Design of a high-throughput grazing-incidence flat-field spectrometer

Grazing-incidence spectrometer for soft X-ray solar imaging spectroscopy

The design and realization of a stigmatic grazing-incidence instrument for space applications to solar imaging spectroscopy is presented. We propose an optical layout in which imaging and spectral capabilities are decoupled by the use of crossed cylindrical mirrors. The design consists of a double telescope and a spectrograph: telescope I consists of a single cylindrical mirror with parabolic section, focusing the radiation on the entrance slit of the spectrograph in the spectral dispersion plane; telescope II consists of two cylindrical mirrors with aspherical section in Wolter configuration focusing the radiation on the spectrograph focal plane in the direction perpendicular to the spectral dispersion plane; the spectrograph consists of a grazing-incidence spherical variable-line-spaced grating with flat-field properties. Telescope II is crossed with respect to the grating and telescope I, i.e., is mounted with its tangential planes coincident with the grating equatorial plane, to decouple spectral and spatial focusing properties. The spectral resolution is preserved also for off-axis angles. The instrument that has been realized operates in the 4-26 nm spectral range and has a field of view of 0.5 deg to image the full Sun disk.

Triple-path collector optics for grazing incident x-ray emission spectrometer

A new type of collector optics was developed for grazing incident x-ray emission spectrometer. The collector optics used two cylindrical mirrors to add two extra light paths while keeping the center light path that directly illuminates the grating. The design and properties of the spectrometer using the triple-path collector optics were evaluated using ray-tracing simulations, and validity of this design in terms of throughput and energy resolution was confirmed by the experimentally obtained spectra.

Optical design of a stigmatic extreme-ultraviolet spectroscopic system for emission and absorption studies of laser-produced plasmas

The design of a stigmatic spectroscopic system for diagnostics of laser-produced plasmas in the 2.5-40-nm region is presented. The system consists of a grazing-incidence toroidal mirror that focuses the radiation emitted by a laser-produced plasma onto the entrance slit of a spectrograph. The latter has a grazing-incidence spherical variable-line-spaced grating with flat-field properties coupled to a spherical focusing mirror that compensates for the astigmatism. The mirror is crossed with respect to the grating; i.e., it is mounted with its tangential plane coincident with the equatorial plane of the grating. The spectrum is acquired by an extreme-UV- (EUV-) enhanced CCD detector with high quantum efficiency. This stigmatic design also has spectral and spatial resolution capability for extended sources: The spectral resolution is also preserved for off-plane points, whereas the spatial resolution decreases for points far from the optical axis. The expected performance is presented and compared with that of a stigmatic design with a plane variable-line-spaced grating illuminated in converging light.

Spherical-grating monochromator with a variable-line-spaced grating for synchrotron radiation

An optical design for spherical-grating monochromators for application to synchrotron radiation is presented. High spectral and spatial performance is obtained with a spherical variable-line-spaced grating coupled to a spherical mirror with its tangential plane coincident with the grating's equatorial plane. The monochromator works without an entrance slit in an off-Rowland configuration with a fixed entrance arm and demagnification on the exit slit. The law for groove-space variation of the grating compensates for the main spectral aberrations; spectral focusing in an extended energy range is ensured by a slight change in the exit arm with translations of the order of a few tens of millimeters. The inclusion of a spherical mirror ensures focusing on a plane perpendicular to the plane of spectral dispersion. The ultimate resolution is limited by the slope errors of a single spherical surface. The layout is applied to the design of a high-resolution monochromator for the 1000-250-eV region.