Measurement of the Pfirsh-Schl\"{u}ter and Bootstrap Currents in HSX

Pfirsch-Schl\"{u}ter (PS) and bootstrap currents in the quasihelically symmetric stellarator HSX are unlike those of a conventional stellarator. The lack of toroidal curvature in HSX results in a helical PS current that rotates with toroidal angle. The PS current is smaller in size than for comparable MFEs by a factor of n-m$\iota $ (=3 in HSX). The bootstrap current in HSX is opposite in direction to that in a tokamak, which reduces the rotational transform but increases the effective transform. An external Rogowski and magnetic pickup coil array measure the currents. The bootstrap current rises throughout the discharge on a 10-50 ms timescale, approaching a maximum value between 0.4-0.5 kA. The PS current rises on a 5-10 ms timescale and exhibits a dipole variation. T$_{e}$ and n$_{e}$ profiles are measured with a 10-chord Thomson scattering system, showing central T$_{e}$ (n$_{e})$ up to 1.6 keV (5x10$^{12}$ cm$^{-3})$. Varying the electron pressure profile and gradients adjusts the equilibration times and maximum values. HSX can spoil the symmetry with a set of auxiliary coils which adds a (n, m) = (4, 0) symmetry-breaking term in the $\vert $B$\vert $ spectrum. This degrades the neoclassical properties of HSX and affects the resulting equilibrium currents. The measured currents will be compared to theoretical estimates. Supported by DOE grant number DE-FG02-93ER54222.