Influence of imperfections in a wedged multilayer Laue lens for the focusing of X-rays investigated by beam propagation method

s Using a beam propagation method the focusing properties of a one-dimensional wedged multilayer Laue lens with imperfections have been investigated theoretically. The calculations were done for a lens focusing 20 keV X-rays to <5 nm spot. Our simulations of the intensity in the focal plane and at the far screen show that the systematic errors degrade the performance more than the stochastic ones and that a proper image at the far screen is not a proof for a good quality beam in the focus.