Plasma equilibrium reconstruction
Inferring the internal state of a fusion plasma from external measurements.
The internal magnetic configuration of a tokamak plasma cannot be measured directly. Equilibrium reconstruction is the inverse problem of inferring it — the current profile and the plasma boundary — from external magnetic measurements, subject to the force-balance equation that any equilibrium must satisfy. It is the foundation on which control and physics analysis both rest.
The governing relation is the Grad–Shafranov equation, a nonlinear elliptic equation for the poloidal flux. Reconstruction fits its free functions so that the resulting equilibrium is consistent with the measured signals. The EFIT method established the practical approach the field still builds on, and it remains the reference against which reconstructions are compared.
The fusion studio runs a synthetic reconstruction as a deterministic, bounded demonstration. Because it is validated against analytic and synthetic equilibria rather than a live device, its results are marked as bounded-model and never presented as instrument readings — the boundary is part of the claim.
The vocabulary of the topic.
- Grad–Shafranov equation
- The nonlinear force-balance equation a tokamak equilibrium must satisfy.
- Inverse problem
- Inferring the internal plasma state from external measurements, constrained by physics.
- Poloidal flux
- The magnetic flux function whose contours are the nested flux surfaces of the equilibrium.
- Bounded-model claim
- A result validated against synthetic or analytic references, valid only within that stated scope.
Studios working on this.
Each runs standalone in its own repository and federates its evidence through the platform.
Run it, don't take it on faith.
The runnable lessons and sealed measurements this site ships for the topic.
Read it at source, in order.
Canonical references for the topic, ordered from the foundations to current work. Every one was verified at source — a DOI resolves through doi.org, a standard through its issuer — so each link goes to the real record.
Start with the foundations
- 1
EFIT: the equilibrium reconstruction method the field still builds on.
Current work
- 2
Learned magnetic control demonstrated on the TCV tokamak.
Related topics.
Where this topic connects to the rest of the federation's work.