  Recently it was proposed to apply a bent single crystal with decreasing
curvature instead of uniform bending for improvement of extraction and
collimation of a circulating beam in particle accelerators. In the given paper
created crystal devices with a variable curvature, realizing this idea are
described. Results of measurement of curvature along a crystal plate are
informed. It is shown, that with the help of the developed devices it is
possible to carry out also high energy beam focusing. The mathematical
description of this process is proposed.
