The small-angle X-ray scattering (SAXS) beamline BL4C1 at the 2.5 GeV storage ring of the Pohang Accelerator Laboratory (PAL) has been in its first year of operation since August 2000. During this first stage it could meet the basic requirements of the rapidly growing domestic SAXS user community, which has been carrying out measurements mainly on various polymer systems. The X-ray source is a bending magnet which produces white radiation with a critical energy of 5.5 keV. A synthetic double multilayer monochromator selects quasi-monochromatic radiation with a bandwidth of ca. 1.5%. This relatively low degree of monochromatization is sufficient for most SAXS measurements and allows a considerably higher flux at the sample as compared to monochromators using single crystals. Higher harmonics from the monochromator are rejected by reflection from a flat mirror, and a slit system is installed for collimation. A charge-coupled device (CCD) system, two one-dimensional photodiode arrays (PDA) and imaging plates (IP) are available as detectors. The overall performance of the beamline optics and of the detector systems has been checked using various standard samples. While the CCD and PDA detectors are well-suited for diffraction measurements, they give unsatisfactory data from weakly scattering samples, due to their high intrinsic noise. By using the IP system smooth scattering curves could be obtained in a wide dynamic range. In the second stage, starting from August 2001, the beamline will be upgraded with additional slits, focusing optics and gas-filled proportional detectors.

ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U.S. scientists. The present status and first results are described

No abstract

Onychomycosis, or fungal infection of the nail, is a disease seen frequently in clinical settings. However, the rates of positive identification using potassium hydroxide preparations or fungal cultures are relatively low. Precise diagnosis is possible via histopathologic examination to monitor the existence of fungus and performance of a fungal culture for confirmation. Phase-contrast hard X-ray microscopy using synchrotron radiation provides 70-nm spatial resolution and enables imaging of minute internal cellular structures. This study confirms the feasibility of diagnosing onychomycosis using a phase-contrast hard X-ray microscope developed at 1B2 beam line using a Pohang light source.

The higher order modes (HOM's) of RF cavities at the Pohang Light Source (PLS) storage ring cause longitudinal coupled bunch mode instabilities. A longitudinal feedback system (LFS) is introduced to cure these instabilities. As a key component of the LFS, there is a single-ridged waveguide-overloaded cavity for a longitudinal bunch-by-bunch LFS kicker. Since the RF frequency is 500 MHz, the bandwidth of this kicker should be wider than 250 MHz to damp any coupled bunch mode. Also, a higher shunt impedance of the kicker is selected to use a lower power amplifier. One aluminum kicker is fabricated, and the bandwidth, HOM's, and the shunt impedance of the kicker are measured with a network analyzer. This kicker has several different features from the LFS kicker for DA8NE. First of all, there are four input/output ports to obtain a wider bandwidth. Second, there is a nose cone to obtain a higher shunt impedance. Third, the symmetric frequency response of the shunt impedance around the central frequency is provided. Finally, low beam coupling power (4 W per port at 400 mA) is obtained. According to the simulation result by the high frequency structure simulator (HFSS) code, we obtained the high shunt impedance of 621.3 (transit time factor considered value) and the wide bandwidth of 255 MHz. These are compared with the measured result.Index Terms-Coupled bunch mode instability, HOM, longitudinal feedback system kicker, wake fields.