Theoretical Analysis of the Frequency Jump in E-fishbone Experiments

It is identified that barely passing electrons are the drive of the e-Gshbones,rather than the barely trapped electrons at low frequency.The frequency jump in e-Bshbone experiments is reproduced and analyzed.It is found that the e-Bshbone frequency increases with the hot electron energy,which is consistent with the experiments.The growth rate of the mode(m = 2,n = 2) is greater than that of the mode(m = 1,n = 1).     

Ion-Temperature-Gradient-Driven Modes with Nonthermal Electron Distributions in Bi-ion Dusty Magnetoplasma

The effect of nonthermal distributions of electrons on ion-temperature-gradient (ITG)-driven drift modes in the presence of tiny dust particles for bi-ion magneto plasmas is investigated. The dynamics of bi-ions and dust particles is considered for the study of low-frequency (less than the gyrofrequencies of dust and ions) ITG mode. A new dispersion relation is derived and analyzed numerically as well as analytically. Three different distributions for nonthermal electrons (Kappa, q, and Cairns distribution) are used. It is found that the presence of nonthermal electrons in bi-ion dusty magnetoplasma reduces the growth rate of the ITG instability. These results should be useful for laboratory and space plasmas where nonthermal electrons and dust is always present.     

HL-2A 装置中高能量捕获电子鱼骨模不稳定性研究

结合HL-2A 装置的参数,在电子回旋共振加热(ECRH)离(在)轴加热的情况下,研究高能量捕获电子驱动的鱼骨模不稳定性。数值结果表明,高能量电子极向比压β_h 大于某一个比压阈值β_h,crit 时,鱼骨模会被高能量电子激发,其频率随高能量电子极向比压的增大而缓慢增加且与高能量电子的环向进动频率一致;比压阈值β_h,crit 随着高能量电子密度剖面峰化程度的增加而减小,但当密度剖面增大到一定值时比压阈值β_h,crit 趋近于一个常数。此外,还分析了箍缩角和扰动能对鱼骨模实频和增长率的影响。发现在箍缩角α₀ =1附近增长率有一极小值,表明高能量勉强通行电子对鱼骨模具有稳定作用;而扰动能 δWˆ_c增大时,鱼骨模表现出实频变大而增长率变小的特征,这表明了本底等离子体对鱼骨模有一定的稳定效果。     

β-induced Alfvén eigenmodes destabilized by energetic electrons in a Tokamak plasma

The β-induced Alfvén eigenmode (BAE) excited by energetic electrons has been identified for the first time both in the Ohmic and electron cyclotron resonance heating plasma in HL-2A. The features of the instability, including its frequency, mode number, and propagation direction, can be observed by magnetic pickup probes. The mode frequency is comparable to that of the continuum accumulation point of the lowest frequency gap induced by the shear Alfvén continuous spectrum due to finite β effect, and it is proportional to Alfvén velocity at thermal ion β held constant. The experimental results show that the BAE is related not only with the population of the energetic electrons, but also their energy and pitch angles. The results indicate that the barely circulating and deeply trapped electrons play an important role in the mode excitation.     

Effects of q-profiles of a weak magnetic shear on energetic ion excited q=1 mode in tokamak plasmas

In this paper, we study the effect of safety factor profiles, particularly with a very weak magnetic shear, on the m/n = 1mode excited by energetic ions in tokamak plasmas. It is found that the profile plays a significant role in the onset of the mode, and the thresholds for the instability are also derived. The numerical results for configurations with conventional or reversed non monotonic magnetic shears are discussed. The effects of radial location of rational surfaces, edge q value, and flatness of q-profile on the energetic ion excited mode are further analyzed in detail.     

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结合HL-2A 装置的参数,在电子回旋共振加热(ECRH)离(在)轴加热的情况下,研究高能量捕获电子驱动的鱼骨模不稳定性。数值结果表明,高能量电子极向比压βh 大于某一个比压阈值βh,crit 时,鱼骨模会被高能量电子激发,其频率随高能量电子极向比压的增大而缓慢增加且与高能量电子的环向进动频率一致;比压阈值βh,crit 随着高能量电子密度剖面峰化程度的增加而减小,但当密度剖面增大到一定值时比压阈值βh,crit 趋近于一个常数。此外,还分析了箍缩角和扰动能对鱼骨模实频和增长率的影响。发现在箍缩角α0 =1附近增长率有一极小值,表明高能量勉强通行电子对鱼骨模具有稳定作用;而扰动能 δWˆc增大时,鱼骨模表现出实频变大而增长率变小的特征,这表明了本底等离子体对鱼骨模有一定的稳定效果。     

Entanglement dephasing of spatially separated multiparticle GHZ states coupled to a squeezed environment

In tokamak plasmas, it is recognized that ITG (ion temperature gradient instability) and trapped electron modes (TEM) are held responsible for turbulence giving rise to anomalous transport. The present work focuses on the building of a model including trapped kinetic ions and trapped kinetic electrons. For this purpose, the dimensionality is reduced by averaging the motion over the cyclotron motion and the “banana” orbits, according to the fact that the instabilities are characterized by frequencies of the order of the low trapped particle precession frequency. Moreover, a set of action-angle variables is used. The final model is 4D (two-dimensional phase space parametrized by the two first adiabatic invariants namely the particle energy and the trapping parameter). In this paper, the trapped ion and electron modes (TIM and TEM) are studied by using a linear analysis of the model. This work is currently performed in order to include trapped electrons in an existing semi lagrangian code for which TIM modes are already taken into account. This study can be considered as a first step in order to include kinetic trapped electrons in the 5D gyrokinetic code GYSELA [J. Abiteboul et al., ESAIM Proc. 32, 103 (2011)].     

电子-离子碰撞对超热电子影响的PIC模拟计算

超热电子-离子的产生和输运在传统的ICF方案和“快点火”方案中都是很重要的问题.讨论了电子-离子碰撞对参量不稳定性产生超热电子的过程和超热电子输运过程的影响.指出电子-离子弱碰撞项的加入增强了碰撞吸收,提高了热电子温度,降低了静电波破裂时的场能.这些改变了超热电子的总能量和分布,使之更集中于静电波的相速;电子-离子碰撞的存在还增强了自洽电场,阻碍了超热电子的输运,同样也是超热电子能量下降的原因之一.同时,为确保计算结果的可靠,讨论了初条件对PIC模拟计算的影响,指出空间位置随机热启动容易引入非物理因素,对 关键词：     

Hybrid Two-Dimensional Electron Transport in Self-Consistent Electromagnetic Fields

The paper outlines features of the implicit hybrid simulation code ANTHEM, which uniquely provides histories for the transport and deposition of suprathermal and thermal electrons in laserproduced plasmas. The code models two-dimensional electron transport through steep density gradients and across contiguous collisional and collisionless target regions with the plasma dynamics dominated by self-consistent E and B fields. ANTHEM employs separate Eulerian fluid ion and thermal electron treatments and models suprathermal electrons as either a third fluid or as a set of collisional particle-in-cell (PIC) particles. We outline new techniques required to obtain implicit electromagnetic fields in two spatial dimensions permitting time steps well in excess of the local plasma period. A new implicit scattering model is discussed. The utility of our approach is demonstrated with sample applications to collisional surface transport on foil targets.     

弱相对论捕获电子哨声模不稳定性

本文讨论了弱相对论的捕获电子在磁镜位形中对哨声波不稳定性的影响。在简化的箱子模型下,用摄动法求解了带有弱相对论捕获电子效应的本征方程。发现各向异性热电子可以驱动哨声模不稳定性,而相对论效应使不稳定性的各向异性阈值升高,增长率的最大值减小并使不稳定性向低频方向移动。 关键词：     

Fusion burning waves in degenerate plasmas

The outcome of fusion burning waves in non-degenerate plasmas is limited by the strength of ion–electron Coulomb collisions and subsequent energy loss mechanisms as electron heat conduction and radiation emission. In this Letter, an analysis is presented on the degeneracy effects in the stopping power of suprathermal charged particles and in the energy transmitted from ions to electrons by Coulomb collision. Main results of this analysis is that very powerful fusion burning waves can be launched into previously compressed degenerate plasmas. This can be specially suitable for proton–boron fusion, but it also applicable to any type of fusion reaction, where ignition can be triggered by an incoming ion beam or another external source of energy deposited in a small fraction of the compressed plasma (fast ignition).     

黑腔靶中超热电子特性研究

近几年来,在“神光”装置上进行了1.053μm激光与平面靶及一系列柱形黑腔靶相互作用实验。用一台多道滤波—荧光X光能谱仪(FFS)测得各种靶发射的超热X射线谱,由谱推导超热电子温度T_h和超热电子总能量E_h当照射靶单束激光能量E_(tar)为400～670J、脉宽τ=650～1150ps时,发现黑腔内明显存在两群服从Maxwell分布高能电子(T_h=35～45keV;T_(hh)=150～350kev),而且E_(he)占E_(tar)的份额为10％～12％。实验还表明:腔内的E_(he)与非线性过程特征量(SRS)有较好的线性关系,因此推断出腔内超热电子产生的主要机制是受激Raman散射。在相同照射条件下,黑腔靶产生的超热电子比平面靶严重。     

Effects of trapped electrons on off-axis lower hybrid current drive in tokamaks

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.[第一段]     

Relativistic study of electromagnetic electron cyclotron instability based on trapped electrons in kappa-Maxwellian auroral plasmas

The presence of relativistic electrons in the Earth's magnetosphere may excite EMEC waves via resonant interaction. The understanding of EMEC waves induced by such electrons requires relativistic treatment. Therefore, we present here the investigation of EMEC waves based on relativistic trapped electrons represented by kappa-Maxwellian distribution in auroral plasmas. The analytical expressions of real frequency and relativistic growth rate are derived. Our numerical outcomes report that relativistic approximation increases the wave growth and causes reduction in the threshold value of drift velocity of trapped electrons for instability. The wave frequency that corresponds to the maximum growth decreases as we go from nonrelativistic limit to relativistic. The maximum growth increases with the increment in plasma frequency, perpendicular thermal velocity, drift velocity of trapped electrons, and Lorentz factor γ. Moreover, the relativistic effects on maximum growth are more pronounced for smaller values of drift velocity and perpendicular thermal velocity.     

三角激光脉冲尾波加速粒子模拟

电子俘获是激光尾波场加速电子的主要机理，增大电子的初速度可以使更多的电子被尾波场俘获.提出三角脉冲激发尾波加速电子的方案，三角脉冲平缓上升沿激发受激Raman散射，用以初步加速电子，三角脉冲陡峭下降沿激发尾波场，将更多的电子加速到接近光速.2D3V粒子模拟结果证实了这一点.同时表明：脉冲长度为几个等离子体波长的超强激光在稀薄等离子体中传播时，还激发侧向Raman散射.在侧向受激Raman散射中，静电波增长最快的波矢模式为k_p=(2ω_p/ω₀ 关键词： 有质动力 电子俘获 前向受激Raman散射 侧向受激Raman散射     

Electrical Conductivity of Nonideal Plasma

The electrical conductivity of fully ionized moderately nonideal plasmas with coulomb interaction parameters 0.1 < ? ? 1 where ? = Ze2n1/3/KT is the ratio of coulomb and thermal energies is calculated for displaced Maxwell and Fermi electron distributions, respectively. The electrons are scattered by an effective coulomb potential ?(r) = Zer-1 exp (-r/?) which considers binary (0 < r < ?) and many-body (? < r < ?) interactions. The shielding distance is given by ? = ?(4?n/3Z)-1/3 with ? = ?0?-N ~ 1 for classical plasmas and ? = ?(4?n/3Z)-1/3 with ? = ?0?-N?-M ~ 1 for quantum plasmas, where ? = Ze2n1/3/h2 m-1n2/3 is the ratio of coulomb interaction and quantum potential energies of the electrons. It is shown that the resulting conductivity formulas are applicable to densities up to four orders of magnitude higher than those of the ideal conductivity theory, which breaks down at higher densities because the Debye radius loses its physical meaning as a shielding length and upper impact parameter.     

Nondiffusive suprathermal ion transport in simple magnetized toroidal plasmas

We investigate suprathermal ion dynamics in simple magnetized toroidal plasmas in the presence of electrostatic turbulence driven by the ideal interchange instability. Turbulent fields from fluid simulations are used in the nonrelativistic equation of ion motion to compute suprathermal tracer ion trajectories. Suprathermal ion dispersion starts with a brief ballistic phase, during which particles do not interact with the plasma, followed by a turbulence interaction phase. In this one simple system, we observe the entire spectrum of suprathermal ion dynamics, from subdiffusion to superdiffusion, depending on beam energy and turbulence amplitude. We estimate the duration of the ballistic phase and identify basic mechanisms during the interaction phase that determine the dependencies of the character of suprathermal ion dispersion upon the beam energy and turbulence fluctuation amplitude.     

Excitation of high-frequency fluctuations by suprathermal electrons in a slowly varying magnetic field

Excitation of high-frequency fluctuations by suprathermal electrons in a dense magnetoactive plasma (_p > > _B) is considered. When the magnetic field is slowly varying, the initially stationary function of collisionless particle distribution rearranges considerably due to magnetic moment conservation. It is shown that in this case the system remains stationary relative to high-frequency potential (Langmuir) disturbances. However, anisotropy of the velocity distribution of fast electrons occurring as the magnetic field increases causes excitation of whistler mode electromagnetic waves in the plasma.Siberian Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 8, pp. 879–883, August, 1991.     

X-ray bremsstrahlung and fast-ion measurements from picosecond laser-produced plasmas

Fast-ion and suprathermal electron energies have been measured from plasmas generated by 25 ps duration neodymium laser pulses focussed onto solid targets. The relationship between the fast-ion energy and the energy of the suprathermal electrons in the plasma has been demonstrated and these energies have been found to increase in proportion to I^0.35±0.05 for targets of aluminum and copper, with I the laser intensity.