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Experimental Research on Ultra Intense Magnetic Field in plasma Produced by Circularly Polarized Laser Light

圆偏振激光等离子体中超强磁场的实验研究

基本信息

批准号：
10480102
负责人：
MIYANAGA Noriaki
金额：
$ 8.13万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10480102/
关键词：
Ultra short pulse laser Chirped pulse amplification Laser produced plasma Polarization control Liquid crystal Wavelength plate Faraday rotation DC magnetic field 高密度プラズマ磁場光学プローブ粒子加速

项目摘要

On the laser-plasma interaction using the ultra-short pulse, intense laser, we have done the experiments relevant to the magnetic field generation depending on the laser polarization. The distinctive characteristics and performances are as follows;1) Development of liquid crystal wavelength plate for the laser polarization control :To achieve the laser-assisted alignment control of liquid crystal (LC), we adopted the photo-isomerization effect of azo dyes doped into the alignment layer of LC. The LC alignment was spatially controlled using the linearly polarized ultra violet light (UV : the third harmonic of Nd : YAG laser or a Hg lamp), then the arbitrary polarization/phase pattern was demonstrated by spatially changing the polarization direction of UV light.2) Experimental set up of laser-plasma interaction and ultra-short pulse laser probe :A laser used in this study was Ti : sapphire laser operated with the chirped pulse amplification/compression (wavelength 【approximately equal】 800 nm, pulse width 【approximately equal】 120 fs, output power 【approximately equal】 1 TW, irradiation intensity 【approximately equal】 4×10ィイD116ィエD1 W/cmィイD12ィエD1). A small part of this output was split out as a probe beam which was frequency doubled using a thin Type-I KDP crystal. The synchronization between the main laser pulse and the probe pulse is adjusted by use of Michelson interferometer technique (the first order cross correlation) with an accuracy of 〜 100 fs.3) Interaction experiments :In this term of project, although the polarization dependence on the magnetic field generation was not observed because of an insufficient plasma formation, following new phenomena were observed. a) The efficiency of forward acceleration of energetic ions (protons) was several times higher for the circular polarization compared with linear polarization. b) The self-focusing and beam break-up in the plasma was clearly observed by the ultra-short pulse shadowgraph.

在超短脉冲强激光与等离子体相互作用中，我们进行了磁场产生与激光偏振态有关的实验研究。其主要特点和性能如下：1）激光偏振控制用液晶波片的研制：利用偶氮染料的光致异构效应，将偶氮染料掺杂到液晶的取向层中，实现了液晶的激光辅助取向控制。使用线性偏振紫外光空间控制LC取向（UV：Nd：YAG激光的三次谐波或汞灯），然后通过空间改变UV光的偏振方向来演示任意偏振/相位图案。2）激光-等离子体相互作用和超短脉冲激光探针的实验装置：本研究中使用的激光器是Ti：啁啾脉冲放大/压缩蓝宝石激光器（波长[约等于] 800 nm，脉冲宽度[约等于] 120 fs，输出功率[约等于] 1 TW，辐照强度[约等于] 4×10 - 1000 D116 - 1000 D1 W/cm-1000 D12 - 100D 1）。该输出的一小部分被分离出来作为探测光束，该探测光束使用薄的I型KDP晶体进行倍频。利用迈克尔逊干涉仪技术（一阶互相关）调节主激光脉冲和探测脉冲之间的同步，精度可达100 fs。3）相互作用实验：在本项目中，虽然由于等离子体形成不足，没有观察到偏振对磁场产生的依赖性，但观察到了以下新现象。a）与线极化相比，圆极化的高能离子（质子）的向前加速效率高出数倍。B）利用超短脉冲阴影照相术，清晰地观察到了等离子体中的自聚焦和束分裂现象。