TY - CONF AU - Lee, T.-Y. AU - Ha, T. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Towards a Sextupole-Free Electron Storage Ring J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - This paper studies if it is possible to build an electron storage ring with no or a small number of sextupole mag-nets. If it is possible, the electron storage ring will be great-ly simplified. For the purpose, two methods are presented in the paper to handle head-tail instability: One is to use dielectric vacuum chamber made of such materials as ceramic or glass to reduce broadband impedance signifi-cantly. Then head-tail instability would be extremely weak. The other method is to install a bunch-by-bunch feedback system to suppress the already weak head-tail instability due to the dielectric vacuum chamber. PB - JACoW Publishing CP - Geneva, Switzerland SP - 217 EP - 220 KW - electron KW - vacuum KW - impedance KW - storage-ring KW - feedback DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPGW058 UR - http://jacow.org/ipac2019/papers/mopgw058.pdf ER - TY - CONF AU - Heo, H. AU - Cho, M.-H. AU - Han, J.H. AU - Kang, H.-S. AU - Kim, C. AU - Kim, G. AU - Kim, M.J. AU - Ko, J.H. AU - Lee, H.-S. AU - Min, C.-K. AU - Nam, I.H. AU - Park, K.-H. AU - Shim, C.H. AU - Yang, H. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - XFEL Performance Achieved at PAL-XFEL J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - The hard X-ray free electron laser at Pohang Accelerator Laboratory (PAL-XFEL) successfully completed the commissioning of SASE and started user operation in late 2016. Since then, the facility has demonstrated excellent stability with very small timing jitter of about 20 fs, and commissioned the self-seeding system over a wide range of photon energies, etc. The talk will provide an overview of the last three years at the PAL-XFEL, including some detailed experimental results, as well as future prospects for the laboratory. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1182 EP - 1184 KW - FEL KW - undulator KW - electron KW - photon KW - emittance DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUYPLM1 UR - http://jacow.org/ipac2019/papers/tuyplm1.pdf ER - TY - CONF AU - Kim, M.J. AU - Choi, Choi. AU - Han, J.H. AU - Jeong, S.-H. AU - Jung, Y.G. AU - Kang, H.-S. AU - Kim, D.E. AU - Kim, M.S. AU - Lee, H.-G. AU - Lee, S.B. AU - Lee, S.J. AU - Oh, B.G. AU - Park, K.-H. AU - Suh, H.S. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Design of Analog to Digital Converter Scheme for High - Precision Electromagnet Power supply J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - This paper deals with the design of an analogue-to-digital converter (ADC) scheme for a highly precise magnet current supply (MPS). The MPSs are requires with stable and precise current specification in range of the ppm. To meet the requirements, the AD circuit is composed of parallel ADCs of low-medium resolution. Digitally, the oversampling and averaging are performed to increase both the effective resolution and the signal to noise ratio (SNR). The implemented AD circuit was improved about 18 dB (32 times oversampling). The MPS applied by the proposed ADC scheme provides more precise control and the stable current within 10 ppm at 200 A. The experiment used a dipole magnet of the PAL-XFEL and its results proved feasibility through precisely measurable DVM3458A (Keysight Co.). PB - JACoW Publishing CP - Geneva, Switzerland SP - 1309 EP - 1311 KW - controls KW - FEL KW - hardware KW - experiment KW - dipole DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUPMP032 UR - http://jacow.org/ipac2019/papers/tupmp032.pdf ER - TY - CONF AU - Yang, H. AU - Min, C.-K. AU - Nam, I.H. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Study of FEL Operation Using Collimator without X-band Linearizer in HX Line at PAL-XFEL J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - 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. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1824 EP - 1826 KW - FEL KW - operation KW - electron KW - linac KW - simulation DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUPRB069 UR - http://jacow.org/ipac2019/papers/tuprb069.pdf ER - TY - CONF AU - Yoon, J.Y. AU - Bahng, J. AU - Cha, H.J. AU - Jang, S.W. AU - Kim, E.-S. AU - Kim, K.R. AU - Park, C.S. AU - Park, S.H. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Design Study of 325MHz RF Power Coupler for Superconducting Cavity J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - We present the design study of the RF input power coupler for 325 MHz superconducting cavities. The power coupler, based on a conventional coaxial transmission line, provides RF powers to the cavity up to 12kW in CW mode. The thermal interceptors are considered as 4.5 K and 40 K or 4.5 K and 77 K corresponding to the usage of liquid Helium only or both liquid Helium and Nitrogen for cryogenic temperature to reduce the thermal load. The transition box (T-box), which is assembled with power coupler, is designed and applied for impedance matching and inner conductor cooling. PB - JACoW Publishing CP - Geneva, Switzerland SP - 2937 EP - 2939 KW - cavity KW - impedance KW - superconducting-cavity KW - resonance KW - simulation DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-WEPRB056 UR - http://jacow.org/ipac2019/papers/weprb056.pdf ER - TY - CONF AU - Shu, D. AU - Anton, J.W.J. AU - Kang, H.-S. AU - Kearney, S.P. AU - Kim, K. AU - Min, C.-K. AU - Oh, B.G. AU - Rah, S.Y. AU - Shvyd'ko, Yu. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Mechanical Design of a Diamond Crystal Hard X-Ray Self-Seeding Monochromator for PAL-XFEL J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - 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. PB - JACoW Publishing CP - Geneva, Switzerland SP - 3782 EP - 3785 KW - FEL KW - vacuum KW - controls KW - alignment KW - electron DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-THPGW089 UR - http://jacow.org/ipac2019/papers/thpgw089.pdf ER - TY - CONF AU - Kim, S.H. AU - Kang, H.-S. AU - Kim, K.H. AU - Lee, H.-S. AU - Min, C.-K. AU - Park, S.S. AU - Park, Y.J. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Stability and Reliability Issues of PAL-XFEL Modulator J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - 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. PB - JACoW Publishing CP - Geneva, Switzerland SP - 4096 EP - 4099 KW - FEL KW - klystron KW - operation KW - power-supply KW - electron DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-THPRB117 UR - http://jacow.org/ipac2019/papers/thprb117.pdf ER - TY - CONF AU - Park, S.J. AU - Cha, S.C. AU - Hwang, J.H. AU - Kim, D.H. AU - Park, Y.J. AU - Yu, D.H. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Beam Loss Suppression by Beam Matching in Klystron J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - High power klystrons usually employ large cathodes to generate high currents which are compressed inside the gun to provide optimum beam sizes at the cavity section. We compress the beam by using electrostatic and magnetostatic focusing fields which are established by gun electrodes and external magnets respectively. The geometry of the gun elecrodes and the external magnet is carefully designed to meet the matching condition which results in scalloping-free beam. We have established a systematic design procedures to achieve the beam matching condition at arbitrary beam sizes. In this article we report on the beam-matching design and simulation results with an example case of the 80-MW S-band klystron in the Pohang Accelerator Laboratory. PB - JACoW Publishing CP - Geneva, Switzerland SP - 4218 EP - 4220 KW - klystron KW - simulation KW - gun KW - beam-losses KW - injection DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-THPTS052 UR - http://jacow.org/ipac2019/papers/thpts052.pdf ER -