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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.
Technical design of an axial injection low-energy carbon beam line
Gad Khaled M. M.,Namgoong Ho,Ghergherehchi Mitra,Chai Jong-Seo 한국물리학회 2024 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.84 No.9
Ongoing research and development eff orts are being conducted at Sungkyunkwan University—Korea with the objective of creating an Atomic Mass Spectrometer (AMS) cyclotron that presents a more compact and cost-eff ective alternative to the conventional Tandem AMS system. The construction of cyclotrons frequently encounters diffi culties, mostly arising from instabilities and substantial losses of ion beams, particularly during the injection phase that usually depends on an axial injection mechanism. In this paper, we undertake an in-depth investigation into the comprehensive design exploration of a low-energy carbon ion beam line. The optimization processes were done using Trace3D, TOSCA, and OpticExpert codes. The TOSCA software, in particular, enabled the use of three-dimensional simulations related to the complicated behavior of ion beams. The presented paper off ers an in-depth examination of the beam line, illustrating the engineering elements of essential optical parts, such as quadrupoles and dipoles. Following the production process, all of the beam line parts were subjected to extensive testing. The fi nal results, including magnetic fi eld measurements and fi eld gradients, showed an excellent match with our physical models. At the same time, a thermal study of the air-cooled quadrupole coils was carried out using the ANSYS APDL program. The construction of beam line has been done. An analysis of beam measurements will be carried out and subsequently compared to the calculated models. The objective of this comparison analysis is to ascertain the most optimal design method, with a focus on achieving effi ciency and reliability in the fi nal beam line system.
An efficient simulation method of a cyclotron sector-focusing magnet using 2D Poisson code
Gad Elmowla, K.M.M.,Chai, J.S.,Yeon, Y.H.,Kim, S.,Ghergherehchi, M. North-Holland 2016 Nuclear instruments & methods in physics research. Vol.832 No.-
In this paper we discuss design simulations of a spiral magnet using 2D Poisson code. The Independent Layers Method (ILM) is a new technique that was developed to enable the use of two-dimensional simulation code to calculate a non-symmetric 3-dimensional magnetic field. In ILM, the magnet pole is divided into successive independent layers, and the hill and valley shape around the azimuthal direction is implemented using a reference magnet. The normalization of the magnetic field in the reference magnet produces a profile that can be multiplied by the maximum magnetic field in the hill magnet, which is a dipole magnet made of the hills at the same radius. Both magnets are then calculated using the 2D Poisson SUPERFISH code. Then a fully three-dimensional magnetic field is produced using TOSCA for the original spiral magnet, and the comparison of the 2D and 3D results shows a good agreement between both.
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.
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.
Magnet Design for the 10MeV AVF Cyclotron Accelerator
R. Solhju,H. Afarideh,M. Ghergherehchi,채종서 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.7
In this paper, an azimuthally varying field (AVF) magnet is designed to produce a 10 MeV protonbeam. In order to design and analyze the magnet three-dimensionally, we use the CST program. Also, field mapping results have been obtained by using the CST program and the MATLABprogram to validate the precision of the design. In addition, an iterative process is conducted formagnet shimming. The precision of this design is ensured by using the optimization part of CSTto optimize parameters like the number of mesh cells, the boundary dimension, etc.
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>
Artificial neural network-based sodium nitrite NQR analysis in an urban noisy environment
Mohammad Saleh Sharifi A. M.,Hossein Afarideh,Mitra Ghergherehchi,Mehdi Simiari 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.83 No.3
Using the nuclear quadrupole resonance procedure in non-shielded environments requires special measures. For this purpose, noise reduction and interference suppression algorithms have been used to increase signal-to-noise and interference ratio or SNIR. For this aim, two types of antennas are considered, the ferrite core coil antenna as the main antenna receives the free induction decay or FID signal, radio frequency interference or RFI, and noise, and the omnidirectional auxiliary antenna receives the RFI and noise as the algorithm reference noise. To perform the noise and interference cancelation, the weighting factors in auxiliary antenna data are so important, that an artifcial neural network or ANN model has been used to increase the SNIR. In this research, sodium nitrite has been used as a sample, then algorithms have been tested in a nonshielded environment. The resonant frequency of the 200 g sample, by the signal-to-noise ratio improvement of 18.889 dB, the signal-to-interference ratio improvement of 24.819 dB, and the FID signal amplifcation of 16.925 dB, were measured at 4.649 MHz. The main technique in this study was to use an auxiliary antenna to estimate the noise and interference and compute the learned weighting factor before sending the NQR pulse.