• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.149-152
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• 2004

물 흡수선량 표준에 토대를 두고 있는 프로토콜에서는 저에너지 전자선의 경우 평행평판형이온함의 사용과 기준 선질 $^{60}$CO 감마선의 물 흡수선량 교정정수를 받은 원통형이온함을 사용하여 고에너지 전자선에서 평행평판형이온함을 교차교정하도록 권고하고 있다. 따라서 본 연구에서는 국제원자력기구의 프로토콜(IAEA TRS-398)에서 권고하고 있는 절차에 따라 저에너지 전자선에 대한 원통형이온함의 선질보정정수를 계산하고, 원통형이온함과 평행평판형이온함의 교정방법에 따른 흡수선량을 상호 비교하였다. 그 결과 전자선에너지 10 MeV 이상에서는 두 이온함간의 선량이 잘 일치하였으나 전자선에너지 6, 9 MeV에서 최대 3.3%까지 선량 차이를 보여 저에너지 전자선에서는 반드시 평형판판형이온함의 사용하여 선량측정 할 것을 권고한다. 교정방법 차이에 의한 평행평판형이온함의 선량은 서로 잘 일치하는 것으로 나타나 표준기관에서 직접 교정받은 $^{60}$Co 감마선의 물 흡수선량교정정수를 사용하여 전자선 물 흡수선량을 결정해도 큰 영향은 없을 듯하다. 또한 평행평판형이온함을 교차 교정하기 위한 전자선 에너지에 따른 흡수선량을 상호 비교한 결과 20MeV이외 12, 16 MeV의 전자선 에너지에서도 잘 일치하여 교차교정을 위한 전자선의 기준 선질에 대한 연구가 더 진행되어야 한다고 사료된다.

• ETRI Journal
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• v.13 no.2
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• pp.91-98
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• 1991

저에너지 광이온선 (broad ion beam) 을 이용한 건식식각과 박막증착에 있어서 이온선 및 증착의 조건들에 따른 영향을 살펴보았다. 저에너지 광이온선은 화합물반도체 공정 및 고융점금속의 증착, optical coating, cosputter 에 의한 초전도물질합성 등 사용범위가 넓다. 단일이온선증착과 cosputter 의 경우에 근사수식과 실험치로서 증착비 및 막의 균일도를 최적화하는 target, 웨이퍼, 이온원 사이의 기계적 설계에 대해 고찰하였다. 저에너지 이온선의 이온과 target 원자 그리고 스퍼터된 이온과 시편원자와의 물리적, 화학적 반응기구는 반응성 이온과 보조 이온선 등의 다양한 기술에 응용될 수 있을 것으로 기대된다.

• Journal of Radiation Protection and Research
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• v.33 no.2
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• pp.53-59
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• 2008

We observed DNA damages as a function of mean absorbed dose to identify the indirect effect of high-energy radiation such as x-ray. Monolayer films of lyophilized pGEM-3Zf(-) plasmid DNA deposited on tantalum foils were exposed to Al $K{\alpha}$ X-ray (1.5 keV) for 0, 3, 7 and 10 min, respectively, in a condition of ultrahigh vacuum state. We compared DNA damages by X-ray irradiation with those by 3 eV electron irradiation. X-ray photons produced low-energy electrons (mainly below 20 eV) from the tantalum foils and DNA damage was induced chiefly by these electrons. For electron beam irradiation, DNA damage was directly caused by 3 eV electrons. Irradiated DNA was analyzed by agarose gel electrophoresis and quantified by ImagaQuant program. The quantities of remained supercoiled DNA after irradiation were linearly decreased as a function of mean absorbed dose. On the other hand, the yields of nicked circular (single strand break, SSB) and interduplex crosslinked form 1 DNA were linearly increased as a function of mean absorbed dose. From this study, it was confirmed that DNA damage was also induced by low energy electrons ($0{\sim}10\;eV$) even below threshold energies for the ionization of DNA.

• Radiation Oncology Journal
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• v.7 no.1
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• pp.93-100
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• 1989

Several combinations of measuring devices and phantoms were studied to measure electron beams. Silicon Pmt junction diode was used to find the dependence of depth dose profile on field size on axis of electron beam Depths of 50, 80 and $90\%$ doses increased with the field size for small fields. For some larger fields, they were nearly constant. The smallest of field sizes over which the parameters were constant was enlarged with increase of the energy of electron beams. Depth dose distributions on axis of electron beam of $10\times10cm^2$ field were studied with several combinations of measuring devices and phantoms. Cylindrical ion chamber could not be used for measurement of surface dose, and was not convenient for measurement of near surface region of 6MeV electron. With some exceptions, parameters agreed well with those studied by different devices and phantoms. Surface dose in some energies showed $4\%$ difference between maximum and minimum. For 18MeV, depths of 80 and $90\%$ doses were considerably shallower by film than by others. Parallel-plate ion chamber with polystyrene phamtom and silicon PN junction would be recommended for measurement of central axis depth dose of electron beams with considerably large field size. It is desirable not to use cylindrical ion chamber for the purpose of measurement of surface dose or near surface region for lower energy electron beam. It is questionable that film would be recommended for measurement of dose distribution of electron with high energy like as 18MeV.

• Progress in Medical Physics
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• v.4 no.1
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• pp.29-39
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• 1993

Electron beams have found unique and complementary used in the treatment of cancer, but it's very difficult to delineate dose distribution, because of multi-collisions. Numerical solution is more usefull to describe electron distributed in tissue. A semi-empirical eqution is given for the dose at any point at various depths in water. This equation is a modificated model which was based on solutions of a general age diffusion equation. Parameters have been calulated from electron beams data with energies 6～18MeV form a LINAC for use in computerised dosimetry calculations. The depth doses and isodose curves are predicted as a function of the practical range, source skin distance and field size. Depth dose accuracy have been achieved 2% above 50% depth dose and 5% at lower doses, relative to maximum dose. Also, the shape of the isodose curves with the constrictions at higher dose and bulging ot lower values are accurately predicted. Computer calculated beams have been used to generate ever isodose distribution for certain clinical situations.

• Radiation Oncology Journal
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• v.16 no.3
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• pp.337-345
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• 1998

Purpose : To obtain the uniform dose at limited depth to entire surface of the body, the dose characteristics of degraded electron beam of the large target-skin distance and the dose distribution of the six-dual electron fields were investigated Materials and Method : The experimental dose distributions included the depth dose curve, spatial dose and attenuated electron beam were determined with 300 cm of target-skin distance (TSD) and full collimator size (35*35 $cm^2$ on TSD 100 cm) in 4 MeV electron beam energy. Actual collimated field size of 105 cm * 105 cm at the distance of 300 cm could include entire hemibody. A patient was standing on step board with hands up and holding the pole to stabilize his/her positions for the six-dual fields technique. As a scatter-degrader, 0.5 cm of acrylic plate was inserted at 20 cm from the body surface on the electron beam path to induce ray scattering and to increase the skin dose. Results : The full width at half maximum(FWHM) of dose profile was 130 cm in large field of 105*105 $cm^2$ The width of $100\pm10\%$ of the resultant dose from two adjacent fields which were separated at 25 cm from field edge for obtaining the dose unifomity was extended to 186 cm. The depth of maximum dose lies at 5 mm and the 80$\%$ depth dose lies between 7 and 8 mm for the degraded electron beam by using the 0.5 cm thickness of acrylic absorber. Total skin electron beam irradiation (TSEBI) was carried out using the six dual fields has been developed at Stanford University. The dose distribution in TSEBI showed relatively uniform around the flat region of skin except the protruding and deeply curvatured portion of the body, which showed excess of dose at the former and less dose at the latter. Conclusion : The percent depth dose, profile curves and superimposed dose distribution were investigated using the degraded electron beam through the beam absorber. The dose distribution obtained by experiments of TSEBI showed within$\pm10\%$ difference except the protruding area of skin which needs a shield and deeply curvatured region of skin which needs boosting dose.

• Radiation Oncology Journal
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• v.7 no.1
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• pp.85-92
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• 1989

Dosimerty based on electron spin resonance (ESR) analysis of radiation induced free radicals in amino acids is relevant to biological dosimetry applications. Alanine detectors are without walls and are tissue equivalent. Therefore, alanine ESR dosimetry looks promising for use in the therapy level. The dose range of the alanine/ESR dosimetry system can be extended down to 1 Gy. In water phantom the absorbed dose of electrons generated by a medical linear accelerator of different initial energies $(6\~21MeV)$ and therapeutic dose levels (1~60 Gy) was measured. Furthermore, depth dose measurements carried out with alanine dosimeters were compared with ionization chamber measurements. As the results, the measured absorbed doses for shallow depth of initial electron energies above 15 MeV were higher by$2\~5\%$ than those calculated by nominal energy $C_E$ factors. This seems to be caused by low energy scattered beams generated from the scattering foil and electron cones of beam projecting device in medical linear accelerator.

• Radiation Oncology Journal
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• v.4 no.2
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• pp.165-172
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• 1986

In electron therapy, lead cutout or low-melting alloy block is used for shaping the field. Material for shaping electron field affects the output factor as wet 1 as the collimation system. The authors measured the output factors of electron beams for shaped fields from Clinac-18 using ionization chamber of Farmer type in polystyrene phantom. They analyzed the parameters that affect the output factors. The output factors of electron beams depend on the incident energy, collimation system and size of shaped field. For shaped field the variation of output factor for the field size (A/P) has appearence of a smooth curve for all energy and all applicator collimator combination. The output factors for open field deviate from the curves for shaped fields. An output factor for a given field can be calculated by equivalent field method such as A/P method, if a combination of applicator and collimator is fixed.

• Korean Journal of Crystallography
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• v.19 no.1
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• pp.7-13
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• 2008

고체 표면의 구조해석 방법에는 LEED(저에너지 전자선 회절법)나 RHEED(반사 고에너지 전자선 회절법) 등과 같이 표면의 2차원적 회절상을 해석하는 방법이 있고(역격자 공간의 해석), 또는 ISS(이온산란 분광법), RBS(러더포드 후방산란법) 등과 같이 표면 원자의 실공간에 대한 정보를 직접 얻는 방법이 있다. 실제로는 두 가지 종류의 분석법을 상호 보완적으로 조합하여 효율적인 구조해석을 수행한다. 본고에서는 직충돌 이온산란 분광법(ICISS: Impact Collision Ion Scattering Spectroscopy)에 대한 원리, 장치, 측정방법 등을 소개한 전고에 이어서 이를 이용한 반도체 표면구조 해석에 관하여 기술하고자 한다. 표면의 원자구조를 알아내기 위해서는 산란된 입자의 강도를 입사각도와 출사각도에 대하여 조사하여야 하는데, 이온이 원자와 충돌하여 산란될 때 원자의 후방으로 형성되는 shadow cone에 의하여 생성되는 집속 효과(focusing effect) 및 가리움 효과(blocking effect) 중에서 ICISS는 집속 효과만을 고려하여 해석하면 실공간에서의 원자구조를 해석할 수 있다. 본 고에서는 ICISS를 이용하여 금속 또는 절연체 물질이 반도체 표면 위에서 흡착 또는 성장될 때 초기의 계면 구조 해석, 금속/반도체 계면에서 시간에 따른 동적변화 해석, III-V족 반도체의 표면구조 해석, 반도체 기판 위에서 박막 성장 과정 해석 등에 관한 연구 사례를 소개하고자 한다.

• Journal of the Korean Society of Radiology
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• v.9 no.5
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• pp.301-306
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• 2015

X-ray can be applied to obtain a projection image of an object. It is not easy to obtain an high quality image for the object composed of low and high density materials. For the object with large difference in density, it is possible to realize high contrast image using images of low and high tube voltages and image processing. The plastic and metalic parts of the electronic components can be imaged by the dual energy technique which use low and high tube voltages and by processing pixel-by-pixel using visual C++. The contrast-enhanced image can be used to detect and observe defects within the electronic components.