Four-row APPLE-Knot undulator mechanical design and test piece studies for High Energy Photon Source

Abstract

A four-row APPLE-Knot undulator is under developing in the High Energy Photon Source to get polarization adjustable synchrotron radiation and reduce on-axis heat load, because of the exotic magnetic field design, its construction faces challenges in mechanical design of frame, magnet blocks holder and integral field shimming method. In this paper, a mechanical design for APPLE-Knot undulator has been posed and structural deformation has been analysed, a test piece has been manufactured to test the physical design as well as magnetic holder design, integral field shimming method has also been described and realized, the result presents a good repeatability. It's a practical design of four-row APPLE-Knot undulator for the High Energy Photon Source.

The manufacture and magnetic field tuning of a merged four-row APPLE-Knot undulator at HEPS

“…The Ix and Iy on electron beam axis have been measured, sorting was conducted before magnetic blocks assembling. Based on test piece study [4], the six-in-one hold solution (figure 2) was adopted to achieve independent adjustment of Ix and Iy while ensuring installation accuracy, six magnetic blocks and an aluminum holder combine to form a module, in standard period there were 8 kinds of modules list from A to H, which different from each other in magnetization angles and combinations. The magnet force within modules was enormous but variable, dedicated fixtures were designed and manufactured to assemble those modules.…”

“…The field integrals shimming was conducted through three methods. Firstly, the position of magnetic blocks modules could be changed both in horizontal and vertical directions by replacing different thickness of copper shims under magnet holder (figure 2), the theoretical analysis and practical experiments had been discussed extensively in previous work [4], no further elaboration was provided here. Secondly, carbon steel sheet was applied to the surface of magnetic blocks to address magnetic gap correlation and phase correlation issues.…”

Study on the influence of gap dependent error on the cryogenic permanent magnet undulator performance

“…The High Energy Synchrotron Light Source (HEPS), built at the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS), is a 6 GeV synchrotron light source [1]. In the first stage of HEPS, a total of 19 undulators of various types and functions have been mass-produced, including four 5-meters-long in air undulators (IAUs), five 4-meters-long in vacuum undulators (IVUs), six 2-meters-long cryogenic permanent magnet undulators (CPMUs) [2,3], one 5-meters-long APPLE-KNOT (AK) undulator [4], two 1-meter-long in air wigglers (IAWs) and one 1-meter-long MAGON wiggler (MIAW). All insertion devices except the two CPMUs have now been commissioned for magnetic field performance and are awaiting installation toward the storage ring [5,6].…”