Experimental demonstration of the induction-shimming concept in superconductive undulators

Abstract

In an undulator, magnetic field errors limit the quality of the emitted photon beam. In an ideal undulator, the sinusoidal motion of the electron beam and the emitted photons are in phase along the whole trajectory. Small variations in the magnetic field from period to period can produce phase errors and have to be corrected. This procedure is called shimming. Recently, a new scheme for superconductive undulators based on Faraday’s law of induction in a type-II superconductor was proposed in which these errors are automatically minimized. The field errors create currents and therefore magnetic fields in an array of coupled high temperature superconductor loops which minimize the field errors. In this paper the first experimental results of a test of this new concept are described.