Construction and Initial Operation of the Columbia Nonneutral Torus

Abstract

We report on the results from initial testing and operation of the Columbia Nonneutral Torus, a new stellarator experiment constructed at Columbia University to study the confinement of nonneutral plasmas, electron-positron plasmas, and stellarator confinement in the presence of strong electrostatic fields. A new algorithm for automatic identification of good magnetic surfaces, island chains, and stochastic regions in Poincaré maps is also described. We present some of the details of the design of the interlocked in-vessel coils and the vacuum system and report on initial vacuum performance. Magnetic surface mapping and visualization results are also presented, confirming the existence of ultralow aspect ratio magnetic surfaces with excellent quality and good agreement with numerical calculations.