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1.
考虑相对论电子束入射等离子体所产生的离子通道的具体结构,利用线性电磁流体力学理论对离子通道摇摆电子束激发的纵向慢波电磁不稳定性进行研究.通过对导出的系统色散关系的数值分析,给出了系统中电磁波、空间电荷波以及两者在一定条件下互作用形成的电磁-静电混合模式的传播特性.研究发现系统在慢波区域存在电磁不稳定性,并揭示此慢波不稳定性是由电子束的betatron振荡所导致,且系统的不稳定性程度与betatron振动频率密切相关.对betatron振荡激发的慢波电磁不稳定性物理机理进行了分析,并给出了不稳定性存在的条件
关键词:
离子通道
betatron振荡
电磁不稳定性 相似文献
2.
竹锦霞 《原子与分子物理学报》2015,32(6)
利用ECE电子回旋辐射和Ha线辐射等托卡马克物理诊断系统,研究了Slide-away放电过程中提高等离子体密度对非麦克斯维尔分布的逃逸电子所激发的逃逸电子束不稳定性影响作用.实验结果表明:在Slide-away放电模式下,提高等离子体密度能有效抑制逃逸电子束的不稳定性. 相似文献
3.
竹锦霞 《原子与分子物理学报》2014,31(6):941-944
利用ECE电子回旋辐射和Ha线辐射等托卡马克物理诊断系统,研究了Slide-away放电过程中提高等离子体密度对非麦克斯维尔分布的逃逸电子所激发的逃逸电子束不稳定性影响作用。实验结果表明:在Slide-away放电模式下,提高等离子体密度能有效抑制逃逸电子束的不稳定性。 相似文献
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多脉冲强流电子束轰击轫致辐射靶,在靶面形成等离子体层,将对后续电子束脉冲的稳定性产生影响。从基本等离子理论出发,利用成熟的等离子体粒子模拟程序计算在不同等离子条件下电子束流的稳定性。模拟显示在无外场情况下,当等离子体与电子束的密度比小于1时,能量20 MeV、束流强度2.5 kA、焦斑1.5 mm的电子束出现腊肠不稳定性,但相对靶面焦点区而言,束流稳定;当密度比在1~100时,箍缩不稳定性能够改善电子束的聚焦;当密度比在100~1000时,扭曲不稳定性起主导作用,靶面焦点区电子束流仍然稳定;当密度比大于1000后,成丝不稳定性破坏束流,电子束无法在靶面聚焦。 相似文献
6.
应用二、三维相对论电磁粒子模拟程序研究双电子束流在无碰撞等离子体中传播引起的横向 电磁(Weibel类型)不稳定性和纵向静电不稳定性的发展演化过程.讨论了纯粹Weibel不稳定 性的发生和非线性饱和过程,观察到电流束合并、磁场重联等引起的电子横向加热现象.研 究了电流束传播方向激发的静电场对快电子束传播的影响,观察到其导致的束的横向调制、 磁场通道破坏现象.对这些过程的细致研究对更好的理解快点火物理中自生磁场的产生、快 电子输运等过程有重要意义. 相似文献
7.
强激光在冕区等离子体中传播到临界面附近生成相对论电子和相对论电子束流在随后较长一段稠密等离子体区的能量传输是快点火中的关键问题。对快点火条件下的激光等离子体参数,临界面附近产生的前向快电子电流往往超过阿尔芬极限电流,必须在稠密等离子体中产生中和回流,快电子流才能在稠密等离子体中向前输运。横向电磁不稳定性(类Weibel不稳定性,WI)和纵向静电双流不稳定性(TSI)很容易在这种电子双流体系中激发,前向电子束会被调制或成丝状结构,同时激发电磁场,粒子部分动能会转化为电磁场能量。不稳定性在非线性饱和后,发生电流丝的合并、磁场重联等过程,部分电磁场能量会再转化为粒子能量,表现为对离子体的横向加热。Weibel不稳定性的作用可能形成围绕传播电子束的磁通道,对快电子的定向和准直传播是重要的。TSI激发的纵向静电场对磁场通道会有明显的调制甚至破坏作用,直接影响高能电子流从激光吸收区到燃料压缩区的准直传播。 相似文献
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详细推导了具有分布损耗波导结构的回旋行波放大器的色散特性。通过绝对不稳定性振荡出现的条件,给出求解具有损耗波导结构回旋行波管放大器的绝对不稳定性起振电流的数值计算方法。研究结果表明:绝对不稳定性起振电流与损耗波导的集肤深度有关,选择有较大的集肤深度的损耗波导可以提高绝对不稳定性起振电流;绝对不稳定性起振电流同时也与工作磁场偏离饱和磁场的程度以及电子束的纵横速度比有关;通过设计具有分布损耗波导结构的注-波互作用电路,以及工作磁场、电子束的纵横速度比,可以在兼顾带宽、效率的条件下,保证回旋行波管放大器稳定工作。 相似文献
10.
为研究双温电子等离子体中束流不稳定性的演化过程,用二维粒子模拟(PIC)代码对双温电子束流不稳定性进行了模拟,其中泊松方程用松弛迭代法求解,代码满足电荷守恒、动量守恒和能量守恒条件。在电子双流不稳定性的非线性演化过程中,得到相空间的空洞结构,实空间也相应出现了电子空洞。给出了不稳定性增长率以及相应色散关系。 相似文献
11.
Summary A large-amplitude beat wave excited at the beat frequency of two copropagating laser beams is extremely unstable and suffers
strong three- and fourwave parametric instabilities with large growth rates. The relativistic effects are seen to be negligible
on both the decay and modulation instabilities. However, the growth rates of these instabilities are sensitive functions of
the plasma parameters.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
12.
J. Preinhaelter 《Czechoslovak Journal of Physics》1967,17(11):987-995
The instabilities of the electrostatic waves of a hot plasma in a magnetic field, excited by beams of charged particles, have been studied in some special cases within the framework of the linear theory. We are interested in short-wavelength oscillations with a transverse wavelength compareable with the Larmore radius of ions or electrons, with frequencies in the vicinity of the harmonic cyclotron frequency of ions or electrons. Expressions have been derived for the increments of these instabilities in the case of a beam with an isotropic distribution function in the velocity space, as well as with an anisotropic distribution function. The influence of the beam temperature on the character of the instabilities and the conditions of formation of the instabilities are discussed, and the order of magnitude of the increments is estimated.The authors thanks J. Václavík and V. Kopecký for valuable discussions and comments. 相似文献
13.
An analysis is performed of the coherent instabilities which can develop in electron ring beams when an ion component is present in the beam. Increments of the instabilities are introduced, and it is shown that the compensation of an electron beam by ions results in a weakening of the instabilities characteristic of purely electron beams. The most rapidly growing coherent instabilities are determined, and possible methods are pointed out for their stabilization.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 37–53, January, 1978. 相似文献
14.
J. Koperski 《The European physical journal. Special topics》2007,144(1):107-114
Laser induced excitation and dispersed fluorescence spectra of
group-12 metal homoatomic dimers (Zn2, Cd2, Hg2) recorded at a number of
ultraviolet transitions provided information about interatomic potentials
of the ground and lower-lying excited electron energy states of the dimers.
The experimental studies were associated with calculations performed by
Eugeniusz Czuchaj that were related to interatomic potentials as well as
dipole moments for transitions between the ground and the excited
states of the dimers. In experiments the dimers were produced in free-jet
supersonic beams and were excited in a vacuum chamber with dye-laser beams.
Isotopically resolved vibrational transitions in low-resolution excitation
spectra and high-resolution rotational profiles of several vibrational
components as well as Condon internal diffraction patterns in dispersed
fluorescence spectra were recorded. Complex analyses of the spectra yielded
information about the ground- and excited-state potential bond lengths,
well depths as well as shapes of the investigated potentials in limited
regions of internuclear separations. The determined potential energy curves
were compared with results of Czuchaj providing conclusions related to the
accuracy of calculations and/or experiments as well as giving the
experimentalist information about planning experimental studies of molecular
potentials of the group-12 dimers. 相似文献
15.
S. Büttgenbach G. Meisel Prof. Dr. S. Penselin K. H. Schneider 《Zeitschrift für Physik A Hadrons and Nuclei》1970,230(4):329-336
A new universal method for the production of atomic beams of highly refractory elements has been developed. The beams of free atoms are produced by locally heating a small area on a target consisting of the material to be evaporated. The local heating is achieved via the focussed electron beam of a commercial electron gun. The atomic beams so obtained are suitable for studying hyperfine structures by the atomic beam magnetic resonance method. The first observedrf resonances in the ground state4 F 3/2 and the first excited state4 F 5/2 of Ta181 are reported. 相似文献
16.
利用含无电阻广义Ohm定律的可压缩磁流体力学(MHD)理论,研究了在具有剪切磁场的无碰撞电流片中低频电磁模不稳定性,假定等离子体压力各向同性,推导出了三维扰动传播波模的色散关系.色散关系的数值求解集中在电流片中间平面(z=0)和半厚度边缘(z=1)上,并分别考虑了二维传播和三维传播,以及不同的离子惯性长度情况.主要结果如下:1)对 于二维扰动传播(kz=0)的波,在z=0平面上,Alfven波增长率最大,不稳定的波 频率 和波数范围也更宽.离中间平面越远,增长率越小,波数区域越小.同时,随着离子惯性长度 的增大,Alfven波不稳定性的增长率变大.2)对于三维扰动传播(kz≠0)的波, 哨声是 不稳定的.在电流片中间平面上,哨声有明显的增长率;而在离子惯性区外边,哨声的增长 率还变大.3)在电流片中间(z=0)平面上,低频波主要是电流不稳定性激发的.在离中间 平面较远处,电流、密度和压力的梯度不稳定性变得更重要.
关键词:
无碰撞电流片
磁流体力学
色散关系
不稳定性 相似文献
17.
束腔相互作用激发的束流不稳定性是目前高能电子加速器上最重要的不稳定性之一。本文从粒子纵向运动基本方程出发,详尽分析了单束团和多束团情况下束腔纵向偶极不稳定性,并给出了我国合肥同步辐射光源上的计算和实验结果。 相似文献
18.
Tatarakis M Beg FN Clark EL Dangor AE Edwards RD Evans RG Goldsack TJ Ledingham KW Norreys PA Sinclair MA Wei MS Zepf M Krushelnick K 《Physical review letters》2003,90(17):175001
Measurements of energetic electron beams generated from ultrahigh intensity laser interactions (I>10(19) W/cm(2)) with dense plasmas are discussed. These interactions have been shown to produce very directional beams, although with a broad energy spectrum. In the regime where the beam density approaches the density of the background plasma, we show that these beams are unstable to filamentation and "hosing" instabilities. Particle-in-cell simulations also indicate the development of such instabilities. This is a regime of particular interest for inertial confinement fusion applications of these beams (i.e., "fast ignition"). 相似文献
19.
The interaction of intense beams of SF6 and CF3I molecules, excited by powerful IR laser radiation to high vibrational states (0.3 eV ≤ E vib ≤ 2.0 eV), with molecules (clusters) condensed on a cold surface (T s ≈ 80–85 K) has been studied. The probability that the excited and unexcited molecules are reflected from the cold metal surface covered by condensed molecules (clusters), as well as the probability that such excited and unexcited molecules are transmitted through a cooled multichannel metal plate and a converging cone oriented at an angle relative to the molecular beam axis, has been determined. Expressions for these probabilities of reflection and transmission as functions of the angle of incidence and the parameters of the exciting laser radiation and the molecular beam are obtained. It is shown that highly vibrationally excited molecules are reflected from the surface and transmitted through the plates and cones with a much higher probability than unexcited molecules. The results suggest that this phenomenon can be used for the separation of molecules in a beam with respect to isotope (or atomic) composition. 相似文献
20.
C. Lupulescu . Vajda A. Lindinger A. Merli L. Wöste 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):173-176
In this paper we present two-color pump and probe
spectroscopy on Na2F, the smallest of the
non-stoichiometric sodium-fluoride clusters
(NanFn-1), in
molecular beams by employing femtosecond laser pulses. The
molecules were pumped into the first excited state by one
photonic transition and consecutively ionized from there by the
second photon. We resolved the wavepacket oscillatory motion
involving periodical structural rearrangements in the first
excited state of Na2F with a period of
185 fs. The time-resolved
experiments show that sodium fluoride clusters provide
interesting features which can be manipulated in optimal control
experiments. 相似文献