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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%.
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.
Measurement of RF characteristics for Superconducting Quarter-wave Resonator
Jong-Chul Lee,Yacine Kadi,Pei Zhang,Mitra Ghergherehchi,Jong Seo Chai 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.1
RF characteristics of unloaded quality factor $(Q_0)$ and accelerating electric field $(E_{acc})$ were measured for superconducting quarter-wave resonator (QWR) in order to verify the performance. For the accurate measurement of RF characteristics, the measurement method of $Q_0$ based RF power and RF coupling coefficient was used, and the measurement uncertainty was calculated with statistics analysis of systematic error in RF measurement system. The superconducting QWR was designed with a resonant frequency of 101.28 MHz and an accelerating electric field $(E_{acc})$ of 6 MV/m at a cavity dissipation power of 10 W in the high-intensity and energy isotope separator on-line device (HIE-ISOLDE) project at CERN. Q-slopes and RF coupling coefficients were measured for three QWRs at the resonant frequency 101.28 MHz. $Q_0$ values of QWRs were measured 4.55 $\times$ 10$^8$, 3.78 $\times$ 10$^8$ and 3.17 $\times$ 10$^8$ at the 6 MV/m, respectively, and the measurement uncertainty of $Q_0$ and $E_{acc}$ were calculated 2.92\% and 3.32\%. Performances of superconducting QWRs were acceptable to operate the beam acceleration with consideration of cryomodule capacity in HIE-ISOLDE project.