Fast high resolution echelle spectroscopy of a laboratory plasma

An echelle diffraction grating and a multianode photomultiplier tube are paired to construct a high resolution (R=λ∕δλ≈2.5×104) spectrograph with fast time response for use from the UV through the visible. This instrument has analyzed the line shape of CIII impurity ion emission at 229.687nm over the lifetime (≈100μs) of the hydrogen plasmas produced at SSX. The ion temperature and line of sight average velocity are inferred from the observed thermal broadening and Doppler shift of the line. The time resolution of these measurements is about 1μs, sufficient to observe the fastest magnetohydrodynamic activity.