Electric Tokamak
Encyclopedia
The UCLA Electric Tokamak is a low field (0.25 T
) magnetic fusion tokamak
device with a large aspect ratio.
The machine has a major radius of 5 metres, a minor radius of 1 metre, plasma current of 45 kiloamperes
and can produce a core electron
plasma
temperature
of 300 electronvolt
s.
First plasma was achieved in January 1999.
(D or reverse-D). The OH system provides 10 V·s using a 10 kA
power supply. Up to 0.1 T
of vertical field can be applied for horizontal control and this is more than sufficient for all plasma configurations, including high beta. An additional set of coils provide a small horizontal field to correct for error field and to stabilize the plasma vertically. All the coils are located outside the vessel and are constructed out of aluminium
.
A Rogowski
probe outside the vessel and sets of Hall probes
inside the vessel are used to monitor plasma current, position and shaping and are used in the control feedback loop. The poloidal system was designed using an in-house equilibrium code as well as a variety of other codes in order to cross-check computations and to assess the stability of the resulting plasma.
Like most tokamak
s the machine uses a combination of RF
heating and neutral beam injection to drive and shape the plasma.
(DOE). It currently is being used for stress testing of plasma production methods in the Science and Technology Research Building (STRB) on the UCLA campus.
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
) magnetic fusion 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...
device with a large aspect ratio.
The machine has a major radius of 5 metres, a minor radius of 1 metre, plasma current of 45 kiloamperes
Ampere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
and can produce a core electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
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...
temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
of 300 electronvolt
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...
s.
First plasma was achieved in January 1999.
Construction and features
Four sets of independent coils are necessary for OH (ohmic heating) current drive, vertical equilibrium field, plasma elongation and plasma shapingPlasma shaping
Magnetically confined fusion plasmas such as those generated in tokamaks and stellarators are characterized by a typical shape. Plasma shaping is the study of the plasma shape in such devices, and is particularly important for next step fusion devices such as ITER. This shape is conditioning partly...
(D or reverse-D). The OH system provides 10 V·s using a 10 kA
Ampere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
power supply. Up to 0.1 T
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
of vertical field can be applied for horizontal control and this is more than sufficient for all plasma configurations, including high beta. An additional set of coils provide a small horizontal field to correct for error field and to stabilize the plasma vertically. All the coils are located outside the vessel and are constructed out of aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
.
A Rogowski
Rogowski coil
A Rogowski coil, named after Walter Rogowski, is an electrical device for measuring alternating current or high speed current pulses. It consists of a helical coil of wire with the lead from one end returning through the centre of the coil to the other end, so that both terminals are at the same...
probe outside the vessel and sets of Hall probes
Hall effect sensor
A Hall effect sensor is a transducer that varies its output voltage in response to a magnetic field. Hall effect sensors are used for proximity switching, positioning, speed detection, and current sensing applications....
inside the vessel are used to monitor plasma current, position and shaping and are used in the control feedback loop. The poloidal system was designed using an in-house equilibrium code as well as a variety of other codes in order to cross-check computations and to assess the stability of the resulting plasma.
Like most 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 machine uses a combination of RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
heating and neutral beam injection to drive and shape the plasma.
Financial status
The Electric Tokamak had run out of funding, and its principal investigator and designer, Robert Taylor, a UCLA professor, has retired. Factors leading to loss of funding are attributed to include its lack of extensive plasma diagnostics, its large size (it was the largest tokamak in the world), and its place in the politics of fusion. When it was operating, The Electric Tokamak was funded mostly by the Department of EnergyUnited States Department of Energy
The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...
(DOE). It currently is being used for stress testing of plasma production methods in the Science and Technology Research Building (STRB) on the UCLA campus.