PROGRESS OF PLS 2-GeV LINAC* W. Namkung, I. Ko, M. Cho, C. Ryu, J. Bak, S. Nam, and H. Lee Pohang Accelerator Laboratory, POSTECH P. 0. Box 125, Pohang 790-600, Korea Abstract Pohang Accelerator Laboratory (PAL) is constructing the 2-GeV Pohang Light Source(PLS). The 2-GeV electron linear acceleratorwill be used as a full energy injector to the storage ring. There are42 accelerating columns in the 150-mlong linac. The linac is powered by 11 klystrons of 80-MW maximum output power, which are driven by 200-MW modulators. Two 200-MW modulators connected to the klystrons are already under normal operation,and assembly work for the nine remain- ing modulators is in progress. In the tunnel, about half of the linac hasbeeninstalled The cooling system is completed along with the precision temperature controllers. The installation work will be completed by the end of 1993. We presentthe updatedconstruction progress of the PLS 2-GeV linac. I. INTRODUCTION The PLS 2-GeV linear accelerator is a full energy injector to the storage ring (SR) which will serve as a low-emittance light sourcefor various research:basic science,applied science, and industrial and medical applications [l]. There will be 11 klystrons andmodulators,and 10SLAC-type pulsecompressors in the linac gallery. In the linac tunnel, which is 6-m below the gallery floor, therewill be42 accelerating cohmms, 6 quadmpole triplets, and various components to fotm the 150-mlong hnac. The approximately 215-m long linac building is completed. The installation work started on July 1, 1992 is progressing smoothly. As of May 1,1993, up to K6 module in the tunnel has been completed This location is about 80-m from the e-gun. There are 22 acceleratingcolumns and four quadrupole triplets up to this place. The completion of the installation is expected by the end of 1993. The commissioningof the 2-GeV linac will be carried out during the fii half of 1994. II. TECHNICAL DESCRIPTION A. General Description The nominal beamenergy of the PLS linac is 2-GeV andthe operating frequency is 2,856 MHz. The maximum repetition rate of the linac is 60 Hz However, this repetition rate will be reduced to 10 Hz when the linac serves as an injector to the storagering due to limitation on the SR injection system. The higher repetition rate will be useful for the testing of the machine or other purposes in the future. The normalized emittsnce for the electron beamof the linac is 0.015 x MeV/c cm rad. It corresponds to 7.5 x IO-* K m rad at 2 GeV. The energy spread of the electron beamis z!zO.6% at FWHM Major parameters are summarized in Table 1. * Work supported by Pohang Iron t Steel Co. and Ministry of Science and Technology, Korea. B. Preinjector The PLS 2-GeV linac is consideredto consist of two parts: the preinjector and the main linac. The preinjector is the first 60 MeV sectionof thewhole linac. It consists of atriode type e-gun, an S-bandprebuncher and buncher, two accelerating columns, and various components. It is powered by a 25-MW klystron, The preinjector wascompletedon February28,1992. At that time, 6 1.2MeV electron beamwas achieved [2]. Since then, it is being usedto train PLS personnel. Table 1: Major parameters of PLS 2-GeV linac. Beam Energy 2Gev Accelerating Gradient 15.5MV/m (mm.) Energy Spread < 0.6 % Machine Length 150m RF Frequency 2,856 MHz Repetition Rate 60 Hz max. E-gun > 2 A, 2 nsec Emittance 0.015 rt MeV/c cm rad Klystron Output Power 80 MW max. Number of Klystrons 11 (=l+iO) Number of Pulse Compressor 10 Number of Accelerating Column 42 Number of Quadrupole Triplet 6 Number of Support t Girder 22 BeamExit at 80 MeV, 1 GeV, 2 GeV C. Main Linac The electron beamsfrom the preinjector are accelerated to 2-GeV by 10 high-power klystrons and 10 SLAC-type pulse compressors [3]. Each klystron provides 80 MW maximum output power, andfeedsRF power to four acceleratingcolumns. Ten pulsecompressors areemployed to obtain a higher acceler- ating gradient. The acceleratinggradient exceeds15.5MeV/m. To obtain the 2-GeV beam, the klystron output power is about 64MW andtheenergy gainfactoroftbepulsecompressoris 1.5. In this way, we can avoid operating the klystron at its maximum power level, and can, therefore, extend the lifetime of the klystron. There sre 40 acceleratingcolumns in the main linac. The 3.072-m long accelerating column has a SLAC-type constant gradient structure with 27cDoperating mode. Its distinctive featureis the conflat flangesfor easyinstallation. There are six quadrupole triplets altogetherin the 2-GeV linac. Thesewill be sufficient to focus and guide the electron beameven in event of a power failure in any one of the klystron, with the exception of the preinjector klystron, which provides the driving power to the rest of the klystrons. 581 © 1993 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. PAC 1993