Glossary

ADX

The “Advanced Divertor eXperiment”, a proposed new experiment at MIT which would study advanced ways of driving currents using waves and the interaction of fusion plasma with materials at high magnetic fields.

Alcator C-Mod

MIT's tokamak fusion experiment. Alcator C-Mod holds the record for the highest magnetic field and plasma pressure achieved in any tokamak built.

ARC

Conceptual fusion power plant design from MIT using high-temperature superconductors to achieve very high magnetic fields in a tokamak configuration.

B

The symbol used to denote the strength of the magnetic field given in units of “Tesla”. The Earth's magnetic field is 0.00005 Tesla.

Density

The number of plasma particles in one cubic meter. Normal air has a density of 2x1025m-3. The density of a fusion plasma is 2x1020m-3, 100,000 times less than that of air. This is one of the reasons why fusion is so safe—there is an extremely low amount of fuel in the core at any one time.

Deuterium/Tritium

Two types of heavy hydrogen ions which are used as fusion fuel. The deuterium-tritium reaction is the easiest fusion reaction to utilize for energy production.

Divertor

The magnetic “exhaust pipe” of a tokamak. Most of the plasma heat and particles are exhausted in this region.

Electrons

The light, negatively charged particles in a plasma.

FLiBe

Molten salt which contains the elements Fluorine (F), Lithium (Li), and Beryllium (Be). FLiBe becomes a liquid at 459 ºC and remains liquid until 1427 ºC.

Fusion Reaction

In a fusion reaction, two ions combine in order to make a new set of particles that have less total mass. The difference in mass is released in the form of energy as a result of E=mc2.

HTS

“High temperature superconductor”; a material which can become superconducting at temperatures significantly above absolute zero (for example, liquid nitrogen temperature at -196 ºC).

Ions

The heavy, positively charged particles in a plasma.

ITER

Large, international tokamak experiment being constructed in the south of France. Uses conventional superconductors, resulting in a moderate magnetic field and very large size.

Magnet Coil

An object in which current is made to go in a loop, producing a magnetic field which passes through the loop. The strength of the magnetic field is set by the amount of electrical current in the loop.

Magnetic Field

A fundamental field in nature, that cannot be seen, produced by electrical currents. Magnetic fields exert a force on charged particles that causes them to spiral around the magnetic field direction.

MW

Megawatt; a unit used to describe how much electricity a power plant can produce. One MW is the same as 1,000,000 watts. For example, the average microwave uses 1,000 watts, or 0.001 MW. Each MW of power produced serves approximately 160 American households.

Plasma

A gas which is so hot that most of its particles have a net electric charge due to removal of electrons. A plasma can conduct electricity and is called the “fourth state of matter”.

Pressure

The plasma temperature and density multiplied together. Indicates the energy contained per unit volume. Magnetic fusion occurs at a pressure of about 10 atmospheres.

R

Denotes the radius across the toroid. For a fixed-shape toroid, the volume goes as the cube of R (R3).

Superconductor

Material which can conduct electricity without any resistance. Materials become superconducting when very cold, typically a few degrees above absolute zero (-273 ºC).

Temperature

Just like air, which has a typical temperature of 20 ºC, it describes the average energy of the plasma's particles. Plasmas occur for temperatures above 10,000 ºC and fusion energy requires a temperature above 50,000,000 ºC.

Toroid

An object that has a “doughnut” shape.