ECH assisted start up in the Lithium Tokamak eXperiment-β (LTX-β)

Electron Cyclotron Heating (ECH)-assisted plasma startup can reduce ohmic flux consumption during breakdown, leading to higher-performance discharges. Here we describe the ECH system and startup scenarios for The Lithium Tokamak eXperiment- β (LTX-β) for preionization. The LTX-β has previously relied on a hot, biased filament to provide seed electrons for plasma breakdown. Breakdown and null formation are complicated by the large eddy currents driven in the shells or conducting walls by the ohmic heating (OH) coil. As a result, at least 25% of the available volt-second capability of the OH can be consumed before and during breakdown. A pulsed (up to 15 msec) 3 kW, 10.36 GHz ECH system has been implemented. LTX-β plasma operations have resumed, and startup experiments will be conducted with various magnetic field configurations and prefill pressures, to determine the breakdown scenario that consumes the least ohmic flux, with the addition of ECH power. Analysis of the magnetic field configuration using TokaMaker equilibrium reconstructions, the resulting pressure-driven currents, and the effects on the startup plasma will be presented. Using DYON-EC with the LTX-β geometry, we will further analyze the burnthrough phase in the presence of ECH power.