Superconducting elliptical undulator

Circularly polarized photons are widely used for conducting experiments to study magnetic structures of matter. On the basis of superconducting coils developed at Budker Institute of Nuclear Physics for a short-period superconducting planar undulator, a superconducting elliptical undulator with a period of ∼2.2 cm and an elliptic coefficient of∼0.7 is proposed. The poles of the upper and lower halves of the undulator are located at an angle of 45 degrees to each other in the horizontal plane, which creates periodic vertical and horizontal elliptical fields of up to 1 T vertically and 0.7 T horizontally. Fast switching of the electron orbit using correction magnets external to the cryostat (up to hundreds of Hz) enables fast switching of the left and right polarizations of the zero-angle radiation from two sequentially installed undulators. A short prototype of elliptical superconducting undulator was fabricated and magnetic measurements were made in a bath cryostat. The paper presents numerical calculations of the undulator fields, spectra, and experimentally measured field.