Spherical Tokamak

The NSTX-U user facility at PPPL is designed to explore the physics of plasmas confined in a spherical torus (ST) configuration. With its unusually strong magnetic curvature, powerful heating systems, and advanced diagnostics, NSTX-U uniquely enables the detailed study of plasmas at ratios of plasma pressure to the pressure of the confining magnetic field, or plasma beta, many times higher than are accessible in the world’s other tokamaks. The implications of a successful NSTX-U research program are therefore significant: high plasma pressures translate to high fusion reactivity, making the NSTX-U geometry a candidate for a future neutron source for scientific study of fusion materials and components. Also, the high beta plasmas and measurement capabilities on NSTX-U will enable first-of-a-kind detailed laboratory study of plasma processes that are relevant to astrophysical systems. The upgraded neutral beam heating systems combines with the plasma properties to make NSTX-U and ideal test bed for studying interactions between plasma waves and fast fuel ions that are relevant to burning plasma science. The liquid metal divertor research program planned for NSTX-U also will enable assessment of a potential break-out path for fusion heat and particle exhaust handling.

Following an extensive series of reviews (e.g. design validation and verification, extent of condition) in FY 2017, NSTX-U activities is focused on recovery efforts to repair or replace essential components.

Back to Overview