Boro-silicate polycapillary lens for collimation of x-rays

Abstract

The purpose of this thesis is to investigate the collimation of x rays produced by transition radiation using the NPS Electron Linear Accelerator. These measurements support the theory that x rays can be focused using a boro-silicate array of polycapillaries consisting of 258 bundles with 1387 micro- channels each. A 90 MeV electron beam incident upon a non-resonant mylar stack formed transition radiation spatially distributed in an annular cone. The electron beam was deflected 30 degrees using a rare earth permanent magnet. The diverging x-rays incident upon the lens array were transported through total external reflection and directed out of the array onto a phosphor screen. A digital camera recorded the phosphorescing image of the screen. Pixel intensity was analyzed to determine x ray intensity as a function of two dimensional spatial distribution. Column average profiles of the pixel intensity show that the transition radiation intensity retains its Gaussian distribution after being redirected from a diverging beam into a mostly parallel beam. The intensity of the x-rays decreased by a factor of 0.72 due to the obstructed area at the face of the array and to imperfect admittance of the diverging x ray cone into the polycapillary array.