• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.211-213
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• 2002

The purpose of this work is acquiring some parameters of therapeutic heavy ion beams after penetrating a thick target. The experiments were performed using a pencil-like $\^$12/C beam of about 3 mm in diameter from NIRS-HIMAC, and the data were taken at several points of the target thickness for $\^$12/C beam of 290 MeV/u and 400 MeV/u. By the simultaneous measurements using some detectors, the atomic number of each fragment particle was identified, and the beam profile, the dose distribution and the LET spectrum for each element were derived.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.129-133
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• 2007

Focused Ion Beam(FIB) systems is a useful tool for the fabrication of micro-nano scale structures. In this study, the effects of FIB etching on the Au microstructure are systematically investigated. As the fabrication parameters, ion dose, dwell time and beam overlap ratio are studied. First, the increases of Ga ion dose makes the milling yield higher and the sidewall of milling profile steeper. Dwell time is found to have little effects on the milling profile due to the relatively large milling area of $1\times1{\mu}m^2$ used in this study. However, beam overlap significantly affects not only milling rate but also milling profile. As the beam overlap ratio changes from positive to negative, the development of regular cross-stripe patterns at the bottom with low milling rate is observed.

• Laser Solutions
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• v.15 no.2
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• pp.11-14
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• 2012

In this paper, we have made a proposal concerning the beam shaping mask(BSM) using random-array slits to control intensity distribution profile of laser beam and demonstrated its proprieties experimentally. When a lot of slits are set out irregularly, diffraction patterns of light does not appear but granularity patterns as a bundle of fibers appear. Intensity distribution profile is controlled by densities distribution of circular slits arrayed randomly because the number of slits and its area means amount of light energy through BSM. Namely as the number of slits in high intensity area is increased and that in low intensity area decreased, amount of light energy is same over all local parts. So gaussian intensity distribution could be changed to flat-top.

• The Journal of Korean Society for Radiation Therapy
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• v.7 no.1
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• pp.15-31
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• 1995

The radiosurgery treatment is one time, non surgical approach to the treatment of patients with intracranial disorders whose conditions would be difficult or dangerous to treat with conventional sugical procedures. The LINAC based radiosurgery is based on the combination of multiple isocentric arc irradiation with small fields centered in the stereotactic target. The absorption of the beam in a tissue equivalent medium, such as water, as well as the uniformity, or profile, of the beam must be precisely documented. The beam characteristics and dosimetric measurememts of the 6MV X-ray beam from a ML-6M linear accelerator are examined. The percent depth dose (PDD) and beam profile (including flatness, symmetry and penumbra) is calibrated with the radiosurgery cone in water phantom. The cone is made of lead which size is from $10{\times}10mm{\phi}$ to $30{\times}30mm{\phi}$ All of these dosimetric measurements sufficiently characterized the beam to permit safe clinical use.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.200-210
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• 2016

The neutron radiography reactor (NRAD) is a 250 kW Mark-II Training, Research, Isotopes, General Atomics (TRIGA) reactor at Idaho National Laboratory, Idaho Falls, ID, USA. The East Radiography Station (ERS) is one of two neutron beams at the NRAD used for neutron radiography, which sits beneath a large hot cell and is primarily used for neutron radiography of highly radioactive objects. Additional fuel elements were added to the NRAD core in 2013 to increase the excess reactivity of the reactor, and may have changed some characteristics of the neutron beamline. This report discusses characterization of the neutron beamline following the addition of fuel to the NRAD. This work includes determination of the facility category according to the American Society for Testing and Materials (ASTM) standards, and also uses an array of gold foils to determine the neutron beam flux and evaluate the neutron beam profile. The NRAD ERS neutron beam is a Category I neutron radiography facility, the highest possible quality level according to the ASTM. Gold foil activation experiments show that the average neutron flux with length-to-diameter ratio (L/D) = 125 is $5.96{\times}10^6n/cm^2/s$ with a $2{\sigma}$ standard error of $2.90{\times}10^5n/cm^2/s$. The neutron beam profile can be considered flat for qualitative neutron radiographic evaluation purposes. However, the neutron beam profile should be taken into account for quantitative evaluation.

• Journal of radiological science and technology
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• v.45 no.5
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• pp.449-455
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• 2022

This study is to present a Geant4 code for the simulation of the absorbed dose distribution given by a medical linac for 6 MV photon beam. The dose distribution was verified by comparison with calculated beam data and beam data measured in water phantom. They were performed for percentage depth dose(PDD) and beam profile of cross-plane for two field sizes of 10 × 10 and 15 × 15 cm². Deviations of a percentage and distance were obtained. In energy spectrum, the mean energy was 1.69 MeV. Results were in agreement with PDD and beam profile of the phantom with a tolerance limit. The differences in the central beam axis data 𝜹₁ for PDD had been less than 2% and in the build up region, these differences increased up to 4.40% for 10 cm square field. The maximum differences of 𝜹₂ for beam profile were calculated with a result of 4.35% and 5.32% for 10 cm, 15 cm square fields, respectively. It can be observed that the difference was below 4% in 𝜹₃ and 𝜹₄. For two field sizes of 𝜹_50-90 and RW₅₀, the results agreed to within 2 mm. The results of the t-test showed that no statistically significant differences were found between the data for PDD of 𝜹₁, p>0.05. A significant difference on PDD was observed for field sizes of 10 × 10 cm², p=0.041. No significant differences were found in the beam profile of 𝜹₃, 𝜹₄, RW₅₀, and 𝜹_50-90. Significant differences on beam profile of 𝜹₂ were observed for field sizes of 10 × 10 cm², p=0.025 and for 15 × 15 cm², p=0.037. This work described the development and reproducibility of Geant4 code for verification of dose distribution.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.263-266
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• 2002

An optical method for surface roughness estimation based on statistical analysis of the light intensity of a scattered laser beam pattern. The method is very simple but has a disadvantage that no more information than the averaged roughness is estimated. In this study a new try was conducted to derive more advanced surface information from the details of the light intensity distribution. Some periodic ripples among the light intensity distribution being assumed to relate with scratch left on the machined surface, a corresponding surface profile is estimated from the ripples using FFT and IFFT algorithm. IFFT technique is used to extract some dominant signal components among the intensity distribution. Compared to the measured profiles by a stylus type surf-tester, the profiles obtained through the proposed method are probably acceptable in a sense of the profile shape. Calibration of the amplitude needs more works in the future.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1265-1267
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• 1995

In the fiber-photodiode(PD) coupling module using v-groove, the paraxial approximation is no longer valid because the beam enters obliquely the PD substrate with the angle of $20^{\circ}$ after being reflected from the $55^{\circ}$ mirror formed by anisotropically etching of the (100) silicon wafer. In this paper, we study the beam profile incident on the PD active area and fiber-PD coupling efficiency for this case.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.273-274
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• 2011

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.146-151
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• 2009

A Gaussian beam of single mode fiber laser was changed into a ring-shaped pattern after it was transmitted through the hollow optical fiber. The ring-shaped beam was focused on a plane by an f-. lens and it was scanned by a Galvano-mirror. The spatial profile of laser energy incident on a plane had two peaks at both sides of the scanned linear track. The profile was compared with the result obtained when the Gaussian beam was dithered transversely by an acousto-optic modulator. It is found that hollow optical fiber beam shaper can replace acousto-optic beam dithering device which is employed in a laser induced thermal printing system.