Seedlabs

Negative-Triangularity Confinement-Upside Calculator

A calculator for fusion reactor designers to see how changing the machine's shape increases energy gain.

A calculator that tells a tokamak design team how much extra plasma gain they would get by reshaping their machine to negative triangularity, using gyrokinetic transport-suppression factors demonstrated on a compact spherical-tokamak design.

Physics and AstronomyMagnetic confinement fusion research
Urban Stormwater and Fluid ManagementTokamak design teams running plasma-shaping trade studies for next-generation compact fusion machines.

Concept

A design-trade calculator for tokamak teams weighing plasma shaping. Input: an existing positive-triangularity operating point (geometry, field, current, profiles). The tool applies benchmarked nonlinear gyrokinetic transport ratios to estimate the confinement gain from reshaping to delta ≈ −0.3, then propagates that through a 0-D Bosch–Hale power balance to return the new plasma gain Q and fusion power. The anchors are the paper's converged nonlinear gyrokinetic results: negative triangularity suppresses ion-scale transport by 40–45% and electron-scale (ETG) transport by 79–80% relative to a positive-triangularity twin, with the advantage robust (56–66%) across a factor-sixteen collisionality scan. The payoff is demonstrated in a closed design: the reshaped machine (R_0 = 1.20 m, A = 2.5) closes its power balance at Q = 3.076 and P_fus = 85.04 MW at demonstrated confinement, with a free-boundary equilibrium that is Mercier-, ballooning- and external-kink-stable at a 1.64× Troyon no-wall margin. Output: a one-page quantified upside case — or a clear 'no meaningful upside' — before the team commits to the expensive part, an equilibrium and divertor redesign.

Why now

Paper [0] reports the strongest quantified case yet that negative triangularity is a confinement lever rather than a curiosity: converged nonlinear CGYRO gyrokinetics (run in a GPU HPC campaign) show 40–45% ion-scale and 79–80% ETG transport suppression versus a positive-triangularity twin, robust at 56–66% across a 16× collisionality scan, and the design built on it closes at Q = 3.076 / P_fus = 85.04 MW at demonstrated confinement while staying subcritical and MHD-stable. Shaping is a live, expensive design choice for the next generation of compact machines, and experimental negative-triangularity campaigns on devices such as DIII-D and TCV have made the option credible to designers. A calculator that converts these suppression factors into a Q delta for a specific operating point is exactly the decision-sized product the evidence now supports.

Written by GLM · 12 Oct 2026

AI assessment

Backed by 1 paper92

A highly focused, evidence-backed decision tool that converts specific gyrokinetic transport gains into a high-value design metric (Q) for fusion engineers.

Evidence strength
5/5
The idea is directly derived from the paper's specific, converged nonlinear gyrokinetic results and a demonstrated closed power balance for a specific machine geometry.
Market pull
4/5
The named beneficiaries are the primary global players in compact fusion, who face immense capital costs and high urgency to optimize plasma gain.
Novelty & moat
4/5
While similar to other 'design-stage screens' in the catalog, it applies a very specific, newly quantified physics lever (negative triangularity) to a critical engineering trade-off.
Feasibility
5/5
The tool is essentially a 0-D power balance calculator using fixed suppression factors from the research, making it trivial to build as a prototype.
Wedge clarity
5/5
The wedge is extremely sharp: a single-purpose calculator to determine if a costly divertor/equilibrium redesign is justified by a specific gain in Q.
Simplicity / focus
5/5
It avoids 'platform' creep, focusing solely on the conversion of transport suppression factors into a power balance outcome.

Scored by Gemma 4 · 12 Oct 2026. Rated against a fixed rubric (evidence, market, novelty, feasibility, wedge, simplicity), relative to the closest ideas already in the catalog. A prior estimate to compare ideas before real-world signal arrives.

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Who benefits

  • Tokamak Energycompany

    Its compact spherical-tokamak line could adopt negative-triangularity shaping as a confinement lever; the calculator quantifies the Q gain before it commits to a divertor and equilibrium redesign.

  • General Atomicscompany

    GA runs DIII-D negative-triangularity experiments and designs pilot-plant concepts; the calculator extrapolates its experimental data to reactor operating points.

  • EPFL Swiss Plasma Centerorganization

    TCV pioneered negative-triangularity operation; the tool converts TCV-relevant results into quantified reactor-scale upside for its design partners.

  • Commonwealth Fusion Systemscompany

    Post-ARC machine studies weigh shaping options; a quantified 40–45% ion-scale suppression estimate informs that choice cheaply.

  • UKAEAorganization

    STEP follow-on design trade studies could use a defensible, gyrokinetics-anchored number for the confinement upside of negative triangularity.

Research it builds on

  1. Hyperion as a Strategic-Materials Platform: Gain, Tritium Breeding, He-3 Co-Production, and 14 MeV Neutron Output from a Compact Spherical-Tokamak
    Priyanca Ford, G L Kulcinski · 2026 · 87 citations
    All ideas from this paper →
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