General purpose high-resolution x-ray crystal spectrometer (abstract)

Abstract

This spectrometer was designed to give access to a wide range of Bragg angles and crystal focal lengths while using the Rowland circle radius as a free parameter. Stability is achieved using a rigid beam or ‘‘Rowland chord,’’ which provides a reference axis for all the critical alignments, the chord length being variable between about 0.2 and 5 m. Crystals of size up to 100×30×0.5 mm can be accommodated in a novel four-pillar jig, (λ/δλ) is typically 104 in the wavelength range from 0.1 to 1.3 nm, depending on the crystal. Various detectors have been used, including photographic film, multiwire gas proportional counters and large area CCD detectors, the latter having a 2-D spatial resolution of 22.5 μm (1152×1242 pixels, 26×28 mm2), a quantum efficiency greater than 20% between 0.7 and 12 keV and an energy resolution of about 150 eV. By sacrificing energy resolution, a one-dimensional mode with on-chip binning allows ∼ms time resolution of spectra from high flux sources such as tokamaks and synchrotrons. Results presented include photographic spectra from tokamak, beam foil and laser produced sources, and CCD spectra from tokamak and standard electron-beam excitation laboratory sources.