C. Neumeyer, P. Heitzenroeder, J. Chrzanowski, J. Spitzer, R. Wilson, L. Dudek, R. Kaita, S. Ramakrishnan, D. Bashore, E. Perry, and the NSTX Team
Princeton University Plasma Physics Laboratory
Princeton, NJ 08540
B. Nelson
Oak Ridge National Laboratory
Oak Ridge, TN
The NSTX Project will provide a national facility for the study of plasma confinement, heating, and current drive in a low aspect ratio, spherical torus (ST) configuration. The ST configuration is an alternate confinement concept which is characterized by high b, high elongation, high bootstrap fraction, and low BT configurations compared to conventional tokamaks. NSTX is the next step ST experiment following smaller experiments such as the PPPL CDX-U (Current Drive Experiment, Upgrade), the START (Small Tight Aspect Ratio Tokamak) at Culham, and the HIT (Helicity Injected Tokamak) at University of Washington, and similar in scale to the MAST (Meg-Amp Spherical Tokamak) machine whose design is now underway at Culham.
This paper provides a description of the NSTX mission and gives an overview of the main engineering features of the design of the machine as well as the balance of the facilities.
The core of the NSTX machine consists of a narrow center stack bundle which contains the inner legs of the Toroidal Field (TF) winding, an Ohmic Heating (OH) solenoid and associated tension cylinder, a pair of inner Poloidal Field (PF) coils, thermal insulation, and a Center Stack Casing which forms the inner wall vacuum vessel boundary. The Center Stack Casing is electrically isolated from the remainder of the machine via ceramic insulator assemblies which permit the use of Coaxial Helicity Injection (CHI) as one of the means of advanced current drive. This center stack bundle presents one of the main engineering challenges of NSTX and is described in more detail in a companion paper.
The NSTX vacuum vessel outer sections are formed using a cylindrical section which is capped off by upper and lower domes taken from the retired Spheromak-1 (S-1) machine at PPPL. Similarly the outer PF coils are taken from S-1. NSTX will be installed in the Hot Cell of the D-site facility at PPPL which supported TFTR until its recent retirement. Extensive use of the infrastructure including magnet and RF power supplies, cooling water systems, etc., is made to minimize the overall cost of the experiment.
*Work supported by USDOE contract #DE-AC02-76-CHO3073.