In this paper, the principle of discharge-based pulsed I–V technique is introduced. By using it, the energy and spatial distributions of electron traps within the 4-nm HfO_2 layer have been extracted. Two peaks are o...In this paper, the principle of discharge-based pulsed I–V technique is introduced. By using it, the energy and spatial distributions of electron traps within the 4-nm HfO_2 layer have been extracted. Two peaks are observed, which are located at ?E ^-1.0 eV and-1.43 eV, respectively. It is found that the former one is close to the SiO_2/HfO_2 interface and the latter one is close to the gate electrode. It is also observed that the maximum discharge time has little effect on the energy distribution. Finally, the impact of electrical stress on the HfO_2 layer is also studied. During stress, no new electron traps and interface states are generated. Meanwhile, the electrical stress also has no impact on the energy and spatial distribution of as-grown traps. The results provide valuable information for theoretical modeling establishment, material assessment,and reliability improvement for advanced semiconductor devices.展开更多
We perform the total ionizing radiation and electrical stress experiments to investigate the electrical characteristics of the modified silicon-on-insulator(SOI) wafers under different Si ion implantation conditions...We perform the total ionizing radiation and electrical stress experiments to investigate the electrical characteristics of the modified silicon-on-insulator(SOI) wafers under different Si ion implantation conditions. It is confirmed that Si implantation into the buried oxide can create deep electron traps with large capture cross section to effectively improve the antiradiation capability of the SOI device. It is first proposed that the metastable electron traps accompanied with Si implantation can be avoided by adjusting the peak location of the Si implantation reasonably.展开更多
By performing one-dimensional particle-in-cell simulations,the nonlinear effects of electronacoustic(EA)waves are investigated in a multispecies plasma,whose constituents are hot electrons,cold electrons,and beam elec...By performing one-dimensional particle-in-cell simulations,the nonlinear effects of electronacoustic(EA)waves are investigated in a multispecies plasma,whose constituents are hot electrons,cold electrons,and beam electrons with immobile neutralized positive ions.Numerical analyses have identified that EA waves with a sufficiently large amplitude tend to trap cold electrons.Because EA waves are dispersive,where the wave modes with different wavenumbers have different phase velocities,the trapping may lead to the nlixing of cold electrons.The cold electrons finally get thermalized or heated.The investigation also shows that the excited EA waves give rise to a broad range of wave frequencies,which may be helpful for understanding the broadband-electrostatic-noise spectrum in the Earth's auroral region.展开更多
Interface engineering in atomically thin transition metal dichalcogenides(TMDs)is becoming an important and powerful technique to alter their properties,enabling new optoelectronic applications and quantum devices.Int...Interface engineering in atomically thin transition metal dichalcogenides(TMDs)is becoming an important and powerful technique to alter their properties,enabling new optoelectronic applications and quantum devices.Interface engineering in a monolayer WSe_(2)sample via introduction of high-density edges of standing structured graphene nanosheets(GNs)is realized.A strong photoluminescence(PL)emission peak from intravalley and intervalley trions at about 750 nm is observed at the room temperature,which indicated the heavily p-type doping of the monolayer WSe_(2)/thin graphene nanosheet-embedded carbon(TGNEC)film heterostructure.We also successfully triggered the emission of biexcitons(excited state biexciton)in a monolayer WSe_(2),via the electron trapping centers of edge quantum wells of a TGNEC film.The PL emission of a monolayer WSe_(2)/GNEC film is quenched by capturing the photoexcited electrons to reduce the electron-hole recombination rate.This study can be an important benchmark for the extensive understanding of light–matter interaction in TMDs,and their dynamics.展开更多
An experimental measurement of the lifetime of 3d^(9) ^(2)D_(3/2) metastable level in Mo^(15+)is reported in this work.The Mo^(15+)ions are produced and trapped in an electron beam ion trap with a magnetic field of 0....An experimental measurement of the lifetime of 3d^(9) ^(2)D_(3/2) metastable level in Mo^(15+)is reported in this work.The Mo^(15+)ions are produced and trapped in an electron beam ion trap with a magnetic field of 0.65 T.The decay photons emitted from 3d^(9) ^(2)D_(3/2) level are subsequently recorded via a cooled photomultiplier tube.Through meticulous scrutiny of potential systematic uncertainties affecting the measurement outcomes,we have determined the lifetime of Mo^(15+)3d^(9)2D_(3/2)metastable level to be 2.83(22)ms.The experimental result provides a clear distinguishment from existing calculations based on various theoretical approaches.展开更多
Photoelectron is the foundation of latent image formation, the decay process of photoelectrons is influenced by all kinds of trapping centres in silver halide. By analysing the mechanism of latent image formation it i...Photoelectron is the foundation of latent image formation, the decay process of photoelectrons is influenced by all kinds of trapping centres in silver halide. By analysing the mechanism of latent image formation it is found that electron trap, hole trap, and one kind of recombination centre where free electron and trapped hole recombine are the main trapping centres in silver halide. Different trapping centres have different influences on the photoelectron behaviour. The effects of all kinds of typical trapping centres on the decay of photoelectrons are systematically investigated by solving the photoelectron decay kinetic equations. The results are in agreement with those obtained in the microwave absorption dielectric spectrum experiment.展开更多
Trivalent rare-earth ions (La3+,Pr3+,Nd3+,Sm3+,Gd3+,Tb3+,Dy3+,Ho3+,Er3+,Tm3+,and Yb3+) were investigated as the codoped auxiliary sensitizer for the electron trapping materials SrS:Eu2+ in order to enha...Trivalent rare-earth ions (La3+,Pr3+,Nd3+,Sm3+,Gd3+,Tb3+,Dy3+,Ho3+,Er3+,Tm3+,and Yb3+) were investigated as the codoped auxiliary sensitizer for the electron trapping materials SrS:Eu2+ in order to enhance the fluorescence properties.It was found that Sm3+ and Tb3+ had the best photoluminescence stimulated luminescence (PSL) effect among the selected trivalent rare-earth ions.All the SrS:Eu2+ samples doped by different trivalent rare-earth ions could be stimulated by 980 nm laser after being exposed to the conventional sunlight,and they emitted PSL with the peak located at 615 nm.The result also indicated that some co-doped rare earth ions could increase fluorescence intensities of the traditional electron trapping materials SrS:Eu2+.展开更多
An investigation is carried out for understanding the properties of ion–acoustic(IA) solitary waves in an inhomogeneous magnetized electron-ion plasma with field-aligned sheared flow under the impact of q-nonextens...An investigation is carried out for understanding the properties of ion–acoustic(IA) solitary waves in an inhomogeneous magnetized electron-ion plasma with field-aligned sheared flow under the impact of q-nonextensive trapped electrons. The Schamel equation and its stationary solution in the form of solitary waves are obtained for this inhomogeneous plasma. It is shown that the amplitude of IA solitary waves increases with higher trapping efficiency(β), while the width remains almost the same. Further, it is found that the amplitude of the solitary waves decreases with enhanced normalized drift speed, shear flow parameter and the population of the energetic particles. The size of the nonlinear solitary structures is calculated to be a few hundred meters and it is pointed out that the present results are useful to understand the solar wind plasma.展开更多
In order to investigate the influence of sintering temperature on the Schottky barrier and bulk electron traps of ZnO varistors,ZnO-Bi2O3 based varistor ceramic samples were sintered at 1000,1100,1200 and 1300°C,...In order to investigate the influence of sintering temperature on the Schottky barrier and bulk electron traps of ZnO varistors,ZnO-Bi2O3 based varistor ceramic samples were sintered at 1000,1100,1200 and 1300°C,respectively.The measured results indicate that the sample sintered at 1300°C possesses the lowest voltage gradient and nonlinear coefficient,compared with other samples.The barrier height of the samples decreased as the sintering temperature increased,which resulted in the deterioration of nonlinearity.Furthermore,two bulk electron traps determined by admittance spectroscopy were generally independent of sintering temperature,which indicated that these two traps might originate from the intrinsic defects in ZnO lattice.展开更多
Urbach’s formula for evaluation of electron trapping parameter that happens to be the earliest has emerged as a popular method amongst researchers of persistent luminescence. In this study, we analysed the thermolumi...Urbach’s formula for evaluation of electron trapping parameter that happens to be the earliest has emerged as a popular method amongst researchers of persistent luminescence. In this study, we analysed the thermoluminescence curves of glow-in-the-dark phosphors. Those included some curves recorded by us and others that solely used the Urbach’s formula. Using the parameter obtained by rigorous analysis by fitting the whole TL curves, we presented a comprehensive picture of the potentialities and limitations of the simple Urbach’s relation E=T_m/500, where E is the trap-depth and T_m the peak temperature in absolute scale, first proposed by Urbach in 1930. Some simple thumb rules on the use of the formula were presented for beginners as well as non-specialists so that entry of physically unrealistic data into the literature was prevented.展开更多
A brief introduction to the historical background and current status of electron beam ion traps (EBITs)is presented. The structure and principles of an EBIT for producing highly charged ions are described. Finally,EBI...A brief introduction to the historical background and current status of electron beam ion traps (EBITs)is presented. The structure and principles of an EBIT for producing highly charged ions are described. Finally,EBITs as a potential tool in hot-plasma diagnostics and in studying frontier problems of highly charged ion physicsare discussed.展开更多
The long persistent phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02) were prepared by a high temperature solid state reaction. All samples showed a broad band emission peaking at 510 nm, which coul...The long persistent phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02) were prepared by a high temperature solid state reaction. All samples showed a broad band emission peaking at 510 nm, which could be ascribed to Eu2+ transition between 4f65d1 and 4f7 electron configurations. With the increase of substitution of Ho3+ ions for the Dy3+ ions in the as-prepared phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02), the initial intensity of the afterglow obviously decreased. From the thermoluminescence (TL) curves of the samples, we concluded that codoped Ho3+ ions led to a decline of the trap depth and redistribution of the trap. This may be responsible for the change of afterglow of Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02).展开更多
We study the Landau resonance between geodesic acoustic mode(GAM) and trapped electrons as a GAM’s collisionless damping. The assumption of ˉωde 〈〈ωbeis adopted.The damping rate induced by trapped electrons is...We study the Landau resonance between geodesic acoustic mode(GAM) and trapped electrons as a GAM’s collisionless damping. The assumption of ˉωde 〈〈ωbeis adopted.The damping rate induced by trapped electrons is found to be an increasing function of q. In low q range, circulating-ion-induced damping rate is larger than that induced by trapped electrons.As q increases, the latter becomes larger than the former. The reason is that trapped electrons’ resonant velocity is close to vtefrom the lower side, whiles circulating ions’ resonant velocity gets bigger further from vti. So the number of resonant trapped electrons increases, whiles the number of resonant circulating ions decreases. The amplitude of damping rate induced by trapped electrons in the edge plasma can be comparable to that induced by circulating ions in the low q range.Another phenomenon we found is that in the chosen range of, the damping caused by trapped electrons has a maximum value at point εq for different q. The reason is that as is close to q,trapped electorns’ resonant velocity is close to vte.展开更多
In this work, the effects of superthermal and trapped electrons on the oblique propa- gation of nonlinear dust-acoustic waves in a magnetized dusty (complex) plasma are investigated. The dynamic of electrons is simu...In this work, the effects of superthermal and trapped electrons on the oblique propa- gation of nonlinear dust-acoustic waves in a magnetized dusty (complex) plasma are investigated. The dynamic of electrons is simulated by the generalized Lorentzian (k) distribution function (DF). The dust grains are cold and their dynamics are simulated by hydrodynamic equations. Using the standard reductive perturbation technique (RPT) a nonlinear modified Korteweg-de Vries (mKdV) equation is derived. Two types of solitary waves; fast and slow dust acoustic solitons, exist in this plasma. Calculations reveal that compressive solitary structures are likely to propagate in this plasma where dust grains are negatively (or positively) charged. The properties of dust acoustic solitons (DASs) are also investigated numerically.展开更多
The ion temperature gradient(ITG)mode in the presence of impurity ions and trapped electrons(TEs)is numerically investigated in tokamak plasmas with hollow density profiles,using the gyrokinetic integral eigenmode equ...The ion temperature gradient(ITG)mode in the presence of impurity ions and trapped electrons(TEs)is numerically investigated in tokamak plasmas with hollow density profiles,using the gyrokinetic integral eigenmode equation.It is found that in the inverted density plasma,the increase of the ITG enhances the growth rate and frequency of the ITG,and the density gradient plays an important role in the ITG modes.For weak density gradient situations,the trapped electron effects increase the instability of the ITG,while the impurity has an obviously stabilizing effect.For the strong density gradient cases,both the impurities and trapped electrons enhance the ITG instabilities.In addition,it is shown that the growth rate of the ITG decreases with positive magnetic shear s while the real frequency increases with positive magnetic shear.The growth rate of the ITG increases with negative magnetic shear s while the real frequency decreases with negative magnetic shear.The length of the calculated mode structure in the positive and negative magnetic shear intervals is also presented.展开更多
The effects of trapped electrons on off-axis lower hybrid current drive (LHCD) in tokamaks are studied, A computer code for solving the Fokker-Planck equation in a toroidal geometry is developed and employed. The co...The effects of trapped electrons on off-axis lower hybrid current drive (LHCD) in tokamaks are studied, A computer code for solving the Fokker-Planck equation in a toroidal geometry is developed and employed. The code is suitable for various auxiliary heating and current drive schemes in tokamak plasmas. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped particle fraction on the current drive efficiency are emphasized. It is shown that, as an electrostatic force, the lower hybrid wave causes some of the trapped electrons to be untrapped and lose their energy, which can cut the LHCD efficiency by about 30%. The ITER scaling law is also used to estimate the trapped electron effects.展开更多
In EAST,synchrotron radiation is emitted by runaway electrons in the infrared band,which can be observed by infrared cameras.This synchrotron radiation is mainly emitted by passing runaway electrons with tens of MeV e...In EAST,synchrotron radiation is emitted by runaway electrons in the infrared band,which can be observed by infrared cameras.This synchrotron radiation is mainly emitted by passing runaway electrons with tens of MeV energy.A common feature of radiation dominated by passing runaway electrons is that it is strongest on the high field side.However,the deeply trapped runaway electrons cannot reach the high field side in principle.Therefore,in this case,the high field side radiation is expected to be weak.This paper reports for the first time that the synchrotron radiation from trapped runaway electrons dominates that from passing runaway electrons and is identifiable in an image.Although the synchrotron radiation dominated by trapped runaway electrons can be observed in experiment,the proportion of trapped runaway electrons is very low.展开更多
In this report, an introduction to the structure of Shanghai EBIT, a brief description of the status ofShanghai EBIT project, and a short discussion of the first results of Shanghai EBIT are presented.
The formation and propagation of nonlinear dust acoustic waves(DAWs) as solitary and solitary/shock waves in an unmagnetized, homogeneous, dissipative and collisionless dusty plasma comprising negatively charged mic...The formation and propagation of nonlinear dust acoustic waves(DAWs) as solitary and solitary/shock waves in an unmagnetized, homogeneous, dissipative and collisionless dusty plasma comprising negatively charged micron sized dust grains in the presence of free and trapped electrons with singly charged non-thermal positive ions is discussed in detail. The evolution characteristics of the solitary and shock waves are studied by deriving a modified Korteweg–de Vries–Burgers(mKdV–Burgers) equation using the reductive perturbation method. The mKdV–Burgers equation is solved considering the presence(absence) of dissipation. In the absence of dissipation the system admits a solitary wave solution, whereas in the presence of dissipation the system admits shock waves(both monotonic and oscillatory) as well as a combination of solitary and shock wave solutions. Standard methods of solving the evolution equation of shock(solitary) waves are used. The results are discussed numerically using standard values of plasma parameters. The findings may be useful for better understanding of formation and propagation of waves in astrophysical plasma.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61334002,61106106,and 61474091)the New Experiment Development Funds for Xidian University,China(Grant No.SY1434)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,China(Grant No.JY0600132501)
文摘In this paper, the principle of discharge-based pulsed I–V technique is introduced. By using it, the energy and spatial distributions of electron traps within the 4-nm HfO_2 layer have been extracted. Two peaks are observed, which are located at ?E ^-1.0 eV and-1.43 eV, respectively. It is found that the former one is close to the SiO_2/HfO_2 interface and the latter one is close to the gate electrode. It is also observed that the maximum discharge time has little effect on the energy distribution. Finally, the impact of electrical stress on the HfO_2 layer is also studied. During stress, no new electron traps and interface states are generated. Meanwhile, the electrical stress also has no impact on the energy and spatial distribution of as-grown traps. The results provide valuable information for theoretical modeling establishment, material assessment,and reliability improvement for advanced semiconductor devices.
基金Supported by the National Natural Science Foundation of China under Grant No 61504047the Fujian Provincial Department of Science and Technology under Grant No 2016J05159
文摘We perform the total ionizing radiation and electrical stress experiments to investigate the electrical characteristics of the modified silicon-on-insulator(SOI) wafers under different Si ion implantation conditions. It is confirmed that Si implantation into the buried oxide can create deep electron traps with large capture cross section to effectively improve the antiradiation capability of the SOI device. It is first proposed that the metastable electron traps accompanied with Si implantation can be avoided by adjusting the peak location of the Si implantation reasonably.
基金the support from Chinese Academy of Science(CAS)TWAS for his Ph.D studies at the University of Science and Technology of China in the category of a 2016 CAS-TWAS President’s Fellowship Awardee(Series No.2016-172)+1 种基金partially supported by National Natural Science Foundation of China(Nos.41331067,41774169,and 41527804)the Key Research Program of Frontier Sciences,CAS(QYZDJ-SSW-DQC010)
文摘By performing one-dimensional particle-in-cell simulations,the nonlinear effects of electronacoustic(EA)waves are investigated in a multispecies plasma,whose constituents are hot electrons,cold electrons,and beam electrons with immobile neutralized positive ions.Numerical analyses have identified that EA waves with a sufficiently large amplitude tend to trap cold electrons.Because EA waves are dispersive,where the wave modes with different wavenumbers have different phase velocities,the trapping may lead to the nlixing of cold electrons.The cold electrons finally get thermalized or heated.The investigation also shows that the excited EA waves give rise to a broad range of wave frequencies,which may be helpful for understanding the broadband-electrostatic-noise spectrum in the Earth's auroral region.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Nos.62104155,52275565,52005343,and 62204117)of Chinathe Natural Science Foundation of Guangdong Province(No.2022A1515011667)+1 种基金the financial support from Jiangsu Province Science Foundation for Youths(No.BK20210275)Guangdong Kangyi Special Fund(No.2020KZDZX1173).
文摘Interface engineering in atomically thin transition metal dichalcogenides(TMDs)is becoming an important and powerful technique to alter their properties,enabling new optoelectronic applications and quantum devices.Interface engineering in a monolayer WSe_(2)sample via introduction of high-density edges of standing structured graphene nanosheets(GNs)is realized.A strong photoluminescence(PL)emission peak from intravalley and intervalley trions at about 750 nm is observed at the room temperature,which indicated the heavily p-type doping of the monolayer WSe_(2)/thin graphene nanosheet-embedded carbon(TGNEC)film heterostructure.We also successfully triggered the emission of biexcitons(excited state biexciton)in a monolayer WSe_(2),via the electron trapping centers of edge quantum wells of a TGNEC film.The PL emission of a monolayer WSe_(2)/GNEC film is quenched by capturing the photoexcited electrons to reduce the electron-hole recombination rate.This study can be an important benchmark for the extensive understanding of light–matter interaction in TMDs,and their dynamics.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1602500)the National Natural Science Foundation of China(Grant No.12274352)。
文摘An experimental measurement of the lifetime of 3d^(9) ^(2)D_(3/2) metastable level in Mo^(15+)is reported in this work.The Mo^(15+)ions are produced and trapped in an electron beam ion trap with a magnetic field of 0.65 T.The decay photons emitted from 3d^(9) ^(2)D_(3/2) level are subsequently recorded via a cooled photomultiplier tube.Through meticulous scrutiny of potential systematic uncertainties affecting the measurement outcomes,we have determined the lifetime of Mo^(15+)3d^(9)2D_(3/2)metastable level to be 2.83(22)ms.The experimental result provides a clear distinguishment from existing calculations based on various theoretical approaches.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10274017 and 10354001), and the Natural Science Foundation of Hebei Province, China (Grant Nos 103097 and 603138).
文摘Photoelectron is the foundation of latent image formation, the decay process of photoelectrons is influenced by all kinds of trapping centres in silver halide. By analysing the mechanism of latent image formation it is found that electron trap, hole trap, and one kind of recombination centre where free electron and trapped hole recombine are the main trapping centres in silver halide. Different trapping centres have different influences on the photoelectron behaviour. The effects of all kinds of typical trapping centres on the decay of photoelectrons are systematically investigated by solving the photoelectron decay kinetic equations. The results are in agreement with those obtained in the microwave absorption dielectric spectrum experiment.
基金Project supported by the National Natural Science Foundations of China (20876002, 20976002)the Beijing Natural Science Foundation (2091002)Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality
文摘Trivalent rare-earth ions (La3+,Pr3+,Nd3+,Sm3+,Gd3+,Tb3+,Dy3+,Ho3+,Er3+,Tm3+,and Yb3+) were investigated as the codoped auxiliary sensitizer for the electron trapping materials SrS:Eu2+ in order to enhance the fluorescence properties.It was found that Sm3+ and Tb3+ had the best photoluminescence stimulated luminescence (PSL) effect among the selected trivalent rare-earth ions.All the SrS:Eu2+ samples doped by different trivalent rare-earth ions could be stimulated by 980 nm laser after being exposed to the conventional sunlight,and they emitted PSL with the peak located at 615 nm.The result also indicated that some co-doped rare earth ions could increase fluorescence intensities of the traditional electron trapping materials SrS:Eu2+.
文摘An investigation is carried out for understanding the properties of ion–acoustic(IA) solitary waves in an inhomogeneous magnetized electron-ion plasma with field-aligned sheared flow under the impact of q-nonextensive trapped electrons. The Schamel equation and its stationary solution in the form of solitary waves are obtained for this inhomogeneous plasma. It is shown that the amplitude of IA solitary waves increases with higher trapping efficiency(β), while the width remains almost the same. Further, it is found that the amplitude of the solitary waves decreases with enhanced normalized drift speed, shear flow parameter and the population of the energetic particles. The size of the nonlinear solitary structures is calculated to be a few hundred meters and it is pointed out that the present results are useful to understand the solar wind plasma.
基金supported by the National Natural Science Foundations of China(Grant Nos.50425721 and 50737001)
文摘In order to investigate the influence of sintering temperature on the Schottky barrier and bulk electron traps of ZnO varistors,ZnO-Bi2O3 based varistor ceramic samples were sintered at 1000,1100,1200 and 1300°C,respectively.The measured results indicate that the sample sintered at 1300°C possesses the lowest voltage gradient and nonlinear coefficient,compared with other samples.The barrier height of the samples decreased as the sintering temperature increased,which resulted in the deterioration of nonlinearity.Furthermore,two bulk electron traps determined by admittance spectroscopy were generally independent of sintering temperature,which indicated that these two traps might originate from the intrinsic defects in ZnO lattice.
基金supported by University Grant Commission New Delhi of India
文摘Urbach’s formula for evaluation of electron trapping parameter that happens to be the earliest has emerged as a popular method amongst researchers of persistent luminescence. In this study, we analysed the thermoluminescence curves of glow-in-the-dark phosphors. Those included some curves recorded by us and others that solely used the Urbach’s formula. Using the parameter obtained by rigorous analysis by fitting the whole TL curves, we presented a comprehensive picture of the potentialities and limitations of the simple Urbach’s relation E=T_m/500, where E is the trap-depth and T_m the peak temperature in absolute scale, first proposed by Urbach in 1930. Some simple thumb rules on the use of the formula were presented for beginners as well as non-specialists so that entry of physically unrealistic data into the literature was prevented.
基金the Outstanding Young Scientist Program of the Natural Science Foundation of China(No.10125520)by the Outstanding Young Professor Project of the Ministry of Education of China
文摘A brief introduction to the historical background and current status of electron beam ion traps (EBITs)is presented. The structure and principles of an EBIT for producing highly charged ions are described. Finally,EBITs as a potential tool in hot-plasma diagnostics and in studying frontier problems of highly charged ion physicsare discussed.
基金Project supported by the National Natural Science Foundation of China (20871033)
文摘The long persistent phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02) were prepared by a high temperature solid state reaction. All samples showed a broad band emission peaking at 510 nm, which could be ascribed to Eu2+ transition between 4f65d1 and 4f7 electron configurations. With the increase of substitution of Ho3+ ions for the Dy3+ ions in the as-prepared phosphors Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02), the initial intensity of the afterglow obviously decreased. From the thermoluminescence (TL) curves of the samples, we concluded that codoped Ho3+ ions led to a decline of the trap depth and redistribution of the trap. This may be responsible for the change of afterglow of Sr3Al2O6:Eu0.012+,Dy0.02-x3+,Hox3+ (x=0, 0.01, 0.02).
文摘We study the Landau resonance between geodesic acoustic mode(GAM) and trapped electrons as a GAM’s collisionless damping. The assumption of ˉωde 〈〈ωbeis adopted.The damping rate induced by trapped electrons is found to be an increasing function of q. In low q range, circulating-ion-induced damping rate is larger than that induced by trapped electrons.As q increases, the latter becomes larger than the former. The reason is that trapped electrons’ resonant velocity is close to vtefrom the lower side, whiles circulating ions’ resonant velocity gets bigger further from vti. So the number of resonant trapped electrons increases, whiles the number of resonant circulating ions decreases. The amplitude of damping rate induced by trapped electrons in the edge plasma can be comparable to that induced by circulating ions in the low q range.Another phenomenon we found is that in the chosen range of, the damping caused by trapped electrons has a maximum value at point εq for different q. The reason is that as is close to q,trapped electorns’ resonant velocity is close to vte.
文摘In this work, the effects of superthermal and trapped electrons on the oblique propa- gation of nonlinear dust-acoustic waves in a magnetized dusty (complex) plasma are investigated. The dynamic of electrons is simulated by the generalized Lorentzian (k) distribution function (DF). The dust grains are cold and their dynamics are simulated by hydrodynamic equations. Using the standard reductive perturbation technique (RPT) a nonlinear modified Korteweg-de Vries (mKdV) equation is derived. Two types of solitary waves; fast and slow dust acoustic solitons, exist in this plasma. Calculations reveal that compressive solitary structures are likely to propagate in this plasma where dust grains are negatively (or positively) charged. The properties of dust acoustic solitons (DASs) are also investigated numerically.
基金supported by the National Key R&D Program of China(Nos.2018YFE0303102 and2017YFE0301702)US SciDAC GSEP+2 种基金the NSFC(Nos.11905109 and 11947238)the China Postdoctoral Science Foundation(No.2018M640230)the Fundamental Research Funds for the Central Universities,Nankai University(63191351)。
文摘The ion temperature gradient(ITG)mode in the presence of impurity ions and trapped electrons(TEs)is numerically investigated in tokamak plasmas with hollow density profiles,using the gyrokinetic integral eigenmode equation.It is found that in the inverted density plasma,the increase of the ITG enhances the growth rate and frequency of the ITG,and the density gradient plays an important role in the ITG modes.For weak density gradient situations,the trapped electron effects increase the instability of the ITG,while the impurity has an obviously stabilizing effect.For the strong density gradient cases,both the impurities and trapped electrons enhance the ITG instabilities.In addition,it is shown that the growth rate of the ITG decreases with positive magnetic shear s while the real frequency increases with positive magnetic shear.The growth rate of the ITG increases with negative magnetic shear s while the real frequency decreases with negative magnetic shear.The length of the calculated mode structure in the positive and negative magnetic shear intervals is also presented.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10675043, 10575031 and 10675042).
文摘The effects of trapped electrons on off-axis lower hybrid current drive (LHCD) in tokamaks are studied, A computer code for solving the Fokker-Planck equation in a toroidal geometry is developed and employed. The code is suitable for various auxiliary heating and current drive schemes in tokamak plasmas. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped particle fraction on the current drive efficiency are emphasized. It is shown that, as an electrostatic force, the lower hybrid wave causes some of the trapped electrons to be untrapped and lose their energy, which can cut the LHCD efficiency by about 30%. The ITER scaling law is also used to estimate the trapped electron effects.
基金the National Natural Science Foundation of China(Grant No.11775263)the National Magnetic Confinement Fusion Energy Research Project of China(Grant No.2015GB111003).
文摘In EAST,synchrotron radiation is emitted by runaway electrons in the infrared band,which can be observed by infrared cameras.This synchrotron radiation is mainly emitted by passing runaway electrons with tens of MeV energy.A common feature of radiation dominated by passing runaway electrons is that it is strongest on the high field side.However,the deeply trapped runaway electrons cannot reach the high field side in principle.Therefore,in this case,the high field side radiation is expected to be weak.This paper reports for the first time that the synchrotron radiation from trapped runaway electrons dominates that from passing runaway electrons and is identifiable in an image.Although the synchrotron radiation dominated by trapped runaway electrons can be observed in experiment,the proportion of trapped runaway electrons is very low.
文摘In this report, an introduction to the structure of Shanghai EBIT, a brief description of the status ofShanghai EBIT project, and a short discussion of the first results of Shanghai EBIT are presented.
文摘The formation and propagation of nonlinear dust acoustic waves(DAWs) as solitary and solitary/shock waves in an unmagnetized, homogeneous, dissipative and collisionless dusty plasma comprising negatively charged micron sized dust grains in the presence of free and trapped electrons with singly charged non-thermal positive ions is discussed in detail. The evolution characteristics of the solitary and shock waves are studied by deriving a modified Korteweg–de Vries–Burgers(mKdV–Burgers) equation using the reductive perturbation method. The mKdV–Burgers equation is solved considering the presence(absence) of dissipation. In the absence of dissipation the system admits a solitary wave solution, whereas in the presence of dissipation the system admits shock waves(both monotonic and oscillatory) as well as a combination of solitary and shock wave solutions. Standard methods of solving the evolution equation of shock(solitary) waves are used. The results are discussed numerically using standard values of plasma parameters. The findings may be useful for better understanding of formation and propagation of waves in astrophysical plasma.