Spherical tokamaks with outboard stellarator windings

Abstract

The possibility of adding stellarator features to the extremely compact configuration of a spherical tokamak (ST) is analysed. This is accomplished by introducing outboard stellarator windings (OSWs). Two types of OSW are studied, a classical stellarator type and a torsatron type, and both are shown to be effective. Numerical calculations are presented for a simplified model of the NSTX tokamak. Among the main potential advantages of using OSWs in a ST are the possibility of non-inductive plasma startup or improved inductive operation caused by the existence of closed vacuum flux surfaces and an external rotational transform.

Novel stellarator configuration with double helix centre post

“…The only helical elements of the DHS configuration considered are the two helical windings replacing the centre post of a standard spherical tokamak coil system. Actually, the DHS features one of the most compact and most spherical plasmas among all the SS configurations [2][3][4][5][6][7][8][9][10][11] and satisfies all the SS requirements. Thus, it can be considered a new member of the SS family as well.…”

“…More recently, a few other publications [7][8][9][10][11][12][13][14][15][16] have appeared on this topic and some other US institutions have become involved in this kind of low aspect ratio stellarator research. Researchers at ORNL focus on J * transport optimization.…”

Confinement Analysis of Spherical Tokamak-Stellarator Hybrid Configurations with Simple Shaped Coils

“…This configuration can produce low-aspect-ratio vacuum flux surface produced by currents of simple helical coils, so it is inexpensive to be built and suitable for doing basic fusion research relevant to spherical stellarator system and tokamak-stellarator hybrid system. Although the other compact hybrid systems have been proposed [3] so far, our TOKASTAR configuration is characterized by its simplicity and a small number of helical coils.…”

Helical post stellarator

“…In parallel to the development of the world spherical tokamak (ST) program [7][8][9][10][11][12][13][14], which promises more compact, higher β, and a less disruptive approach for tokamaks, the spherical stellarator (SS) program has been initiated recently [15][16][17][18][19][20][21][22] for machines with stellarator features and the aspect ratio A below 3.5. The plasma current enhancing the vacuum rotational transform is one of the key elements of the SS approach.…”