Initial Results from the LTX-β Magnetics Upgrade

The newly upgraded Lithium Tokamak eXperiment—Beta (LTX-β) has begun plasma operation to study the low-recycling, high-performance regime previously observed in LTX [D.P. Boyle et al. PRL July 2017]. The addition of neutral beam core-fueling and heating for longer-lasting low-recycling plasmas with more steady-state plasma parameters is expected also to increase plasma β and MHD instability drive. We describe the first measurements of the new toroidal array (TA), shell eddy sensor array (SESA), and upgraded re-entrant poloidal array (REPA) of Mirnov coils, and summarize the previously existing magnetic diagnostics such as poloidal flux loops and Rogowski coils. The TA and REPA are analyzed for preliminary signs of n ≤ 5 MHD activity, and the SESA is studied for comparison to the eigenmode modeling of predicted shell eddy currents. Initial reconstructions in the PSI-Tri equilibrium code [C. Hansen et al. PoP Apr. 2017], employing the full upgraded magnetic diagnostics suite, are compared against prior LTX reconstructions.