Systems Analysis of a Compact Next Step Burning Plasma Experiment

Abstract

A new burning plasma systems code (BPSC) has been developed for analysis of a next step compact burning plasma experiment with copper-alloy magnet technology. We consider two classes of configurations: Type A, with the toroidal field (TF) coils and ohmic heating (OH) coils unlinked, and Type B, with the TF and OH coils linked. We obtain curves of the minimizing major radius as a function of aspect ratio, R(A) for each configuration type for typical parameters. These curves represent, to first order, cost minimizing curves, assuming that device cost is a function of major radius. The Type B curves always lie below the Type A curves for the same physics parameters, indicating that they lead to a more compact design. This follows from that fact that a high fraction of the inner region, r < R-a, contains electrical conductor material. However, the fact that the Type A OH and TF magnets are not linked presents fewer engineering challenges and should lead to a more reliable design. Both the Type A and Type B curves have a minimum in major radius R at a minimizing aspect ratio A typically above 2.8 and at high values of magnetic field B above 10 T. The minimizing A occurs at larger values for longer pulse and higher performance devices. The larger A and higher B design points also have the feature that the ratio of the discharge time to the current redistribution time is largest so that steady-state operation can be more realistically prototyped. A sensitivity study is presented for the baseline Type A configuration showing the dependence of the results on the parameters held fixed for the minimization study.

04/00212 Next step spherical torus design studies

“…In order to arrive at a design point for NSST, parametric studies were performed using a Systems Code [3] which includes a 0-d analysis of the plasma along with engineering algorithms [4] which calculate the stress, temperature rise, power, and energy consumption of the Toroidal Field (TF), OH, and Poloidal Field (PF) magnets. Using this tool an optimization was performed which aimed to maximize Q and minimize major radius R 0 with the constraint of the engineering allowables, including the available power (800MW) and energy (4.5GJ) available from the existing motor-generator (MG) system.…”