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

Abstract A merged four-row APPLE-Knot undulator has been manufactured at the High Energy Photon Source(HEPS) and the magnetic field tunning has been completed. Inclined magnetization magnetic blocks are used in this undulator in large scale, new skills are used in magnetic blocks' manufacturing and assembling. Magnet field tunning is conducted by combination of various methods and resulted in a satisfactory photon performance. The practical mechanical deformation of aluminum girder has been measured and compared with theoretical calculation, results indicate a significant discrepancy between these two data, the reasons causing this discrepancy have also been analyzed. The merged four-row APPLE-Knot undulator at HEPS holds significant reference value for its uniqueness and specificity.