Emission spectroscopy measurements on an ECRH non-axisymmetric mirror plasma

Time resolved visible emission spectroscopy (300-700 nm) has been performed on ECr heated He, N/sub 2/, and Ar plasmas in the Michigan Mirror Machine (MIMI). The plasma is generated and heated by whistler-mode ECRH at 7.43 GHz and 500W power in 400 μs pulses. Gas is puffed into the mid-plane region where a 2.5 cm quartz window is used to observe the plasma. The plasma is viewed in a direction perpendicular to the mirror axis. Emission spectra are obtained in 100 μs sampling periods starting from the microwave turn-on time using a 0.275 meter spectrograph coupled to a gated, intensified diode array. The majority of light is found to occur from 200-300 μs from microwave turn-on time. Thermal electron temperatures are inferred from the electronic temperature of Ar and He obtained from Atomic Boltzmann plots. Electron temperature varies from 1 eV to 50 eV depending upon gas pressure, microwave power, and mirror and quadrupole field strengths