Improved Resolution with the X-Ray Projection Microscope

A RESOLUTION of O.lµ (1000 A.) has now been reached with the shadow type of X-ray microscope by using a thin gold-leaf X-ray target. The instrument described previously by Cosslett and Nixon 1–4 was limited to a resolution of 0.5µ due to astigmatism in the electron lens and to electron scattering in the metal target. An attempt was made to reduce the astigmatism by stopping down the aperture of the objective lens used for focusing the electrons. No improvement in resolution was found even for a semi-angular aperture of 2 × 10 −2 rad. giving an astigmatic disk of confusion of 0.2µ for the worst possible machining errors of the pole pieces. This indicated that electron scattering in the metal foil target was the true limit on resolution.