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The Korea Atomic Energy Research Institute (KAERI) has been designing several 3 MeV S-band RF electron linear accelerators (linacs) for non-destructive testing. Until now, the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half cell. To accelerate electron beams more gently, recently, we increased the total number of bunching cells from 1.5 to 2.5. In this paper, we describe design concepts and detailed optimization processes of a 3 MeV linac with the 2.5 bunching cells to optimize RF parameters such as the quality factor, resonance frequency, and uniformity of electric field distribution along the linac. Lastly, we will discuss the application of 3 MeV linac., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Recently, the demand for a new advanced synchrotron light source in Korea is rapidly growing. Six local governments in Korea would like to host the new synchrotron light source project in their own provinces. The new advanced synchrotron light source will be the Diffraction-Limited Storage Ring (DLSR), which is based on the Multi-Bend Achromat (MBA) lattice. For the new synchrotron light source, we would like to build a special 60-m long coherent undulator beamline, which can deliver high-intensity coherent radiation at the hard X-ray region. To design the coherent undulator beamline, we have performed numerous beam dynamics simulations with GENESIS and SIMPLEX codes. In this paper, we report design concepts and those simulation results for the coherent undulator beamline., Proceedings of the 39th Free Electron Laser Conference, FEL2019, Hamburg, Germany

Recently, RTX has been developing a 6/4 MeV European S-band (= 2998 MHz) industrial linac by using a magnetron with a low RF power of about 3 MW for container inspection system (CIS). Its accelerating structure is designed to operate in π/2 mode by coupling 6 accelerating cells together through 5 side-coupled cells. In CIS, high dose rate X-rays from MeV-energy electron beam has been used to detect the possible presence of contrabands in cargoes or truck containers. To determine a dose rate output, the X-ray dose rate can be simulated by using FLUKA Monte Carlo simulation. The aim of this work was to study the effects of thickness of X-ray target on dose rate as well as X-ray dose map at 1.0 m away from the X-ray target. This study gives the thickness of target in which the dose rate can be highest and electron beam current can be lowest., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Ultrafast Electron Microscopy (UEM) is a powerful tool to observe ultrafast dynamical processes in sample materials at the atomic level. By collaborating with KRISS and GIST, the future accelerator R team at KAERI has been developing a UEM facility based on a photo-emission S-band (=2856 MHz) RF gun. Recently, we have added an alpha magnet in the beamline layout of the UEM to improve beam qualities such as emittance, divergence, energy spread, and bunch length. To achieve high spatial and time resolutions, we have been optimizing those beam parameters and other machine parameters by performing numerous ASTRA and ELEGANT code simulations. In this paper, we describe our ASTRA and ELEGANT code optimizations to obtain high-quality beam parameters for the UEM facility with a photo-emission S-band RF gun and an alpha magnet., Proceedings of the North American Particle Accelerator Conference, NAPAC2019, Lansing, MI, USA

Recently, there has been discussions about the need for the next-generation synchrotron light source facility in Korea. The facility in consideration is composed of a super-conducting linear accelerator for the injector, a storage ring for the EUV and soft X-rays, and a main storage ring for hard X-rays. In this study, design concepts of the soft X-ray storage ring is presented. To effectively utilize the small space allocated for the soft X-ray storage ring, a compact storage ring is taken into account. The compact storage ring is a synchrotron accelerator of which diameter is shorter than the length of injector beamline. In this paper, we report design concepts and optimization of the compact storage ring for the EUV and soft X-ray users. The lattice of the storage ring is modelled by utilizing ELEGANT simulation code to optimize beam parameters and performance of the ring., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Korea Atomic Energy Research Institute (KAERI) has been operating a 20 MeV superconducting RF linear accelerator (SRF LINAC) to conduct research on atom/nuclear reaction using neutron Time-Of-Flight (nTOF). It can accelerate electron beams up to 20 MeV with 1 kW continuous wave (CW) operation mode. Unfortunately, this machine has been aged over 15 years that brings about considerably difficulty in normal operation due to the performance degradation of sub-systems. To improve the operation condition of 20 MeV SRF LINAC, we has been carrying out an upgrade project with replacement and repair of old sub-systems from 2018. This paper describes a design study of Low-Level RF (LLRF) feedback system to raise the stability and acceleration efficiency of the electric field generated in the superconducting RF cavity structure in 20 MeV SRF LINAC., Proceedings of the North American Particle Accelerator Conference, NAPAC2019, Lansing, MI, USA

Recently, demands on low energy electron linear accelerators (linacs) for industrial applications are rapidly growing. Their beam energies are lower than 20 MeV, and they require a compact, cheap, and stable accelerator system. For the Container Inspection System (CIS), KAERI successfully developed a 9/6 MeV American S-band (= 2856 MHz) linac with a 5 MW klystron in 2013. To reduce the cost of the RF source, recently, KAERI and RTX also have been developing another 9/6 MeV European S-band (= 2998 MHz) linac by using a magnetron with a lower RF power of about 3.1 MW. Its accelerating structure is designed to be operated in π/2 mode by coupling 13 accelerating cells together through 12 side-coupling cells. The CST Microwave Studio is used for electromagnetic simulations and optimization of the accelerating structure. After various optimizations, a shunt impedance of 84 MΩ/m is obtained at π/2 mode frequency of 2998.31 MHz. In this paper, we describe design concept, optimization, and RF measurement of the new 9/6 MeV European S-band linac structure. Then, we compare it with our old American S-band linac structure., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Ultrafast Electron Microscopy (UEM) can provide snapshot images of a dynamic process in samples with an ultrafast time resolution, which is shorter than picosecond. The Future Accelerator R&D Team at KAERI has been preparing a UEM facility with a photo-emission S-band (= 2856 MHz) RF gun by collaborating with GIST and KRISS. To achieve a higher spatial resolution as well as a higher time resolution, the transverse beam emittance, beam divergence, and energy spread should be smaller, and the bunch length should be shorter. Beam dynamics simulations with ASTRA code is used to optimize those beam parameters in the RF gun. In this paper, we describe ASTRA optimizations of the S-band RF gun to achieve high spatial-temporal resolutions for the UEM facility., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The Korea Atomic Energy Research Institute (KAERI) has been developing several 9/6 MeV dual energy S-band RF electron linear accelerators (linacs) for non-destructive testing such as container inspection system. Until now the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half-cell. The optimization of Q-factor and flatness of electric field along the linac structure can be obtained by adjusting diameters of bunching and power coupling cells. By adjusting gap of the first side-coupling cell, we can optimize the field ratio between the bunching cells and normal accelerating cells. In this paper, we describe design concepts of a 9/6 MeV linac with 1.5 bunching cells as well as optimization of RF parameters such as the quality factor, resonance frequency, and electric field distribution., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

There are growing demands on low energy electron linear accelerator (linac) for industrial applications. Most of industrial electron linacs require a compact structure and limited undesirable neutron production to avoid huge lead shielding. Radiation Technology eXcellence (RTX) and Korea Atomic Energy Research Institute (KAERI) have developed a 6 MeV compact side-coupled linac by using 2998 MHz European S-band RF technology to meet those requirements. To design the linac structure, the 3D CST MICROWAVE STUDIO (CST-MWS) was used for various electromagnetic simulations, and ASTRA code was used for particle beam dynamics simulations. After various optimizations, the shunt impedance of 61 MΩ/m is obtained at 2998.38 MHz. With a peak RF power of 2.2 MW and a 47 cm-long structure, electron beam with a peak current of 150 mA can be accelerated from 25 keV to 6 MeV. For the industrial linac, the electron beam spotsize at an X-ray target, located 5 cm downstream of the linac structure exit should be smaller than 2 mm (FW). In addition, it can supply an X-ray dose rate of 8 Gy/min at 1 m after the X-ray target. In this paper, we describe the design concepts and optimization of the 2998 MHz side-coupled industrial linac structure., Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA

Recently, there is a need of X-ray inspection system around the world to combat terrorism, drug and weapons smuggling, illegal immigration, and trade fraud. A compact standing wave (SW) linear accelerator (linac) for container X-ray inspection system has been produced at Radiation Technology eXcellence (RTX) to meet this growing need. The RF accelerating structure uses standing wave side-coupled structure fed by a 5 MW e2v magnetron with frequency of 2856 MHz. The electrons are accelerated from DC gun with energy of 25 keV to the final energy of 6 or 9 MeV at the X-ray target and generate X-ray with the dose rate of 8 Gy/min at 1 m after X-ray target. In this paper, we describe the design and optimization of side-coupled RF structure operating at π/2 mode. The beam dynamic of particle along the RF structure is also included in this paper by using ASTRA code., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The Radiation Equipment Research Division of the Korea Atomic Energy Research Institute has been op-erating a 10 MeV RF electron linear accelerator, which is used for electron beam irradiation. The beam power and energy of the RF electron linear accelerator are 10 kW and 10 MeV. The accelerator is composed of an electron gun, an S-band (= 2856 MHz) accelerating structure, a klystron, electromagnetic solenoids, a scanning electromagnet, an RF driver, a modulator, and a chiller. The linac components have deteriorated due to a long operation time of 9 years. In this paper, we described Experimental Physics and Industrial Control System (EPICS) to control ODA magnet power sup-plies for solenoids and steering magnets of the 10 MeV electron beam irradiation accelerator., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

Design features and some past experimental results are presented for a sub-THz wave source employing the Advanced Photon Source's RF thermionic electron gun. The setup includes a compact alpha-magnet, four quadrupoles, a novel radiator, a THz transport line, and THz diagnostics. The radiator is composed of a dielectric-free, planar, over-sized structure with gratings. The gratings are integrated into a combined horn antenna and ~90° permanent bending magnet. The magnetic lattice enables operation in different modes, including conversion to a flat beam for efficient interaction with the radiating structure. The experiment described demonstrated the generation of narrow bandwidth THz radiation from a compact, laser and undulator-free, table-top system. This concept could be scaled to create a THz-sub-THz source capable of operating in long-pulse, multi-bunch, and CW modes. Additionally, the system can be used to remove unwanted time-dependent energy variations in longitudinally compressed electron bunches or for various time-dependent beam diagnostics. Plans for future experiments and upgrades are also discussed., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

An RF-photogun-based linear accelerator for ultra-short electron beam generation is under construction at Korea Atomic Energy Research Institute (KAERI). This facility are mainly composed of an 1.5 cell S-band (2856 MHz) RF gun, a travelling wave type linac 3 m long and 90-degree achromatic bends. The emitted electron beams are accelerated in high RF field to ~ 3 MeV. The electrons can be deflected by a first bending magnet installed right after the RF gun. Each beamline has second bending magnet similar to the first one and three quadrupoles between the bending magnets. Two bending and three quadrupole magnets compose the 90-degree achromatic bend. The deflected electron beams will be used for ultrafast electron diffraction (UED) experiments. We have performed computer simulation using ASTRA code to investigate the electron beam dynamics in the system with the input data of bead tested gun electric field distribution and the magnetic fields of the magnets. We will present the simulated and experimental electron beam parameters., Proceedings of the 37th International Free Electron Laser Conference, FEL2015, Daejeon, Republic of Korea

Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The Radiation Instrumentation Research Division of Korea Atomic Energy Research Institute is developing a 2856 MHz dual energy [9, 6 MeV] s-band RF electron linear accelerator for security inspection. The s-band dual energy electron accelerator generates dual x-ray energy by irradiating a bunched electron beam from the cavity to a tungsten target. By detecting an x-ray, the cargo security inspection system can distinguish between organic and inorganic materials. Synchronization of the resonant frequency between the cavity and RF driver is an important factor for the stable operation of an accelerator. With a low RF driver power using the AFC, stable accelerator operations and a uniform output beam power can be obtained. This indicates that an accurate cargo inspection is possible. We used phase a frequency detector that can detect a wide frequency band and synchronize the resonance frequency between the RF driver and cavity. In this paper, we introduce a more advanced AFC system than a conventional AFC system., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The X-band RF linear accelerators (LINAC’s) are popular for medical application due to its compactness. To increase the precision of treatment accuracy under circumstance in which the LINAC is mounted on an apparatus such as gantry frame or robot-arm; this is an advantage as the weight and size are more reduced. It is a 9.3 GHz magnetron with the most readily available RF generator in the X-band frequencies from 8 GHz to 12 GHz and the magnetron is mainly used for the source of the RF power in a compact LINAC. The average power of the magnetron at 9.3~GHz is generally a few MW and this amount could provide a sufficient radiation dose-rate for tumour therapy. KAERI has been developing a new compact 9.3 GHz X-band electron LINAC for a cancer treatment system. The maximum energy of the electron beam is 6 MeV and the average beam power at the tungsten target is about 1 kW. In this paper, we describe the status of development of the 6 MeV X-band LINAC at KAERI., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

We are building a low energy electron storage ring that has many desirable properties, such as varying momentum compaction factor, damping partition numbers, favorable betatron tunes for multiturn accumulations, and excellent dynamic aperture. This storage ring can be used for debunching rf linac beams in one turn, for compression of linac pulses, and more importantly for a compact photon source based on inverse Compton scattering of laser beams., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

At the Indiana University Cyclotron Facility (IUCF), we are developing a new XFEL concept, which is based on the Compton scattering and the laser undulator instead of the conventional magnetic undulator. Since the period of the laser undulator is only about 500 nm, the coherent hard X-rays can be generated by using a compact electron accelerator with a beam energy of about 50 MeV. In this paper, we report an estimation of the energy spread growths due to the Compton scattering itself and their impacts on the XFEL lasing in the laser undulator based XFEL concept., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The Advanced eLectron-PHoton fAcility (ALPHA) is under construction to support Crane Naval Center¿s radiation effect testing program. This paper reports the design of injection and extraction beamlines for the ALPHA and discusses the nonlinear beam spreader which is used to convert transverse Gaussian beam distribution into uniform rectangular beam distribution., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

In bunch compressors for SASE-FEL facilities, the projected transverse emittance can be diluted by magnetic multipole component errors in dipoles and dipole misalignments as well as by coherent synchrotron radiation (CSR). In this paper, we describe the multipole field tolerances and the misalignment tolerances of the first bunch compressor (BC2) for the TESLA Test Facility Phase-2 (TTF-2).