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분리형 감지기를 이용한 흐르는 물의 핵자기공명 측정연구
우병칠(B. C. Woo),김철기(C. G. Kim),박포규(P. G. Park),김창석(C. S. Kim),V. Ya. Shifrin(V. Ya. Shifrin) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.3
NMR measurement has been studied for protons in pre-polarized flowing water by a separated detector working at high field far away from the measured field region where the transition of protons is occurred by the perturbation of RF energy. The conditions for NMR signal were optimized on the amplitude and frequency of modulation field, the RF field of detector, water speed, and RF field at the measured field region. The NMR signal with the full width of 320 nT at the half maximum in Lorentzian curve and with signal to noise ratio of 10.5 was measured in the range from a few μT to mT, and its shape and amplitude were independent of the measured field intensity and its uniformity.
우병칠(B.C. Woo),박포규(P.G. Park),김철기(C.G. Kim),유권상(K.S. Ryu),김창석(C.S. Kim) 한국자기학회 1992 韓國磁氣學會誌 Vol.2 No.2
In the measurement of proton gyromagnetic ratio by a low field technique, the compensation of earth's field is required to keep a zero-field space. The constant earth's fild is compensated by a current flowing through a Helmholtz coil, whereas small time-varying component is compensated automatically by a closed loop of feedback system. A feedback amplifier, and two three-dimensional Helmholtz coils having the same coil constant have been constructed in order to compensate the earth's field. field. Preliminary test performed at the ordinary laboratory showed that the time-varying field of ± 100 nT and the constant field have been reduced to the level of ± 10 nT using the compensating system.
Establishment of KRISS Watt Balance System to Have High Uniformity Performance
김명현,김동민,우병칠,하도경,이성욱,박형순,김진희,이광철 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.7
Watt balance system is the promising equipment to determine Planck constant without accurate measurement of magnetic flux and coil length. To obtain high measurement uncertainty, uniform magnetic flux density and constant velocity control are required during the coil movement. For that KRISS watt balance system incorporates a closed-type cylindrical permanent magnet, vertical linear motor and piston guide. In this paper, the vertical actuating motor including piston guide is controlled to have constant speed and magnet assembly was fabricated to have high uniform magnetic flux density during the vertical coil movement. The velocity of moving coil was controlled within 4 × 10-3 (1σ) at the velocity of 2 mm s-1 using a linear motor and linear encoder feedback. Using 3-vertical homodyne laser interferometer the velocity ripple of coil located inside magnet is measured within the level of 7.35 × 10-3 (1σ) at the same speed. A magnet assembly, which consists of two permanent magnet rings and closed yokes, was fabricated. A flux shunt was designed for the magnet for minimizing the temperature effect. The yokes were divided into three parts: top, center, and bottom yokes. By re-machining of center outer yoke, magnetic flux density uniformity was improved. The uniformity of the magnetic field was within 3.9 × 10-4 over a vertical distance of 20 mm.