A high resolution soft X-ray scintillation detector based on the Young-Weierstrass points of a lens shaped YAG crystal

Abstract

Shaping a YAG scintillator crystal into a truncated-ball lens enables to image with a high numerical aperture its front surface, where the image converted from X-rays to visible is localized. Hence, both resolution and luminosity gains can be expected. Moreover if the plane surface is set at the Young-Weierstrass point of the spherical refractive surface, stigmatic imaging is achieved. On this principle, we have constructed an imaging detector from a 10 mm diameter YAG:Ce sphere and a long working distance plane-apochromatic microscope objective which does not limit the numerical aperture. The effective numerical aperture of the built system is 1.08, giving a Rayleigh resolution limit of 0.3 μm. Images of test objects (diatoms) have been recorded, in contact mode, with 103 eV. Periodic features of 0.4 μm pitch are visible on these images. The field of view is close to 200μm. The device is intended as an aid for X-ray optics fine-tuning and characterization.