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Mitra Ghergherehchi,Xiang-Jie Mu,채종서,김윤상 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.9
Makrofol DE1-4C detectors were exposed to fission fragments and alpha particles (of energy 0.5 -3 MeV) from a 252Cf source in a vacuum chamber. The exposed detectors were etched in 6-N NaOHsolution at 70 C to measure etch induction times. An optical microscope was used to investigatevarious charged particle tracks and diameters in Makrofol detectors. The etch induction times foralpha-particle and fission-fragment tracks were obtained from the intersections of extrapolations ofa graph of track diameters with time. The obtained results will be very useful in nuclear trackstudies, as well as nanotechnology fields.
Dosimetric and Microdosimetric Characteristics of 9.6 to 30α-MeV Proton Beams
Mitra Ghergherehchi,채종서,Hossein Afarideh,Ahmad Mohammadzadeh 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.5
High and intermediate energy protons are not able to directly form a track in an etch detector (TED). Such detectors can, however, be used for the detection and dosimetry of beams of these particles through the registration of secondary charged particles with sufficiently high values of linear energy transfer (LET).Intermediate energy protons (10 to 30 MeV) with low LET values ranging from 5.87 down to 2.40 keV/탆 are considered. Although the LET values are low, this energy range seems to be sufficient to create secondary particles with much higher LET values through nuclear reactions in the irradiated matter. This phenomenon can modify the characteristics of the energy transfer process due to these particles, and it should be taken into account when such particles are used for radiobiology and/or radiotherapy studies. The importance of these secondary particles was studied experimentally by means of a LET spectrometer based on a chemically etched track detector, in which the tracks of the primary protons are not revealed. These studies were performed with protons whose primary energies were in the range of about 10 to 30 MeV, which are available at the Cyclotron Accelerator Department of Nuclear Research Center for Agriculture and Medicine (NRCAM) in Karaj, Iran. The microdosimetric distributions of the secondary particles mentioned above are presented, and their contributions to the absorbed dose of the primary protons are estimated. The contribution of the secondary particle dose increases with decreasing proton energy. The importance of this phenomenon in some applications is discussed. The origin of the secondary particles in interactions with protons having high and intermediate energies due to various nuclear reactions was calculated by using the Alice computer code. There is good agreement between the experimentally obtained and theoretically calculated results.
Improvement of the RF cavity for the SKKUCY-10 cyclotron
Lee Jongchul,Ghergherehchi Mitra,Gad Khaled M. M.,Ha Donghyup,Namgoong Ho,Lee Seunghyun,Song Ho Seung,Karatas Berat Can,Chai Jong-Seo 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.9
The SKKUCY-10 cyclotron based on 83.2 MHz, 40 kV half-wave RF cavity was developed at Sungkyunkwan University for the production of medical radioisotopes. The resonant frequency fRF of the cyclotron and the RF coupling coefficient βc of the RF cavity system were measured at various vacuum, and temperature conditions. The normalized multi-pacting intensities at four positions in the power coupler were analyzed to predict the multi-pacting power. Differences, ΔfRF and Δβc , caused by the vacuum, and temperature conditions were modified based on the coupler and tuner gap distances. During the RF conditioning, a constant 15 kW pulse mode and a variable 1 to 15 kW continuous wave mode were employed. The values of the reflection coefficient Γ and βc were 1.2% and 0.8, respectively, when the cavity dissipation power was 12.4 kW at 83.2 MHz. Good agreement between the simulation and experimental data was obtained.
Optimal design and fabrication of a RF cavity for accelerator mass spectrometry system cyclotron
Ha Donghyup,송호승,Ghergherehchi Mitra,Choi Hyojeong,Shin Seung-wook,Lee Jongchul,Namgoong Ho,Mumyapan Mustafa,채종서 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.8
This study designed a radio frequency (RF) cavity for a cyclotron-based accelerator mass spectrometry (AMS) system. A cyclotron-based AMS system was used to accelerate 12C−, 13C−, and 14C− particles. The experiment results confrmed that three resonant frequencies of the designed RF cavity accelerated the three particles. The RF cavity was a quarter-wavelength resonator (QWR) type and had an external inductor–capacitor (LC) circuit. The operating frequency range of the fabricated RF cavity was 8.5–10 MHz with coupling coefcients of 0.86, 0.99, and 1.11 at resonant frequencies of 8.85, 9.17, and 9.52 MHz, respectively. The refected power at each frequency was less than 1%.
Design of 6 MeV X-Band Electron Linac for Dual-Head Gantry Radiotherapy System
신승욱,이승현,이종철,김휘수,하동협,Mitra Ghergherehchi,채종서,이병노,채문식 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.12
A compact 6 MeV electron linac is being developed at Sungkyunkwan University, in collaboration with the Korea atomic energy research institute (KAERI). The linac will be used as an X-ray source for a dual-head gantry radiotherapy system. X-band technology has been employed to satisfy the size requirement of the dual-head gantry radiotherapy machine. Among the several options available, we selected a pi/2-mode, standing-wave, side-coupled cavity. This choice of radiofrequency (RF) cavity design is intended to enhance the shunt impedance of each cavity in the linac. An optimum structure of the RF cavity with a high-performance design was determined by applying a genetic algorithm during the optimization procedure. This paper describes the detailed design process for a single normal RF cavity and the entire structure, including the RF power coupler and coupling cavity, as well as the beam dynamics results.
Design of cyclotron magnet with tenth harmonics for accelerator mass spectrometry
Namgoong Ho,Choi Hyojeong,Ha Donghyup,Ghergherehchi Mitra,Chai J. S.,Lee Jongchul 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.2
In this study, we developed a carbon-beam cyclotron for accelerator mass spectrometry (AMS). A cyclotron magnet for AMS was developed for particle acceleration systems using cyclotrons rather than the tandem accelerator used in conventional accelerator mass spectrometry systems. Design parameters were selected for the development of cyclotrons for AMS, and the magnetic feld design and equilibrium orbit (EO) analysis beam trajectory were analyzed using the Cyclone and CST Microwave Studio. Additionally, by measuring the magnetic feld of the manufactured cyclotron, magnetic feld optimtableization was performed through shimming, and the beam trajectory was verifed based on the measurement results. The cyclotron magnet was designed with a mass resolution of 2890, with harmonic 10 and turn number 92. The minimum turn separation was optimized at 2 mm to reduce the loss caused by the collision of the beam during acceleration. This cyclotron for AMS could accelerate the 12C−, 13C−, and 14C− particles at 40 keV to obtain a beam of 400 keV.