Development of new S-band SLED for PAL-XFEL Linac

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• 作者：Youngdo Joo^a ; Yongjung Park^a ; Hoon Heo^a ; Jinyul Heo^a ; Sung-Soo Park^a ; Sang-Hee Kim^a ; Kwang-Hoon Kim^a ; Heung-Sik Kang^a ; Heung-Soo Lee^a ; ^{lhs@postech.ac.kr} ; Sungju Noh^b ; Kyoungmin Oh^b
• 关键词：SLED ; High-power operation ; Linac ; PAL-XFEL
• 刊名：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• 出版年：2017
• 出版时间：21 January 2017
• 年：2017
• 卷：843
• 期：Complete
• 页码：50-60
• 全文大小：2610 K
• 卷排序：843

文摘

In order to achieve beam acceleration to the beam energy of 10 GeV at the end of its 716 m-long linear accelerator (Linac), the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) is going to operate the Stanford Linear Accelerator Energy Doubler (SLED) at the maximum klystron output peak power of 80 MW, with a pulse length of 4 μs, and at a repetition rate of 60 Hz. The original SLED that had been used in Pohang Light Source-II (PLS-II) can no longer sustain such a high-power operation because excessive radiation caused by RF breakdown has been frequently detected even at the lower klystron peak power during the PLS-II operation. Therefore, a new SLED is designed by modifying both the 3-dB power hybrid and the waveguide-cavity coupling structure of the original SLED where the excessive radiation has been mainly detected. The finite-difference time-domain (FDTD) simulation in the CST Microwave Studio shows that the new SLED has a peak electric field and a surface current lower than those of the original SLED at the same level of the RF input peak power, which would secure stable high-power operation. All of the 42 SLEDs in the PAL-XFEL Linac are newly fabricated and installed. During the RF conditioning of the PAL-XFEL Linac, no significant vacuum and radiation issue was found in the new SLEDs. Finally, the accelerated electron beam energy of 10 GeV obtained at the end of the PAL-XFEL Linac verified that the RF performance of the new SLED is stable.