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Columbia Non-neutral Torus
Additional recommended knowledge
CNT, which is housed in a cylindrical vacuum chamber made of 316 stainless steel, measures 60 inches in diameter and stands 75 inches tall. The empty chamber is capable of reaching a pressure of 2x10-10 Torr.
CNT is unique in its simple geometry. Magnetic surfaces are created using only 4 electromagnetic coils - two interlocking coils inside the chamber, and two poloidal field coils outside the chamber. The two interlocking coils have a radius of .405m, and the angle between them can be manually selected to be 64o, 78o, or 88o, allowing for different shear and rotational transform values, and magnetic surface configuration. The poloidal field coils have a radius of 1.08m. The coils are powered by a 200kW power supply and are capable of producing magnetic fields of 0.01-0.2T. The configuration of CNT creates a very low aspect ratio of 1.9, the lowest of any stellarator built.
Thomas Sunn Pedersen is the principal investigator of CNT, which studies several areas of theoretical and experimental non-neutral plasma physics. These include the equilibrium of non-neutral plasmas, transport and confinement, and ion-related instabilities. The CNT theory program is run by Pedersen and Prof. Allen Boozer, also at Columbia University.
First studies on CNT showed the successful creation of magnetic surfaces with the simple four coil design. At sufficiently low neutral pressures and sufficiently high magnetic field strengths, the plasmas are essentially pure electron plasmas and are macroscopically stable with confinement times of up to 20 msec. Transport is driven by collisions with neutrals as well as E x B drift along insulating rods inserted into the plasma. At higher neutral pressures (10-7 Torr and above), an ion related instability is observed, with a frequency in the 10-50 kHz range, and a poloidal mode number m=1.
The CNT group plans to install a conducting boundary in August 2007 to study its effects on confinement times, and to allow measurements in the absence of internal rods. Future plans for CNT include the study of electron-positron plasmas confined on magnetic surfaces and further studies of partly neutralized plasmas.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Columbia_Non-neutral_Torus". A list of authors is available in Wikipedia.|