• 대한방사선방어학회:학술대회논문집
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• 2010.04a
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• pp.188-189
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• 2010

• Progress in Medical Physics
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• v.11 no.2
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• pp.123-130
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• 2000

The performance of an electrometer directly affects on the accuracy and precision in radiation dosimetry. This study is to list of the quality control for maintaining performance and to perform evaluation tests of an electrometer. Performance tests selected include proper polarizing voltages, warm-up and equalization time, leakages, long-term stability, linearity, and effect of ambient conditions. An electrometer connected with a rigid stem ionization chamber was evaluated with a Strontium-90 check device. Bias voltage was measured directly on the input socket. Equalization time is the time required for reaching threshold of charged state after the power is on or the bias voltage is changed. Pre- and post-signal leakages are defined as the accumulation of signal with no exposure and after exposure, respectively. Over three months period, the electrometer's long-term stability was measured by comparison of the temperature-pressure corrected readings. Linearity was expressed as the deviation of readings from multiple short exposures from one continuous exposure. Effect of ambient conditions was expressed as the zero drift of the electrometer over 17-34$^{\circ}C$ temperature ranges. For two nominal values, 300 and 500 volts, measured voltages were lower by 2.5 and 5.8%, respectively. The warm-up time, 20 minutes, was longer than the lamp time by 9 minutes and the equalization time was less than 1 minute. Without exposure, the zero-drift was 0.002 scale-unit in 15 minutes and the leakage after 10 minutes exposure was minimal. The IQ-4 was stable over 99.4% for three-month periods. Deviation from the linearity was 0.9% for measurement scale, 0.000-9.991. Over 17-34$^{\circ}C$ temperature range, the zero-drift was minimal, less than 0.2%. For a clinically-used electrometer, a list for the basic peformance evaluations is proposed. By running this program, the measurement error using an electrometer can be reduced and in turn the improvement in accuracy and precision of radiation dosimetry can be achieved.

• Journal of Radiation Protection and Research
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• v.9 no.1
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• pp.11-18
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• 1984

A Standard gamma-ray ionization chamber system was developed with a well type ionization chamber and micro current measuring circuit. Micro current was measured by the automatic Townsend balance with stepwise compensation method. For gamma emitting nuclides such as $^{241}Am,\;^{133}Ba,\;^{60}Co,\;^{134}Cs,\;^{137}Cs,\;and\;^{22}Na$ relative calibration factors to $^{226}Ra$ reference source were calculated and detection .efficiency curve was determined as a fudnction of gamma energy.

• Journal of Radiation Protection and Research
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• v.16 no.2
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• pp.7-16
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• 1991

Measurement of Co-60 gamma rays has been made for establishment of exposure standard and analyze it's overall uncertainties. Exposure rate determined by the charge mode method using vibrating reed amplifier with cylinderical type cavity chamber. The values of a variety of physical constants and the correction factors are evaluated. The resulting exposure rate is 690.81 R/h at the distance of 1m from the source and the related uncertainties is ${\pm}0.8%$

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.13-16
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• 1990

코로나 예비전리를 이용한 KrF 레이저의 장펄스화를 위해 동축형 4단 펄스정형회로 (PFN)를 구성해서 용량이행형의 회로에 인덕턴스가 부가된 방식의 전류, 전압을 비교하여 PFN을 동축형으로 제작함으로 인한 Stray Capacitance (Cs)의 존재로 인해 좋은 효율의 장펄스화를 이루어짐을 밝혔다. 구성된 PFN을 절연유에 넣어 충전전압 15kV, N2 55Torr에서 330ns 펄스폭의 전류파형을 측정했다.

• 전기의세계
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• v.29 no.6
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• pp.349-353
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• 1980

본고에서는 기체중에서 전자의 전이과정을 관찰하기 위하여 많이 적용되어지는 방법에 대해서 기초적인 사항만 언급을 하였으나 이러한 technique를 사용함으로써 전하의 공간적인 분포상태를 파악할 수 있으며 avalanch의 전자나 이온의 이동으로 인하여 외부회로에 전류를 발생시키는데 이것은 amplifier와 oscilloscope에 의하여 측정을 할 수 있다. 또한 인가한 전계의 작용으로 전자가 양극으로 이동할 때 충돌전리작용에 의하여 새로운 전자를 생성할 뿐만 아니라 여기방사작용에 의하여 광자를 생성시킨다. 이러한 광자는 photomultiplier나 image-intensifier를 사용하므로써 감지할 수 있다. 이러한 결과로부터 우리는 전이현상의 기본적인 Data 즉 전자, 양이온 및 음이온의 이동속도, 전리계수 .alpha.와 부착계수 .eta.등을 유도할 수 있다.

• Progress in Medical Physics
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• v.7 no.2
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• pp.29-40
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• 1996

We had designed and made the cylindrical ionization chamber which operated above 5 mR/h. Using commercial electrometer, we investigated the characterictic of charge collection in the ion chamber. The active volume was 190.4㎤ and overall length and diameter in the chamber was 15.5cm, 5.22cm, respectively. The chamber had three electrodes(inner, central, wall electrode). And background current was 8.39${\times}$10$\^$-14/${\pm}$1.5${\times}$10$\^$-15/A to arrange the electrodes which were coaxial in chamber axis. The collection efficiency of chamber for Cs$\^$137/ was 99.7％ when the opreating voltage was applied 400V. Comparing with the commertial dosimetry system, the exposure calibration constant was 4.531${\times}$19$\^$7/R/C. By normalizing to CS$\_$137/ the relative energy response of the chamber was 1.30 for Am$\_$24/, 1.05 for C0$\_$60/, respectively. When the irrarition tranversed to the chamber axis, the isotropic effect of the chamber was not considerable.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.1 no.1
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• pp.55-60
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• 1987

본 연구의 목적은 스펙트럼의 재흡수를 이용하여, 수은-아르곤 방전중의 63P 여기원자 농도를 결정하는 데 있다. 먼저, 평면거울을 사용한 경우의 재흡수 이론을 전개한 다음, 이를 수은-아르곤 방전에 적용시켜, 복잡한 미세구조를 갖는 수은의 visible-triplet lines에 있어서의 스펙트럼의 흡수계수와 측정된 흡수율사이의 수치적 관계를 구하였다. 이와함께, 흡수계수와 흡수원자농도사이의 관계를 이용하여, 방전관의 관벽온도를 변화시킨 경우와 방전전류를 변화시킨 경우에 있어서, 측정 흡수율에 상응하는 수은의 63P 여기원자 농도를 구하였고 다음과 같은 결과를 얻었다. ⅰ) 측정범위내에서 준안정원자의 농도는 63P1 상태의 농도보다 높다. ⅱ) 방전전류를 증가시킴에 따라 435.8[nm]의 재흡수가 급격히 증가하고, 그 결과 63P1 여기상태의 농도는 준안정원자에 비해 상대적으로 높은 증가속도를 보인다. ⅲ) 방전전류 증가시 준안정원자와 전자사이의 충돌이 빈번해져서 준안정원자의 증가속도가 둔화하는 대신 축적여기 또는 전리의 확률이 높아진다.

• Electrical & Electronic Materials
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• v.6 no.6
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• pp.524-535
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• 1993

본 연구에서는 SF$_{6}$가스의 전자이동속도를 더블히트파이프 실험장치를 이용하여 유도전류법에 의해 실험적으로 측정하였다. 그리고 전자수송계수의 정량적인 산출은 볼츠만 수송 방정식의 Backward-Prolongation을 이용하여 계산하고 해석하였다. 이때 전자에너지 분포함수와 전리 및 부착계수를 구하고 운동량변환단면적을 결정하였다. 그리고 실험적으로 측정된 SF$_{6}$가스의 전자이동속도와 계산된 전자수송계수를 비교 검토하여 해석함으로서 절연체의 기초적인 물성자료로 사용할 수 있다.

• Progress in Medical Physics
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• v.16 no.3
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• pp.111-115
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• 2005

We have designed the multi channel detector for the quality assurance of clinical photon beams. The detector was composed of solid phantom inserted by six plane-parallel ionization chambers at different depth. The chamber as a mini plane parallel chamber was made of carbon coated microfilms. In this study the electrical characteristics of the six chambers in the solid phantom were evaluated using 6 MV photon beam. The leakage currents were less than 0.5 pA, reproducibility was less than 0.5$\%$, linearity was less than 0.5$\%$, and dose rate effect was less than 0.7$\%$. In addition the effect of dose variation from other chambers was estimated to maximum 0.8$\%$ approximately. The developed detector can be used for quality determination in output dosimetry or measurement of percentage depth dose approximately for clinical photon beam.