Seong-Hun Jeong

A sub-micrometer resolution hard X-ray microprobe system of BL8C at Pohang Light Source.

A microprobe system has been installed on the nanoprobe/XAFS beamline (BL8C) at PLS-II, South Korea. Owing to the reproducible switch of the gap of the in-vacuum undulator (IVU), the intense and brilliant hard X-ray beam of an IVU can be used in X-ray fluorescence (XRF) and X-ray absorption fine-structure (XAFS) experiments. For high-spatial-resolution microprobe experiments a Kirkpatrick-Baez mirror system has been used to focus the millimeter-sized X-ray beam to a micrometer-sized beam. The performance of this system was examined by a combination of micro-XRF imaging and micro-XAFS of a beetle wing. These results indicate that the microprobe system of the BL8C can be used to obtain the distributions of trace elements and chemical and structural information of complex materials.

Design of Switching Magnet for 20-MeV Beamlines at PEFP

The PEFP (Proton Engineering Frontier Project) proton linac is designed to have two proton beam extraction lines at the 20-MeV and 100-MeV end. The 20-MeV extraction line is branched out into 5 beamlines by using the switching magnet. The magnet bends the proton beam by +20, +10, 0, -10, -20 degrees, respectively, and has an AC frequency of 2.5 Hz with a programmable ac power supply. It employs an H-shape, 0.45 T magnetic fields, 500 mm effective length, and 50 mm pole gap. Laminated steel of 0.5 mm reduces the eddy currents in the yoke, but some heat radiation from the stainless steel of vacuum chamber is inevitable. This paper presents the magnet specification and primary design.

Programmable Power Supply for AC Switching Magnet of Proton Accelerator

The 100 MeV PEFP (Proton Engineering Frontier Project) proton linac has two proton beam extraction lines for user experiment. Each extraction line has 5 beamlines and has 2.5 Hz operating frequency. An AC switching magnet is used to distribute the proton beam to the 5 beam-lines, An AC switching magnet is excited by PWM-controlled bipolar switching-mode converters. This converter is designed to operate at ± 350A, 2.5 Hz programmable current step output. The power supply is employed IGBT modules and has been controlled by a Digital Signal Processor (DSP). This paper describes the design and test results of the power supply.