Delta-8 superconducting undulator to generate helical and low heat load linear polarization

Abstract

In this paper we propose a Delta-8 superconducting undulator with the ability to generate both the helical polarization and the linear polarization radiation with low power density on axis. This Delta-8 superconducting undulator consists of two magnet array pairs, one with single period length and the other with variable period length. The two magnet array pairs have a constant longitudinal shift of a quarter of a period length to each other. In the condition that both pairs have the identical single period λu, the Delta-8 undulator can produce helical polarization. When one array pair works at single period λu and the other pair at double period 2λu, the Delta-8 undulator generates linear polarization radiation with low on-axis power density. We demonstrate the principle of the Delta-8 undulator giving the expressions of the radiation field on axis. The numerical calculation of the on-axis radiation power density from the derived formulae is consistent with the one from the simulation.