National Spherical Torus Experiment Upgrade (NSTX-U)

The National Spherical Torus Experiment Upgrade (NSTX-U) at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) is the world’s most powerful experimental fusion facility, or tokamak, of its kind. The goal of the NSTX-U is to produce spherically-shaped plasmas at extreme temperatures in order to study the characteristics of such plasmas and the methods and materials needed to produce and sustain them. Positive results could strongly influence the design of future fusion reactors and may lead to the realization of an abundant, safe, low-cost, and environmentally-friendly energy source.

The Sun is powered through nuclear fusion, the process in which the nuclei of two atoms fuse together and release energy.  To take advantage of this process to create power on Earth, scientists need to create and maintain plasma—super-hot, ionized gas—in which fusion can occur under the appropriate conditions of pressure and temperature.  Since no material exists that can contain plasmas of such high temperatures, powerful magnetic fields are used to confine plasmas inside a device called a tokamak. 

Conventional tokamaks are shaped like a torus, which has the shape of a “donut.” The NSTX-U utilizes a spherical torus shape, the same shape as a “cored-apple.” Scientists and engineers at PPPL believe that this novel approach to plasma confinement will result in new breakthroughs for fusion energy.  Specifically, the spherical torus shape may allow for the confinement of a higher pressure plasma at a lower magnetic field strength.  This may result in the development of smaller, more efficient, and more economical fusion reactors. 

The NSTX device produced its first plasma on Friday, February 12, 1999.  In 2015, a $94 million dollar upgrade project was completed on the NSTX-U and resulted in a doubling of the magnetic field strength and plasma current.  These improvements allow the NSTX-U to produce hotter and longer lasting plasmas.  In addition to contributing to fusion energy research, the mission of the NSTX-U extends into a number of research areas including electron energy transport, liquid metal plasma-material interfaces, and energetic particle confinement for ITER burning plasmas. Research on NSTX-U is conducted by a collaborative research team of physicists and engineers from 30 U.S. laboratories and universities and 28 international institutions from 11 countries.


The Facility for Laboratory Reconnection Experiments (FLARE) is a new intermediate laboratory facility currently under construction at the Princeton Plasma Physics Laboratory. The design is based on the smaller device, Magnetic Reconnection Experiment. The goal of FLARE is to provide experimental accesses to new regimes of the magnetic reconnection process and related phenomena directly relevant to heliophysics, astrophysics, and fusion plasmas. FLARE is scheduled to be operational in late 2020.