Nuclear Fusion Quarterly Report — Q2 2026
Q2 2026 was the most significant quarter for private fusion investment since the field's emergence as a credible commercial sector. Helion Energy closed a $465 million Series G at a $15.5 billion post-money valuation — the largest…
Q2 2026 was the most significant quarter for private fusion investment since the field's emergence as a credible commercial sector. Helion Energy closed a $465 million Series G at a $15.5 billion post-money valuation — the largest… 1. Executive Summary Q2 2026 was the most significant quarter for private fusion investment since the field's emergence as a credible commercial sector. Helion Energy closed a $465 million Series G at a $15.5 billion post-money valuation — the largest single private fusion financing round in history — signalling that institutional capital now regards near-term commercial fusion as a credible risk/return proposition rather than speculative science. TAE Technologies demonstrated 100 million degrees Celsius sustained plasma for 20 milliseconds in its Norman, California FRC device, a temperature milestone that places its proton-boron fusion approach on a scientifically plausible roadmap. The UK Atomic Energy Authority broke ground on the STEP spherical tokamak demonstration facility in Nottinghamshire, marking the first state-backed fusion pilot plant to move into site preparation. OpenAI's announced compute partnership with Commonwealth Fusion Systems — providing HPC resources for plasma simulation workloads — signals that the compute-intensive nature of fusion AI is beginning to attract big-tech infrastructure interest. Cumulatively, the fusion sector has now secured more than $10.5 billion in private capital, and first-commercial-fusion timelines from leading companies remain clustered in the 2030-2035 window pending demonstration milestones over the next 18-36 months. --- 2. Technical & Scientific Updates — Q2 2026 2.1 Plasma & Confinement Performance TAE Technologies' most public milestone of the quarter arrived in May 2026, when the company announced that its Norman device had sustained a plasma temperature of 100 million degrees Celsius (approximately 8.6 keV mean ion temperature, with peak temperatures significantly higher) for 20 milliseconds — the company's stated threshold for entering the "net energy" development phase of its programme. While 20 milliseconds is far shorter than the steady-state durations demonstrated at EAST in Q1, TAE's FRC approach operates in a fundamentally different physical regime, and the temperature figure is the more critical parameter for the proton-boron (p-11B) fuel cycle it ultimately targets. TAE stated that its next phase will focus on extending pulse duration while maintaining this temperature, with a target of 200 milliseconds by end of 2026. Commonwealth Fusion Systems reported SPARC construction at approximately 57% completion at the close of Q2, slightly ahead of the 55% internal target set at the start of the quarter. The first of the SPARC 18-coil TF magnet set completed cryo-assembly and passed cold-testing at 20.1 tesla without quench events. The central solenoid fabrication, which uses the longest REBCO conductor runs of any coil in the system, was confirmed to be on sc