Shidara, T

CERN Document Server

KLYSTRON OPERATION STATISTICS AT KEKELECTRON/POSITRON INJECTOR LINACTetsuo Shidara and KEK Electron/Positron Injector Linac GroupKEK, Oho, Tsukuba, Ibaraki 305-0801, JapanAbstractThe KEK electron/positron injector linac is supplying 8 GeV electron beamsto the KEKB high-energy ring and 3.5 GeV positron beams to the low-energy ring, as well as 2.5 GeV electron beams to the PF and PF-AR rings.This linac comprises a special accelerator module that includes a bunchingsection and 56 regular accelerator modules, each involves a 40 MW rfsource with SLED and four 2-m accelerator sections operated at 2856 MHz.The operation time of the KEKB linac will amount to 7200 hours for fiscalyear 2000 because of the heavy competition with the PEPB. More than 10050-MW klystrons have been produced. Their average life time and MTBFvalue reached 13500 and 70500 hours, respectively, which shows anaffirmative insight into achieving a desirable average life time of 30000hours.KEK ELECTRON/POSITRON INJECTOR LINACThe KEK electron/positron injector linac was originally designed to provide 2.5 GeV beams to boththe Photon Factory (PF) storage ring [1-2] and the TRISTAN accumulator ring (PF-AR). The linacupgrade for the KEK B-Factory [3] was carried out since 1994, while always keeping beam injectionto the PF and PF-AR rings, and finished upgrading by May, 1998.The major differences between the upgraded and old injectors are listed in Table 1.Table 1Differences between the upgraded and old injectorsOld UpgradedTotal energy 2.5 GeV 8 GeVLinac length 400 m 600 mAccelerator modules 41 59Energy gain 8 MeV/m 20 MeV/mPulse structure multi-bunch single-bunchPulse repetition 50 pulse/s 50 pulse/sPositron intensity 0.032 nC/pulse 0.64 nC/bunchAn 8 GeV beam can be provided by accelerating electrons along the entire linac length. In the3.5 GeV positron-injection mode, a tungsten target is inserted into the beam line at the middle part ofthe linac; a high-current beam hits the target and part of emerged positrons is accelerated in theremaining part of the linac.The electron source for the 2.5 GeV electrons to PF and PF-AR still remains at the original partof the old injector.The upgraded injector comprises a special accelerator module that includes a bunching sectionand 56 regular accelerator modules, each involves a 40 MW rf source with SLED and four 2-maccelerator sections operated at 2856 MHz.50 MW KLYSTRONA 50 MW klystron was developed for new rf system [4-5], expecting an enough margin at 40 MWoperation. The specifications of the 50 MW klystron are shown in Table 2.Table 2Specifications of the 50 MW klystronBeam voltage (kV) 304Beam current (A) 352Microperveance 2.1+-0.1Beam pulse width (ms) 6rf pulse width (ms) 6rf top pulse width (ms) 4Pulse repetition rate (pps) 100rf frequency (MHz) 2856Peak output power (MW) 50Efficiency (%) 45Gain (dB) 53Focusing magnet electromagnetPulse transformer step-up ratio 1 : 13.5OPERATION STATISTICSThe operation time for the KEK electron/positron injector linac is shown in Table 3. It had increasedto 7000 hours during FY 1999 due to the start of the KEKB experiment and will amount to 7200 hoursfor FY 2000 because of its heavy competition with the PEPB.Table 3Operation and failure ratePeriod (FY) Operation time (hours) Failure rate (%)1993 5299 0.881994 5070 0.781995 4563 0.741996 4123 0.621997 3828 2.881998 5906 7.121999 7297 7.362000 7160The cumulative klystron operation status up to March 2000 is shown in Table 4. More than 10050-MW klystrons have been produced. Their average life time and MTBF value reached 13500 and70500 hours, respectively, which shows an affirmative insight into achieving a desirable average lifetime of 30000 hours.Table 4Cumulative klystron operation status up to March 2000Fiscal Total Unused Living Failed Cumulative MTBFyear of No. of No. of No. of Av. op. No. of mean operationproduct tubes tubes tubes time (hrs) tubes age (hrs) (tube-hrs) (hrs)1993   14   2 10 19184   2 20188   232212 1161061994   13   0 11 17624   2   5857   205580 1027901995   23   0 15 16212   8   7191   300705   375881996   15   0 12 14326   3   6707   192031   640101998   20   1 19   6668   0   1266841999   15 14   1   1884   0       1884total 100 17 68 13667 15  8649 1059096   70606References[1] J. Tanaka, Nucl. Instr. and Meth., 177(1980)101.[2] I. Sato, Nucl. Instr. and Meth., 177(1980)91.[3] A. Enomoto, et al., Proc. of the 1993 Particle Accelerator Conference, U.S.A., 1993.[4] S. Anami et al., Proc. of the 1993 Particle Accelerator Conference, U.S.A., 1993.[5] S. Fukuda et al., Proc. of the 1994 Linear Accelerator Conference, Japan, 1994.

Klystron operation statistics at KEK electron/positron injector linac.

Abstract

Similar works

Full text

Available Versions

CERN Document Server