共查询到19条相似文献,搜索用时 78 毫秒
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本文讨论了具有简单结构磁层顶中的低混杂漂移不稳定性,假定在磁层顶中磁场方向是相互平行的,电子与离子的密度处处相等,总压力为一常数,采用1971年Alpers建立的分布函数做为零级分布,计算了下混杂漂移不稳定性的增长率和饱和时相应的反常电阻,计算表明,当磁层顶厚度接近两个质子迴旋半径时,低混杂漂移不稳定性的增长率约为0.26ωLH(ωLH为低混杂频率),反常电阻率为10-5sec,随着磁层顶厚度成倍增加,反常电阻率以指数形式下降。
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在简单磁镜MM-2中,采用15GHZ大功率迴旋管进行了电子迴旋共振加热(ECRH)实验。结果表明,随充气压强的提高,预电离时间迅速变短。在高气压“C-模式”运行区,等离子体径向密度分布呈马鞍形。在迴旋管输出30kW功率的条件下,适于建立热电子环的气体压力窗为(0.4—1.2)×10-5Torr。利用一个可移动Laugmuir探针配合反磁测量的简便方法,在中心场为2.95kG时,确定了电子环半径为7cm,环厚约4cm,环的轴向边界由z=±10cm一直延伸到z=±20cm。热电子温度为140—170keV,热电环平均β值为(4—5)%。观测到了由热电子环不稳定性引起的迸发式径向电子逃逸,并同时发生反磁信号跌落。 相似文献
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Rosenbluth等人曾建议在托卡马克外侧产生少量高能香蕉粒子就可以稳定气球模,使托卡马克过渡到第二稳定区运行。本文就设计了一种用电子迴旋共振加热(简称ECRH)在反应堆托卡马克中产生这样的高能电子的方法:在托卡马克外侧,主要沿小环θ方向射入一束具有有限N∥和某一合适频率ω的射频波,使波束主要在一个磁面附近的窄层内传播,利用高次谐频接力式加热把处于分布函数尾部的少量电子变成这样的高能电子。用各向异性弱相对论介电系数理论作数值计算发现,当N∥和ω取适当值时,寻常模和异常模都有明显的加热作用。
关键词: 相似文献
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从考虑动理学效应的受激散射不稳定性的线性理论出发,对于n=2的Maxwell分布函数直到n=5的饱和情况的超高斯分布函数,计算了电子等离子体波和离子声波的频率和阻尼率。对受激喇曼散射和受激布里渊散射进行分析,结果表明,在激光高Z等离子体中,或者在具有激光热斑的中等Z等离子体中,电子等离子体波的阻尼率降低很多,离子声波的频率比Maxwell分布情况升高约15%。这些结果可和实验进行比较。 相似文献
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在激光等离子体相互作用过程中,受激拉曼散射(SRS)会通过Langmuir波衰减不稳定性(LDI)和电子俘获两种机理饱和.文章给出均匀一维等离子体和低强度非相对论激光作用中,LDI和电子俘获两种机理下的SRS饱和时间的解析表达式.SRS饱和时间与入射激光强度,电子密度,电子温度,初始电子密度微扰等参数有关.解析理论计算得到了与模拟和实验相符的结果.
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受激拉曼散射
饱和
Langmuir波衰变不稳定性(LDI)
电子俘获 相似文献
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Recently saturation of laser power ofCW ion lasers has been observed with large bored laser tubes made of metal segments. The saturation was observed in Argon, Krypton and Xenon in high current regions. In this case it was necessary to calculate the correlation between the electron temperature, electron- and ion-density and on the other hand the discharge quantities as current density and voltage drop. By measuring the discharge quantities at optimum laser power it is possible to determine the optimum electron temperature for any current density. The comparison of the run of these quantities leads to the assumption that the saturation mechanism causes a decrease of the optimum electron temperature. 相似文献
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给出了描述高功率微波脉冲大气非线性传输及微波大气等离子体特征演化的方程组,并在以微波群速度运动的局域坐标系下完成程序编制。据此模拟分析了高功率微波大气长程非线性传输及自产生大气等离子体的基本物理过程,给出了在击穿建立过程中,电子数密度增长与电子温度升高之间的关系。模拟结果表明:由于大气层中本底自由电子数密度较低,高功率微波脉冲到达时会迅速地将大气中现有的自由电子加热至平衡温度,与之相比导致电子数密度雪崩式增长的击穿过程要缓慢得多,而且随着击穿过程的开始电子温度会从平衡温度快速下降。 相似文献
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Experimental study of planar Langmuir probe characteristics in a magnetized plasma with an electron current along the direction of the magnetic field shows that the usual procedure for determination of the electron temperature and plasma density, which is applicable in a current-free magnetized plasma, gives erroneous results for these plasma parameters. When this procedure is applied on the characteristics measured at two opposite orientations of the probe collecting surface with respect to the direction of the electron drift, different values of the electron temperature are obtained. These virtual electron temperatures and corresponding plasma densities calculated from the measured ion saturation currents are higher and/or smaller than the exact local electron temperature and plasma density. Calculation of particular averages of these quantities is proposed as a possible way to obtain correct results for the local electron temperature and plasma density. These averages are used in the approximate evaluation of the electron drift velocity from the electron saturation currents measured at the two orientations of the probe collecting surface. 相似文献
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考虑电子束横向发射度和电子β振荡,将2005年国际上提出的单通过高增益自由电子激光饱和状态分析的统计物理方法发展到三维情形。首先建立一种描述电子三维运动的归一化简化模型,推导了一维光场下包含电子横向运动的Vlasov方程。在螺旋型波荡器情形下通过引入横向运动守恒量发展了三维统计物理分析方法,并编写了相应计算程序,计算自由电子激光达到饱和时系统的光强增益、聚束因子。作为对比验证,编写包含N个电子自由电子激光系统的三维直接数值模拟程序,结果表明数值模拟和统计计算结果相一致。对比文献中一维模拟和一维统计理论计算结果,所得结果反映了电子束横向发射度以及电子在波荡器中的横向β振荡对饱和点参数的影响。 相似文献
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A VHF H2 plasma was produced with the multi rod electrode at high pressure and the plasma parameters were measured as a function of pressure for different VHF powers at 60 MHz. It was found that when the pressure is increased, the ion saturation current peaks at certain pressure and finally decreases at high pressures, while the electron temperature is around 10 eV. The wall potential at high pressure was lower than the values estimated from the electron temperature using the probe theory. Furthermore, the anomalous reduction of the electron saturation current was observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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J. Adámek J. Stöckel M. Hron J. Ryszawy M. Tichý R. Schrittwieser C. Ionită P. Balan E. Martines G. Van Oost 《Czechoslovak Journal of Physics》2004,54(3):C95
A novel probe and approach to the direct measurements of the plasma potential in a strong magnetic field is suggested. The principle of this method is to reduce the electron saturation current to the same magnitude as that of the ion saturation current. In this case, the floating potential of the probe becomes indentical to the plasma potential. This goal is attained by a shield, which screens off an adjustable part of the electron current from the probe collector due to the much smaller gyro-radius of the electrons. First systematic measurements have been perfomred in the CASTOR tokamak. 相似文献
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Effect of normalized plasma frequency on electron phase-space orbits in a free-electron laser 下载免费PDF全文
Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser (FEL). In previous literature, it was demonstrated that the irregularity of the electron phase-space orbits could be caused in several ways, such as varying the wiggler amplitude and inducing sidebands. Based on a Hamiltonian model with a set of self-consistent differential equations, it is shown in this paper that the electron- beam normalized plasma frequency functions not only couple the electron motion with the FEL wave, which results in the evolution of the FEL wave field and a possible power saturation at a large beam current, but also cause the irregularity of the electron phase-space orbits when the normalized plasma frequency has a sufficiently large value, even if the initial energy of the electron is equal to the synchronous energy or the FEL wave does not reach power saturation. 相似文献
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The resoinance diffusion of electrons in velocity space caused by the excited EM wave fields is considered to be the dominant saturation process of cyclotron maser instability that is driven by an electron loss-cone distribution. An upper-bound of the saturation level is derived analytically. Since the resulting saturation level is low the resonance diffusion is indeed responsible for the saturation of the cyclotron maser instability. 相似文献
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用量纲分析和数值计算相结合的方法,给出常参数放大器型毫米波自由电子激光基模辐射的饱和功率和饱和长度的一套定标定律。 相似文献