• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05d
• /
• pp.57-62
• /
• 1996

ANSI N13.32는 손목팬텀과 손가락팬텀에서 말단선량계의 특성조사를 위하여 방향의존성인자를 선량계의 성능평가에 적용하도록 권고하고 있다. 본 연구에서는 말단선량의 정확한 선량평가를 위하여 ANSI N13.32에 제안된 팬텀과 동일하게 모사하고 그 팬텀내의 7mg/$\textrm{cm}^2$ 깊이에서 단일에너지를 가진 광자의 선량당량환산인자 및 방향의존성인자를 MCNP 전산코드를 사용함으로써 계산하였다. 또한 본 연구의 최종목적인 ISO Narrow X-선 빔에 의해 조사된 손가락팬텀에서 선량당량환산인자 및 방향의존성인자를 도출하였다. 전산 수행한 결과 낮은 전압에서 발생된 X-선 빔인 경우, 팬텀의 주축을 따라 수평회전각이 증가할수록 방향의존성인자가 크게 감소하며, 한편 높은 전압에서 생성된 X-선 빔인 경우, 수평회전각이 증가할수록 방향의존성인자간 처음에는 근소하게 감소하지만 90。까지는 증가하고 있음을 알 수 있었다.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.3
• /
• pp.171-176
• /
• 2014

The polarization characteristics of ultracompact polarization-insensitive directional coupler (PIDC) based on double sandwiched rib-type waveguide are explored in detail by using longitudinal modal transmission-line theory (L-MTLT). To obtain the polarization-insensitive condition of ultracompact directional coupler, the coupling length and coupling efficiency as functions of the refractive index and thickness of sandwiched rib-type waveguide are analyzed for quasi-TE and quasi-TM modes. The numerical results show that the ultracompact polarization-insensitive coupler with hundreds of micrometer scales is realized by properly choosing structural and material parameters of double sandwiched layers. Furthermore, the influence of fundamental mode profile, which is distributed in lateral waveguide of coupler, on the coupler performance has been investigated.

• Journal of Radiation Protection and Research
• /
• v.23 no.1
• /
• pp.59-63
• /
• 1998

The light sensitivity and angular dependence of the $Mg_2SiO_4$:Tb(MSO-5) TLD which affect the accuracy of the radiation dose measurement are investigated. Light-induced thermoluminescence of MSO-S TLD under the 200 lux fluorescent and the incandescent lamp for 8 hours are corresponding to 11 and 3 mR exposure, respectively. TL intensity ratio of the incident angle of ${\pm}80^{\circ}$ to normal incidence for MSO-S and badge type MSO-L are about 0.8 and 0.15, respectively.

• Journal of Radiation Protection and Research
• /
• v.21 no.4
• /
• pp.263-271
• /
• 1996

The ANSI N13.32 recommends that a study of the angular response of a dosimeter be carried out once, although no pass/fail criterion is given for angular response. Gamma dose equivalent conversion and angular dependence factors were calculated by using MCNP code for the case of ANSI N13.32 extremity phantoms(finger and arm) at the depth of $7mg/cm^2$. Those extremity dosimeters were assumed to be irradiated from both monoenergitic photons and ISO X-ray narrow beams. These calculated gamma dose equivalent conversion and angular dependence factors were compared to B. Grosswendt's result calculated by using X-ray beams. The result showed that the dose equivalent conversion factors of this study agreed well with that of B. Grosswendt for all energies within 2% except 7% in the case of the low energies. In the case of angular dependence factors comparison, they agreed within 3%. It was shown that angular dependence factors of the finger phantom decreased as the horizontal angle of the phantom increased for the ISO X-ray beams less than 60keV. For the higher energy X-ray beams range they decreased slightly around 40 degree, but then increased from this energy to 90 degree.

• 대한방사선방어학회:학술대회논문집
• /
• 2009.04a
• /
• pp.186-187
• /
• 2009

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.16 no.1
• /
• pp.239-244
• /
• 2016

The polarization characteristics of polarization-insensitive directional coupler based on double sandwiched rib-type and curved waveguides are explored in detail by using conformal transformation method (CTM) and longitudinal modal transmission-line theory(L-MTLT). To obtain the polarization-insensitive condition of polarization-insensitive curved directional coupler(PI-CDC), the coupling length and coupling efficiency according to the inner radius of PI-CDC are analyzed for quasi-TE and quasi-TM modes. The numerical results show that the PI-CDC with a few micrometer scales can be realized by properly choosing the curvature and structural and material parameters of double sandwiched layers. Furthermore, the mode profiles propagating through PI-CDC are evaluated, and the influence on coupler performance has been investigated.

• Korean Journal of Optics and Photonics
• /
• v.18 no.5
• /
• pp.295-302
• /
• 2007

This paper presents a rigorous comparison of the design characteristics of polarization-insensitive directional coupler (DC) and multimode interference (MMI) coupler based on rib type waveguides, by using longitudinal modal transmission-line theory (L-MTLT). It shows that the multimode mixing and interference property of MMI can be structurally designed through the continuous evolution of the two-mode coupling property of DC. It also compares and analyzes the coupling efficiency along with the coupling length and the wavelength between polarization-insensitive DC and MMI. From the design properties obtained, it demonstrates for the first time the integration of polarization-insensitive DC or MMI with a Bragg grating and evaluates precisely the filtering characteristics. The numerical results reveal that the DC, as long as it is designed to have the same coupling length for TE and TM modes, has better performance than the MMI in polarization-insensitive filtering behaviour. However, it shows that the MMI with much less coupling length than DC is preferred in the miniaturization of integrated devices.

• Progress in Medical Physics
• /
• v.22 no.1
• /
• pp.52-58
• /
• 2011

Our goal is to assess the suitability of a glass dosimeter on detection of high-energy electron beams for clinical use, especially for radiation therapy. We examined the dosimetric characteristics of glass dosimeters including dose linearity, reproducibility, angular dependence, dose rate dependence, and energy dependence of 5 different electron energy qualities. The GD was irradiated with high-energy electron beams from the medical linear accelerator andgamma rays from a cobalt-60 teletherapy unit. All irradiations were performed in a water phantom. The result of the dose linearity for high-energy electron beams showed well fitted regression line with the coefficient of determination; $R^2$ of 0.999 between 6 and 20 MeV. The reproducibility of GDs exposed to the nominal electron energies 6, 9, 12, 16, and 20 MeV was ${\pm}1.2%$. In terms of the angular dependence to electron beams,GD response differences to the electron beam were within 1.5% for angles ranging from $0^{\circ}$ to $90^{\circ}$ and GD's maximum response differencewas 14% lower at 180o. In the dose rate dependence, measured dose values were normalized to the value obtained from 500 MU/min. The uncertainties of dose rate were measured within ${\pm}1.5%$ except for the value from 100 MU/min. In the evaluation of the energy dependence of the GD at nominal electron energies between 6 and 20 MeV, we obtained lower responses between 1.1% and 4.5% based on cobalt-60 beam. Our results show that GDs have a considerable potentiality for measuring doses delivered by high-energy electron beams.

• Proceedings of the Korean Society of Radiological Science
• /
• 1995.05a
• /
• pp.143-145
• /
• 1995

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.4
• /
• pp.187-192
• /
• 2017

Rigorous longitudinal modal transmission-line theory (L-MTLT) is applied to analyze maximum power transfer in asymmetric grating-assisted directional couplers(A-GADC). By defining a coupling efficiency amenable to rigorous analytical solutions and interference between symmetric and asymmetric supermodes, the power exchange of TE modes as a function of propagation distance is numerically evaluated. The numerical result reveals that maximum power transfer occurs at a grating period ${\Lambda}_{eq}$, in which the insertion loss of supermodes is equal to each other. That is, it is generally different from conventional phase-matching condition of GADC. Furthermore, as the asymmetric profile of grating change to symmetrical profile, the coupling length decreases and the coupling efficiency for power transmission increases.