"Explore The Universe" - Featured Artifacts

Focusing X-Rays with Cylinders and Straws

X-rays either pass through or are absorbed by most substances, and they can't be focused with lenses or ordinary mirrors. But they will glance off a solid surface if they strike at a very shallow angle.

The orbiting x-ray telescope ROSAT used sets of wide metallic cylinders to "scoop up" incoming x-rays and focus them onto a detector called a High-Resolution Imager, or HRI. The x-rays ricocheted down the cylinders and into a bundle of microscopic metallic straws in the HRI. The x-rays knocked electrons off the sides of the straws, which channeled the electrons onto a fine wire mesh screen. The resulting electrical impulses were used to create an image showing the intensity and distribution of the x-ray energy.