The Design of a Pair of Elliptically Polarized Undulators at SSRF

Abstract

The magnetic design of a pair of elliptically polarized undulators with APPLE-II type which will be used in a soft X-ray beam line for ARPES and PEEM at SSRF is presented. The undulators will cover the energy range from 20 eV to 2000 eV of arbitrary polarized light including the horizontal, vertical, elliptical and circular polarization. The quasi-periodic design to minimize the contributions of the higher harmonics of the low energy undulator is also described.

Study of the Beam Tune-Shift Effects for DEPU at SSRF

“…According to the potential of focusing, the effect of DEPU to beam tune-shift can be deduced easily and the corresponding beta function lengths in the vertical and horizontal direction are 2.5 m and 3.6 m respectively for the calculation [1] [2]. The variation of the effect to tune-shift with the phase for the EPU148 and EPU58 is shown in Fig.…”

“…SSRF (Shanghai Synchrotron Radiation Facility) is an intermediate energy (3.5 GeV) light source [1] and a soft X-ray beam line for ARPES and PEEM is being built [2]. The source of this beam line is designed to use a pair of EPUs including EPU148 and EPU58 to enlarge the photon energy range and reduce the heat load to the optics instrument simultaneously [2].…”

“…The main parameters for the Double EPUs are listed in Table I. Two EPU's girders will be connected with the same support frame and the frame can be moved transversely so the beam line user can choose each undulator according to the experimental requirement [2]. The whole geometry of the DEPU is shown in Fig.…”

“…The main parameters of the SSRF storage ring are listed in Table II [1]. The DEPU will be installed in 6.5 m long straight section [2].…”