The SPARC tokamak, a joint project of MIT's Plasma Science and Fusion Center and Commonwealth Fusion Systems, is designed to be the first magnetic confinement experiment to produce net fusion energy. A foundational paper published in *Physics of Plasmas* outlines the device's scientific basis, leveraging high-temperature superconducting (HTS) magnets to achieve a toroidal field of 12.2 T on-axis. This high-field approach enables a compact machine, with a major radius of 1.85 m and a minor radius of 0.57 m, to access burning plasma regimes. The primary mission objective is to demonstrate a plasma energy gain, or Q_plasma, greater than two, with simulations predicting values as high as 11. This would validate the high-field path to commercial fusion energy and provide critical data for the subsequent ARC-class power plant. Source: Pubs

SPARC's operational plan is structured in two main phases. The initial phase will use hydrogen and helium plasmas to commission the device, test diagnostics, and establish baseline operational scenarios without activating the machine with neutrons. This phase focuses on validating magnet performance, heat exhaust systems, and plasma control before introducing tritium. The second, primary phase will utilize deuterium-tritium (D-T) fuel to explore high-performance, burning plasma physics. The research program aims to study alpha particle heating, a key characteristic of a self-sustaining fusion reaction, and its effects on plasma turbulence and stability. The experiment is designed for a plasma current of 8.7 MA and pulse durations of approximately 10 seconds in the D-T phase. Source: Pubs

This phase focuses on validating magnet performance, heat exhaust systems, and plasma control before introducing tritium.

The physics projections for SPARC are based on an extensive set of integrated modeling simulations, anchored to empirical performance observed in existing tokamaks. According to the published analysis, the reference D-T operational scenario is predicted to produce 50-140 MW of fusion power. This level of performance corresponds to a plasma gain Q_plasma between 2 and 11, satisfying the project's core scientific goal. These simulations incorporate detailed models for plasma transport, magnetohydrodynamic (MHD) stability, and boundary physics. The results give confidence that SPARC will not only achieve net energy gain but also serve as a flexible platform for studying the dynamics of a burning plasma, a scientific domain directly relevant to future reactors like ITER and commercial power plants. Source: Pubs

Beyond its primary Q > 2 mission, SPARC is designed to address several key scientific questions for tokamak-based fusion. The research plan includes experiments to test advanced divertor solutions and power handling strategies under reactor-relevant heat fluxes. It will also investigate the confinement and transport of energetic particles, particularly the 3.5 MeV alpha particles produced by D-T reactions, which must be well-confined to heat the plasma efficiently. Another critical area of study is the mitigation of plasma disruptions, which remain a significant challenge for steady-state tokamak operation. By operating in a new regime of high magnetic field and compact size, SPARC will provide essential data to refine the physics models used to design future fusion power plants and advance the general field of fusion science. Source: Pubs