Fabrication and evaluation of variable focus X-ray lenses

We report on the fabrication, preliminary metrology, and X-ray transmission results of variable-focus cylindrical beryllium lenses. Each lens consists of a number of 1-mm-diameter lenslets made by precision computer numerical control (CNC) drilling into a beryllium substrate. The substrate is then cut into five parts, each having a different number of lenslets, ranging from 10 to 50. Each lens is then cut diagonally, using an electron discharge machine, to provide it with focusing ability. Unlike the traditional lenses having a fixed focal distance for a given energy, the present lenses provide for a wide range of photon energies and focal distances. Additionally, X-ray transmission through the lens is enhanced by reducing lenslet wall thickness to about 50 μm, the thinnest reported to date.