The Design, Fabrication, and Initial Operation of the Interchangeable Module Stellarator

A modular stellarator has been designed, fabricated, and operated based upon twisted coils derived from the ultimate stellerator concept. The device, the Interchangeable Module Stellarator (IMS), was designed to provide a close approximation to the gross macroscopic magnetic parameters of the continuous-helix Proto-Cleo Stellarator; l = 3, seven field periods, a major radius of forty centimeters, plasma volume of eleven liters, and a parabolic rotational transform profile with no transform on axis and \= .6 at the plasma edge. The efficiency of the modular coils allows over a doubling of attainable magnetic field strength as compared to Proto-Cleo utilizing the same power supply. The conceptual design is discussed, and the engineering design and fabrication techniques are presented. The initial operation of IMS has shown that the desired magnetic topology has been achieved. Preliminary results obtained through introduction of plasma by electron cyclotron resonant breakdown of a hydrogen gas background indicate confinement similar to that previously obtained in the Proto-Cleo Stellarator. The predicted modular bundle divertors in IMS have been confirmed experimentally with the ECR-produced plasmas.