摘要：
The current driven by combined electron cyclotron wave (ECW) and high harmonic fast wave is investigated using the GENRAY/CQL3D package. It is shown that no significant synergetic current is found in a range of cases with a combined ECW and fast wave (FW). This result is consistent with a previous study [Harvey et al., in Proceedings of IAEA TCM on Fast Wave Current Drive in Reactor Scale Tokamaks (Synergy and Complimentarily with LHCD and ECRH), Arles, France, IAEA, Vienna, 1991]. However, a positive synergy effect does appear with the FW in the lower hybrid range of frequencies. This positive synergy effect can be explained using a picture of the electron distribution function induced by the ECW and a very high harmonic fast wave (helicon). The dependence of the synergy effect on the radial position of the power deposition, the wave power, the wave frequency, and the parallel refractive index is also analyzed, both numerically and physically.
摘要：
The effect of toroidal plasma rotation on q = 3 double tearing modes (DTMs) was studied numerically in cylindrical geometry using the method of reduced magnetohydrodynamic simulation. The results indicate that toroidal plasma rotation can reduce the growth rate of DTMs, but the magnitude of toroidal velocity has weak effect, especially without shear. When the shear of toroidal velocity exists, the suppression effect becomes better. Whether the velocity flow has shear or not, the growth rate of DTMs decreases as the magnitude of toroidal velocity increases. With the increase of velocity shear, the DTMs grow slowly. And the suppression effect of toroidal plasma rotation in early growth and transition stage is better, which means that the toroidal plasma rotation can suppress the linear growth of islands. Furthermore, the toroidal plasma rotation can suppress the evolution of poloidal stream. And the toroidal velocity shear on the q = 3 rational surface is more dominant than the magnitude of toroidal velocity in determining the DTM characteristics.
关键词：
gas electron multiplier;cosmic muon;X-ray;rising time;discrimination
摘要：
Gas electron multiplier (GEM) detectors have been used in cosmic muon scattering tomography and neutron imaging over the last decade. In this work, a triple GEM device with an effective readout area of 10 cm x 10 cm is developed, and a method of discriminating between cosmic muons and X-rays based on rise time is tested. The energy resolution of the GEM detector is tested by ~(55)Fe ray source to prove the GEM detector has a good performance. Analysis of the complete signal-cycles allows us to get the rise time and pulse heights. The experiment result indicates that cosmic muons and X-rays can be discriminated with an appropriate rise time threshold.
作者：
Cao, Jinjia;Gong, Xueyu*;Xiang, Dong;Huang, Qianhong;Yu, Jun
期刊：
PHYSICS OF PLASMAS,2016年23(8):082301 ISSN：1070-664X
通讯作者：
Gong, Xueyu
作者机构：
[Xiang, Dong; Huang, Qianhong; Gong, Xueyu; Cao, Jinjia] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Yu, Jun] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.
通讯机构：
[Gong, Xueyu] U;Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.
关键词：
plasma interactions;plasma transport processes
摘要：
The structure of the drift-island surface of passing fast ions (PFIs) is investigated in the presence of the resonant interaction with a magnetic island. Two overlapping regions of the drift-island surface and the magnetic island surface are found, one corresponding to local overlapping region and the other to non-local one. Here, the word “nonlocal” denotes that the resonances in the core plasma can have effects on the PFIs near the plasma boundary, while the “local” represents that the PFIs just near the resonant location are influenced. The nonlocal overlapping constructs a transport path along which the PFIs can become losses. There are three kinds of drift-island surfaces to join in forming the transport paths. A pitch angle region, which is called pitch angle gap, is found near the plasma boundary, where the drift-island surface cannot be formed and few PFIs are lost. The pitch-angle selective features of PFI losses are obtained by analyzing the three kinds of drift-island surfaces. The coupling between the crowd drift island surfaces and the collision can induce the prompt losses of PFIs and rapidly slowing down of PFI energy. The time of the prompt losses and the slowing down rate are calculated. Qualitatively, the theoretical results are in well agreement with the experimental observations in ASDEX Upgrade [M. García-Muñoz et al., Nucl. Fusion 47, L10 (2007)].
作者机构：
[Guo, Ping; Sun, Xiao-Dong] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.;[Li, Xiao-Hua] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Li, Xiao-Hua] Univ South China, Cooperat Innovat Ctr Nucl Fuel Cycle Technol & Eq, Hengyang 421001, Peoples R China.
通讯机构：
[Li, Xiao-Hua] U;Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;Univ South China, Cooperat Innovat Ctr Nucl Fuel Cycle Technol & Eq, Hengyang 421001, Peoples R China.
摘要：
α decay is a common and important process of natural radioactivity of heavy and superheavy nuclei. The α decay half-lives for even-even nuclei from Z=62 to Z=118 are systematically studied based on the two-potential approach with a quasistationary state approximation. As for the nuclear potential, the isospin effect is considered, which slightly improves the results by 6.8%. To reduce the deviations between experimental half-lives and calculated results due to the nuclear shell structure, the analytic expression of hindrance factors is employed. Our results can reproduce the experimental half-lives as good as using the density-dependent cluster model and the generalized liquid drop model.
作者机构：
[Guo, Ping; Sun, Xiao-Dong] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.;[Li, Xiao-Hua] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Li, Xiao-Hua] Univ South China, Cooperat Innovat Ctr Nucl Fuel Cycle Technol & Eq, Hengyang 421001, Peoples R China.
通讯机构：
[Li, Xiao-Hua] U;Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;Univ South China, Cooperat Innovat Ctr Nucl Fuel Cycle Technol & Eq, Hengyang 421001, Peoples R China.
摘要：
In this work, we systematically investigate the favored α-decay half-lives and α preformation probabilities of both odd- A and doubly-odd nuclei related to ground and isomeric states around the doubly magic cores at Z=82, N=82 and at Z=82, N=126, respectively, within a two-potential approach from the view of the valence nucleon (or hole). The results show that the α preformation probability is linearly related to NpNn or NpNnI, where Np, Nn, and I are the number of valence protons (or holes), the number of valence neutrons (or holes), and the isospin of the parent nucleus, respectively. Fitting the α preformation probabilities data extracted from the differences between experimental data and calculated half-lives without a shell correction, we give two analytic formulas of the α preformation probabilities and the values of corresponding parameters. Using those formulas and the parameters, we calculate the α-decay half-lives for those nuclei. The calculated results can well reproduce the experimental data.
摘要：
By employing atomistic simulations based on an empirical potential model and a self-consistent-charge density-functional tight-binding method, the collision dynamics process of an energetic carbon ion impinging on the Stone-Wales defect in a single-walled carbon nanotube was investigated. The outwardly and inwardly displacement threshold energies for the primary knock-on atom in the Stone-Wales defect were calculated to be 24.0 and 25.0 eV, respectively. The final defect configuration for each case was a 5-1DB-T(DB=dangling bond) defect formed in the front surface of the nanotube. Moreover, the minimum incident energy of the projectile prompting the primary knock-on atom displacement was predicted to be 71.0 eV, and the time evolutions of the kinetic and potential energies of the projectile and the primary knock-on atom were both plotted to analyze the energy transfer process.
作者机构：
[Wang, Chao; Wang, Zhen-Yang; Guo, Xin-Heng] Beijing Normal Univ, Coll Nucl Sci & Technol, Beijing 100875, Peoples R China.;[Zhang, Zhen-Hua] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Hunan, Peoples R China.;[Wang, Chao] Northwestern Polytech Univ, Ctr Ecol & Environm Sci, Xian 710072, Shaanxi, Peoples R China.
通讯机构：
[Guo, Xin-Heng] B;Beijing Normal Univ, Coll Nucl Sci & Technol, Beijing 100875, Peoples R China.
摘要：
We study the localized direct CP violation in the hadronic decays B±→ρ0(ω)π±→π+π−π±, including the effect caused by an interesting mechanism involving the charge symmetry violating mixing between ρ0 and ω in the QCD factorization approach. We find that ρ−ω mixing makes the localized integrated CP asymmetry move toward the negative direction when the low invariant mass of π+π− [ m(π+π−)low] is near ρ0(770). The localized integrated direct CP violation obtained in the QCD factorization approach varies from −0.0724 to −0.0389 in the ranges of parameters when 0.750<m(π+π−)low<0.800 GeV. This result, especially the sign, agrees with the experimental data. We also calculate the localized integrated direct CP violating asymmetries in the QCD factorization approach in the regions 0.470<m(π+π−)low<0.770 GeV and 0.770<m(π+π−)low<0.920 GeV. We find that these results agree with the experimental data and are more accurate than the results obtained through the naive factorization approach. It is more clear that ρ−ω mixing contributes to the sign change in these two regions.
关键词：
medical radioisotope;photonuclear reaction;gamma beam facility;radioisotope production
摘要：
The radioisotope production has a crucial role in medical diagnostic imaging or therapy. Historically, the radionuclides were produced using accelerated beams or nuclear reactors. The radioisotopes are used to precisely localize the pathological process or treat the illness by selectively targeting the site using a bioactive molecule as carrier. The applications of radioisotopes in molecular nuclear medicine require high specific activity, which can be usually obtained using nuclear reactions induced by high intensity accelerated beams of light charged particles or neutrons coming from nuclear reactors. The radioactive element is transmuted from the target isotope and can be separated by chemical procedures. The present Technical Design Report proposes the study of medical radioisotope production using a new route, by gamma-induced reaction mechanism where the reaction cross-sections are as low as 0.1 barn. We propose an experimental setup for testing this alternative method using the intense gamma-ray beam at ELI-NP facility, with an irradiation area, a target transport system and a test area. An intensity of 10(11) gamma/s for the new gamma beam at ELI-NP will allow in the first stage the possibility to obtain radioisotopes in quantities and specific activities (1-2 mCi/g) suitable for medical research.
摘要：
We investigate the properties of strange quark matter (SQM) and quark stars (QSs) in the framework of SU(3) Nambu–Jona-Lasinio (NJL) model with two types of vector interactions under strong magnetic fields: (1) the flavor-dependent repulsion among u, d, and s quarks with the coupling constant GV, and (2) the universal repulsion and the vector-isovector interaction with the coupling constants gV and GIV. The effects of the two types of vector interactions on the constituent quark mass, vacuum quark mass, quark chemical potential, and quark fraction in SQM under strong magnetic fields are studied, and the results indicate that these physical quantities for SQM are all sensitive to the two types of vector interactions in NJL model under magnetic fields. Using a density-dependent magnetic field profile which is introduced to describe the magnetic field strength distribution inside the magnetars, we calculate the properties of spherical QSs by using two extreme cases for the orientation of the magnetic field inside the stars, i.e., the radial orientation in which the magnetic fields are along the radial direction in stars, and the transverse orientation in which the magnetic fields are randomly oriented in the plane which is perpendicular to the radial direction. Our results indicate that the maximum mass of QSs may dependent on both the strength distribution and the orientation of the magnetic fields inside QSs by using SU(3) NJL model.
摘要：
With the dispersion relation derived for the geodesic acoustic mode in toroidally rotating tokamak plasmas using the fluid model, the effect of the toroidal rotation on the collisional viscous damping of the geodesic acoustic mode is investigated. It is found that the collisional viscous damping of the geodesic acoustic mode has weak increase with respect to the toroidal Mach number.
摘要：
The collisional damping of the geodesic acoustic mode (GAM) is analytically investigated in toroidally rotating tokamaks by using the gyrokinetic equation. It is found that the toroidal rotation could decrease the collisional damping of the GAM in the small safety factor region and increase the collisional damping of the GAM in the large safety factor region at low ion collision rate; while at high ion collision rate, the toroidal rotation will increase the collisional damping of the GAM with arbitrary safety factor. Furthermore, the change quantity of collisional damping rate of the GAM due to the toroidal rotation at high collision rate is larger than that at low collision rate.
摘要：
The radioisotope production has a crucial role in medical diagnosis and therapy. In this work, we investigated the possibility of obtaining radioisotopes of medical interest through photo-neutron reactions using the highintensity γ beams at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility. The specific activity for three benchmark radioisotopes, 99Mo/99mTc, 186Re and 225Ra/225Ac, was obtained as a function of γ-beam energy, target geometry and irradiation time. Optimization for the generation of these radioisotopes at ELI-NP was investigated. We estimated that a saturation specific activity of the order of 1-2 mCi/g could be obtained for a thin target (radius 1-2 mm, thickness 1 cm) and for a conservative γ-beam flux of 1011 s-1. The ELI-NP, based on these estimations, could provide the possibility for the production of certain radioisotopes in sufficient quantities for nuclear medicine research.
摘要：
The detection efficiency of electrostatic collection radon monitors is influenced by the humidity of the air in the collection cell. This is due to the recombination of positively charged 218Po with OH− ions, whose concentration depends on humidity. A novel design of an electrostatic collection cell, in which the air pressure in the cell is less than the atmospheric pressure, is proposed to eliminate the impact of humidity. As a result of the lower air pressure, the drift velocity of the positively charged 218Po in the electric field increases, so the collection time decreases. A model predicting the collection efficiency of positively charged 218Po in this kind of electrostatic collection cell is presented. Based on the model, if the air pressure in the cell is sufficiently low, the collection efficiency will be approximately a constant and the dependency of the collection efficiency of the positively charged 218Po upon the water vapor concentration can be ignored. This approach can be applied to develop a new radon monitor.
