Klystron-modulator system performance in PLS 2-GeV electron linac

A total of 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 an 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 hour of the system is about 5000 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 42,000-hours as of May 1999, and summation of all the units' high voltage run time is approximately 458,000 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, the authors review overall system performance of the klystron-modulator system. The operational status of the klystrons and thyratrons, and the overall system availability statistics for the period of 1994 to May 1999 are also discussed.