Theoretical and simulation research of hydrodynamic instabilities in inertial-confinement fusion implosions

Inertial fusion energy(IFE)has been considered a promising,nearly inexhaustible source of sustainable carbon-free power for the world's energy future.It has long been recognized that the control of hydrodynamic instabilities is of critical importance for ignition and high-gain in the inertial-confinement fusion(ICF)hot-spot ignition scheme.In this mini-review,we summarize the progress of theoretical and simulation research of hydrodynamic instabilities in the ICF central hot-spot implosion in our group over the past decade.In order to obtain sufficient understanding of the growth of hydrodynamic instabilities in ICF,we first decompose the problem into different stages according to the implosion physics processes.The decomposed essential physics processes that are associated with ICF implosions,such as Rayleigh-Taylor instability(RTI),Richtmyer-Meshkov instability(RMI),Kelvin-Helmholtz instability(KHI),convergent geometry effects,as well as perturbation feed-through are reviewed.Analytical models in planar,cylindrical,and spherical geometries have been established to study different physical aspects,including density-gradient,interface-coupling,geometry,and convergent effects.The influence of ablation in the presence of preheating on the RTI has been extensively studied by numerical simulations.The KHI considering the ablation effect has been discussed in detail for the first time.A series of single-mode ablative RTI experiments has been performed on the Shenguang-Ⅱlaser facility.The theoretical and simulation research provides us the physical insights of linear and weakly nonlinear growths,and nonlinear evolutions of the hydrodynamic instabilities in ICF implosions,which has directly supported the research of ICF ignition target design.The ICF hot-spot ignition implosion design that uses several controlling features,based on our current understanding of hydrodynamic instabilities,to address shell implosion stability,has been briefly described,several of which are novel.     

Phenomena of the Cold Pulse Propagation during Pulsed Molecular Beam Injection

As an advanced fuelling method on tokamak, molecular beam injection （MBI） has successfully been developed in HL-1M firstly and applied to HL-2A later. Many advantages such as peaked density profile and the energy confinement time increasing have been found in the MBI experiments. Some interesting phenomena have been observed in the previous MBI experiments. But up to now the mechanism of the MBI seems not very clear.     

Sterilization of E. coli bacterium with an atmospheric pressure surface barrier discharge

The atmospheric pressure surface barrier discharge (APSBD) in air has been used in killing Escherichia coli (E.coli), There is almost no bacterial colony in the sample after treatment by discharge plasma for 2rain, A diagnostic technique based on mass spectrum has been applied to the discharge gas and the mechanism of killing is discussed. Ozone and monatomic oxide are considered to be the major antimicrobial active species. There is almost no harmful by-product. The experiment proves that APSBD plasma is a very simple, effective and innocuous tool for sterilization.     

Design and fabrication of a silicon miniature condenser microphone

1 IntroductionMicromachining is one of the most challenging tasks in research and development today. This technique hajs been successfully applied to the fabrication of various microsensors.Micromachining has potential adVantages in these applications, such as small size, excellelltmechanical properties and batch fabrication at low cost. Integration of electronic circultry withmicrosensors is also possible, which makes a full microsystem.Over the last two decades, extensive efforts have been …     

An improved method of unfolding neutron TOF spectrum for low ion temperature inertial confinement fusion

The fuel ion temperature in inertial confinement fusion can be determined from the neutron energy spectrum. For the implosion experiment with low neutron yield, and thus low signal-to-noise ratio, a new technique to unfold the neutron energy spectrum from the observed neutron time-of-flight signal is presented in this paper. This method uses a low-pass filter to remove noise from the signal with a threshold value determined by power spectrum analysis. This technique has been applied to the analysis of the observed neutron time-of-flight signals in the indirect drive implosion experiment conducted on Shenguang III prototype laser facility, and fuel ion temperatures of about 1.0 keV are obtained.     

An improved method of unfolding neutron TOF spectrum for low ion temperature inertial confinement fusion

The fuel ion temperature in inertial confinement fusion can be determined from the neutron energy spectrum. For the implosion experiment with low neutron yield, and thus low signal-to-noise ratio, a new technique to unfold the neutron energy spectrum from the observed neutron time-of-flight signal is presented in this paper. This method uses a low-pass filter to remove noise from the signal with a threshold value determined by power spectrum analysis. This technique has been applied to the analysis of the observed neutron time-of-flight signals in the indirect drive implosion experiment conducted on Shenguang Ⅲ prototype laser facility, and fuel ion temperatures of about 1.0 keV are obtained.     

Estimating topological charge of propagating vortex from single-shot non-imaged speckle

Encoding information using the topological charge of vortex beams has been proposed for optical communications. The conservation of the topological charge on propagation and the detection of the topological charge by a receiver are significant in these applications and have been well established in free-space. However, when vortex beams enter a diffuser,the wavefront is distorted, leading to a challenge in the conservation and detection of the topological charge. Here, we present a technique to measure the value of the topological charge of a vortex beam obscured in the randomly scattered light. The results of the numerical simulations and experiments are presented and are in good agreement. In particular, only a single-shot measurement is required to detect the topological charge of vortex beams, indicating that the method is applicable to a dynamic diffuser.     

X射线质量衰减截面和光电截面的高精度测量

利用特征Ｘ射线源系统地测量了Ｓｉ、Ｆｅ、Ｃｕ、Ｙ、Ｉｎ、Ｓｎ等六种元素及ＳｉＨ４的Ｘ射线质量衰减系数,实验误差为±１％． By using the characteristic X ray sources and the Si( Li) detector system, the X ray mass attenuation coefficients for Si,Fe,Cu,Y,In,Sn and SiH 4 have been systematically measured in the energy range of 1.486～29.109 keV. The accuracy of experimental data has been reduced to ±1% .     

Experimental investigation of sound field separation technique with double holographic planes

A multi-channel acoustic holographic measurement and analysis system has been developed and been applied to validate sound field separation technique with double holographic planes. Moreover, some methods to enhance separation precision have also been given, based on the error analysis of the technique. The holographic pressures on double planes are measured and analyzed by the developed holographic system when some background sources exist. The experimental results show that the separation technique proposed can suppress the influence of the background sources on holographic reconstruction effectively, and the reconstructed sound field and source identification can be obtained correctly.     

Mechanochemical Coupling of Kinesin Studied with a Neck-Linker Swing Model

A neck-linker swing model has been proposed in this work to investigate the mechanochemical coupling of kinesin. The difference between force-velocity curves given by force clamp and fixed trap respectively has been satisfactorily interpreted by this model. The study implies that ADP releasing and ATP hydrolysis are much less forcedependent in force clamp experiments than that in fixed trap experiments in the regime of moderate loading force, which might be a consequence of the delayed response of servo system in force clamp experiments.     

惯性约束聚变靶三维成像研究

利用计算机层析技术，采用乘代数重建法，编制出三维图像重建程序ＣＴ３Ｄ，通过五个方位对“星光Ⅱ”装置的惯性约束聚变靶进行Ｘ光成像，重建出靶等离子体的三维图像，获得了较好的结果，表明该技术在惯性约束聚变实验中应用的可能性。     

高灵敏GaAs探测器及应用

在ICF实验研究中,我们应用新研制的经快中子辐照处理过的GaAs晶体材料做成的光导电探测器首次实验观察到各种结构的内爆靶发射的硬X光时间波形信号以及硬X光的空间角分布。这种探测器对X光有很高的灵敏度(约10~(-18)C/keV),有快的响应(约100ps),具有抗干扰能力强,灵敏度高体积小,用于ICF实验的X光诊断有独特优点。     

Application of proton radiography in experiments of relevance to inertial confinement fusion

Multi-Mev proton beams generated by target normal sheath acceleration (TNSA) during the interaction of an ultra intense laser beam (I≥10¹⁹ W/cm²) with a thin metallic foil (thickness of the order of a few tens of microns) are particularly suited as a particle probe for laser plasma experiments. The proton imaging technique employs a laser-driven proton beam in a point-projection imaging scheme as a diagnostic tool for the detection of electric fields in such experiments. The proton probing technique has been applied in experiments of relevance to inertial confinement fusion (ICF) such as laser heated gasbags and laser-hohlraum experiments. The data provides direct information on the onset of laser beam filamentation and on the plasma expansion in the hohlraum’s interior, and confirms the suitability and usefulness of this technique as an ICF diagnostic.     

激光惯性约束聚变中光学汤姆逊散射研究进展

当前，激光惯性约束聚变在越来越接近点火的极端能量密度条件下，实验与模拟的偏离逐渐增大，一个关键原因是缺乏对黑腔等离子体状态及其影响黑腔能量学和内爆对称性的细致研究和判断。光学汤姆逊散射主动式、诊断精确、参数完备的优点，使之成为激光惯性约束聚变黑腔等离子体状态参数精密诊断的标准方法。中国面向激光惯性约束聚变研究的光学汤姆逊散射实验技术的发展与神光系列激光装置的建设和在其上开展的物理实验紧密相关。近年来，四倍频汤姆逊散射实验技术在神光III原型和100 kJ激光装置上相继建立，部分实验结果不仅加深了对激光惯性约束聚变靶物理的认识，还反映了实验条件对汤姆逊散射诊断的影响，促进了实验技术的精密化发展。在未来，还需要进一步发展多支路汤姆逊散射、五倍频汤姆逊散射和超热相干汤姆逊散射等新技术，面向点火黑腔条件，大幅提升激光等离子体状态参数的诊断精度，开展新物理机制的探索和研究，在激光惯性约束聚变和其他高能量密度物理科学领域发挥更重要的作用。     

X射线CT技术体积重构法表征异形泡沫金密度

采用X射线CT(XCT)技术进行体积重构的研究方法,解决了异形泡沫金密度表征中体积难以精确测量的问题,密度表征结果为978.68mg/cm3。同时,为了研究该方法的有效性与不确定度,开展了XCT体积重构法与排水法对具有不规则外形橡皮泥样品的密度表征对比实验,结果表明两者之间的相对误差小于1%。     

燃料均化过程中红外光体加热率控制模拟

通过光线追迹程序对红外光在黑腔中的传播进行模拟,得到红外光聚焦位置不同时靶壳和燃料的体加热率。模拟结果表明:当燃料冰层实现均化时,相比靶壳,燃料吸收了少部分红外光能量。靶壳和燃料的体加热率随着红外光在黑腔上的聚焦位置而改变,聚焦位置偏移量的增加,靶壳的红外光加热率峰值对应的高度角逐渐变大,而燃料的红外光体加热率逐渐变小。因此,通过改变红外光的聚焦位置对靶丸以特定的体积热率加热,从而达到燃料均化所需的温度场。     

针孔辅助点投影诊断方法实验研究

针孔辅助点投影背光成像是近几年国外新兴的等离子体诊断技术,在惯性约束聚变相关物理实验诊断中具有重要的应用前景.为验证这一诊断方法的实用性,在神光Ⅱ第九路平台上开展了演示实验.利用激光驱动平面Ti靶获得约4.7 keV的Ti K壳层X射线,在十几微米的针孔约束下作为次级点源并对Au栅格样品投影成像,并用CCD记录.实验成功获得了清晰的样品二维空间分辨的时间积分图像,空间分辨力优于16.1 μm.实验结果表明针孔辅助点投影具有较高的空间分辨力、较大的视场、较高的图像对比度,将成为瑞利泰勒不稳定性研究、激光状态方程研究等物理实验的重要诊断方法之一.     

微靶装配中靶球几何量的高精度测量

为满足微靶装配过程中靶球和靶腔相对位置的严格的要求,保障惯性约束聚变实验的成功,针对机器视觉的几何量测量精度很难达到5 m以下的不足,设计了利用具有亚m级精度的激光共焦测头对装配中的靶球进行采点扫描以获取其尺寸和位置的非接触测量方法,借助于在线监测系统运动轴的高精度定位,通过上下两个激光共焦测头的组合测量,并采用一种快速而准确的基于点阵插值细分和目标两级提取的测量算法,使在线监测系统的球体几何量测量精度达到了2 m。     

薄壁玻璃靶丸低温保气性能研究

 对薄壁玻璃靶丸在液氮保存状态下保气性能进行了研究。实验结果表明：在－196℃环境中,薄壁靶丸的保气半寿命由常温的3~10d延长到100~500d左右,靶丸的表面粗糙度没有明显变化,能满足ICF打靶要求。     

激光惯性约束聚变综合诊断系统

 概述了为在强激光装置“神光 II”、“星光 II”上开展惯性约束聚变实验而建立的综合诊断系统的构成与指标。重点介绍了近期在X光、光学波段、聚变产物、诊断精密化等方面的进步，以及该诊断系统在黑腔靶物理、内爆动力学、不透明度研究中的应用。