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Detection of a Single Lithium Atom in a Magneto-optical Trap
한혁상,윤석찬,조동현 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.11
We report fluorescence detection of a single 7Li atom in a magneto-optical trap (MOT). We use a double MOT system, which allows us to control the loading rate of the second MOT by simply turning on or off the first MOT and to use a modest magnetic field gradient of 46 G/cm. A single atom is trapped for longer than 100 s. The fluorescence from the trapped atoms is imaged onto an electron-multiplying charge-coupled device with a unit magnification factor by a pair of aspheric lenses. The numerical aperture of the objective lens is 0.22 with a collecting efficiency of 1.3%. Accumulated fluorescence is extracted by integrating the signal over a region of interest of 500×350 μm2. For a 200-ms exposure time, the fluorescence count from a single atom is 8.8×103 and the background count from scattered MOT beams is 6.8 × 104. We actively stabilize the trap beam power to reduce the noise and the measured noise is two times the statistical noise. Overall signal-to-noise ratio of the single-atom detection is 37/ p Hz. We also describe a modification of the system that is adapted to an experimental configuration for quantum manipulation of single atoms in a 1D optical lattice.
한혁상 한국비파괴검사학회 1992 한국비파괴검사학회지 Vol.12 No.1
The purpose of this report is to obtain a practical expression for estimating the compressive strength of concrete using the non-destructive method of testing combining rebound number and ultrasonic pulse velocity at the construction sites for obtaining highest accurracy in predicting the compressive strength.
강변여과수와 천부 지하수를 이용하는 지하수 열펌프시스템의 적정유량
한정상,한혁상,한찬,전재수,김형수,Hahn, Jeong-Sang,Han, Hyuk-Sang,Hahn, Chan,Jeon, Jae-Soo,Kim, Hyong-Soo 대한자원환경지질학회 2007 자원환경지질 Vol.40 No.6
지하수열펌프시스템(GWHP)은 지원열펌프시스템(GSHP)가운데 성능이 가장 우수하며 저온의 천부지하수열을 이용하는 시스템이다. GWHP시스템은 지중연결 열펌프시스템(GCHP)에 비해 최대 블록부하와 전 시스템 성능에 부합되는 지하수유량을 기준으로 하여 설계를 하며 최적 지하수유량은 해당지역의 지하수온도, 판형열교환기의 규격과 전체펌프와 배관류의 전 양정고에 따라 결정한다. 대체적으로 전형적인 빌딩루프순환수의 필요유량은 1RT당 $9.5{\sim}11.4lpm$ 정도인데 비해 GWHP시스템이 필요로 하는 최적 지하수유량은 이보다 꿜씬 적은 $3.8{\sim}9.5lpm$정도이다. The groundwater heat pump system(GWHP) is one of the most efficient ground source heat pump system(GSHP) which uses low grade and shallow geothermal energy for cooling and heating purpose. The GWHP system shall be designed properly based on peak block load performance and optimum pumping rate of groundwater comparable to ground coupled heat pump system(GCHP). The optimum pumping rate depends on groundwater temperature at a specific site, size of plate heat exchanger, and total head loss occurred by whole system comprising pumps and pipings. The required optimum flow rates of the system per RT are ranged from 3.8 to 9.8lpm being less than the typical building loop flow of 9.5 to 11.4lpm.
수주지열정(SCW)을 이용한 천부지열 냉난방시스템 설계지침
한정상,한혁상,한찬,김형수,전재수,Hahn, Jeong-Sang,Han, Hyuk-Sang,Hahn, Chan,Kim, Hyong-Soo,Jeon, Jae-Soo 대한자원환경지질학회 2006 자원환경지질 Vol.39 No.5
For the reasonable use of low grade-shallow geothermal energy by Standing Column Well(SCW) system, the basic requirements are depth-wise increase of earth temperature like $2^{\circ}C$ per every 100m depth, sufficient amount of groundwater production being about 10 to 30% of the design flow rate of GSHP with good water quality and moderate temperature, and non-collapsing of borehole wall during reinjection of circulating water into the SCW. A closed loop type-vertical ground heat exchanger(GHEX) with $100{\sim}150m$ deep can supply geothermal energy of 2 to 3 RT but a SCW with $400{\sim}500m$ deep can provide $30{\sim}40RT$ being equivalent to 10 to 15 numbers of GHEX as well requires smaller space. Being considered as an alternative of vertical GHEX, many numbers of SCW have been widely constructed in whole country without any account for site specific hydrogeologic and geothermal characteristics. When those are designed and constructed under the base of insufficient knowledges of hydrgeothermal properties of the relevant specific site as our current situations, a bad reputation will be created and it will hamper a rational utilization of geothermal energy using SCW in the near future. This paper is prepared for providing a guideline of SCW design comportable to our hydrogeothermal system. 내 수문지열계 가운데 수주지열정(SCW)시스템을 합리적으로 설치이용할 수 있는 조건들은 심도별 지온증가율이 명확하고($2^{\circ}C/100m$심도), 기존의 지하수 열펌프가 필요로 하는 순환수의 유량에 비해 최소 $10{\sim}30%$의 중온의 심부지하수가 산출될 수 있어야 하며, 순환수를 공내로 재주입시 공내붕괴가 일어나지 않는 견고한 암석들이 존재 하여야 한다. 수주지열정의 1개공당 굴착심도는 평균 $400{\sim}500m$이며, 이로 부터 개발가능한 지열에너지는 공당 약 $30{\sim}40RT$ 규모인데 비해 1개 수직지중열교환기가 공급가능한 지열에너지는 $2{\sim}3RT$ 정도이다. 즉 수주지열정 1개공은 $10{\sim}15$개의 수직지중열교환기 역할을 한다. 따라서 이 방식은 수직루프 설치장소의 공간 문제를 해소할 수 있는 유일한 대안으로 인식되어, 현재 전국 각지에서 많은 수의 SCW들이 무분별 하게 비과학적으로 설치되고 있다. 이와 같이 해당지역 수문지열계의 수리 지질학적인 특성과 열적인 특성을 명확히 파악하지 않은 상태에서 수주지열정을 설계 시공하는 경우에 나타날 문제점들은 추후 합리적인 천부지열 개발 이용에 지대한 장애요인이 될 것이다. 따라서 본고는 국내 수문지열계에 적합한 수주지열정을 설계 하는데 있어 필요한 일종의 지침서를 제시하기 위해 작성되었다.
최재민,김휘동,한혁상,조동현 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.4
We investigate the possibility of detecting atoms in a 1D optical lattice with the nearest-site resolution by using a magnetic resonance technique. A superimposed magnetic field gradient introduces a position-dependent Zeeman shift to label each site. Among the line-broadening mechanisms, we focus on sideband transitions between the motional states of the lower and the upper hyperfine levels. In addition to the sidebands of the axial motion induced by the field gradient itself, we consider those of the transverse motion induced by field misalignments with respect to the optical lattice. Parameters that determine the sideband strengths are identified in a manner analogous to the Lamb-Dicke parameter. The analysis shows that it is advantageous to use light and cold atoms in a deep optical potential well. An explicit expression for the lineshape of the hyperfine transition is obtained. We use it to calculate lineshapes for a cesium and a lithium atom in a typical optical lattice as well as those for the previously reported experiments using cesium atoms.