PAL, Pohang, Kyungbuk
In 1994, ESRF in Grenoble opened the era of third-generation light sources, and the first batch of third-generation machines immediately followed with ALS, Elettra, TLS, PLS, and Spring-8 in hard and soft X-ray regimes. For high brightness, these machines adopted a low-emittance storage-ring lattice and many straight sections for advanced undulators. With ever-growing user demands from materials science to life science research, many more facilities followed in this decade. The machine operations dramatically improved for more effective user services, along with technological advances in advanced diagnostics and controls, survey and alignments, top-up injections, super-conducting cavities, and in-vacuum undulators. There are now about 70 light sources in the world, and important scientific discoveries are driven from these facilities, including research resulting in a few Nobel Prizes. In this paper, we review the advancement of these third-generation machines.
Kyungpook National University, Daegu
POSTECH, Pohang, Kyungbuk
PAL, Pohang, Kyungbuk
CHEP, Daegu
We report the activities by using the pulsed neutron facility which consists of an electron linear accelerator, a water-cooled Ta target, and a 12-m time-of-flight path. It can be possible to measure the neutron total cross-sections in the neutron energy range from 0.01 eV to few hundreds eV by using the neutron time-of-flight method. A 6LiZnS(Ag) glass scintillator was used as a neutron detector. The neutron flight path from the water-cooled Ta target to the neutron detector was 12.1 m. The background level was determined by using notch-filters of Co, In, Ta, and Cd sheets. In order to reduce the gamma rays from Bremsstrahlung and those from neutron capture, we employed a neutron-gamma separation system based on their different pulse shapes. The present measurements of several samples (Dy, Nb) are in general agreement with the evaluated data in ENDF/B-VII. The resonance parameters were extracted from the transmission data from the SAMMY fitting and compared with the previous ones. We also report the isomeric yield ratios for isomeric pairs produced from photonuclear reactions by using the bremsstrahlung photons from the 70-MeV electron linac.
POSTECH, Pohang, Kyungbuk
KAPRA, Cheorwon
NFRI, Daejon
An intense L-band electron linac is now being commissioned at ACEP (Advanced Center for Electron-beam Processing in Cheorwon, Korea) for irradiation applications in collaboration with POSTECH (Pohang University of Science and Technology) and KAPRA (Korea Accelerator and Plasma Research Association). It is capable of producing 10-MeV electron beams with average 30-kW. For a high-power capability, we adopted the L-band traveling-wave structure operated with a 2π/3 mode. The RF power is supplied by the pulsed 25-MW and average 60-kW klystron with the matched pulse modulator and the inverter power supplies. The accelerating gradient is 4.2 MV/m with the beam current of 1.45 A which is fully beam-loaded condition. The solenoidal magnetic field is 700 Gauss to focus the electron beam and suppress the BBU instability. In this paper, we present commissioning status with details of the accelerator system.
POSTECH, Pohang, Kyungbuk
KAPRA, Cheorwon
NFRI, Daejon
A C-band standing-wave electron accelerator for a compact X-ray source is being commissioned at ACEP (Advanced Center for Electron-beam Processing in Cheorwon, Korea). It is capable of producing 4-MeV electron beam with pulsed 50-mA. The RF power is supplied by the 5-GHz magnetron with pulsed 1.5 MW and average 1.2 kW. The accelerating column is a bi-periodic and on-axis-coupled structure operated with π/2-mode standing-waves. It consists of 3 bunching cells, 6 normal cells and a coupling cell. As a result of cold tests, the resonant frequency of the accelerating column is 4999.17 MHz at the π/2-mode and the coupling coefficient is 0.92. The field flatness was tuned to be less than 2%. In this paper, we present commissioning status with design details of the accelerator system.