Performance investigation of conduction-cooled cryogenicpermanent magnet undulator at high beam currents

A conduction-cooled cryogenic permanent magnet undulator, CU15, with a period length of 15 mmand 133 periods has been successfully developed. This undulator has been operated at the Taiwan PhotonSource (TPS) storage ring at a beam current of 500 mA for more than 3 years. In CU15, two cryocoolersare used to cool the PrFeB magnets to 80 K. The effective magnetic field measures 1.33 Tesla for amagnet gap of 4.2 mm, maintaining an rms phase error below 2.6 degrees. The bunch length of the electron beamin TPS is as short as 16 psec, leading to a serious issue with high beam-induced heating in CU15.This report addresses the above issues and provides detailed adaptations of CU15 to operate at a beamcurrent of 500 mA.