VUV and soft X-Ray spectroscopy using a toroidal grating spectrograph

Optical spectroscopy is a key tool to monitor and therefore analyse properties of laser emission light sources such as X-Ray lasers. A spectrograph instrument that produces flat field detection over relative wide spectral range enables quick and reliable analysis of X-Ray laser emitted spectra thanks to the easy coupling with CCD camera or MCP detector. We present a compact spectrograph design based on aberration corrected toroidal diffraction gratings dedicated to optical spectroscopy in the VUV and Soft X-Ray wavelength range. The toroidal aberration corrected grating acts as a diffractive and focusing element allowing compact design with only one optical element. Such compact design provides high throughput, good wavelength purity as well as great stability and reproducibility. After a review of the flat field toroidal grating parameters design, we present the performances of several toroidal gratings optimised for operation in the 2.5 to 170 nm wavelength range. Measured spectra of pinch discharge sources are presented to illustrate the performance of toroidal spectrograph instruments