UW-Madison table-top stellarator experiment - parameters and design

A new table-top stellarator experiment, based on initial work from [1], has been designed with one planar and one helical coil to produce closed flux surfaces with five-fold symmetry. Detailed field line following studies show the use of only two coils is possible since the average vertical magnetic field along the magnetic axis is approximately zero. The 3D shape of the helical coil has been optimized to produce a large plasma volume and sufficient space between the coils and the plasma vessel. The vessel will be a pentagonal glass structure with a circular cross-section made from off-the-shelf components. The design of the plasma vessel and coils has been modeled with SolidWorks, considering three windings of the helical coil. VMEC equilibria produced using these three windings and the planar coil demonstrate a rotational transform of 0.15, though significant regions of parameter space have been identified for further optimization. Considering currents of up to 3.3 kA per turn, the expected magnetic field strength will be 0.05 T. This will allow the stellarator to be used in table-top plasma heating experiments using helicon waves, which provide excellent power coupling to the plasma. 

[1] H. Yamaguchi 2019 Nucl. Fusion 59 104002