共查询到18条相似文献,搜索用时 203 毫秒
1.
2.
3.
4.
激光诱导击穿光谱(LIBS)信号的不确定性限制了其定量测量的能力。基于等离子体声学信号的光谱校正方法能够有效降低LIBS信号的不确定性,但仍缺乏在高温环境中的研究。在甲烷/空气预混火焰产生的高温气中,测量了不同激光入射能量下等离子体的吸收能量,并同步采集了等离子体的光谱信号和声学信号,对声学波形的正峰进行了修正,利用修正后正峰的脉冲积分强度(PII)对光谱进行了校正,有效降低了LIBS信号强度的不确定性。研究发现,在激光入射能量为80~280 mJ时,等离子体的吸收能量和激光入射能量间具有显著的线性关系,1 150和1 350 K下,线性决定系数(R2)分别为0.997 9和0.998 9,随着激光能量从80 mJ升高至280 mJ, 1 150和1 350 K下等离子体吸收能量的RSD(relative standard deviation)分别从33.17%和34.20%降至6.68%和6.79%。同时,在同一激光入射能量下,由于温度的升高导致了气体密度的下降,1 350 K下等离子体的吸收能量低于1 150 K的吸收能量。等离子体的光谱信号和声学信号源于等离... 相似文献
5.
HL—1M装置等离子体离子温度测量 总被引:3,自引:3,他引:0
张集泉 《核聚变与等离子体物理》1998,18(A07):33-38
在HL-1M托卡马克装置上,利用8通道中性粒子能谱仪测量的等离子体离子温度。在等离子体电流和密变化、激光吹气、弹丸注入,超声分子束注入和低混杂波加热等实验条件下,观测了Ti的变化。 相似文献
6.
7.
《光谱学与光谱分析》2020,(5)
放电等离子体光谱技术及激光诱导击穿光谱技术由于实验系统相对简单、信号强,很早就被应用于组分测量领域。由于自由放电在时间和空间上都具有随机性,这使得放电等离子体空间分辨光谱的精确测量变得十分困难;而激光诱导击穿光谱技术又局限于点测量。介绍了一种基于飞秒激光诱导的放电等离子体一维空间分辨光谱的高精度测量方法。飞秒激光自聚焦可以形成一段丝状弱等离子体通道,将该等离子体通道靠近高压直流脉冲电极时,可作为高压电极放电的触发源。这种触发方式可在规定的时刻触发高压电并诱导其沿着等离子体通道的路径击穿气体。实验多次测量放电开始时刻与激光到达时刻的时间间隔的波动小于0.01μs,证实了使用本方法诱导高压放电具有很高的重复性。由此可知,利用飞秒激光自聚焦成丝产生的弱等离子体通道诱导高压放电,可实现对高压放电的空间和时间的精确控制,进而可以采集放电等离子体通道的一维空间分辨光谱。实验结果表明,在喷管结构主导的流场环境中,由于喷管中纯N_2与喷管外空气的组分不同,在高空间分辨光谱中,可以清晰地看到一维等离子体通道上不同位置的组分浓度变化情况。在一维空间分辨光谱中将N~+和O光谱信号强度与N_2和O_2的浓度进行关联,可实现流场组分的一维在线诊断。该方法不仅具有纳秒激光诱导击穿光谱技术的相同优点,还具有一维空间分辨能力,在组分一维精确测量方面极具优势。同时,该方法还有望实现高时间分辨测量,对研究放电等离子体的时空演化过程具有重要的意义。 相似文献
8.
9.
具有合适径向密度分布的等离子体通道可以用于超短超强激光导引,这使得等离子体通道在激光尾波加速中有着重要的应用.本文介绍了在上海交通大学激光等离子体实验室开展的毛细管放电和光导引实验.通过光谱展宽法测量了充氦气的放电毛细管中的等离子体密度分布,在长度为3 cm、内径为300μm的毛细管中实现了轴向均匀,径向呈抛物线型的等离子体密度分布.通过改变放电延时和喷气时长,确定和优化了产生等离子体通道的参数区间,得到的最大通道深度为28μm,与实验中使用的激光焦斑半径匹配.在此基础之上,开展了不同能量的激光脉冲在放电等离子体通道中的导引研究,结果发现当通道深度与焦斑半径匹配时,激光可以不散焦地在通道中传输,实现激光导引.这项研究为未来的激光尾波级联加速和锁相加速等研究奠定了基础. 相似文献
10.
通过改进的马赫-曾德尔干涉仪获得了高质量的Nd:YAG激光诱导大气等离子体干涉条纹图.利用快速傅里叶变换(FFT)分析法恢复了干涉图波面,通过Abel逆变换进行密度反演,重建了不同时刻激光等离子体电子密度的三维分布,并得到了激光等离子体膨胀速度与延迟时间的关系.结果显示,纳秒激光诱导大气击穿形成的等离子体具有等离子体通道结构,等离子体膨胀速度的迅速衰减,对等离子体通道的塌陷起到了促进作用,等离子体形状的离心率在大约48 ns时达到最大值,然后开始向圆形演变.
关键词:
激光等离子体电子密度
干涉测量
Abel逆变换 相似文献
11.
Using a dusty plasma ratchet, one can realize the rectification of charged dust particle in a plasma. To obtain the ratchet potential dominating the rectification, here we perform quantitative simulations based on a two-dimensional fluid model of capacitively coupled plasma. Plasma parameters are firstly calculated in two typical cross sections of the dusty plasma ratchet which cut vertically the saw channel at different azimuthal positions. The balance positions of charged dust particle in the two cross sections then can be found exactly. The electric potentials at the two balance positions have different values. Using interpolation in term of a double-sine function from previous experimental measurement, an asymmetrical ratchet potential along the saw channel is finally obtained. The asymmetrical orientation of the ratchet potential depends on discharge conditions. Quantitative simulations further reproduce our previous experimental phenomena such as the rectification of dust particle in the dusty plasma ratchet. 相似文献
12.
激光等离子体通道天线被等效为电子在横向旋转、轴向漂移的均匀冷磁化等离子体束,且该等离子体束的横截面为沿轴向不改变的圆形。在考虑离心力、科里奥利力等惯性力的影响下,结合麦克斯韦方程和本构关系,得出了激光等离子体通道天线的散射场。为了简化,计算了一特例,发现了一些有趣的现象。 相似文献
13.
G. L. Chen H. Y. Lu C. Wang J. S. Liu R. X. Li G. Q. Ni Z. Z. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):303-307
We propose a plasma channel scheme to obtain an improved
table-top laser driven fusion neutron yield as a result of explosions of
large deuterium clusters irradiated by an intense laser pulse. A cylindrical
plasma channel is created by two moderate intensity laser prepulses at the
edge of a deuterium cluster jet along which an intense main laser pulse
propagates several nanoseconds later. With the aid of this plasma channel,
the main laser pulse will be allowed to deposit its energy into the central
region of the deuterium gas jet where the cluster sizes are larger and the
atomic density is higher. The plasma channel formation and its impact on the
deuterium ion energy spectrum and the consequent fusion neutron yield have
been investigated. The calculated results show that a remarkable increase of
the table-top laser driven fusion neutron yield would be expected. 相似文献
14.
De Wispelaere E Malka V Hüller S Amiranoff F Baton S Bonadio R Casanova M Dorchies F Haroutunian R Modena A 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,59(6):7110-7120
We report on a detailed study of channel formation in the interaction of a nanosecond laser pulse with a He gas jet. A complete set of diagnostics is used in order to characterize the plasma precisely. The evolution of the plasma radius and of the electron density and temperature are measured by Thomson scattering, Schlieren imaging, and Mach-Zehnder interferometry. In gas jets, one observes the formation of a channel with a deep density depletion on axis. Because of ionization-induced defocusing which increases the size of the focal spot and decreases the maximum laser intensity, no channel is observed in the case of a gas-filled chamber. The results obtained in various gas-jet and laser conditions show that the channel radius, as well as the density along the propagation axis, can be adjusted by changing the laser energy and gas-jet pressure. This is a crucial issue when one wants to adapt the channel parameters in order to guide a subsequent high-intensity laser pulse. The experimental results and their comparison with one-dimensional (1D) and two-dimensional hydrodynamic simulations show that the main mechanism for channel formation is the hydrodynamic evolution behind a supersonic electron heat wave propagating radially in the plasma. It is also shown from 2D simulations that a fraction of the long pulse can be self-guided in the channel it creates. The preliminary results and analyses on this subject have been published before [V. Malka et al., Phys. Rev. Lett. 79, 2979 (1997)]. 相似文献
15.
16.
N. Vujičić H. Skenderović T. Ban D. Aumiler G. Pichler 《Applied physics. B, Lasers and optics》2006,82(3):377-382
We present an investigation of the plasma channel formed along the trail of an intense femtosecond (fs) laser pulse propagating
through helium, air and nitrogen at low pressures. The lifetime of the generated plasma channel of up to 60 μs was measured.
We determined the electron-attachment mechanism as a dominant mechanism for the plasma relaxation. The initial electron densities,
electron-attachment coefficients and plasma channel conductivity for different experimental conditions were obtained.
PACS 52.50.Jm; 52.25.-b; 51.50.+v 相似文献
17.
利用皮秒和飞秒激光研究了激光在空气中聚焦产生单个等离子体通道的条件.研究发现,能量为8—12mJ皮秒激光被焦距为15cm的透镜聚焦后,可以产生较为稳定的单个通道.通过横向纵向阴影成像分析发现,通道的管壁对聚焦产生的自发光具有箍缩作用,而通道内部却有利于光的传输.同时还发现,当采用短焦距透镜时,能量低于10mJ的飞秒激光在空气中较易形成单个等离子通道.
关键词:
等离子体通道
皮秒激光
飞秒激光
阴影成像 相似文献
18.
Physical properties of relativistic electron beam during long-range propagation in space plasma environment 下载免费PDF全文
《中国物理 B》2021,30(10):104103-104103
It is known that ion channel can effectively limit the radial expansion of an artificial electron beam during its longrange propagation in the space plasma environment. Most prior studies discussed the focusing characteristics of the beam in the ion channel, but the establishment process and transient properties of the ion channel itself, which also plays a crucial role during the propagation of the relativistic electron beam in the plasma environment, were commonly neglected. In this study, a series of two-dimensional(2 D) particle-in-cell simulations is performed and an analytical model of ion channel oscillation is constructed according to the single-particle motion. The results showed that when the beam density is higher than the density of plasma environment, ion channel can be established and always continues to oscillate periodically over the entire propagation. Multiple factors, including the beam electron density, initial beam radius, and the plasma density can affect the oscillation properties of ion channel. Axial velocity of the beam oscillates synchronously with the ion channel and this phenomenon will finally develop into a two-stream instability which can seriously affect the effective transport for relativistic electron beam. Choosing appropriate beam parameters based on various plasma environments may contribute to the improvement of the stability of ion channel. Additionally, radial expansion of the beam can be limited by ion channel and a stable long-range propagation in terrestrial atmosphere may be achieved. 相似文献