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State of the art 技术水平
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-07-23 DOI: 10.1007/978-3-662-61886-8_2
Juan Pablo Calderón Urbina
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引用次数: 0
Density jump for parallel and perpendicular collisionless shocks 平行和垂直无碰撞冲击的密度跳跃
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s0263034620000117
A. Bret, R. Narayan
In a collisionless shock, there are no binary collisions to isotropize the flow. It is therefore reasonable to ask to which extent the magnetohydrodynamics (MHD) jump conditions apply. Following up on recent works which found a significant departure from MHD in the case of parallel collisionless shocks, we here present a model allowing to compute the density jump for collisionless shocks. Because the departure from MHD eventually stems from a sustained downstream anisotropy that the Vlasov equation alone cannot specify, we hypothesize a kinetic history for the plasma, as it crosses the shock front. For simplicity, we deal with non-relativistic pair plasmas. We treat the cases of parallel and perpendicular shocks. Non-MHD behavior is more pronounced for the parallel case where, according to MHD, the field should not affect the shock at all.
在无碰撞激波中,没有二元碰撞使流各向同性。因此,有理由提出磁流体力学(MHD)跳跃条件在多大程度上适用的问题。在最近的研究中,我们发现平行无碰撞冲击与MHD有很大的不同,我们在这里提出了一个模型,允许计算无碰撞冲击的密度跳变。由于偏离MHD最终源于持续的下游各向异性,而Vlasov方程无法单独说明,因此我们假设了等离子体穿过激波锋面时的动力学历史。为简单起见,我们处理非相对论对等离子体。我们处理平行激波和垂直激波的情况。非MHD行为在平行情况下更为明显,根据MHD,场不应该影响冲击。
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引用次数: 4
Experimental optimization of the hundred-keV electron source from laser-driven wire target 激光驱动线靶百kev电子源的实验优化
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s0263034620000051
Y. Zeng, Chuliang Zhou, R. Qi, Zhongpeng Li, Haiyi Sun, Ye Tian, Jiansheng Liu, Zhi‐zhan Xu
We present the experimental optimization of electrons in the several hundred keV energy range originated from laser-irradiated wire targets. Accelerated by a femtosecond laser pulse, an electron pulse emitted from the wire target was collimated immediately along the wire to a filter unit for the manipulation of energy and spatial distributions. It is shown in simulation that with a pair of magnets as the filter unit, the optimized electrons could serve as a compact and tunable electron source. The proposed system was demonstrated in a proof-of-principle experiment where we attained 1 fC bunch charge with transverse coherence length approaching 1 nm based on a 0.2 TW laser platform. This indicates the scheme as a promising candidate for single-shot electron diffraction.
本文对激光辐照线靶产生的几百keV能量范围内的电子进行了实验优化。在飞秒激光脉冲的加速下,从线靶发射的电子脉冲立即沿着线对准滤波器单元,用于操纵能量和空间分布。仿真结果表明,以一对磁体作为滤波单元,优化后的电子可以作为紧凑可调的电子源。在一个原理验证实验中,我们在0.2 TW激光平台上获得了1 fC束荷,横向相干长度接近1 nm。这表明该方案是单次电子衍射的一个有希望的候选方案。
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引用次数: 0
LPB volume 38 issue 2 Cover and Back matter LPB第38卷第2期封面和封底
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s026303462000021x
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引用次数: 0
LPB volume 38 issue 2 Cover and Front matter LPB第38卷第2期封面和封面
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s0263034620000208
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引用次数: 0
Selective amplification of the chirped attosecond pulses produced from relativistic electron mirrors 相对论性电子镜产生的啁啾阿秒脉冲的选择性放大
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s0263034620000142
F. Tan, Shaolong Wang, Bo Zhang, Z. Zhang, B. Zhu, Yu Chi Wu, Mingyang Yu, Yue Yang, Gang Li, Tiankui Zhang, Yong-hong Yan, F. Lu, W. Fan, Wei Zhou, Y. Gu
In this paper, the generation of relativistic electron mirrors (REMs) and the reflection of an ultra-short laser off this mirrors are discussed, applying two-dimensional particle-in-cell (2D-PIC) simulations. REMs with ultra-high acceleration and expanding velocity can be produced from a solid nanofoil illuminated normally by an ultra-intense femtosecond laser pulse with a sharp rising edge. Chirped attosecond pulse can be produced through the reflection of a counter-propagating probe laser off the accelerating REM. In the electron moving frame, the plasma frequency of the REM keeps decreasing due to its rapidly expanding. The laser frequency, on the contrary, keeps increasing due to the acceleration of REM and the relativistic Doppler shift from the lab frame to the electron moving frame. Within an ultra-short time interval, the two frequencies will be equal in the electron moving frame, which leads the resonance between laser and REM. The reflected radiation near this interval and the corresponding spectra will be amplified due to the resonance. Through adjusting the arriving time of the probe laser, certain part of the reflected field could be selectively amplified or depressed, leading to the selectively adjusting of the corresponding spectra.
本文应用二维粒子池(2D-PIC)模拟,讨论了相对论性电子镜(REMs)的产生和超短激光在电子镜上的反射。在具有明显上升沿的超强飞秒激光脉冲的正常照射下,固体纳米箔可以产生具有超高加速度和膨胀速度的REMs。通过反向传播的探测激光反射加速的REM,可以产生啁啾阿秒脉冲,在电子运动框架中,REM的等离子体频率由于快速膨胀而不断降低。相反,由于REM的加速和从实验室框架到电子运动框架的相对论多普勒频移,激光频率不断增加。在一个超短的时间间隔内,两个频率在电子运动框架内相等,导致激光和REM之间发生共振,在这个间隔附近的反射辐射和相应的光谱会因为共振而被放大。通过调整探测激光到达的时间,可以选择性地放大或抑制部分反射场,从而选择性地调整相应的光谱。
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引用次数: 0
Optimization of laser parameters for proton acceleration using double laser pulses in TNSA mechanism 双脉冲TNSA机制下质子加速激光参数的优化
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s0263034620000063
Saurabh Kumar, D. N. Gupta
The energy of protons accelerated by ultra-intense lasers in the target normal sheath acceleration (TNSA) mechanism can be greatly enhanced by the laser parameter optimization. We propose to investigate the optimization of laser parameters for proton acceleration using double laser pulses in TNSA mechanism. The sheath field generation at the rear side of the target is significantly affected by the introduction of second laser pulse in TNSA mechanism, and consequently, the energy of the accelerated protons is also modified. The second laser pulse was introduced with different delays to study its impact on proton acceleration. Our study shows that the interplay of laser intensity and pulse duration of both laser pulses affects the proton acceleration. It was found that the proton maximum energy is the function of both laser intensity and pulse duration. A number of simulations have been performed to obtain maximum proton energy data under different combinations of laser intensity and pulse duration for the two laser pulses. The simulation results account for the underline physics for the proton bunch energy and the sheath field as a function of pulse intensity and pulse delay.
在靶正常鞘层加速(TNSA)机制中,通过对激光参数的优化,可以大大提高超强激光对质子的加速能量。我们建议在TNSA机制下研究双激光脉冲质子加速的激光参数优化。在TNSA机制中,第二激光脉冲的引入对靶后侧鞘层场的产生有显著影响,从而使加速质子的能量发生改变。以不同的延迟时间引入第二束激光脉冲,研究其对质子加速的影响。我们的研究表明,激光强度和两种激光脉冲的脉冲持续时间的相互作用影响质子的加速。发现质子的最大能量是激光强度和脉冲持续时间的函数。为了获得两种激光脉冲在不同激光强度和脉冲持续时间组合下的最大质子能量数据,进行了大量的模拟。模拟结果解释了质子束能量和鞘层场随脉冲强度和脉冲延迟的基本物理特性。
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引用次数: 5
Nano-wrinkles, compactons, and wrinklons associated with laser-induced Rayleigh–Taylor instability: I. Bubble environment 与激光诱导的瑞利-泰勒不稳定性相关的纳米皱纹、压实物和皱纹:1 .气泡环境
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s0263034620000105
S. Lugomer
We study dynamics, structure and organization of the new paradigm of wavewrinkle structures associated with multipulse laser-induced RayleighTaylor (RT) instability in the plane of a target surface in the circumferential zone ( C -zone) of the spot. Irregular target surface, variation of the fluid layer thickness and of the fluid velocity affect the nonlinearity and dispersion. The fluid layer inhomogeneity establishes local domains arranged (organized) in the «domain network». The traveling wavewrinkles become solitary waves and latter on become transformed into stationary soliton wavewrinkle patterns. Their morphology varies in the radial direction ofaussian-like spot ranging from the compacton-like solitons to the aperiodic rectangular waves (with rounded top surface) and to the periodic ones. These wavewrinkles may be successfully juxtapositioned with the exact solution of the nonlinear differential equations formulated in the KadomtsevPetviashvili sense taking into account the fluid conditions in particular domain. The cooling wave that starts at the periphery by the end of the pulse causes sudden increase of density and surface tension: the wavewrinkle structures become unstable what causes their break-up. The onset of solidification causes formation of an elastic sheet which starts to shrink generating lateral tension on the wavewrinkles. The focusing of energy at the constrained boundary causes the formation of wrinklons as the new elementary excitation of the elastic sheets.
我们研究了与多脉冲激光诱导的靶表面在光斑周向区(C -区)的平面上的RayleighTaylor (RT)不稳定性相关的波皱结构新范式的动力学、结构和组织。目标表面不规则、流体层厚度和流体速度的变化会影响非线性和色散。流体层的不均匀性建立了在“域网络”中排列(组织)的局部域。行波皱褶变成孤立波,然后变成静止的孤立波皱褶。它们的形态在类奥色斑的径向上有变化,从类紧子孤子到非周期矩形波(顶面为圆形),再到周期波。考虑到特定区域的流体条件,这些波皱可以成功地与KadomtsevPetviashvili意义下的非线性微分方程的精确解并列。脉冲末端从外围开始的冷却波导致密度和表面张力的突然增加:波皱结构变得不稳定,这导致了它们的破裂。凝固的开始导致弹性薄片的形成,弹性薄片开始收缩,在波纹上产生侧向张力。在约束边界处能量的集中导致褶皱的形成,成为弹性板的新的初等激励。
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引用次数: 2
Evaluation of electron temperature and electron density of laser-ablated Zr plasma by Langmuir probe characterization and its correlation with surface modifications 用Langmuir探针表征激光烧蚀Zr等离子体的电子温度和电子密度及其与表面修饰的关系
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s026303462000004x
Zul Irfan, S. Bashir, S. Butt, Asma Hayat, R. Ayub, K. Mahmood, M. Akram, Amna Batool
The plasma parameters of laser-ablated Zirconium (Zr) using a Langmuir probe technique have been investigated by employing a Q-switched Nd:YAG laser (532 nm, 6 ns) at various irradiances ranging from 8.6 to 15.5 GW/cm 2 . All the measurements have been performed under an ultra-high vacuum condition while keeping the probe at a fixed distance of 4 mm from the target. By varying the biasing voltages from 1 to 75 V, the corresponding values of electric currents are measured by the probe on the oscilloscope. Laser-induced Zr plasma parameters such as electron temperature, electron number density, plasma potential, Debye length, and thermal velocity have been evaluated from I–V characteristic curves of Langmuir probe data. It is found that both the electron temperature and thermal velocity of Zr plasma reveal an increasing trend from 18 to 41 eV and 2.8 × 10 8 to 4.3 × 10 8 cm/s, respectively, with increasing laser irradiance which is attributed to more energy deposition and enhanced ablation rate. However, the electron number density of Zr plasma exhibits a non-significant increase from 6.5 × 10 14 to 6.7 × 10 14 cm −3 with increasing irradiance from 8.6 to 10.9 GW/cm 2 . A further increase in irradiance from 12 to 15.5 GW/cm 2 causes a reduction in the number density of Zr plasma from 6.1 × 10 14 to 5.6 × 10 14 cm −3 which is attributed to the formation of thick sheath, ambipolar electric field, and laser-supported detonation waves (Shock front). Scanning electron microscope analysis has been performed to reveal the surface morphology of irradiated Zr. It reveals the formation of cracks, ridges, cones, and grains. It was observed at high irradiances the ridges are vanished, whereas cones and cracks are dominant features. By controlling plasma parameters, surface structuring of materials can be controlled, which has a vast range of applications in the industry and medicine.
利用Langmuir探针技术,利用调q Nd:YAG激光器(532 nm, 6 ns)在8.6 ~ 15.5 GW/ cm2的辐照度范围内研究了激光烧蚀锆(Zr)的等离子体参数。所有的测量都是在超高真空条件下进行的,同时探头与目标保持4毫米的固定距离。通过改变1 ~ 75v的偏置电压,示波器上的探头测量相应的电流值。利用Langmuir探针数据的I-V特性曲线,对激光诱导Zr等离子体的电子温度、电子数密度、等离子体势、德拜长度和热速度等参数进行了评价。结果表明,随着激光辐照强度的增加,Zr等离子体的电子温度和热速度分别从18 ~ 41 eV和2.8 × 10 8 ~ 4.3 × 10 8 cm/s呈上升趋势,这是由于能量沉积和烧蚀速率的增加。辐照度从8.6 GW/cm 2增加到10.9 GW/cm 2时,Zr等离子体的电子数密度从6.5 × 10 14增加到6.7 × 10 14 cm−3,但没有明显的增加。辐照度从12 GW/cm 2进一步增加到15.5 GW/cm 2,导致Zr等离子体的密度从6.1 × 10 14降低到5.6 × 10 14 cm−3,这是由于形成了厚鞘层、双极电场和激光支持的爆震波(激波锋)。扫描电镜分析了辐照Zr的表面形貌。它揭示了裂缝、脊、锥和颗粒的形成。在高辐照度下观察到脊状结构消失,而锥状结构和裂纹是主要特征。通过控制等离子体参数,可以控制材料的表面结构,在工业和医学上有着广泛的应用。
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引用次数: 1
Bernstein mode acceleration of electrons in a magnetic mirror 磁镜中电子的伯恩斯坦模式加速
IF 0.9 4区 物理与天体物理 Q4 PHYSICS, APPLIED Pub Date : 2020-06-01 DOI: 10.1017/s0263034620000038
Ram Jeet, Asheel Kumar
Electron dynamics in an axially localized large amplitude electron Bernstein mode in a magnetic mirror is studied. The mode is localized due to plasma density and magnetic field profiles and could be driven by an electron cyclotron wave, launched from outside, via linear mode conversion. Energetic electrons of finite gyro-radius resonantly interact with the mode and gain primarily transverse energy favoring stronger mirror confinement. At Bernstein wave normalized amplitude of A00 = 0.01 and for other normalized parameters Zn0 = 40, k⊥c/ω = 10, ${L}^{prime}_m = 215$, ωc0/ω = 0.9, ψn0 = 3π/2, the electrons can gain energy in the hundreds of keV range.
研究了磁镜中轴向局域大振幅电子伯恩斯坦模式下的电子动力学。由于等离子体密度和磁场分布,该模式是局域化的,并且可以由从外部发射的电子回旋波通过线性模式转换驱动。有限回旋半径的高能电子与模式共振相互作用,主要获得横向能量,有利于更强的镜像约束。在伯恩斯坦波归一化振幅A00 = 0.01和其他归一化参数Zn0 = 40, k⊥c/ω = 10, ${L}^{prime}_m = 215$, ωc0/ω = 0.9, ψn0 = 3π/2时,电子可以获得数百keV范围内的能量。
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引用次数: 1
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Laser and Particle Beams
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