• Nuclear Engineering and Technology
• /
• 제46권3호
• /
• pp.387-394
• /
• 2014

A Slowing Down Time Spectrometer (SDTS) system is a highly efficient technique for isotopic nuclear material content analysis. SDTS technology has been used to analyze spent nuclear fuel and the pyro-processing of spent fuel. SDTS requires an external neutron source to induce the isotopic fissile fission. A high intensity neutron source is required to ensure a high for a good fissile fission. The electron linear accelerator system was selected to generate proper source neutrons efficiently. As a first step, the electron generator of an 80-keV electron gun was manufactured. In order to produce the high beam power from electron linear accelerator, a proper beam current is required form the electron generator. In this study, the beam current was measured by evaluating the performance of the electron generator. The beam current was determined by five parameters: high voltage at the electron gun, cathode voltage, pulse width, pulse amplitude, and bias voltage at the grid. From the experimental results under optimal conditions, the high voltage was determined to be 80 kV, the pulse width was 500 ns, and the cathode voltage was from 4.2 V to 4.6 V. The beam current was measured as 1.9 A at maximum. These results satisfy the beam current required for the operation of an electron linear accelerator.

• 한국의학물리학회지:의학물리
• /
• 제22권2호
• /
• pp.85-91
• /
• 2011

GEANT4 Medical Linac 2 예제 코드를 이용하여 선형가속기 전자선의 에너지 분포를 계산하였다. 입사 전자의 평균 에너지는 6, 9, 12, 16, 20 MeV이었으며, 전자선 특성에 영향을 주는 전자선 산란박 물질, 두께, 위치에 따른 에너지 분포를 계산하였다. 산란박 물질은 납, 구리, 알루미늄, 금을 사용하였다. 산란박 위치를 변경하여 선형 가속기 헤드 속 산란박 위치가 전자 및 광자 에너지 분포에 미치는 영향을 분석하였다. 의료용 선형가속기 시뮬레이션의 기초자료인 에너지 분포에 대해 여러 가지 산란박 조건을 적용하여 경향을 나타내었다. 이 결과는 선형가속기 헤드 설계에 이용될 수 있을 것으로 본다.

• Journal of Radiation Protection and Research
• /
• 제41권3호
• /
• pp.286-290
• /
• 2016

Background: Activation of air and water in the electron linear accelerator for medical use has not been considered severely. By the new Japanese regulation for protection of radiation hazard, it became indispensable to evaluate of activation of air and water in the accelerator room. The measurement of induced activity in air and water components in the electron energy region of 10 to 20 MeV is very difficult, because this energy region is close to the threshold energy region of photonuclear reactions. Then, we measured the photonuclear reaction yields of $^{13}N$, $^{15}O$, and $^{11}C$ by using the electron linear accelerator. Obtained data were compared with the data calculated by the Monte Carlo method. Materials and Methods: An activation experiment was performed at the Research Center for Electron Photon Science, Tohoku University. Highly purified $SiO_2$, $Si_3N_4$, and carbon disks were irradiated for 10 minutes by bremsstrahlung converted by a tungsten plate. Induced activity from C, N, and O was obtained. Monte Carlo calculation was performed using MCNP5 and AERY (DCHAIN-SP) to simulate the experimental condition. Cross section data were adopted the KAERI dataset. Results and Discussion: In our experiment in hospital, calculated values were not agreed with experimental values. It might be three possible reasons as the cause of this deference, such as irradiation energy, calculation procedure and cross section data. Obtained data of this work, calculated and experimental values were good agreement with each other within one order. In this work, we used KAERI dataset of photonuclear reaction instead of JENDL. Therefore, it was found that the photonuclear cross section data of light elements are most important for yield calculation in these reactions. Conclusion: Further improvement for calculation using a new dataset JENDL/PD-2015 and considering electron energy spreading will be needed.

• Journal of Radiation Protection and Research
• /
• 제43권1호
• /
• pp.10-19
• /
• 2018

Background: Monte Carlo (MC) simulation is the most accurate for calculating radiation dose distribution and determining patient dose. In MC simulations of the therapeutic accelerator, the characteristics of the initial electron must be precisely determined in order to achieve accurate simulations. However, It has been computation-, labor-, and time-intensive to predict the beam characteristics through predominantly empirical approach. The aim of this study was to analyze the relationships between electron beam parameters and dose distribution, with the goal of simplifying the MC commissioning process. Materials and Methods: The Varian Clinac 2300 IX machine was modeled with the Geant4 MC-toolkit. The percent depth dose (PDD) and lateral beam profiles were assessed according to initial electron beam parameters of mean energy, radial intensity distribution, and energy distribution. Results and Discussion: The PDD values increased on average by 4.36% when the mean energy increased from 5.6 MeV to 6.4 MeV. The PDD was also increased by 2.77% when the energy spread increased from 0 MeV to 1.019 MeV. In the lateral dose profile, increasing the beam radial width from 0 mm to 4 mm at the full width at half maximum resulted in a dose decrease of 8.42% on the average. The profile also decreased by 4.81% when the mean energy was increased from 5.6 MeV to 6.4 MeV. Of all tested parameters, electron mean energy had the greatest influence on dose distribution. The PDD and profile were calculated using parameters optimized and compared with the golden beam data. The maximum dose difference was assessed as less than 2%. Conclusion: The relationship between the initial electron and treatment beam quality investigated in this study can be used in Monte Carlo commissioning of medical linear accelerator model.

• 한국방사선학회논문지
• /
• 제14권3호
• /
• pp.193-201
• /
• 2020

본 연구 목적은 선형가속기를 통해 입사된 전자가 표적(target)을 구성하는 물질과 두께에 따른 광자 특성을 평가하는 것이다. 전산모사 설계는 2 mm 두께의 텅스텐 단일물질과 1.8 mm 와 2.3 mm 두께의 텅스텐과 구리 복합물질로 구성된 선형가속기 표적(Target)이다. 연구 방법은 첫째, 표적 내 일차 입자의 거동은 전자플루언스와 전자 에너지 축적으로 평가하였다. 둘째, 표적 내에서 발생하는 광자는 광자 플루언스로 평가하였다. 셋째, 표적으로부터 1 m 거리에서의 광자 각-에너지 분포는 광자 플루언스로 평가하였다. 그 결과 첫째, 단일물질과 복합물질 표적에서의 전자 플루언스와 에너지 축적을 통해 일차 입자인 전자가 표적 밖으로 방출되지 않았으며, 표적 두께에 따라 전자가 음의 선형적으로 감쇄하였다. 둘째, 복합물질 표적이 단일물질 표적보다 광자 생성이 더 높은 것으로 나타났다. 이는 물질 구성 성분과 두께가 광자 생성에 영향을 준다는 사실을 확인하였다. 셋째, 차폐 해석에 필요한 각 분포에 따른 광자 플루언스를 계산하였다. 이러한 결과는 선형가속기 표적을 구성하는 물질과 두께에 따라 광자 생성률이 차이 나는 것을 확인할 수 있었다. 따라서, 본 연구는 국가에서 도입 중인 컨테이너 보안 검색용 선형가속기 사용시설의 설계 및 운영 시 필요한 자료이며, 방사선 방호에 기초 자료로 활용될 수 있을 것으로 생각된다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2011년도 제42회 하계학술대회
• /
• pp.1580-1581
• /
• 2011

The linear accelerator of Pohang Accelerator Laboratory(PAL) will drive a top-up mode operation in PLS-II(Pohang Light Source-II). Due to this kind of the operation mode, the electron gun is expected to have shorter life time of the cathode. Further in the PLS-II, two gate valves will be installed in front of the electron gun. The distance between the pre-bunching section and the electron gun will increase by 400 mm compared to the existing system due to the insertion of these gate valves. As a result the incident electron beam. One of the goals to improve the beam pulse width is by incorporating suitable biased voltage. In this paper, we will present test results of beam pulse width as a function of different biased voltage and focusing solenoid coil.

• 한국의학물리학회지:의학물리
• /
• 제31권2호
• /
• pp.9-19
• /
• 2020

Purpose: This study aims to develop a multi-purpose electron beam irradiation device for preclinical research and material testing using the research electron linear accelerator installed at the Dongnam Institute of Radiological and Medical Sciences. Methods: The fabricated irradiation device comprises a dual scattering foil and collimator. The correct scattering foil thickness, in terms of the energy loss and beam profile uniformity, was determined using Monte Carlo calculations. The ion-chamber and radiochromic films were used to determine the reference dose-rate (Gy/s) and beam profiles as functions of the source to surface distance (SSD) and pulse frequency. Results: The dose-rates for the electron beams were evaluated for the range from 59.16 Gy/s to 5.22 cGy/s at SSDs of 40-120 cm, by controlling the pulse frequency. Furthermore, uniform dose distributions in the electron fields were achieved up to approximately 10 cm in diameter. An empirical formula for the systematic dose-rate calculation for the irradiation system was established using the measured data. Conclusions: A wide dose-rate range electron beam irradiation device was successfully developed in this study. The pre-clinical studies relating to FLASH radiotherapy to the conventional level were made available. Additionally, material studies were made available using a quantified irradiation system. Future studies are required to improve the energy, dose-rate, and field uniformity of the irradiation system.

• Journal of Astronomy and Space Sciences
• /
• 제40권4호
• /
• pp.259-266
• /
• 2023

The Standard Model (SM) does not provide an information for 26% of dark matter of the universe. In the dark sector, dark matter is supposed to be linked with the hypothetical particles called dark photons that have similar role to photons in electromagnetic interaction in the SM. Besides astronomical observation, there are studies to find dark matter candidates using accelerators. In this paper, we searched for dark photons using future electron-positron colliders, including Circular Electron Positron Collider (CEPC)/CEPC, Future Circular Collider (FCC-ee)/Innovative Detector for Electron-positron Accelerator (IDEA), and International Linear Collider (ILC)/International Large Detector (ILD). Using the parameterized response of the detector simulation of Delphes, we studied the sensitivity of a double dark photon mode at each accelerator/detector. The signal mode is double dark photon decay channel, e⁺e^- → A'A', where A' (dark photon with spin 1) decaying into a muon pair. We used MadGraph5 to generate Monte Carlo (MC) events by means of a Simplified Model. We found the dark photon mass at which the cross-sections were the highest for each accelerator to obtain the maximum number of events. In this paper we show the expected number of dark photon signal events and the detector efficiency of each accelerator. The results of this study can facilitate in the dark photon search by future electron-positron accelerators.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.113-115
• /
• 2002

The Monte Carlo simulation method is a numerical solution to a problem that models objects interacting with other objects or their environment based upon simple object-object or object-environment relationships. In spite of its great accuracy, It was turned away because of long calculation time to simulate a model. But, it is used to simulate a linear accelerator frequently with the advance of computer technology. To simulate linear accelerator in Monte Carlo simulations, there are many parameters needed to input to Monte Carlo code. These data can be supported by a linear accelerator manufacturer. Although the model of a linear accelerator is the same, a different characteristic property can be found. Thus, we performed a commissioning process of 6MV photon beam in Varian 2300C/D model with BEAM/EGS4 Monte Carlo code. The head geometry data were put into BEAM/EGS4 data. The mean energy and energy spread of the electron beam incident on the target were varied to match Monte Carlo simulations to measurements. TLDs (thermoluminescent dosimeter) and radiochromic films were employed to measure the absorbed dose in a water phantom. Beam profile was obtained in 40cm${\times}$40cm field size and Depth dose was in 10cm${\times}$10cm. At first, we compared the depth dose between measurements and Monte Carlo simulations varying the mean energy of an incident electron beam. Then, we compared the beam profile with adjusting the beam radius of the incident electron beam in Monte Carlo simulation. The results were found that the optimal mean energy was 6MV and beam radius of 0.1mm was well matched to measurements.

• 진공이야기
• /
• 제3권4호
• /
• pp.4-7
• /
• 2016

An X-ray Free Electron laser facility (PAL-XFEL) has been built in Pohang Accelerator Laboratory to provide X-ray FEL radiations for photon users. The machine consists of a 10 GeV normalconducting S-band linear accelerator and two undulator beamlines. The hard and soft X-ray beamlines will provide FEL radiations with wavelengths of 0.6 to 0.1 nm and 4.5 to 1 nm, respectively. Beam commissioning of PAL-XFEL is ongoing and user service will start in 2017. In this report, the PAL-XFEL layout and the working principle are discussed.