A New Optical System for Solar Soft X-Ray Spectrophotometry

Extract

At the Institute of Applied Physics TNO-TH at Delft a strongly off-plane grating mounting has been developed for the soft X-ray wavelength region. In this mounting a parallel beam is incident on the grating surface nearly parallel to the grooves. We found herewith a remarkable improvement of the grating efficiency compared with the grazing incidence perpendicular to the grooves. The focal distance is nearly independent on the wavelength, so scanning of the spectrum can be provided by a simple rotation of the cylindrical grating around the central groove. The exit slit and the detector have fixed positions. The lightspot on the detector cathode does not move and has a moderate size; a standard detector can be used.