazerson et al., 10 Jul 2026). The optimization workflow used both Genetic Algorithm/Differential Evolution and modified Levenberg-Marquardt minimization strategies (Lazerson et al., 10 Jul 2026).

The broader toolchain included NEO for effective helical ripple, COBRAVMEC for ballooning stability, TERPSICHORE for global ideal MHD kink stability, STELLGAP for Alfvén continuum analysis, BEAMS3D and ASCOT5 for fast-ion confinement, STELLA for post hoc turbulent transport estimates, and PENTA/BOOTSJ for neoclassical current, flows, and electric field (Lazerson et al., 10 Jul 2026). The underlying equilibrium condition is the ideal-MHD force balance

$2 \times 10^{20}$1

Methodologically, the GIGA work extends standard stellarator optimization by bringing bootstrap-current control, radial-electric-field targeting, and fixed-$2 \times 10^{20}$2 / fixed-volume constraints into the optimization loop itself (Lazerson et al., 10 Jul 2026). This suggests a shift from shape optimization alone toward shape optimization under explicit reactor-level normalization conditions.

4. Design evolution from seed equilibrium to evolved configuration

The workflow proceeded from an initial scaled modified W7-X equilibrium to a conceptual design and then to an evolved fixed-boundary equilibrium (Lazerson et al., 10 Jul 2026). The conceptual design, labeled “GIGA_v515,” used bounded global minimization with multi-objective targets including ballooning stability, ripple, ion confinement $2 \times 10^{20}$3, rotational transform, turbulence proxy, and symmetry (Lazerson et al., 10 Jul 2026).

That intermediate design exposed several issues: bootstrap current too large, rotational transform near low-order resonance, marginal alpha confinement, and non-CERC behavior (Lazerson et al., 10 Jul 2026). These deficiencies then determined the direction of the next optimization stage.

The evolved configuration, labeled “GIGA_v549,” placed stronger emphasis on further reduction of bootstrap current using DKES and PENTA, on a fast-ion proxy, and on securing core electron root conditions (Lazerson et al., 10 Jul 2026). More variables were allowed to vary, and a higher radial grid in VMEC was used for PENTA accuracy (Lazerson et al., 10 Jul 2026). The paper states that the final shape modifications were subtle, but led to significant physics improvement (Lazerson et al., 10 Jul 2026).

This staged progression is notable because it shows that reactor-relevant stellarator optimization was not completed in a single global search. Instead, the design moved through a conceptual equilibrium that already satisfied many goals but still failed key self-consistency and resonance-margin tests. In that sense, GIGA_v549 is best understood as an evolved equilibrium produced by tightening reactor-relevant constraints rather than by changing the overall architectural concept.

5. Performance of the evolved equilibrium

The final evolved equilibrium is reported to achieve all the necessary requirements for the GIGA fusion power plant through more detailed modeling of stability, fast ion confinement, and transport (Lazerson et al., 10 Jul 2026). The published achieved values are summarized below.

Quantity	Evolved equilibrium
Edge rotational transform	0.963
Core rotational transform	0.818
Alpha power confinement	>520 MW (>85%)
Effective ripple	0.00111
Max. heat flux	430 kW/m²
Bootstrap current	+20 kA
Ballooning stability	Stable
Kink $2 \times 10^{20}$4	Stable
Alfvénic gaps	None (safe)
Core $2 \times 10^{20}$5 at $2 \times 10^{20}$6	+7.4 kV/m (CERC)

These values satisfy the headline targets on alpha confinement, effective ripple, bootstrap current, heat flux, and edge rotational transform (Lazerson et al., 10 Jul 2026). In particular, effective ripple is far below the target threshold of 0.01, and the net toroidal current is comfortably below the 50 kA cap (Lazerson et al., 10 Jul 2026).

Post-optimization validation provides the main evidence that the equilibrium is reactor-oriented rather than merely numerically optimized. For fast ions, BEAMS3D and ASCOT5 showed that the evolved shape improved over the conceptual version, with collisionless fraction losses from mid-radius deeply trapped alphas below 1% (Lazerson et al., 10 Jul 2026). For neoclassical transport, effective ripple was always well below 0.01, and PENTA/NEO modeling confirmed low transport (Lazerson et al., 10 Jul 2026). For turbulence, a posteriori STELLA simulations showed both particle and heat fluxes significantly below those in W7-X for similar gradient drive (Lazerson et al., 10 Jul 2026).

The stability assessment is similarly broad. Ballooning, Mercier, and magnetic well were all satisfied; no magnetic hill was found; and kink stability was confirmed via TERPSICHORE even including bootstrap current self-consistency (Lazerson et al., 10 Jul 2026). STELLGAP analysis showed no core-to-edge gaps in the Alfvén continuum, which the source interprets as ensuring no global fast ion redistribution from Alfvénic instabilities (Lazerson et al., 10 Jul 2026).

6. Engineering interpretation, adjacent methods, and broader context

The fixed-boundary equilibrium is presented as a robust physics basis for engineering design rather than as a complete plant description (Lazerson et al., 10 Jul 2026). The source explicitly links the fixed plasma volume and boundary to downstream neutronics, tritium blanket, coil design, and system engineering (Lazerson et al., 10 Jul 2026). This is significant because reactor design credibility depends on maintaining traceability from plasma configuration to surrounding plant systems.

That downstream workflow has close analogues in recent fusion design literature. Fast predictive neutronic capabilities have been identified as crucial for efficient design processes because neutron interactions determine parameters such as coil-plasma distance and breeding blanket composition (Bogaarts et al., 2024). A deterministic neutronics method using discontinuous Galerkin spatial discretization, discrete-ordinates angular discretization, multigroup energy discretization, arbitrary-order anisotropic scattering, and matrix-free iterative solvers has been benchmarked through blanket simulation (Bogaarts et al., 2024). A plausible implication is that fixed-boundary equilibria such as the GIGA basis can serve as stable geometric inputs for this class of rapid neutronics iteration.

Integrated design and optimization frameworks provide a second adjacent context. FUSE is described as a modular, open-source, Julia-based framework that integrates first-principle models, reduced models, machine learning surrogates, engineering, and costing, with multi-objective optimization and steady-state or time-dependent workflows (Meneghini et al., 2024). Comparative plant studies using FUSE have explored over 200,000 integrated design evaluations under constraints including net electric power, tritium breeding ratio, power exhaust limits, and flattop time (Slendebroek et al., 25 Jul 2025). These results do not define GIGA itself, but they show the broader optimization environment in which gigawatt-class fusion plants are now being compared.

Costing and deployment analyses provide a third context. The extension of the fusion power plant costing standard reorganizes cost accounting around architecture-defining driver tracks for MFE, IFE, and MIFE, adds probabilistic costing, safety-informed costing, and value metrics such as NPV, IRR, MIRR, revenue requirements, and WACC-based annualization (Woodruff et al., 22 Feb 2026). Early-market analysis identifies high-priced electricity markets, integrated thermal storage, and cost targets of roughly $2 \times 10^{20}$7–$2 \times 10^{20}$8 for broad competitiveness, with higher-cost early opportunities in selected regions (Handley et al., 2021). These studies are not specific performance claims about GIGA, but they indicate the economic and regulatory frameworks likely to shape interpretation of any one-GW-electric fusion plant design basis.

A second common misunderstanding is to equate satisfaction of plasma targets with commercial readiness. The published GIGA basis argues instead for a staged interpretation: the equilibrium establishes the physics performance envelope and the system integration interface, while engineering realization still depends on neutronics, coils, blanket design, costing, safety, and deployment pathways (Lazerson et al., 10 Jul 2026). The source further identifies Technical Readiness Levels for crucial processes at TRL5–6, with full demonstration in a reactor environment forming TRL7–9 (Lazerson et al., 10 Jul 2026). This suggests that the present GIGA result is best read as a reactor-grade fixed-boundary plasma basis rather than as a completed power-plant design.