• Title/Summary/Keyword: helmholtz coils

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Sources of uniform and 2nd-order gradient fields for testing SQUID performance (SQUID 2차미분기 성능 평가용 균일자기장 및 2차 미분 자기장 발생원)

  • Lee, Soon-Gul
    • Progress in Superconductivity
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    • v.8 no.2
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    • pp.152-157
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    • 2007
  • Uniaxial square Helmholtz coils for testing SQUID sensors were designed and their field distributions were calculated. Optimum parameters for maximizing the uniform region in the Helmholtz mode were obtained for different uniformity tolerances. The coil system consists of 2 pairs of identical square loops, a Helmholtz pair for generating uniform fields and the other for the 2nd-order gradient fields in combination with the Helmholtz pair. Full expressions of the axial component of the field were calculated by using Biot-Savart's law. To understand the behavior of the field near the coil center, analytical expressions were obtained up to the 4th-order in the midplane and along the coil axis. The Helmholtz condition for generating uniform fields was calculated to be $d/{\alpha}=0.544505643$, where 2d is the inter-coil distance and $2{\alpha}$ is the side length of the coil square. Maximized uniform range can be obtained for a given nonuniformity tolerance by choosing $d/{\alpha}$ slightly lower than the Helmholtz condition. The pure second-order gradient field can be generated by subtracting the Helmholtz field from the field of the 2nd pair with equal magnitudes of the center fields of the two pairs. The coil system is useful for testing balance and sensitivity of SQUID gradiometers.

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Study on the evaporation of high melting temperature metal by using the manufactured electron hem gun system (전자총 시스템 제작과 이를 이용한 고융점 금속 증발에 관한 연구)

  • 정의창;노시표;김철중
    • Journal of the Korean Vacuum Society
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    • v.12 no.1
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    • pp.1-6
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    • 2003
  • An axial electron beam gun system, which emits the electron beam power of 50 kW, has been manufactured. The electron beam gun consists of two parts. One is the electron beam generation part. including the filament, cathode, and anode. The maximum beam current is 2 A and the acceleration voltage is 25 kV. The other part includes the focusing-, deflection-, and scanning coils. The beam diameter and ham trajectory can be controlled by these coils. The characteristic of each part is measured ior the optimum condition of evaporation process. Moreover, Helmholtz coil is installed inside the vacuum chamber to adjust the incident angel of the beam to the melting surface for the maximum evaporation. We report on the evaporation rates for zirconium(Zr) and gadolinium(Gd) metals which have the high melting temperatures.

Design of Magnetic Field Compensation System Model for AC Magnetic Field Shielding (교류자기장 차폐를 위한 자기장 상쇄장치 모델의 설계)

  • Choi, Hak-Yun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.7
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    • pp.78-82
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    • 2011
  • In this paper, magnetic field compensation system with an open architecture and can be installed indoors is designed and measured by fabricated. To verify the shielding effectiveness, two rectangular helmholtz coils with 3-axis are fabricated to generate magnetic field and measured magnetic field inside compensation coil for 1~60[Hz], According to measurements, AC shielding effectiveness of compensation system is 96[%] of 1[Hz], 95[%] of 30[Hz] and 90[%] of 60[Hz]. The performance of system therefore can be used as the magnetically shielded room for medical and industrial field.

The generation of Uniform High Density Plasma of Inductively Coupled Plasma Etcher Enhanced by Alternating Axial Magnetic Field (축방향 자기장의 주기적 단속을 이용한 유도결합형 플라즈마 식각장비의 고품위 플라즈마 형성)

  • 정재성;김철식
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.589-592
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    • 1998
  • The performance of inductively coupled plasma (ICP) is enhanced by axial magnetic field driven by alternating current Helmholtz coils in this work. Langmuir pobe is used to characterize the plasma, and the etching performance is demonstrated with phororesist stripping process. It is shown that its density and uniformity depends on the frequency of driving current to the magnetic field.

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Analysis of Novel Helmholtz-inductively Coupled Plasma Source and Its Application for Nano-Scale MOSFETs

  • Park, Kun-Joo;Kim, Kee-Hyun;Lee, Weon-Mook;Chae, Hee-Yeop;Han, In-Shik;Lee, Hi-Deok
    • Transactions on Electrical and Electronic Materials
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    • v.10 no.2
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    • pp.35-39
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    • 2009
  • A novel Helmholtz coil inductively coupled plasma(H-ICP) etcher is proposed and characterized for deep nano-scale CMOS technology. Various hardware tests are performed while varying key parameters such as distance between the top and bottom coils, the distance between the chamber ceiling and the wafer, and the chamber height in order to determine the optimal design of the chamber and optimal process conditions. The uniformity was significantly improved by applying the optimum conditions. The plasma density obtained with the H-ICP source was about $5{\times}10^{11}/cm^3$, and the electron temperature was about 2-3 eV. The etching selectivity for the poly-silicon gate versus the ultra-thin gate oxide was 482:1 at 10 sccm of $HeO_2$. The proposed H-ICP was successfully applied to form multiple 60-nm poly-silicon gate layers.

Swimming Microrobot Actuated by External Magnetic Field (전자기 구동 유영 마이크로로봇)

  • Byun, Dong-Hak;Kim, Jun-Young;Baek, Seung-Man;Choi, Hyun-Chul;Park, Jong-Oh;Park, Suk-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.11
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    • pp.1300-1305
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    • 2009
  • The various electromagnetic based actuation(EMA) methods have been proposed for actuating microrobot. The advantage of EMA is that it can provide wireless driving to microrobot. In this reason a lot of researchers have been focusing on the EMA driven microrobot. This paper proposed a swimming microrobot driven by external alternating magnet field which is generated by two pairs of Helmholtz coils. The microrobot has a fish-like shape and consists of a buoyant robot body, a permanent magnet, and a fin. The fin is directly linked to the permanent magnet and the magnet is swung by the alternating magnet field, which makes the propulsion and steering power of the robot. In this paper, firstly, we designed the locomotive mechanism of the microrobot boy EMA. Secondly, we set up the control system. Finally, we demonstrated the swimming robot and evaluated the performance of the microrobot by the experiments.

Construction of an Earth's Field Compensation System for the Mcasurement of. Proton Gyromagnetic Ratio (양성자 자기회전비율 측정을 위한 지자장 상쇄장치 제작)

  • 우병칠;박포규;김철기;유권상;김창석
    • Journal of the Korean Magnetics Society
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    • v.2 no.2
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    • pp.156-162
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    • 1992
  • In the measurement of proton gyromagnetic ratio by a low field cechnique, the compensation of earth's field is required to keep a zero-field space. The constant earth's fild is compensated by a cur-rent 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-vary-ing field of ${\pm}100nT$ and the constant field have been reduced to the level of ${\pm}10nT$ using the compensating system.

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Construction of Measuring System for Magnetic Properties Measurement of Azimuth Angle Sensor (방위각센서의 자기특성 측정 장치 제작)

  • Son, Derac
    • Journal of the Korean Magnetics Society
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    • v.24 no.1
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    • pp.22-27
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    • 2014
  • North indicating azimuth angle sensors have been used in airplanes, ships traditionally and nowadays employed in smart phones. For the azimuth and roll angle measurement of the sensor, 3-axis acceleration sensor was added to the 3-axis magnetic field sensor. In this work, we have constructed a measuring system for the measurement of the magnetic field and the angle uncertainty of the magnetic field sensors. Measuring system could be useful not only in non-magnetic laboratory but also in normal laboratory, we constructed small size of 3-axis Helmholtz coils for the compensation environment magnetic field (Earth magnetic field and magnetic field from building) and the generation of magnetic field for the test of magnetic field sensor. The constructed measuring system could compensate environment magnetic field below 10 nT level and generate 3-dimensional magnetic field with magnitude uncertainty of 0.2 % and angle error of $0.2^{\circ}$ within the volume of ${\pm}30mm$ diameter at center of Helmholtz coils. For the conformation of developed measuring system, We tested commercially available 3-axis magnetometer and heading sensor.

Helmholtz Coil and Performance of Magnetic Compass (인공자장발생장치와 자기 컴퍼스의 성능)

  • Ahn, Young-wha;Jeong, Kong-heun;Ahn, Jang-young;Sin, Hyeong-il
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.19 no.2
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    • pp.111-116
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    • 1983
  • In order to furnish the fundamental data for the domestic production of magnetic compass and the prescription of standardization about it in Korea, authors made the helmholtz coil and investigated the characteristics of them. Subsequently, the damping curves of T190 and T165 compasses in the helmholtz coil were measured and analyzed the performance of those compass. The results obtained are as follows; 1. The relation between electric current (I sub I) to flow in the helmholtz coils, that the thickness of coil is 1mm, diameter 1m, winding number 117, and intensity of magnetic field is presented as follows. Vertical magnetic force: Z(Gauss)=0.34+1.506 I sub(i) Horizontal magnetic force: H(Gauss)=0.183+1.506 I sub(i) 2. Period of T190 compass is longer than T165 compass in all horizontal magnetic force. In the amplitude, the former is larger than the latter above 0.08 Gauss, but this phenomenon is opposed to that below 0.08 Gauss. 3. As the porizontal magnetic force is intensive, period of magnetic compass is short, amplitude is large, and damping degree and damping factor are small. The time elapsed to the principal points of damping curve is proportional to the -0.65 power of the horizontal magnetic force.

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Characteristics of Superconductive Pb shield for a Whole Head MEG System (헬멧형 뇌자도 장치로의 활용을 위한 Pb 초전도 차폐의 특성)

  • Yu, K.K.;Kim, K.;Lee, Y.H.;Kwon, H.
    • Progress in Superconductivity
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    • v.11 no.1
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    • pp.30-35
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    • 2009
  • We have investigated the characteristics of a superconductive Pb shield for hemispherical shape and plate to improving signal-to-noise ratio(SNR) of biomagnetism. We measured the shielding factor for the position of helmet shape Pb and for changing the distance from Pb surface. To make a uniform magnetic field, a $1.5m{\times}1.5m$ set of the helmholtz coils activated at several frequencies. The shielding factor of hemispherical shape Pb was from 20 to 57 dB and of Pb plate was about $6{\sim}26dB$ as a function of distance from the lead surface. The shielding factor was rapidly reduced as increasing the distance from Pb surface. The white noise of superconductive quantum interference device(SQUID) with a superconductive shield was about $12fT/Hz^{1/2}$ at 1 Hz, $7fT/Hz^{1/2}$ at 100 Hz. The white noise was more increased about two times than conventional SQUID system without Pb shielding. An auditory signal was measured by first order gradiometer and magnetometer with Pb superconductive shield and compared the SNR. The SQUID system with Pb shield had better performance at low frequency noise level.

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