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A 4th generation storage ring based light source is being developed in Korea since 2021. It features 100 pm rad emittance, about 800 m circumference, 4 GeV e-beam energy, full energy booster injection, and more than 40 beamlines which includes more than 24 insertion device (ID) beamlines. This machine requires about ~1000 magnets including dipole, longitudinal gradient dipole, transverse gradient dipole, sextupoles, and correctors. The apertures are small and the lattice space requirements are very tight. In this report, a preliminary design of the each magnet is presented with detailed plan for the future., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

All 18 photon beam position monitors (PBPM) installed on the PLS-II are tungsten blade types. The elliptical polarized undulator (EPU) has the characteristic that the spatial profile of the beam varies depending on the polarization mode. This relates to the thermal load of the blade and changes in the blade material at fixed blade gaps are inevitable. In this paper, we analyze power density and flux density according to EPU mode and describe the process of installing PBPM with CVD-diamond blades on the PLS-II beamline for the first time., Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea

The beam diagnostics beamline BL7B using synchrotron radiation with 8.6 keV critical photon energy from bending magnet has been used to measure the electron-beam size and photon-beam profile on real-time basis. After the completion of the PLS-II, the Compound Refractive Lens (CRL) system was implemented in the optical hutch at BL7B to measure the electron-beam size from X-ray imaging. But we could not have a good image due to short focal length caused by limited space of the optical hutch. To solve this problem a Pinole Camera is implemented in the front-end of BL7B in return for the beamline extension. The progresses on the new x-ray imaging system is introduced in this presentation., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

In order to realize and test advanced accelerator concepts and hardware, the existing beamline with both old and new components are being reconfigured in Linac Extension Area (LEA) of APS linac. Photo injector, which had been installed in the beginning of APS linac, will provide low emittance electron beam into the LEA. The thermionic RF gun beam for storage ring and photo-cathode RF gun beam for LEA will be operated though the LINAC in an interleaved fashion. In this presentation, technical issues as well as beam dynamics on the design for interleaving operation will be described., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

Accelerator-Driven system (ADS) can transmute long lived nuclear waste to short lived species. For this system to be fully realizable, a very stable high energy and high power proton beam (typically, 1 GeV beam energy and 10 MW beam power) is required, and preparing such a powerful and stable proton beam is very costly. Currently, the most promising candidate is superconducting linear accelerators. However, high power cyclotrons may be used for ADS particularly at the stage of demonstrating proof of principle of ADS. This paper discusses how cyclotrons can be used to demonstrate ADS., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

A high power cyclotron is a good candidate as a driver of the accelerator driven system for the transmutation of long lived nuclear wastes. In this work, a simulation code has been developed for describing the beam dynamics in the high power cyclotron. By including higher order terms in transverse transfer matrix and space charge effects, we expect to describe the beam motion more accurately. The present code can describe equivalent orbit at each energy, calculate the tunes, and also perform multi-particle tracking. We report the initial results of the code for the simulation of a 13 MeV cyclotron. Lastly, an upgrade plan is discussed to add more features and to increase calculating efficiency., Proceedings of the 21st Int. Conf. on Cyclotrons and their Applications, Cyclotrons2016, Zurich, Switzerland

Beam dynamic phenomena described by bunch-by-bunch motion are important issues for a storage ring and are described by various theoretical formalisms. Direct measurements of the beam position related to different dynamical mechanisms are a useful information to accelerator optimization. In PLS-II, 20 GHz sampling oscilloscope synchronized with injection event (or triggered by beam loss signal) is used to measure direct bunch by bunch motion. Based on the measured data, the principal component analysis had been performed to get the insight into beam dynamic phenomena such as couple bunch instability and beam oscillation due to kicker leakage. In this paper, we will describe the measurement method and the result of analysis for coupled bunch instability., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

Accelerator-Driven system (ADS) is considered the fu-ture nuclear reactor. In principle, it is safer and creates less waste than the conventional nuclear reactor, and provides the transmutation function that converts spent fuel into short-lived elements. However, to fully realize this system, a huge proton accelerator (typically, 1 GeV beam energy and over 10 MW beam power) with ex-tremely high operational stability is necessary. This paper discusses how the currently available technology can be applied for nuclear transmutation., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The transverse position of the electron beam in the Pohang Light Source-II (PLS-II) is stabilized by the global orbit feedback system. Currently, 2 Hz slow orbit feedback (SOFB) system is operating, and 1 kHz fast orbit feedback (FOFB) system is installed recently. This FOFB system is consists of 96 electron beam position monitors (BPMs), 48 horizontal fast correctors, 48 vertical fast correctors and VME control system. We present the design and implementation of the FOFB system and its test result. Analysis through the simulation is presented and future improvement is discussed, Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

During the beam store test up to 400 mA in the storage ring, it was observed that the vacuum pressure around the RF window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. An equivalent physical modeling was developed using a finite-difference time-domain (FDTD) simulation and it revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Three superconducting RF cavities were commissioned with electron beam in way of one by one during the last 3 years, and now PLS-II is in user service on the way of beam current to 400mA, the target of PLS-II. The cavities and cryomodules were prepared with SRF standard technology and procedures, then vertical test, windows conditioning, cryogenic test in each cryomodule, horizontal power test, conditioning, and commissioning without and with beam at PLS-II tunnel by collaboration with industries. All the cavities showed stable performances as good as not-observing any RF instability from cavities, couplers and windows up to 400 mA beam store, but observing several cavity quenches and minor vacuum bursts by abrupt power with control and human errors. The initial beam current for user run were recorded as 150 mA with one cavity, 280 mA with two cavities and 320 mA with three cavities. The 400 mA beam was also achieved with two cavities by decay mode and also with three cavities by top-up mode. The stabilities of RF amplitude and phase are good enough not to induce beam instabilities., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The Advanced Photon Source and other existing storage ring light sources are contemplating replacing an existing, operating storage ring with a multi-bend achromat lattice. One issue is that existing light sources have large user communities who are greatly inconvenienced by extended shutdowns. Hence, there will be a premium placed on rapid commissioning of the new lattice. To better understand the possibilities, we undertook a survey of recent commissioning experience at third-generation light sources. We present a summary of that survey here., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The measurement and the control of the coupling is essential to maximize synchrotron performance. Small coupling is required for small vertical size and high brightness. The Pohang Light Source has a 2.5 GeV storage ring and its coupling constant is measured as about 1%. In addition to errors at quadrupole or sextupole, the condition varying of the insertion device affects the coupling. The coupling for various condition is measured by the resonance and the response matrix and compared with the beam size and the lifetime. The correction and the control of the coupling is presented., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, with a focus on operational techniques and performance., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan