Development of a wideband multilayer grating with a new layer structure for a flat-field spectrometer attached to transmission electron microscopes in the 2-4 keV range, 2

Imazono, Takashi; Kuramoto, Satoshi*; Koike, Masato

A soft X-ray spectrograph to attach to transmission electron microscopes has been developed. Original TEM-SXES instruments can detect soft X-ray emission (SXE) spectra of the 60-2000 eV range. However it is necessary to develop a new SXES instrument that covers a wider energy range from 2 keV to 4 keV. Observation of the SXE spectra in this energy range needs a multilayer grating because in which a typical grating with a gold coating is no longer practical. A conventional multilayer grating has high diffraction efficiency but narrow band at a fixed angle of incidence. It indicates that the SXES instrument should employ a mechanism for wavelength scanning to cover the required energy range and is unsuitable for the spectrograph to attach to a TEM. To overcome this problem, a new multilayer structure was invented, which uniformly enhances the reflectivity in a few keV energy range at a fixed angle of incidence. The multilayer was deposited on a laminar varied-line-spacing replica grating. The diffraction efficiency of the multilayer grating was evaluated by a goniometric apparatus, soft X-ray diffractometer, at a double-crystal Si monochromator BL-11B at Photon Factory, KEK. It varies from 0.6% to 2.7% over the whole energy range. This means the wide-band multilayer replica grating was developed successfully.