This paper presents the fully differential cross sections （FDCS） for 102eV electron impact single ionization of helium for both the coplanar and perpendicular plane asymmetric geometries within the framework of dyna...This paper presents the fully differential cross sections （FDCS） for 102eV electron impact single ionization of helium for both the coplanar and perpendicular plane asymmetric geometries within the framework of dynamically screened three-Coulomb-wave theory. Comparisons are made with the experimental data and those of the three-Coulomb wave function model and second-order distorted-wave Born method. The angular distribution and relative heights of the present FDCS is found to be in very good agreement with the experimental data in the perpendicular plane geometry. It is shown that dynamical screening effects are significant in this geometry. Three-body coupling is expected to be weak in the coplanar geometry, although the precise absolute value of the cross section is still sensitive to the interaction details.展开更多
This paper describes an n-i-p-i-n model heterostructure with a manganese （Mn）-doped p-type base region to check the stability of a positively charged manganese A＋Mn centre with two holes weakly bound by a negativel...This paper describes an n-i-p-i-n model heterostructure with a manganese （Mn）-doped p-type base region to check the stability of a positively charged manganese A＋Mn centre with two holes weakly bound by a negatively charged 3dS（Mn） core of a local spin S = 5/2 in the framework of the effective mass approximation near the F critical point （k -0）. By including the carrier screening effect, the ground state energy and the binding energy of the second hole in the positively charged centre A＋Mn are calculated within a hole concentration range from 1 ×10^16 cm-3 to 1 × 10^17 cm^-3, which is achievable by biasing the structure under photo-excitation. For comparison, the ground-state energy of a single hole in the neutral AMn centre is calculated in the same concentration range. It turns out that the binding energy of the second hole in the A＋Mn centre varies from 9.27 meV to 4.57 meV. We propose that the presence of the A＋Mn centre can be examined by measuring the photoluminescence from recombination of electrons in the conduction band with the bound holes in the A＋Mn centre since a high frequency dielectric constant of ε∞ = 10.66 can be safely adopted in this case. The novel feature of the ability to tune the impurity level of the A＋Mn centre makes it attractive for optically and electrically manipulating local magnetic spins in semiconductors.展开更多
Impurity transport was investigated at both edge and core regions in large helical de- vice （LHD） with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The ...Impurity transport was investigated at both edge and core regions in large helical de- vice （LHD） with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The edge impurity behavior was studied recently using four carbon resonant transitions in different ionization stages of CIII （977A）, CIV （1548A）, CV （40.3A） and CVI （33.7A）. When the line-averaged electron density, ne, is increased from 1 to 6 × 10^13 cm-3, the ratio of （CIII^CIV）/ne increases while the ratio of （CV＋CVI）/ne decreases. Here, CIII^CIV （CV＋CVI） expresses the sum of CIII （CV） and CIV （CVI） intensities. The CIII＋CIV indicates the carbon influx and the CV＋CVI indicates the emissions through the transport in the ergodic layer. The result thus gives experimental evidence on the impurity screening by the ergodic layer in LHD, which is also supported by a three-dimensional edge particle simulation. The core impu- rity behavior is also studied in high-density discharges （ne 〈 1 × 10^15 cm 3） with multi H2-pellets injection. It is found that the ratio of V/D （V： convection velocity, D： diffusion coefficient） decreases after pellet injection and Zeff profile shows a flat one at values of 1.1,-1.2. These results confirm no impurity accumulation occurs in high-density discharges. As a result, the iron density, rife, is analyzed to be 6 × 10^-7（=- nFe/ne） of which the amount can be negligible as radiation source even in such high-density discharges. One- and two-dimensional impurity distributions from space-resolved VUV and EUV spectrometers newly developed for further impurity transport study are also presented with their preliminary results.展开更多
基金Project supported by the Natural Science Foundation of Shanxi Province,China (Grant No 20051008)the Science Foundation for Returnee of Shanxi Province of China (Grant No 02-16)
文摘This paper presents the fully differential cross sections （FDCS） for 102eV electron impact single ionization of helium for both the coplanar and perpendicular plane asymmetric geometries within the framework of dynamically screened three-Coulomb-wave theory. Comparisons are made with the experimental data and those of the three-Coulomb wave function model and second-order distorted-wave Born method. The angular distribution and relative heights of the present FDCS is found to be in very good agreement with the experimental data in the perpendicular plane geometry. It is shown that dynamical screening effects are significant in this geometry. Three-body coupling is expected to be weak in the coplanar geometry, although the precise absolute value of the cross section is still sensitive to the interaction details.
基金supported by the National Basic Research Program of China (Grant Nos. 2007CB924904 and 2011CB932901)
文摘This paper describes an n-i-p-i-n model heterostructure with a manganese （Mn）-doped p-type base region to check the stability of a positively charged manganese A＋Mn centre with two holes weakly bound by a negatively charged 3dS（Mn） core of a local spin S = 5/2 in the framework of the effective mass approximation near the F critical point （k -0）. By including the carrier screening effect, the ground state energy and the binding energy of the second hole in the positively charged centre A＋Mn are calculated within a hole concentration range from 1 ×10^16 cm-3 to 1 × 10^17 cm^-3, which is achievable by biasing the structure under photo-excitation. For comparison, the ground-state energy of a single hole in the neutral AMn centre is calculated in the same concentration range. It turns out that the binding energy of the second hole in the A＋Mn centre varies from 9.27 meV to 4.57 meV. We propose that the presence of the A＋Mn centre can be examined by measuring the photoluminescence from recombination of electrons in the conduction band with the bound holes in the A＋Mn centre since a high frequency dielectric constant of ε∞ = 10.66 can be safely adopted in this case. The novel feature of the ability to tune the impurity level of the A＋Mn centre makes it attractive for optically and electrically manipulating local magnetic spins in semiconductors.
基金the LHD project (NIFS08ULPP527)the JSPS-CAS Core-University program in the field of Plasma and Nuclear Fusion
文摘Impurity transport was investigated at both edge and core regions in large helical de- vice （LHD） with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The edge impurity behavior was studied recently using four carbon resonant transitions in different ionization stages of CIII （977A）, CIV （1548A）, CV （40.3A） and CVI （33.7A）. When the line-averaged electron density, ne, is increased from 1 to 6 × 10^13 cm-3, the ratio of （CIII^CIV）/ne increases while the ratio of （CV＋CVI）/ne decreases. Here, CIII^CIV （CV＋CVI） expresses the sum of CIII （CV） and CIV （CVI） intensities. The CIII＋CIV indicates the carbon influx and the CV＋CVI indicates the emissions through the transport in the ergodic layer. The result thus gives experimental evidence on the impurity screening by the ergodic layer in LHD, which is also supported by a three-dimensional edge particle simulation. The core impu- rity behavior is also studied in high-density discharges （ne 〈 1 × 10^15 cm 3） with multi H2-pellets injection. It is found that the ratio of V/D （V： convection velocity, D： diffusion coefficient） decreases after pellet injection and Zeff profile shows a flat one at values of 1.1,-1.2. These results confirm no impurity accumulation occurs in high-density discharges. As a result, the iron density, rife, is analyzed to be 6 × 10^-7（=- nFe/ne） of which the amount can be negligible as radiation source even in such high-density discharges. One- and two-dimensional impurity distributions from space-resolved VUV and EUV spectrometers newly developed for further impurity transport study are also presented with their preliminary results.
