Diagnostic upgrades for the Lithium Tokamak eXperiment-β enable recycling analysis and scrape-off layer characterization*

The Lithium Tokamak eXperiment (LTX) and its upgrade LTX-?? is the only tokamak in the world capable of operating with near complete coverage of lithium on its PFCs. LTX and LTX-?? have demonstrated plasma performance improvement due to flat electron temperature profiles, lowered recycling and reduced radiative loss from impurities. Experiments on LTX demonstrated that high edge temperatures and low edge density, likely due to a low recycling boundary, lead to a low collisionality scrape-off layer (SOL). However, the connection between flattening electron temperature profiles and recycling, particularly as it relates to the SOL characteristics, remains to be made. To study this unique SOL and to quantify fuel recycling in LTX-??, a new, movable, low field side, off-midplane, swept single Langmuir probe was installed to measure SOL edge density and temperature. Additionally, the neutral particle influx from the high field side limiter was measured using a hydrogen Lyman-?? array. Core electron temperature and density were measured using the LTX-?? Thomson scattering system. The data from these diagnostics indicate a reduction in line integrated Lyman-?? emission intensity and an increase in edge temperature and energy confinement times after fueling termination at higher plasma currents compared to LTX. The DEGAS2 code is being used to assess how sources of neutrals can affect the interpretation of the data. These results will be presented, along with a preliminary characterization of the SOL as it relates to recycling analysis.