Improved neutral beam injection and diagnostics on LTX-β

Neutral Beam Injection (NBI) plays a vital role in heating and sustaining low recycling plasmas in the Lithium Tokomak Experiment-β (LTX-β). Earlier results showed limited beam coupling and heating, influenced by variations in beam and plasma parameters during discharges, with effective operation peaking at a modest beam energy of 13 keV (below the 20 keV max). Modeling predicted higher heating than experimentally observed, highlighting the need for detailed characterization of the fast ions, beam power, and beam profile shape. During a recent vent, the NBI was realigned to improve injection geometry. Modeling showed optimal beam coupling at a tangency radius near 35 cm. The realignment moved the tangency radius from 19 to 33 cm (restricted by scrape-off at the injection port), and is predicted to increase beam coupling by 30% at a beam energy of 13 keV, and double at the 20 keV maximum beam energy. A 2D tungsten wire calorimeter and a new segmented beam dump were developed and installed, providing shot specific beam profiles before and after traversing the plasma volume and improving constraints for modeling. A recently installed neutral particle analyzer (NPA) provides direct measurements of the fast ion population energy distribution. Initial discharge data, beam profile measurements, and NUBEAM modeling including neutral beam halo effects will be presented.