Columbia Non-Neutral Torus

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

It was developed by Thomas Sunn Pedersen , Wayne Reiersen and Fred Dahlgren from the Princeton Plasma Physics Laboratory to study 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 through a Faculty Early Career Development (CAREER) award of US $ 800,000, which was awarded to Pedersen.

Allen Boozer is also part of the scientific management .

Technical specifications

The CNT is located inside a cylindrical vacuum chamber made of stainless steel and is approximately 1.5 m in diameter and 1.9 m in height. The vacuum chamber reaches a vacuum that  corresponds to a pressure of about 1.3 · 10 −8 Pa. The CNT only uses four magnetic coils , two parallel coils outside and two poloidal field coils inside the steel chamber. They are supplied with up to 200 kW of electrical power and generate magnetic fields in the range from 0.01 to 0.2 T. The structure has an aspect ratio of less than 1.9.

parameter value
Particle density n e 10 12 -10 14  m -3
Particle energy T e 1-100 eV
Magnetic field B 0.01-0.2 T
Pressure P 1.3 · 10 −8  Pa

research

The research at the CNT serves the experimental investigation of charged plasmas: their equilibrium, transport phenomena, containment and ion-related instabilities.

The first investigations showed that magnetic surfaces can be generated with the simple four-coil structure. With a sufficiently low pressure and a high magnetic field, an essentially pure electron plasma can be stably retained for up to 20 milliseconds. The transport is driven by collisions with neutral particles. There is also a drift (force on electric charge in magnetic field) along insulating rods that are introduced into the plasma. At a pressure above 10 −5  Pa, an instability with a frequency in the range from 10 to 50 kHz and a poloidal (in field direction) mode number m = 1 was observed.

Web links

Individual evidence

  1. News on Columbia University website: Columbia's Stellarator Project Gets Jolt from National Science Foundation.
  2. TS Pedersen, N. Ahmad et al .: Experimental demonstration of a compact stellarator magnetic trap using four circular coils. In: Physics of Plasmas. 13, 012502, 2006 doi : 10.1063 / 1.2149313 ( apam.columbia.edu , PDF; 838 kB).
  3. TS Pedersen, N. Pomphrey, X. Sarasola et al .: Construction and Initial Operation of the Colombia Nonneutral Torus. In: Fusion Science and Technology . 50, October 2006 ( apam.columbia.edu , PDF; 489 kB).