High-resolution X-ray projection microscopy

Abstract

The X-ray shadow projection microscope has been limited previously to a resolution of 0.5/4. A resolution of 0.1μ has now been achieved with the same exposure time of 5 min. This has been done by using a very thin gold-leaf X-ray target (0.1μ thick) to avoid enlargement of the point source of X-rays due to electron scattering in a thick target. Electron lens aberrations such as astigmatism and spherical aberration are considered but dismissed as possible limitations on X-ray microscope resolution. This improved resolution is tested by observing Fresnel edge diffraction fringes 0.1μ wide, and this fringe width method is suggested as a resolving power test for all X-ray microscopes. An X-ray micrograph of gold-shadowed bull spermatozoa, tails 0.3μ diameter, shows this resolution with an actual biological specimen. Finally, electron-induced contamination on test grids has been observed at atmospheric pressure due to electrons penetrating this thin gold-leaf target.