A toroidal focusing mirror based vacuum ultraviolet diagnostic for TJ-II

We describe a vacuum ultraviolet spectrometer having spatial, spectral, and temporal resolution capabilities that is being built as a diagnostic for t he TJ-II flexible heliac device. The system is based around a renovated 0.5 m radius Rowland circle grazing incidence duochromator and will cover the wavelength range from 300 to 2000 Angstrom with good spatial resolution. A toroidal mirror used at grazing incidence, mounted on a specially designed mounting positioned between the plasma and spectrometer, will permit simila r to 80% of the bean shaped plasma cross section to be scanned with spatial resolution on the order of 10 mm. In addition, filters and slits are incor porated to tailor the incident light beam. The duochromator was coupled dir ectly to the TJ-II during the machine start up phase to check the good oper ation of the duochromator. These data have been fed back into the design pr ogram in order to optimize the instrument design. (C) 1999 American Institu te of Physics. [S0034-6748(99)60401- 4].