Columbia Non-Neutral Torus

The Columbia Non- neutral Torus ( CNT ) is a small stellarator at the Laboratory for Plasma Physics at Columbia University.

It was developed by Thomas Sunn Pedersen, Wayne Reiersen and Fred Dahlgren by the Princeton Plasma Physics Laboratory to investigate charged plasmas, trapped between magnetic surfaces. The experiment started in November 2004 and is funded by the National Science Foundation and the United States Department of Energy, among others, by means of a "Faculty Early Career Development ( CAREER ) " price above $ 800,000, which was awarded to Pedersen.

For scientific leadership includes Allen Boozer.

Specifications

The CNT is within a cylindrical vacuum chamber made of stainless steel and has about 1.5 m diameter and 1.9 m height. The vacuum chamber achieves a vacuum corresponding to a pressure of about 1.3 x 10-8 Pa. The CNT uses only four solenoids, two parallel coils outside and two poloidal field coils inside the steel chamber. They are provided with up to 200 kW of electric power and generate magnetic fields in the range of 0.01 to 0.2 T. The structure has an aspect ratio of less than 1.9.

Research

The research on CNT serve the experimental study of charged plasmas: their equilibrium transport phenomena, containment and ion - induced instabilities.

The first studies showed that magnetic surfaces may be formed with the simple four -coil configuration. At sufficiently low pressure and high magnetic field can be a substantially pure electron plasma for up to 20 milliseconds to hold stable. The transport is driven by collisions with neutral particles. There is a drift ( force to electrical charge in the field) along insulating rods, which are introduced into the plasma. At a pressure of about 10-5 Pa at a frequency instability in the range of 10-50 kHz and a poloidal ( the field direction ) mode number m = 1, was observed.