Status and Plans for the National Spherical Torus Experimental Research Facility

Abstract

An overview of the research capabilities and the future plans on the MA-class National Spherical Torus Experiment (NSTX) at Princeton is presented. NSTX research is exploring the scientific benefits of modifying the field line structure from that in more conventional aspect ratio devices, such as the tokamak. The relevant scientific issues pursued on NSTX include energy confinement, MHD stability at high β, non-inductive sustainment, solenoid-free start-up, and power and particle handling. In support of the NSTX research goal, research tools are being developed by the NSTX team. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a high β Demo device based on the ST, are being considered. For these, it is essential to develop high performance (high β and high confinement), steady-state (non-inductively driven) ST operational scenarios and an efficient solenoid-free start-up concept. We will also briefly describe the Next-Step-ST (NSST) device being designed to address these issues in fusion-relevant plasma conditions.

Steady Burning Criteria for D-3He Spherical Tokamak Reactor with Internal Transport Barrier

“…7(b) Therefore, the < β > do not have to be high, but β 0 ≈ 1 is important in order to obtain D- 3 He burning. In the NSTX experiment, the plasma with β 0 ≈ 1 is already obtained (5) . So the β value for the D-3 He burning is available in ST reactors.…”

“…It is well known that the high β and high temperature plasma with long confinement time is required for a D- 3 He fusion reactor, where the β is the ratio of the plasma pressure to the magnetic pressure. In recent tokamak experiments, the plasma performance is remarkably improved as follows: (1) the ion temperature has been achieved 40 keV (1) , which is high enough for the D-3 He fusion; (2) the plasma confinement has been improved due to the internal transport barrier (ITB) (2) , which leads better confinement time than the ITER scaling (3) ; (3) in spherical tokamak (ST), the averaged β has been achieved 40 % (4) and the central β has been achieved unity (5) . These results encourage us to consider a D- 3 He tokamak reactor.…”