A High Resolution Soft X-Ray Scintillation Detector Based On The Young-Weierstrass Points Of A Lens Shaped Yag Crystal

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 mu m. Images of test objects (diatoms) have been recorded, in contact mode, with 103 eV. Periodic features of 0.4 mu m pitch are visible on these images. The field of view is close to 200 mu m. The device is intended as an aid for X-ray optics fine-tuning and characterization.