Diagnostic Neutral Beam and Beam-Based Diagnostic Development to Study Non-Inductive Startup Techniques

An 80 kV, 4 A, H$^{\mathrm{0}}$ beam is being developed as a plasma diagnostic tool for studying non-inductive tokamak plasma startup methods in the \textsc{Urania} experiment. The new diagnostics will provide measurements of equilibrium magnetic fields and possibly field fluctuations, ion temperatures, and plasma density profiles. These beam-based diagnostics will address important aspects of helicity injection startup and sustainment. These include examining dissipation mechanisms during helicity drive ($e.g.$ anomalous ion heating through magnetic reconnection, anomalous resistivity, etc.), the role of impurities, and plasma magnetic field structures. A washer stack arc plasma source is implemented as the source of H$^{\mathrm{+\thinspace }}$for the DNB. Its plasmas are characterized with a double tip Langmuir probe, a spectrometer, and measurements of the arc voltage and current. Initial results show that stable density plasmas ($n_{e} \approx 10^{17}$m$^{\mathrm{-3}})$ with steady electron temperatures of 0.5--4 eV can be generated by the source, which are expected to produce a full energy species fraction of greater than 80{\%}. A novel 80 kV resonant DC-DC converter power supply has been constructed and is being optimized for minimal output voltage ripple. Initial tests have produced a 10 ms pulse at 40 kV.