Electron Density Measurements on LTX Using Microwave and Millimeter-Wave Diagnostics

The dynamic evolution of the electron density profile is tracked using microwave and millimeter-wave diagnostics on LTX. The 296 GHz ($\lambda$$=$1 mm) interferometer provides a radial line density measurement at the midplane, while an FMCW (frequency-modulated continuous-wave) reflectometer (13.5$-$33 GHz, or O-mode $0.2$$-$$1.3$$\times$$10^{13}$ cm$^{-3}$) provides density profile measurements for the low-field side. Data taken during FY2015 will be compared with measurements from Thomson scattering and estimates of the plasma position from LRDFIT. Measurements of density fluctuations due to low-frequency ($<$100 kHz) MHD instabilities will also be shown. Future plans include the installation of a correlation reflectomter (Ka-band, 27-40 GHz) with dual tuneable sources and a frequency bandwidth of up to 5 MHz. This system will utilize the same antennas as the profile reflectometer to provide radial and/or toroidal/poloidal correlations. Further diagnostic details will be presented at the meeting.