National Spherical Torus Experiment
Encyclopedia
The National Spherical Torus Experiment (NSTX) is an innovative magnetic fusion device based on the spherical tokamak
concept that was constructed by the Princeton Plasma Physics Laboratory
(PPPL) in collaboration with the Oak Ridge National Laboratory
, Columbia University
, and the University of Washington
at Seattle.
Fusion is the energy source of the Sun and all the stars. Scientists believe it can provide an inexhaustible, safe, and environmentally attractive source of energy on earth.
First plasma
was obtained on NSTX on Friday, February 12, 1999 at 6:06 p.m. NSTX is being used to study the physics principles of spherically shaped plasmas—hot ionized gases in which nuclear fusion will occur under the appropriate conditions of temperature, density, and confinement in a magnetic field.
Magnetic fusion experiments use plasmas composed of one or more of the isotopes of hydrogen. For example, in 1994, PPPL's Tokamak Fusion Test Reactor (TFTR) produced a world-record 10.7 megawatts of fusion power from a plasma composed of equal parts of deuterium
and tritium
, the fuel mix likely to be used in commercial fusion power reactors. NSTX is a "proof of principle" experiment and therefore employs deuterium plasmas only. If successful it will be followed by similar devices, eventually including a demonstration power reactor, burning deuterium-tritium fuel.
NSTX produces a plasma that is shaped like a sphere with a hole through its center (a "cored apple" profile, see Mega Ampere Spherical Tokamak
), different from the "donut" (toroidal) shaped plasmas of conventional tokamak
s. The low aspect ratio A (that is, an R/a of 1.31, with the major radius R of 0.85m and the minor radius a of 0.65m) experimental NSTX device has several advantages including plasma stability through improved confinement, but requires a very careful design of the toroidal and poloidal field coils, vacuum vessels and plasma facing components. Moreover, this innovative plasma configuration has the major advantage of being able to confine a higher pressure plasma than a doughnut tokamak of high aspect ratio for a given, confinement magnetic field strength. Since the amount of fusion power produced is proportional to the square of the plasma pressure, the use of spherically shaped plasmas could allow the development of smaller, more economical and much more stable fusion reactors. NSTX's attractiveness may be further enhanced by its ability to trap in a high "bootstrap" electric current. This self-driven internal plasma current would significantly reduce the power requirements of externally driven plasma currents required to heat and confine the plasma.
Spherical tokamak
A spherical tokamak is a type of fusion power device based on the tokamak principle. It is notable for its very narrow profile, or "aspect ratio". A traditional tokamak has a toroidal confinement area that gives it an overall shape similar to a donut, complete with a large hole in the middle...
concept that was constructed by the Princeton Plasma Physics Laboratory
Princeton Plasma Physics Laboratory
Princeton Plasma Physics Laboratory is a United States Department of Energy national laboratory for plasma physics and nuclear fusion science located on Princeton University's Forrestal Campus in Plainsboro Township, New Jersey. Its primary mission is research into and development of fusion as an...
(PPPL) in collaboration with the Oak Ridge National Laboratory
Oak Ridge National Laboratory
Oak Ridge National Laboratory is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle. ORNL is the DOE's largest science and energy laboratory. ORNL is located in Oak Ridge, Tennessee, near Knoxville...
, Columbia University
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...
, and the University of Washington
University of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
at Seattle.
Fusion is the energy source of the Sun and all the stars. Scientists believe it can provide an inexhaustible, safe, and environmentally attractive source of energy on earth.
First plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
was obtained on NSTX on Friday, February 12, 1999 at 6:06 p.m. NSTX is being used to study the physics principles of spherically shaped plasmas—hot ionized gases in which nuclear fusion will occur under the appropriate conditions of temperature, density, and confinement in a magnetic field.
Magnetic fusion experiments use plasmas composed of one or more of the isotopes of hydrogen. For example, in 1994, PPPL's Tokamak Fusion Test Reactor (TFTR) produced a world-record 10.7 megawatts of fusion power from a plasma composed of equal parts of deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
and tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
, the fuel mix likely to be used in commercial fusion power reactors. NSTX is a "proof of principle" experiment and therefore employs deuterium plasmas only. If successful it will be followed by similar devices, eventually including a demonstration power reactor, burning deuterium-tritium fuel.
NSTX produces a plasma that is shaped like a sphere with a hole through its center (a "cored apple" profile, see Mega Ampere Spherical Tokamak
Mega Ampere Spherical Tokamak
The Mega Ampere Spherical Tokamak, or MAST experiment is a nuclear fusion experiment in operation at Culham, Oxfordshire, England since December 1999. It follows the highly successful START experiment...
), different from the "donut" (toroidal) shaped plasmas of conventional tokamak
Tokamak
A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus . Achieving a stable plasma equilibrium requires magnetic field lines that move around the torus in a helical shape...
s. The low aspect ratio A (that is, an R/a of 1.31, with the major radius R of 0.85m and the minor radius a of 0.65m) experimental NSTX device has several advantages including plasma stability through improved confinement, but requires a very careful design of the toroidal and poloidal field coils, vacuum vessels and plasma facing components. Moreover, this innovative plasma configuration has the major advantage of being able to confine a higher pressure plasma than a doughnut tokamak of high aspect ratio for a given, confinement magnetic field strength. Since the amount of fusion power produced is proportional to the square of the plasma pressure, the use of spherically shaped plasmas could allow the development of smaller, more economical and much more stable fusion reactors. NSTX's attractiveness may be further enhanced by its ability to trap in a high "bootstrap" electric current. This self-driven internal plasma current would significantly reduce the power requirements of externally driven plasma currents required to heat and confine the plasma.
External links
- The National Spherical Torus Experiment (NSTX) official site
- Overview of The National Spherical Torus Experiment from PPPL