http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Beam Characterization at the KAERI UED Beamline
Sadiq Setiniyaz,Hyun Woo Kim,In-Hyung Baek,Jinhee Nam,MoonSik Chae,Byung-Heon Han,Boris Gudkov,Kyu Ha Jang,Sunjeong Park,Sergey Miginsky,Nikolay Vinokurov,Young Uk Jeong 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.6
The UED (ultrafast electron diffraction) beamline of the KAERI’s (the Korea Atomic Energy Research Institute’s) WCI (World Class Institute) Center has been successfully commissioned. We have measured the beam emittance by using the quadrupole scan technique and the charge by using a novel measurement system we have developed. In the quadrupole scan, a larger drift distance between the quadrupole and the screen is preferred because it gives a better thin-lens approximation. A high bunch-charge beam, however, will undergo emittance growth in the long drift caused by the space-charge force. We present a method that mitigates this growth by introducing a quadrupole scan with a short drift and without using the thin-lens approximation. The quadrupole in this method is treated as a thick lens, and the emittance is extracted by using the thick-lens equations. Apart from being precise, our method can be readily applied without making any change to the beamline and has no need for a big drift space. For charge measurement, we have developed a system consisting of an in-air Faraday cup (FC) and a preamplifier. Tests performed utilizing 3.3- MeV electrons show that the system was able to measure bunches with pulse durations of tens of femtoseconds at 10 fC sensitivity.
Ultrafast Electron Diffraction Technology for Exploring Dynamics of Molecules
Kyu Ha Jang,Key Young Oang,In-Hyung Baek,Sadiq Setiniyaz,Ki-TaeLee,Young Uk Jeong,Hyunwoo Kim 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.4
With the recent successful development of X-ray free electron lasers (X-FELs), it became possible to explore sub-nano structure dynamics of materials with 100-fs temporal accuracy. Ultrafast electron diffraction (UED) can achieve similar performance at a much lower cost and on a smaller scale by using ultrashort and low-energy electron beams. The UEDs are suitable for studying thin films, surfaces, and gas samples that are difficult to study with the X-FELs. Starting from non-relativistic UEDs using low-energy electron beams of less than 100 keV, it led to the development of relativistic UEDs using a-few-MeV electron beams. These efforts have contributed to the identification of the unexplored mechanism of matter by observing the dynamics of atoms with higher temporal accuracy. Electron beam is easier to handle than X-rays, and various technologies are being developed to improve the performance of UED. We review UEDs historically based on the development of core technologies. And application researches with the UEDs will be outlined in this paper.