Varied-line-spacing laminar-type holographic grating for the standard soft X-ray flat-field spectrograph

摘要

An aspheric wave-front recording system was designed to produce a holographic grating for use in a standard soft X-ray flat-field spectrograph interchangeably with a mechanically ruled varied-line-spacing (VLS) grating. The grating grooves recorded with the designed aspheric wave-front recording system were processed to form a laminar groove profile by means of reactive ion etching. Measurements done with synchrotron radiation and a laboratory X-ray source are reported for this laminar-type grating and a commercial grating replicated from a mechanically ruled VLS grating that was specifically designed and fabricated for the standard soft X-ray flat-field spectrograph. The laminar-type holographic grating is found to have an absolute first-order efficiency of approx10percent for wavelengths of approx4.5-12 nm. It is also shown that the holographic grating is effective in suppressing the higher orders and stray-light level for soft X-ray of 4.36 nm (C-K) and has a comparable spectral resolution to the replica VLS grating.