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X-Band Amplifier for the PAL-XFEL
Hoon Heo,Jinyul Hu,Heung-Soo Lee,Heung-Sik Kang,Su Hyun Lee,Jin Ho Chang,Dong Heon Lee 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.7
Recent X-ray free electron lasers based on a high-energy high-current linear accelerator, such as the Pohang Accelerator Laboratory (PAL-XFEL) uses a third harmonic radio-frequency (RF) linearizer system to improve the laser's longitudinal beam quality. Because the X-ray free electron laser at the PAL-XFEL uses 2856 MHz RF accelerators, we realized a RF linearizer of 11.424 GHz which afforded a 50 MW RF power by using a SLAC X-band klystron. Operation of the X-band klystron required an X-band amplifier with a 1 kW level at the specified frequency of 11.424 GHz. We tested two types of X-band amplifier, a traveling wave tube amplifier and a solid state amplifier. In this work, we present the test results and discuss the features, especially focusing on the X-band solid state amplifier.
High-power Test of a New Bethe-hole Directional Coupler for the PAL XFEL S-band Linac RF System
주영도,박용정,허훈,Jinyul Hu,Sung-Soo Park,Sang-Hee Kim,황운하,Gun-Young Moon,Sosung Lee,이흥수,노성주,오경민 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.10
The directional coupler to be used in the Pohang Accelerator Laboratory X-ray free electronlaser (PAL XFEL) under construction since 2011 must satisfy the conditions for operating at apeak power of 400 MW and a repetition rate of 120 Hz. In these operational conditions of the PALXFEL, the old Bethe-hole directional coupler that was originally designed to be used in the PohangLight Source linac is more likely to inflict damages on the ceramic window that cause vacuumleaks. Therefore, for the new Bethe-hole directional coupler, the original design has been modifiedto use a conventional N-type RF vacuum feedthrough for vacuum sealing instead of the ceramicwindow. The new Bethe-hole directional coupler is designed by using a finite-difference time-domainsimulation. We have fabricated a prototype, and the result of a high-power test indicates that theRF performance of the new DC satisfies the specifications of the PAL XFEL S-band Linac RFsystem.
High-power Test of the New 3-dB Power Splitter for the PAL XFEL S-band LINAC RF System
주영도,박용정,허훈,Jinyul Hu,Sung-Soo Park,이상희,황운하,Gun-Young Moon,Sosung Lee,이흥수 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.8
The 3-dB power splitter to be used in the Pohang Accelerator Laboratory X-ay Free-electronLaser (PAL XFEL), which have been under construction since 2011, must operate at a peak powerof 400 MW and a repetition rate of 120 Hz. For these operational conditions of the PAL XFEL,the old 3-dB power splitter that was originally designed to be used in the PLS LINAC will mostsuffer from RF breakdown. Therefore, for the new 3-dB power splitter, the original design hasbeen modified to reduce the field gradient and the surface current. The new 3-dB power splitteris designed by using a finite-difference time-domain (FDTD) simulation. We have fabricated aprototype, and the result of a high-power test indicates that the RF performance of the new 3-dBpower splitter satisfies the specifications of the PAL XFEL S-band LINAC RF system.
S-band Traveling-Wave Deflecting Structures for the PAL-XFEL
Hoon Heo,Yong-Jung Park,Jinyul Hu,Sang-Hee Kim,Sung-Soo Park,Kwang-Hoon Kim,Heung-Soo Lee,Gyujin Kim,Geon-Yeong Moon,Changbum Kim,Dong-Hyun Na,Heung Sik Kang,Kyung-Min Oh,Sung-Ju No 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.8
We designed a 20-MV S-band traveling-wave de ecting structure to measure the bunch length of the electron beams for the PAL-XFEL. Since the start of commissioning of all RF systems of the PAL-XFEL on 12 April 2016, two out of three fabricated structures are currently being operated; one each in the hard X-ray and the soft X-ray branches. These de ecting structures were carefully tuned by using a 4-m-long nodal phase scanner in a precisely temperature and humidity controlled cleanroom considering the phase predictions calculated using RF field solvers. We carried out RF conditioning and beam commissioning with highly-stable high-power S-band RF systems and an EPICS-based control system. We brie y present our design of S-band de ecting structure and discuss the test results, including the results of the RF and the beam measurements.
Hard X-ray free-electron laser with femtosecond-scale timing jitter
Kang, Heung-Sik,Min, Chang-Ki,Heo, Hoon,Kim, Changbum,Yang, Haeryong,Kim, Gyujin,Nam, Inhyuk,Baek, Soung Youl,Choi, Hyo-Jin,Mun, Geonyeong,Park, Byoung Ryul,Suh, Young Jin,Shin, Dong Cheol,Hu, Jinyul Springer Science and Business Media LLC 2017 Nature photonics Vol.11 No.11
<P>The hard X-ray free-electron laser at the Pohang Accelerator Laboratory (PAL-XFEL) in the Republic of Korea achieved saturation of a 0.144 nm free-electron laser beam on 27 November 2016, making it the third hard X-ray free-electron laser in the world, following the demonstrations of the Linac Coherent Light Source (LCLS) and the SPring-8 Angstrom Compact Free Electron Laser (SACLA). The use of electron-beam-based alignment incorporating undulator radiation spectrum analysis has allowed reliable operation of PAL-XFEL with unprecedented temporal stability and dispersion-free orbits. In particular, a timing jitter of just 20 fs for the free-electron laser photon beam is consistently achieved due to the use of a state-of-the-art design of the electron linear accelerator and electron-beam-based alignment. The low timing jitter of the electron beam makes it possible to observe Bi(111) phonon dynamics without the need for timing-jitter correction, indicating that PAL-XFEL will be an extremely useful tool for hard X-ray time-resolved experiments.</P>