Compact storage rings Siberia-AS and Siberia-SM synchrotron radiation sources for lithography

Abstract

The paper deals with two projects of compact superconducting storage rings for industrial production of integrated circuits (IC) using x-ray lithography within the 8- to 20-Å wavelengths range. The azimuthally symmetric superconducting storage ring Siberia-AS at an energy of 600 MeV is a superconducting analog of VEP-1, one of the earliest storage rings in the world intended for the purposes of high-energy physics. Unlike the conventional design, no iron yoke is used in the storage ring under consideration to form the magnetic field at the equilibrium orbit and to close the return magnetic flux—this is performed by some inner and outer superconducting windings. Such a scheme enables the size of the storage ring to be substantially reduced (a cylinder of 2 m in diameter and 2 m long), and as a result, its weight decreases, too (about 10 tons). The eight-magnet storage ring Siberia-SM is of four-order symmetry so that the periodicity element comprises two rectangular magnets and three lenses. Its basic component is a superconducting bending rectangular magnet at a 6-T magnetic field. Two variants of such magnets have been proposed: in the first, the iron yoke is utilized to form the magnetic field and to close the return flux, while the second is an ironless C-shaped magnet manufactured on the basis of original wedgelike coils.