nT-Tao quasi-axisymmetric Stellarator design and experiments

nT-Tao is developing the compact-core fusion concept. This concept aims to reach fusion conditions in toroidally confined D-T plasma of T~10keV, n~10²²m^-3 with τ_E~10’s of milliseconds. The base confinement approach relies on Stellarator field topology. The small scale of the vacuum chamber enables direct inductive coupling of energy from surrounding coils into the plasma using pulse power generators. Unlike RF heating, pulse power can provide the high power needed to heat the dense plasma within the available confinement time.

On the research and development route, different prototypes are built. The C-2A device is a compact Stellarator with a major radius of 0.7 m and a minor radius of 30 mm. Its main purpose is to test the feasibility of inductive coupling of energy to the plasma. The Stellarator was designed as a quasi-axisymmetric Stellarator with optimized toroidal and helical coil sets using the DESC optimization code. The design was validated by measurement of the flux surfaces in vacuum.

The plasma in the Stellarator is ignited using pulsed magnetrons. The main heating is established using inductively coupled external coils driven by power electronics generators. Visible spectroscopy, X-ray diodes, laser interferometry and magnetic diagnostics were developed and used to characterize the plasma. The design properties as well as recent results from the C-2A experiments will be presented.