NSTX Upgrade Project

Motivation and Enhancements 

Scientific motivations for upgrading the original NSTX facility include:  

1. Accessing 3 to 6 times lower collisionality at high normalized pressure (beta) to study confinement (see Figure 1) and stability in a unique physics parameter regime much closer to ST-FNSF and Pilot Plant parameters.

2. Accessing fully non-inductive plasma current start-up, ramp-up, and sustainment.

3. Developing and utilizing high-power long-pulse divertor solutions compatible with high plasma performance - including the use of liquid metals as plasma facing components.

4. Supporting ITER burning plasma research through access to unique parameters regimes, such as strong drive for energetic particle instabilities and transport.

Figure 1

The Upgrade Project consisted of 3 major enhancements - see Figure 2:

1. A new centerstack (CS) of larger diameter enabling a doubling of the toroidal field (up to 1 Tesla), a tripling of the solenoid flux (up to 2.1 Webers), and up to fives times longer flat-top duration. 

2. A second Neutral Beam Injector (NBI) to double the NBI heating and current drive power (up to 10MW for 5s) while aiming more tangentially to provide a factor of 1.5-2 times higher current drive efficiency and improved control of the NBI-driven current profile.  A large penetration in the vessel wall and a new port was required for this more tangential NBI.

3. Substantial structural enhancements to the toroidal field  coils, poloidal field coils, the vacuum vessel, and vacuum vessel supports to withstand electromagnetic loads up to four times higher than NSTX resulting from the simultaneous doubling of the toroidal field and plasma current (up to 2MA).

Figure 2

Many diagnostic and rack relocations were also required in the NSTX test-cell  to provide sufficient floor space for the second NBI and associated high-power electrical equipment - see Figure 3.

For additional technical information on the NSTX Upgrade project see the following links:

NOTE: Nearly all NSTX-U technical information has been updated and/or superseded by the NSTX-U Recovery Project initiated in 2017.

Figure 3