Operational characteristics of PLS 2-GeV electron linac klystron-modulator system

Total 12 units of high power klystron-modulator systems are under continuous operation in the Pohang Light Source (PLS) linac. The peak powers of the modulator and the klystron are 200 MW and 80 MW, respectively. The klystron output frequency is 2856 MHz. Each klystron output is compressed with a SLED and supplied to four of three-meter long accelerating columns. Final electron energy of PLS linac is 2 GeV. The linac has been operated as a full energy injector for the PLS since December 1994. Annual operation hours of the system is about 6000-hours. Since the commissioning of the PLS linac, the total high voltage run time of an oldest unit among the 12 systems has been accumulated over 50000-hours as of May 2000, and summation of all the units´ high voltage run time is approximately 541000 hours. The overall system availability is well over 90%. To enhance the klystron lifetime, a ´cathode backheating´ operation mode was adopted from May 1999. In this paper, we review overall system performance of the klystron-modulator systems. The operational status of the klystrons and thyratrons, and the overall system availability statistics for the period of 1994 to May 2000 are also discussed.