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题名	强场激光产生的高能粒子在等离子体中的传输
作者	李雪梅
学位类别	博士
答辩日期	2008
授予单位	中国科学院上海光学精密机械研究所
导师	沈百飞
关键词	高能离子 稠密等离子体 密度重建
其他题名	The propagating in plasma of fast particles generated by ultra-short and ultra-intense laser beam
中文摘要	随着激光技术的迅速发展，人们已能获得聚焦强度超过1022W/cm2，单脉冲宽度小于10fs的超强超短激光脉冲，它与等离子体作用可以产生高能电子和高能离子。在惯性约束核聚变中，用来点火的超强超短激光脉冲在大于临界密度的等离子体中很难传输，但是在临界密度附近产生的电子可以继续往聚变靶的中心处传输，输运能量给点火区的离子，使它们获得点火温度来实现核聚变点火。除了电子点火，还可以用一束高能量的离子束（特别是质子束）照射预压缩的燃料引发点火。电子和离子要传输很长的距离才能到达点火区域，在稠密等离子体中传输会受到存在的电场、磁场、介质的电导率、碰撞过程等的影响，能量和传输方向会发生改变。所以需要研究高能电子和离子在高密度等离子体中的传输和能量沉积问题。此外，激光与等离子体作用所产生的高能质子由于其具有比较长的射程、小的发射源、比较短的持续时间和较大的密度等优点可以作为稠密等离子体参数探测的很好的工具。 本论文的主要工作可概况如下： 1. 用相对论福克－普朗克方程对高能离子在稠密氘氚等离子体中的碰撞动力学进行了研究，用球谐函数来展开方程的解：格林函数，然后简明地求出了不同能量质子和 粒子在等离子体中的停止时间、减速距离、纵向弥散距离和横向偏转距离。相比以前研究离子在等离子体中运动的方法：没有假设高能离子在等离子体中损失能量远远小于入射离子能量，求解了纵向弥散距离；并且可以求解横向偏转距离。这些计算对实验上用高能离子加热冷的稠密等离子体，然后进行科学研究具有参考作用，并且对研究快点火的可能性有一些帮助。根据不同能量和不同种类的高能离子在等离子体中的传输情况，可以选择合适的离子束引发快点火。 2. 同样用相对论福克-普朗克方程求解了高能谬介子在稠密等离子体中的传输情况。高能谬介子可以用来催化核聚变反应的发生，所以本文提出了用谬介子作为快点火的驱动粒子束，使通常的惯性约束聚变可以在相对比较低的温度下产生。 谬介子在点火区产生聚变火花，然后放出的能量会使聚变反应自发继续下去。 3. 利用高能质子在稠密等离子体中的库仑能量损失来重建不均匀等离子体的密度分布。用质子束照射划分为许多小格子的等离子体，得到以每个小格子密度为变量的大型病态方程组，求解方程组可以得到不均匀等离子体的密度分布情况。 ① 用Tikhonov正则化方法重建了冷的等离子体的密度分布情况。当质子源数目增大的时候，重建精度会提高，但是会增大实验的困难，本文的密度重建使用四个质子源。分别求解了出射质子束中含有不同的随机噪声时重建密度的误差，噪声越大，误差越大。 ② 改变重建方法，使用同时迭代代数重建迭代算法（SIRT）重建冷的等离子体的密度分布。发现SIRT方法的重建精度比较高，SIRT方法还可以在数据量不足的情况下重建等离子体的密度分布情况。 ③ 主要用代数重建算法（SIRT）重建高温等离子体的密度分布情况，并比较了SIRT方法的误差和Tikhonov正则化方法的误差，同样发现SIRT方法的重建精度较高。SIRT方法可以在数据量不足的情况下重建等离子体的密度分布情况。
英文摘要	With the development of laser technology，the ultra-short（<10fs） and ultra-intense （>1022W/cm2） laser becomes available and high-energy electrons and ions can be generated in the laser-plasma interaction. Since it is not easy for the laser propagating in plasma with density larger than critical density in the process of the ICF (Inertial Confinement Fusion), the high-energy electrons generated near the critical density become important. They can go on propagating and arive at the core area of the fusion target, transporting the energy to the fusion ions and generating the sparking spot at suitable high temperature. High ions (especially protons) can also be used as the ignition tools while they irradiate the compressed target. However, the interaction of electrons(ions) and dense plasmas are very complicated resulted from the effect of electromagnetic fields、conductance of the plasmas and the collsions between particles. So it’s important to study the interaction of high-energy particles with dense plasmas, such as the propagating and energy deposition of electrons and ions. Furthermore, the high-energy protons have become an effective tool for plasma diagonostic because of their large stopping range in plasmas, small source size, short duration and large number density. Main results in this paper are given as follows: 1. The collisional dynamics of the fast ion population in ultra-dense DT plasmas are investigated and analyzed within the framework of the relativistic Fokker-Planck Equation. The Green-Function expanding on the spherical harmonics is used to express the solution of the equation. With the Green-Function we can calculate the stopping time, the ion range, the straggling range, and the mean transverse dispersion of different kinds of ions in plasmas. Compared to the previous ways studying the movement of ions in plasmas, we not only calculate the straggling range without the approximation that the energy loss of the ions is much smaller than the energy of the ions, but we also calculate the stopping time and the mean transverse dispersion. This calculation is important for the experimental study of high energy density plasmas and fast ignition of laser fusion. The suitable energy of protons or ions can be choosed for the ignition according to the results we have obtained. 2. We also use the relativistic Fokker-Planck Equation to study the high-energy muons propagating and depositon in the dense DT plasma mainly for our suggested muon-driven fast ignition in which a muon beam generates an ignition sparkle and then the self-heating fusion follows. In this kind of ignition, the high temperature doesn’t have to be reached because of the catalysis of the muons for the fusion. The data calculated here can give some preliminary and theoretical instruction for this kind of ignition. 3. The density distribution of unhomogeneous dense DT plasmas is revealed by the energy loss of fast protons going through the plasmas in our simulation of a plasma density diagnostics. Dividing a two dimensional (2D) area into grids and knowing the initial and final energies of the protons, we can obtain a large linear equation set for the densities of each grid. Solving the ill-posed equation set，the density of each grid comes out and the density distribution of plasmas can be obtained. ① We use the Tikhonov regularization method for the density reconstruction for the cold and dense plasma. When more proton sources are used, the experiment will be more difficult, although the accuracy of revealing can be improved. So the number of the protons sources will be as few as possible. In this article, four proton sources will be used. We do the density reconstrutions for different random final proton energies noises and find that the accuracy will decrease with the increase of the noise of the final proton energies. ② We use another method, simultaneous iterative reconstruction technique (SIRT), for the density reconstrution for cold and dense plasmas. After the calculation, we find that the accuracy of the SIRT method is better than the Tikhonov regularization method. The SIRT method is also feasible for incomplete data of final proton energies. ③ We mainly use the better reconstruction method (SIRT) for the density reconstruction for hot and dense plasmas, also the accuracy is better than that of the Tikhonov regularization method. The SIRT method is also feasible for incomplete data of final proton energies.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15220]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	李雪梅. 强场激光产生的高能粒子在等离子体中的传输[D]. 中国科学院上海光学精密机械研究所. 2008.

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