• 한국건축시공학회지
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• 제12권6호
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• pp.566-574
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• 2012

To address the problem of global warming, consumption of cement, the main material of concrete, should be decreased. Unfortunately, when industrial by-products are used in large quantities as admixture, the early age strength of concrete will be decreased, reducing its viability for use in concrete structures. Therefore, in this study, the application of an ionization accelerator and alkaline activator as addition agent of superplasticizer were investigated to secure a similar early age strength to that of normal concrete, thus increasing the viability of low cement concrete. Through the investigation, it was found that specimens that used a combination of Alkaline-activator (Na2Sio3) and ionization accelerator (Amine) had the highest early and long-age compressive strength. From this, we can determine an appropriate range of application of superplasticizer to improve early-age compressive strength of low cement concrete.

• 대한디지털의료영상학회논문지
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• 제12권1호
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• pp.51-58
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• 2010

Ionization chambers often exhibit a stem effect, caused by interactions of radiation with air near the chamber end, or with dielectric in the chamber stem or cable. In this study measured stem effect correction factor for length of ionization chamber from medical linear accelerator recommend to with the use of stem correction method. For a model of the Farmer-type chamber, were used to calculate the beam quality correction factor. These interactions contribute to the apparent measured exposure. Additionally, it needs to consider ionization chamber use of small volume and stem effect of cable by a large field. Linear accelerator generated photons energy and increased dose repeatedly measured by using stem correction method. Stem effect was dependence of the energy and increases with photon energy conditions improved of beam quality. In conclusion, stem effect correction factor was measured within 0.4% calculated according to the exposures stem length and also supposed to determined below 1% of another stem correction method.

• Journal of the Optical Society of Korea
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• 제10권4호
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• pp.157-161
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• 2006

A synchrotron light source is useful in the vacuum ultraviolet (VUV) regime for olecular spectroscopy, such as photo absorption, photoionization, and dissociative hotoionization. In this research, we used a double-ion chamber (DIC) to measure hotoabsorption cross sections of a NO molecule in the wavelength range from 90 to 135 nm of 3B1 beam-line of the Pohang synchrotron light source with the resolution of the onochromator being 0.06 nm. The appearance wavelength for ionization was measured to be $134.19{\pm}0.09nm$ that is placed in the middle of the reported values though they don't agree with each other within the relative error limits. The auxiliary experimental works ave been done to test if there are any systematic error sources. The resultant ross-sections agree with previous results in general.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1370_1372
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• 2009

A conventional linear accelerator system requires a flat-topped pulse with less than $\pm$ 0.5% ripple to meet the beam energy spread requirements and to improve pulse efficiency of RF systems. A a line-type pulsed modulator is widely used in pulsed power circuits for applications such as accelerators, radar, medical radiation, or ionization systems. The high-voltage pulse generator system with an output voltage of 284 kV, a pulse width of $10{\mu}s$, and a rise time of $0.84{\mu}s$ has been designed and fabricated to drive a klystron which has 30-MW peak and 60-kW average RF output power. The high-voltage test was performed using the klystron load. This thesis describes the design and test results of high-power pulse generator system for industrial accelerator application. The experimental results were analyzed and compared with the design.

• 한국방사선학회논문지
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• 제10권1호
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• pp.15-19
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• 2016

본 연구는 선형가속기를 이용한 방사선 조사에서 선속평탄 여과판 사용 유무에 따른 산란선을 측정하고 자 한다. 산란선 측정은 전리함을 사용하였으며, 조사한 방사선의 에너지는 6 MV와 10 MV 이다. 갠트리 회전 중심에서 전리함을 15, 25, 35, 45 cm 거리에 위치시키고 선속평탄 여과판 사용 유무와 거리에 따른 산란선을 측정하였다. 각각의 에너지에 대하여 100 cGy 조사한 결과 6 MV에서 선속평탄 여과판을 사용하지 않은 것에서 65% 정도로 낮게 발생되었고, 10 MV 에서는 55% 정도로 낮게 발생되었다. 즉, 방사선 치료에서 결정 장기 주변의 선량은 선속평탄 여과판을 사용하지 않을 때 산란선이 적게 발생되어 방사선에 대한 확률적인 영향을 줄이기 위한 유용한 방법으로 판단되어진다.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4636-4643
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• 2022

A time-of-flight and energy (TOF-E) detection system for the measurement of ²³⁶U accelerator mass spectrometry (AMS) has been developed to improve the ²³⁶U/²³⁸U sensitivity at Micro Analysis Laboratory, Tandem accelerator (MALT), The University of Tokyo. With observing TOF distribution of ²³⁵U, ²³⁶U and ²³⁸U, this TOF-E detection system has clearly separated ²³⁶U from the interference of ²³⁵U and ²³⁸U when measuring three kinds of uranium standards. In addition, we have developed a novel method combining kernel-based density estimation method and multi-Gaussian fitting method to estimate the ²³⁶U/²³⁸U sensitivity of the TOF-E detection system. Using this new estimation method, 3.4 × 10^-12 of ²³⁶U/²³⁸U sensitivity and 1.9 ns of time resolution are obtained. ²³⁶U/²³⁸U sensitivity of TOF-E detection system has improved two orders of magnitude better than that of previous gas ionization chamber. Moreover, unknown species other than uranium isotopes were also observed in the measurement of a surface soil sample, which has demonstrated that TOF-E detection system has a higher sensitivity in particle identification. With its high sensibility in mass determination, this TOF-E detection system could also be used in other heavy isotope AMS.

• 한국의학물리학회지:의학물리
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• 제22권2호
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• pp.92-98
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• 2011

방사선의 출력선량계수는 모든 선량계획과 치료선량결정에 영향을 주게 되므로, 정확한 선량평가가 강조되고 있다. 저자들은 물흡수선량을 결정하는 선량프로토콜을 종전의 TG-21에서 TG-51로 전환하여 2007년부터 새로운 버전과 새로운 공동전리함으로 선량을 평가하기 위해 SSDL의 $N_k$를 $N_{dw}{^{Co-60}}$로 변환하여 적용하였다, 평가된 물흡수선량계수는 치료선량결정과 RPC의 선량모니터링을 통해 비교되었으며, 선량평가는 2% 이내를 보였지만 불안정성을 확인하게 되었으며, 선량평가과정을 후향적으로 모니터하였다. 점검결과 새 전리함의 교정계수가 -2.8% 낮은 것을 확인하고 PSDL의 물흡수선량교정계수를 구하여 출력선량계수를 구하였으며, 선량평가 결과 2010년부터 안정되었고 지속적으로 1% 이내의 오차를 나타내었다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.252-254
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• 2002

A new protocol for dosimetry in external beam radiotherapy is published by the Japan Society of Medical Physics (JSMP) in 2002. The protocol deals with proton and heavy ion beams as well as photon and electron beams, in accordance with IAEA Technical Report Series No. 398. To establish inter-institutional uniformity in proton beam dosimetry, an intercomparison program was carried out with the new protocol. The absorbed doses are measured with different cylindrical ionization chambers in a water phantom at a position of 30-mm residual range for a proton beam, that had range of 155 mm and a spread out Bragg peak (SOBP) of 60-mm width. As a result, the intercomparison showed that the use of the new protocol would improve the +/- 1.0 % (one standard deviation) and 2.7 % (maximum discrepancy) differences in absorbed doses stated by the participating institutions to +/- 0.3% and 0.9 %, respectively. The new protocol will be adopted by all of the participants.

• 한국의학물리학회지:의학물리
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• 제9권2호
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• pp.105-113
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• 1998

고에너지 광자선을 발생시키는 의료용선형가속기의 선질은 경우에 따라 변이를 가져오게 된다. 이러한 변이를 정확하게 판정하여 줄 수 있는 방사선측정법의 활용은 매우 중요하다. 보편적으로 광자선의 측정에 있어서 전리함의 사용이 아주 빈번하였으나 전자포탈영상장치(EPID)의 등장은 새로운 방사선측정법에 대한 가능성의 시작을 예견해준다. 실험은 6MV 광자선의 대칭성, Light/Radiation congruence, 그리고 Wedge filter를 통한 간편한 에너지의 변화에측과 위치의 정확도에 대하여 측정을 시행하였다. 사실 방사선측정의 대표적인 방법은 물팬톰-전리함응 이용한 모델인데 본 실험에서는 영상의 화소가 지니는 디지탈 값을 적절한 소프트웨어로 읽어내어서 데이터를 환산하여 결과를 얻었다. 선행실험에서 얻은 상대선량률을 적용하여 대칭성에서는 조사야영역이 l0$\times$10$cm^2$ 일 때 횡축과 종축에서 1.2%, 1.2%로 비교적 오차가 적었다. 그리고 Light/Radiation field congruence 여부는 횡축이 0.3%, 그리고 종축이 0.2%로서 예상한 기대값에 접근하였다. 다음으로 wedge filter를 활용한 에너지의 변이와 위치의 정확도에 대한 움직임을 알 수 있었다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.235-236
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• 2002

A Klystron powered dual photon energy electron linear accelerator 2300 C/D from Varian Associates has been installed in our center. From the radiological safety view as well as treatment planning, the output (contamination) of Bremsstrahlung Radiation with electron beam energy determined accurately. It has been found 0.5% to 4.7% with increasing the electron beam energy which is the clinically not much significant in the treatment of the malignant diseases with the treatment of electron beam.