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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.
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.
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.
Development of an 83.2 MHz, Three-Stage RF Amplifier for the SKKUCY-9 Cyclotron
Song, H. S.,Ghergherehchi, M.,Lee, S. H.,Cong, T. V.,Kim, J. H.,Chai, J. S. IEEE 2014 IEEE transactions on nuclear science Vol.61 No.6
<P>In this paper, we describe the whole process of designing and manufacturing an 83.2 MHz, three-stage radio frequency (RF) amplifier for a SKKUCY-9 cyclotron. It consisted of a preamplifier, intermediate power amplifier (IPA), and power amplifier (PA) stage. The maximum power value for each stage is 0.05 kW, 1.5 kW, then 20 kW RF power. Formula calculation, circuit design, and electromagnetic analysis were implemented in the RF amplifier design. Along with the power stage and anode power supply, an RF amplifier control system for the RF amplifier was developed. After design and manufacturing, we conducted impedance matching measurements with a network analyzer to achieve 50Ω for the IPA and PA. Finally, we analyzed the RF amplifier characteristics by implementing RF testing with both a dummy load and a RF coupler. The expected and measured RF characteristics were in agreement, and a detailed analysis is described.</P>
Nikbakht M.,Afarideh H.,Ghergherehchi M. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.12
A low-energy dielectric loaded accelerator with a non-uniform, multi-segment structure is studied and optimized. So far, no analytical solution is provided for such structures. Also, due to the existing nonlinear behavior and a large number of geometric parameters, the problem of numerical optimizations is complex. For this reason, a method is presented to design and optimize such structures using the Genetic Algorithm (GA). Moreover, the GA output results are compared with Trust Region (TR) and Nelder-Mead Simplex (NMS) methods. Comparative results show that the GA is more efficient in achieving optimization goals and also has a higher speed than the two other methods. Finally, an optimized accelerating tube is integrated into a proper coupler. Then, the accelerator is simulated for full electromagnetic investigations using the CST suite of codes. This design leads to a structure with a power of about 80 kW in the X-band, which delivers electrons to the output energy in the range of 300e459 kV. The length and outer diameter of the accelerating tube obtained are 10 cm and 1 cm, respectively.
Characterization of electron temperature by simulating a multicusp ion source
Yeon, Y.H.,Ghergherehchi, M.,Kim, S.B.,Jun, W.J.,Lee, J.C.,Mohamed Gad, K.M.,Namgoong, H.,Chai, J.S. Elsevier BV * North-Holland 2016 Nuclear Instruments & Methods in Physics Research. Vol. No.
Multicusp ion sources are used in cyclotrons and linear accelerators to produce high beam currents. The structure of a multicusp ion source consists of permanent magnets, filaments, and an anode body. The configuration of the array of permanent magnets, discharge voltage of the plasma, extraction bias voltage, and structure of the multicusp ion source body decide the quality of the beam. The electrons are emitted from the filament by thermionic emission. The emission current can be calculated from thermal information pertaining to the filament, and from the applied voltage and current. The electron trajectories were calculated using CST Particle Studio to optimize the plasma. The array configuration of the permanent magnets decides the magnetic field inside the ion source. The extraction bias voltage and the structure of the multicusp ion source body decide the electric field. Optimization of the electromagnetic field was performed with these factors. CST Particle Studio was used to calculate the electron temperature with a varying permanent magnet array. Four types of permanent magnet array were simulated to optimize the electron temperature. It was found that a 2-layer full line cusp field (with inverse field) produced the best electron temperature control behavior.
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%.