PAL, Pohang, Kyungbuk, Republic of Korea
PAL, Pohang, Republic of Korea
A Hard X-ray (HX) line in PAL-XFEL consists of an e-gun, a Laser Heater (LH), S-band accelerators, an X-band LINearizer (XLIN), three Bunch Compressors (BC), a dog-leg, and an undulator line. It generates 2.5 - 15-keV FEL with over than 1-mJ pulse energy. The XLIN before BC1 is used for linearizing the energy chirp in the longitudinal phase space and provides the flexibility for FEL optimization and operation. However, it causes the instability of FEL by large jitters and drift because of higher frequency. We study the FEL operation without XLIN. The collimator in the center of BC1 is used removing the slices to cause nonlinear compression. We optimize the FEL by short electron bunch with under 30 fs. In this paper, we present details of the optimizing sequence and performance for the FEL operation without XLIN.
ANL, Argonne, Illinois, USA
PAL, Pohang, Kyungbuk, Republic of Korea
As a part of the Argonne Strategic Partnership Project (SPP) 85H21, a collaboration between Advanced Photon Source (APS), Argonne National Laboratory (ANL) and Pohang Accelerator Laboratory (PAL), we have designed, constructed, and tested a thin-film-diamond monochromator for the PAL X-ray Free-Electron-Laser (PAL-XFEL) hard x-ray self-seeding project*. The mechanical design of the PAL-XFEL diamond crystal hard x-ray self-seeding monochromator is based on the APS design of a diamond-crystal monochromator for the LCLS hard x-ray self-seeding project** with enhanced diamond crystal holder for two thin-film-diamond crystals with thicknesses of 30 microns and 100 microns***. The customized high quality thin-film-diamonds and special graphite holder were provided by the Technological Institute for Super-hard and Novel Carbon Materials of Russia (TISNCM)****, and tested at the APS***. An in-vacuum multi-axis precision positioning mechanism is designed to manipulate the duo-thin-film diamonds holder with resolutions and stabilities required by the hard x-ray self-seeding physics. Mechanical specifications, designs, and preliminary test results of the diamond monochromator are presented in this paper.
*Chang-Ki Min, et al, sub. J. Sync. Rad., 2018
**D. Shu, et al, J. Phys.: Conf. Ser. 425 (2013) 052004
***Y. Shvyd’ko, et al, FEL2017, Santa Fe
****Polyakov S, et. al, 2011 Diam. Rel. Mat. 20 726
PAL, Pohang, Kyungbuk, Republic of Korea
The Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL) employs 51 units of the pulse modulator in order to obtain the 10 GeV electron beam, which drive one X-band to linearize and 50 S-band klystrons. The PAL-XFEL requires very tight control of the klystron RF phase jitter 0.03-degree for S-band RF, 0.1-degree for X-band RF and the beam voltage stability of below 50 ppm. The RF phase jitter is directly related to the amplitude stability of modulator output pulses. There are several factors to satisfy the stability and reliability for the PAL-XFEL modulator. The largest sources of pulse-to-pulse instability are a current charging power supply (CCPS) for PFN charging, a thyratron switch, and a klystron focusing magnet power supply (MPS). In this paper, the operation and debugging results of those devices are described.