Three dimensional equilibrium solutions for a current-carrying reversed-field pinch plasma with a close-fitting conducting shell

Abstract

In order to characterize the Madison Symmetric Torus (MST) reversed-field pinch (RFP) plasmas that bifurcate to a helical equilibrium, the V3FIT equilibrium reconstruction code was modified to include a conducting boundary. RFP plasmas become helical at a high plasma current, which induces large eddy currents in MST's thick aluminum shell. The V3FIT conducting boundary accounts for the contribution from these eddy currents to external magnetic diagnostic coil signals. This implementation of V3FIT was benchmarked against MSTFit, a 2D Grad-Shafranov solver, for axisymmetric plasmas. The two codes both fit B h measurement loops around the plasma minor diameter with qualitative agreement between each other and the measured field. Fits in the 3D case converge well, with q-profile and plasma shape agreement between two distinct toroidal locking phases. Greater than 60% of the measured n ¼ 5 component of B h at r ¼ a is due to eddy currents in the shell, as calculated by the conducting boundary model. V

Fast ion transport in the quasi-single helical reversed-field pinch

“…The shear-Alfv en continuum was calculated with the STELLGAP code across a variety of helical perturbation strengths utilizing three dimensional equilibria created with the V3FIT reconstruction code. [23][24][25] Figure 3 displays the resultant q-profiles and n ¼ 5 Alfv en continua. As the topology transitions from the MH to QSH regime, the q-profile becomes non-monotonic and shrinks.…”

Linear Pinch Equilibrium of Non-Neutral Plasma Revisited: Phenomenological Consequences of a Numerical Accuracy Problem

“…Motivated by the skin effect, that was not reported in literature, we performed a scan of the parameters space (β, M/kT ) for fixed initial potentials (u(x 0 ), y(x 0 )). And by direct integration of equations (5) and (6), determined which set of parameters were associated with confining and non-confining equilibrium.…”

“…In order to determine the plasma column equilibrium configuration -confining or non-confining, it was necessary to solve equations (5) and (6). As depicted by [10], the entire system is dependent on four parameters, n ± (0)/n 0 , β and M/kT .…”

“…In each one of these cases, the nonlinearity and the number of differential equations that govern the physical environment are higher when compared for example with a linear pinch configuration. In spite of its simplicity, this setting has been investigated and reported previously in the literature by [5][6][7][8][9][10], and others. A significant part of these studies was intrinsically related to magnetic confining of fusion plasma [11], and in general, the phenomenological scenario obtained for the plasma column exhibit a generous amount of physical effects and other characteristics, even in simple cases of the linear pinch.…”

Effect of resonant magnetic perturbations on three dimensional equilibria in the Madison Symmetric Torus reversed-field pinch

“…A further improvement to the V3FIT reconstructions for MST has been recently achieved by including the contribution of the edge helical perturbation from the eddy current induced in the shell. 49 Figure 3 shows an example of a reconstruction with V3FIT. A comparison of measured and reconstructed line-integrated densities is shown on the left (a).…”