Electron density measurements in STPX plasmas

Diagnostics have been installed to measure the electron density of Spheromak Turbulent Physics Experiment (STPX) plasmas at Florida A. {\&} M. University. An insertable probe, provided by Auburn University, consisting of a combination of a triple-tipped Langmuir probe and a radial array consisting of three ion saturation current / floating potential rings has been installed to measure instantaneous plasma density, temperature and plasma potential. As the ramp-up of the experimental program commences, initial electron density measurements from the triple-probe show that the electron density is on the order of 10$^{\mathrm{19}}$ particles/m$^{\mathrm{3}}$. For a passive measurement, a CO$_{\mathrm{2}}$ interferometer system has been designed and installed for measuring line-averaged densities and to corroborate the Langmuir measurements. We describe the design, calibration, and performance of these diagnostic systems on large volume STPX plasmas.