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감경보,조병익 한국물리학회 2021 Current Applied Physics Vol.30 No.-
The advent of high-power lasers has provided insights into laboratory high energy density (>1011 J/m3) physics. In particular, the properties of warm dense matter (WDM) with temperatures of 104–106 K and near-solid densities is a research area that has garnered significant interest recently. However, owing to the high temperatures and pressures associated with WDM, the measurement of fundamental properties is difficult, and insufficient data has been a significant setback in WDM research. Herein, we review recent developments in timeresolved X-ray absorption spectroscopy with synchrotron and X-ray free electron lasers for WDM research. Various physical properties, such as atomic bonding, electronic structures, electron–phonon coupling, and thermal conductivity of various elements in WDM conditions are investigated via this noble X-ray technique at various time scales from 100 ps to 100 fs.
Advanced materials characterization using synchrotron radiation
최준우,서정화,황충규,조병익,이동렬,장영준 한국물리학회 2021 Current Applied Physics Vol.30 No.-
Fundamental research on the basic properties (structural, chemical, electrical, magnetic, optical, etc.) of materials has led to many breakthroughs in technology development. Systematic and rigorous investigations are required to properly characterize condensed matter systems due to (i) the various competing energy terms and degrees of freedom existing in the system, and (ii) many advanced materials exhibit strong coupling between a material’s electrons with other electrons, magnetism, or the material lattice itself. In addition, the ability to measure and manipulate matter at the nanoscale has gained significance particularly owing to the recent progress in nanomaterials and nanodevices. In this sense, synchrotron radiation-based x-ray techniques are ideal tools which allow for nondestructive probing of materials characteristics. The high brilliance, highly polarized, highly collimated, pulsed, and wavelength tunable electromagnetic radiation produced from synchrotron light sources enables examining atomic and electronic structures of matter with high sensitivity. In Korea, the nation’s first synchrotron facility, the Pohang Light Source (PLS), has been providing user service since 1995, while an x-ray free electron laser (FEL) facility, PAL-XFEL, has been operating since 2017 (Fig. 1). The facilities have been instrumental in achieving breakthroughs in fundamental scientific research and technological development. In order to meet the everincreasing user demands, there are specific plans to build a 4th generation light source with a diffraction-limited storage ring at Cheongju, Korea, aiming to be operational by 2028.
Coherent transition radiation from thin targets irradiated by high intensity laser pulses
L.J. Bae,조병익 한국물리학회 2015 Current Applied Physics Vol.15 No.3
A theoretical examination on coherent transition radiations (CTR) from the surface of thin solid density target irradiated by high intensity laser is presented. The theory is extended to consider the expansion dynamics of thin foils. The motion of target surfaces leads to the modulation on the temporal structure of micro bunches in the electron beam as well as the spectrum of CTR. The spectral shifts of radiation are owing to the enhancement of electron bunch separation and the relativistic Doppler effects. The radiation power distribution is strongly affected by the temporal coherence of electron beam structure, so thus the electron temperature and velocity dispersions. With these effects accounted for, the spectral properties of coherent transition radiation can provide insights into the expansion of thin foil targets irradiated by intense laser pulse as well as the fast electron transport through it.