Abstract
Development of superconducting undulators (SCUs) continues at the Advanced Photon Source (APS). Several planar SCUs were designed and built, and two of them are currently in operation at the APS. In January 2018 a new helical SCU (HSCU) was installed on the storage ring at the APS. It has a 1.2 m-long magnet with bifilar winding that generates on its axis a single harmonic of about 6 keV x-rays. The magnet is housed in the newly designed compact cryostat equipped with four cryocoolers. The HSCU was extensively tested prior to its installation on the APS storage ring, and it demonstrated cryogenic and magnetic performance in accordance with the design specifications. The HSCU was rapidly and successfully commissioned, and in February 2018 it was transferred to user operations. Its performance as an x-ray radiation source has been studied and spectral characteristics confirmed. The HSCU is currently used to support unique scientific program at the APS.
Highlights
The design and construction of a novel helical SCU (HSCU) has been completed at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL)
We describe the results of a stand-alone cool down test, including magnetic measurements and cryogenic behavior of the HSCU
Due to the mechanical structure of the HSCU assembly, the magnet cannot be cooled via liquid helium (LHe) through a channel in the mandrel like the planar SCUs developed at the APS [1,2]; we decided to place the LHe channels in the mold
Summary
The design and construction of a novel HSCU has been completed at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). Magnetic simulations suggest and recent experimental results clearly prove that superconducting technology can provide an on-axis undulator field higher than permanent magnet technology for both planar and helical undulators It has been demonstrated at the APS and ANKA [8] that planar SCUs could be built and operated under stringent requirements applied to 3rd-generation light sources and FELs. the focus of this project was to develop and build a helical undulator that incorporates the benefits of superconducting technology and to demonstrate the ability of an HSCU to meet the operational requirements of the APS storage ring. A beam line has the opportunity to greatly increase the central aperture flux by eliminating the need for optical components, including a monochromator Another distinctive characteristic of helical undulators is that the emitted on-axis radiation is circularly polarized. We present our experience operating the HSCU in the APS storage ring by describing the observed heat loads in the HSCU, the undulator performance, and its effect on the electron beam
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