Investigations of Resolution Degradation Due to Scattering in a Long Focal Length Monochromator

• Published in: Review of scientific instruments 1988-08, Vol.60 (7-IIB), p.2113-2115
• Main Authors: Hansen, R W C, Pruett, C H, Salehzadeh, A, Wallace, D J
• Format: Article
• Language: English
• ISSN: 0034-6748

Scattering of light by optical surfaces causes broadening of focused images and can limit the resolution of monochromators and other optical systems. This problem is most troublesome in the vacuum ultraviolet and X-ray region of the spectrum with long focal length, high resolution instruments. The resolution of a 4 m normal-incidence monochromator was found to be limited by scattering due to damaged replica grating surfaces. The effect of scattering on resolution was documented by scanning the zero-order peak with detectors sensitive to different wavelengths of light. In one case, a scan of zero order with a visible sensitive photomultiplier tube gave a linewidth of 0.05 A. The same image scanned with a Au diode detector which is sensitive < 1100 A gave a peak width of 0.39 A. Microscopic examination and knife-edge bench tests of the gratings provided additional evidence that this problem was caused by scattering. It is suggested that use of image scans at different wavelength could be used as a simple test of mirror or grating performance at shorter wavelengths where scattering is a more severe problem. , . 7 ref.--AA