【作者】 马瑾怡；

【导师】 邱锡钧；

【作者基本信息】 上海大学 ， 无线电物理， 2003， 博士

【摘要】 本文主要在理论上研究了高温等离子体中相对论电子的集体行为。然后，在此基础上研究了相对论性超热电子束(REB)在多路激光打靶产生高温等离子体中的DT核实施快点火的可行性。随后，为了能在实验台上实现可增益的轻核聚变，对于处于强超声场中的高温压缩含DT气泡，我们也探讨了采用飞秒级强脉冲激光快点火的可行性。 论文主要包括以下四部分内容及结果： 一、高温等离子体中相对论电子的集体振动行为。目前人们普遍接受的等离子体中电子的集体行为是Pines和Bohm在1952年所做的工作。他们主要研究了稠密电子气中电子的行为。本论文将此内容推广到高温等离子体的情况，研究高温等离子体中相对论电子的集体振动行为。(1)通过引入李纳——维谢尔相对论性电磁势来描述相对论电子产生的场，然后由密度函数把在库仑势作用下的多电子系统划分为集体部分和个体部分，进而着重对集体部分进行研究以得到相对论修正的高温等离子体的振动频率和“德拜长度”。我们的理论结果表明：不同于通常低温等离子体的情况(密度固定，振动频率也就固定了)，高温等离子体的振动频率会随着其温度的变化而变化。随着等离子体温度的上升，电子的运动速度加快，洛伦兹因子逐渐增加，使得高温等离子体的振动频率随之减小，而德拜长度则逐渐增大。并且，等离子体温度越高，这种变化越明显。(2)我们研究了快电子束在高温等离子体中传输时，由于电子集体振动的激发而导致的能量损失。理论结果表明：相对论修正的集体激发引起的单位距离能量损失率比非相对论性的集体激发引起的单位距离能量损失率明显减小。我们知道，稠密电子气中，在大于德拜长度λ_D的范围，系统倾向于产生集体振动行为；而在小于德拜长度λ_D的范围，则2003年上海大学博士学位论文与单个电子的自由热运动相关。由此我们得出:对具有相同电子密度分布的高温等离子体而言，由于德拜长度随等离子体温度的上升而增大，这就使得“德拜球”外参与集体振动的电子数减少，而“德拜球”内参与自由热运动的电子数增加。从而，在相对论性的高温等离子体中，集体激发引起的能量损失比通常等离子体中的刁、。 二、我们在第一部分的基础上对高温等离子体采用相对论的动力学模型，研究由超快强激光所产生的能量在 0.SMeV一1 .SMeV范围内的相对论性电子束(REB)与密度为300g/em3一l000g/em，、温度为skov一zookev的超压缩nT靶的相互作用。由于经历了相对论修正的集体激发和两体碰撞两种主要的能量损失机制，使得侧月3在DT核中不断损失能量，并将能量全部沉积在靶中。理论结果表明:随着等离子体温度的上升，由集体激发引起的能量损失逐渐减小，而由两体碰撞引起的能量损失逐渐增加。随后，通过计算连续曲折射程、最大穿透深度和特征时间三个重要物理参量来估算REB对球对称超压缩DT靶产生点火热斑的能力;重新检验了对超压缩DT芯实施快点火的可行性，修正了前人田eLltsch，et al.P. R.L(1996，;2000)]的若干理论结果。 三、对声致发光单气泡产生的高温动力学行为作了一些分析和研究。(l)介绍了单泡声致发光的过程、特点及研究意义。根据单泡声致发光的动力学特性，对现有的解释声致发光的理论模型进行简要的分析。(2)在Taleyarkhan小组用氖化丙酮蒸气泡研究核聚变的实验基础上，我们将快点火概念应用于气泡内部的高温高密度等离子体，提出可采用飞秒级的超快超强脉冲激光同步地聚焦于已预热的氖化丙酮蒸气泡，以触发气泡中的DD和D丁发生热核聚变反应。同时，初步研究了这一建议的可行性;特别对超快超强激光束所产生的、能量在MeV量级的相对论性电子束与靶子(氖化丙酮蒸气泡)的祸合作用作了初步计算和研究。基于能2003年上海大学博士学位论文量转移机制及有关物理参数的优化，在理论上我们得出:对于在实验室中研究轻核聚变，氖化丙酮溶液(C3 D6O)是一种比重水(DZ口)更好的试验液体。这一结论正好与Taleyarlthan小组从实验中得到的结论相一致。他们是根据相变系数。做出判断的。氖化丙酮有接近于1的相变系数，而重水的相变系数只有约0.075。我们则是在假定气泡内的C3 D6O分子全部电离的前提下，根据相对论性超热电，子在单位路程长上的均方偏离才，这个物理量得出相同结论的. 四、我们在非相对论量子场论的框架下研究了能量远低于IMev的电子系统在强光场中的动力学行为。在强光场中除光场线性项外，非线性项即AZ项的作用不容忽视。故我们给出电子场与光量子场相互作用时整个系统的哈密顿量，用Fermi一Dira。统计的schrjdinge:量子波场来描述电子系统，并采用“自洽平均场”和“有效质量”近似，基于位移谐振子的相干态方法，推导出电子波一一光量子场函数、电子能谱、电子自能和质量重整化等物理量的有关理论计算公式。更多还原

【Abstract】 My thesis is mainly related to the collective behavior of the relativistic electrons in the hot plasma. We study the feasibility for the relativistic electron beam (REB) realizing fast ignition in the hot plasma produced by multi-path lasers focusing on the target. In addition, in order to attain table-top controllable nuclear fusion, we show theoretically that the feasibility for applying femto-second intense laser pulse realizing fast ignition to the pre-compressed hot bubble in an acoustic field.The thesis is organized as follows:(1) The collective behavior of the relativistic electrons in the hot plasma. At present, the collective behavior of the electrons in the plasma done by Pines and Bohm (1952) is generally accepted. They mainly studied the behavior of the electrons in a dense electron gas. Here, we develop it to the case of the hot (high-temperature) plasma, and study the collective behavior of the relativistic electrons in the hot plasma, (a) By introducing the Lienard-Weichert potential for the relativistic electrons and splitting the electron density fluctuations into the individual part and the collective part, we study the collective oscillation of the relativistic electrons resulting from the Coulomb interactions. Consequently, we derive the oscillation frequency of the hot plasma and the "Debye length" with the relativistic modification. We show that the increase of the plasma temperature, as well as that of the velocity of the electrons, leads to the decrease of the plasma frequency p and the increase of the "Debye length". Moreover, thistrend becomes more obvious when the plasma temperature is higher, (b) We study the energy loss of a fast-electron beam due to the excitation of the collective oscillation in the hot plasma. It is shown that the energy loss based on the relativistic modified collective excitation is smaller than that based on the conventional collective mode, and with the increase in the hot plasma temperature the difference becomes more obvious. In a dense electron gas, we know that for phenomena involving distances greater than the Debye length, the system behaves collectively; for distances shorter than this length, it may be treated as a collection of approximately free individual particles. For the hot plasma with the same electron density, the increase of the "Debye length" causes the decrease in the number of the electrons participating in the collective oscillation, while the increase in the number of the electrons participating in the random thermal motion. Therefore, in the hot plasma, the energy loss based on the relativistic modified collective excitation becomes smaller than that based on the conventional one.(2) Basing on the above theoretical results, we further study the interactions between the relativistic electron beams (REB) with 0.5MeV ~ 1.5MeV energies produced by ultra-short and ultra-intense lasers and the super-compressed DT core atdensities 300g/cm3 ~ 1000g/cm3 and temperatures 5keV ~ lOOkeV. The REB continuously loses energies when passing through the DT core because of experiencing two main energy-loss-mechanics such as the collective excitation and the two-body collision with relativistic modification. We show that with the increase of the plasma temperature, the energy loss caused by the collective excitation gradually decreases while that caused by the two-body collision opposes it. Then, by calculating three important physical parameters: the continuous winded range R , the maximum penetration depth l0 and the stopping time tstop, we re-examine the possibility for theREB efficiently igniting the hot spots in a DT target, and modify some theoretical results obtained by Deutsch et al. (Phys. Rev. Lett., 1996, and 2000).(3) We analyze and study the dynamic behavior for the high-temperature single bubble sonoluminescence (SBSL). (a) We introduce the characters, and the significances of SBSL, and according to its dynamic character, we briefly review the existent light-emitting mechanism, (b) Basing on the experiment更多还原