Search for possible radiation damage on a NdFeB permanent magnet structure after two years of operation

Recently there has been some concern about possible radiation damage due to ionizing particles present in high energy storage rings such as multi-GeV electrons, fast neutrons, or hard photons. Partial demagnetization has been observed on undulators after mis-steering of the injected electron beam. Our interest was focused to possible radiation damage of a permanent magnet insertion device during routine operation of a storage ring. Therefore, we repeated the magnetic measurements on one of the three 4.0 m long x-ray wigglers used at place #2 in DORIS III. This device is in operation since 1991. The results were compared to the data taken before installation. The total dose was determined from measurements with thermoluminescence dosimeters and the known number of stored ampere hours. The results which show no significant degradation of the magnetic performance are presented and discussed.