Core Diagnostics

Diagnostics measure the plasma's temperature, density, current, and shape in real time, both to control the discharge and to test the physics.

Seeing the plasma

A tokamak cannot be run blind. Diagnostics measure the plasma's key quantities, temperature, density, current profile, position, shape, and impurity content, continuously during a discharge. They serve two purposes: feeding the real-time control that holds the plasma stable, and recording the data that tests whether the machine behaves as the design predicts.

What is measured

Magnetic sensors track position, shape, and current for control and vertical stabilization. Interferometers and scattering systems measure density and temperature. Spectroscopy reveals impurities and helium content. Neutron detectors measure fusion output directly, tying the diagnostics to the Q_sci and power figures. Each measurement supports both operation and the scientific verification of the design point.

Access and survival

Diagnostics need sightlines through the vessel wall, so like heating ports they occupy blanket area and compete with breeding coverage, and their in-vessel components must survive heat and neutron flux. The diagnostic set is chosen to give the control system what it needs and to measure the quantities that will confirm or challenge the confinement, stability, and breeding predictions during the first-of-a-kind campaign.

From measurement to validated physics

The diagnostics are also how the design point stops being a projection and becomes a measured result. Neutron yield tests the 85.0 MW and Q_sci 3.076 figures; profile measurements test the confinement and bootstrap assumptions; magnetic reconstruction tests that the plasma holds its negative-triangularity shape at 9.66 MA. Because these measurements feed both live control and the scientific record, the diagnostic system is designed for accuracy and calibration, not only for the fast response that stabilization demands, and its data will drive the updates to the frozen canon after first plasma.

• Measure temperature, density, current, shape, output
• Serve both real-time control and physics verification
• Diagnostic ports compete with breeding coverage

This page describes a design and simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030.