间接驱动内爆靶丸示踪元素Ar发射X光谱线的理论模拟研究

惯性约束聚变内爆物理研究中, 示踪元素X光谱线诊断方法是推测内爆压缩温度、密度以及燃料混合的有效办法, 因此, 对示踪元素X光发射的规律及其与内爆过程的关系的研究非常必要, 有助于通过谱线发射特征诊断内爆状态. 以SGIII原型装置的实验条件下的内爆过程为例, 对内爆靶丸示踪元素Ar发射X光谱线进行了理论模拟. 研究了谱线自吸收效应、Ar掺杂浓度、等离子体空间分布不均匀等对Ar发射的X光谱线分布的影响. 还对Ar发射X光谱线强度的时间演化及其与内爆过程的关系进行了研究. 结果表明, 增加掺杂浓度, 谱线强度增强, 但是谱线自吸收效应的影响也明显增强. 示踪元素Ar发射的X光谱线强度的峰值时刻与中子产生速率的峰值时刻接近(前者延迟约15 ps). 高温、高密度及合适的电离度是谱线发射的3个条件, 在X光谱线发射的峰值时刻, 由于燃料芯部Ar等离子体过电离, Ar等离子体发射的X光谱线的空间峰值区域靠近燃料边界区域, 占燃料总体积56%的薄壳(厚度～4 μm), 其发射的X光谱线强度约为总强度的72%. 因此, 对发射谱线分布拟合得到的空间平均的等离子体温度、密度主要反映这一区域的等离子体状态.     

神光Ⅱ间接驱动内爆实验ArX射线谱线模拟研究

ICF内爆物理研究中,示踪元素X射线谱诊断方法是推测内爆压缩温度、 密度以及燃料混合状态的有效方法.针对其中的非平衡物理过程, 研制了非局域热动平衡(non-LTE)下一维谱线输运程序Alpha.程序以辐射流体计算给出的温度、 密度等量为输入条件,求解细致组态(DCA)模型下的原子动力学方程和辐射输运方程, 自洽给出谱线不透明度,和成像面上的X射线谱分布.
利用该程序,模拟了神光Ⅱ装置上的掺Ar靶丸内爆示踪元素X射线谱诊断实验, 研究结果表明,谱线的自吸收效应影响发射的X射线谱的强度和形状, 谱线的宽度对自吸收效应的强弱也有影响.因此,在对X射线谱的数值模拟中应该考虑自吸收效应. 另外,与LTE近似下的发射谱的比较表明, LTE近似下,等离子体电离度大～1, 发射谱的形状与non-LTE的结果不同,且LTE近似下,谱线的强度比non-LTE的谱线强度大5-10倍, 采用LTE近似是不合适的.     

利用时间分辨Ar的K壳层发射光谱诊断内爆靶丸芯区电子温度的时间演化过程

在神光Ⅱ装置上的内爆实验中,通过在充氘气(D2)的靶丸中掺入氩(Ar)元素,利用晶体谱仪配条纹相机测量得到了内爆停滞阶段Ar的K壳层发射光谱随时间的变化。在实验中,观测到Ar的Heα,Heβ以及Lyα线发射,持续时间大约200ps。用Heα线与Lyα线强度比值来推断靶丸芯区电子温度。利用碰撞辐射模型,从理论上计算出Heα线与Lyα线强度比值随电子温度、数密度的变化。通过将实验上观测到的Heα线与Lyα线强度比与理论计算值相比较,获得了芯区电子温度随时间的演化。并计算比较了不同电子密度条件下推断出来的电子温度的差异,证明诊断电子温度的方法对电子数密度的变化不敏感。利用逃逸因子修正了自吸收效应,从计算的结果可以看出在目前的实验中Heα线和Lyα线是光学薄的。     

第十五届全国原子与分子物理学术会议:非局域热动平衡等离子体K壳层电离平衡模型

发展了针对非局域热动平衡等离子体的K壳层电离平衡模型。模型中详细计算了各原子过程参数,并通过求解速率方程的稳态解得到各电离态的布居分布。在此基础之上,研究了谱线强度比值对等离子体温度、密度的依赖关系。最后,我们根据此模型的计算结果,分析了在神光II装置上获得的内爆靶丸掺Ar发射光谱实验数据,推断出靶丸芯区电子温度随时间的演化过程。     

非局域热动平衡等离子体K壳层电离平衡模型

发展了针对非局域热动平衡等离子体的K壳层电离平衡模型.模型中详细计算了各原子过程参数,并通过求解速率方程的稳态解得到各电离态的布居分布.在此基础之上,研究了谱线强度比值对等离子体温度、密度的依赖关系.最后,我们根据此模型的计算结果,分析了在神光Ⅱ装置上获得的内爆靶丸掺Ar发射光谱实验数据,推断出靶丸芯区电子温度随时间的演化过程.     

大气压等离子体炬电子密度的光谱诊断

利用空心针-板放电装置产生了大气压等离子体炬,采用光谱法测量了其内部及表面的电子密度. 向空心针中通入氩气,在大气环境中产生了长度为1cm的等离子体炬.实验分别测量了Hα谱线和ArⅠ(696.54nm)谱线,通过反卷积方法分离出其相应的Stark展宽,并由此计算了电子密度.结果发现,采用Hα谱线和ArⅠ(696.54nm)谱线Stark展宽计算得到的等离子体的电子密度分别为1.0×10¹⁵cm^－3和3.78×10^{15关键词： 等离子体炬 电子密度 气体温度 Stark展宽}     

双层喷气Z箍缩氖等离子体K层辐射研究

报道了"强光一号"(1.6 MA,70 ns)加速器驱动双层喷Ne气Z箍缩负载产生K层辐射(光子能量约1 keV)的实验研究.喷气负载出口半径为1.5—1.4 cm和0.75—0.6 cm(半径比2 ∶1).充气压力相同情况下外层和内层质量比约2.8 ∶1.在内爆时间约120 ns、负载线质量估计值60—70 μg/cm时,获得K层辐射产额约7 kJ、峰值功率0.28 TW,脉冲宽度20 ns.X射线分幅图像表明内爆阶段的不稳定性影响较小,最终内爆速度超过25 cm/μs,等离 关键词： 双层喷气 Z箍缩等离子体 K层辐射')" href="#">K层辐射 雪耙内爆     

Spatially-resolved spectroscopic diagnosing of aluminum wire array Z-pinch plasmas on QiangGuang-I facility

Spatially-resolved crystal spectrometers with a high spectral resolution are developed to diagnose K-shell x-ray radiation from Z-pinch plasmas. These diagnostic apparatuses are successfully applied to aluminum wire array Z-pinch experiments on QiangGuang-I facility, a driver with a pulsed current up to about 1.5 MA in 80 ns. Time-integrated experimental results show that the K-shell x-ray emission lines of aluminum Z-pinch plasmas are dominated by line emissions from helium-like ionisation state. Bright spots that might have higher electron temperature or density are produced randomly in location and size along the z-axis during implosions. According to the experimental data, the electron temperature and the ion density are estimated to be between 250 eV and 310 eV, and between 7.0×10¹⁹cm^-3 and 4.0×10¹⁹ cm^-3 respectively, while the ion temperature is inferred to be about 10.2 keV, which is much higher than the electron temperature.     

激光间接驱动内爆靶丸的X光诊断

 报道了神光Ⅱ激光聚变实验中内爆燃料靶丸区电子温度、电子密度以及燃料面密度的X光诊断结果。在电子温度诊断中，采用X射线光谱学方法，根据聚变靶丸燃料区的Ar示踪元素的Ly-β线与He-β线的强度比推断出靶丸燃料区电子温度为(950±100) eV；在电子密度诊断中，利用靶丸燃料区Ar元素的He-β线Stark展宽确定聚变靶丸芯部的电子密度为(0.9±0.2)×10²⁴ cm^-3；在燃料区面密度诊断中，利用X光单能照相技术获得了内爆靶丸的燃料面密度为（3.2±0.5） mg/cm²。     

Evolution Characteristics of the Laser-Plasma Electron Temperature of Heavy Metal Cr in Liquid Matrix

Using the nanosecond single-pulse laser-induced breakdown-spectroscopy (LIBS) technique, we determine the LIBS spectrum of a mixed solution of soluble compounds as a sample. Based on the LIBS measurement system established and the best experimental parameters, we measure the plasma emission spectrum of some lines of the Cr element. When the ICCD gate delay is measured from 500 to 2500 ns every 500 ns, and the liquid sample flow rate is set in the range of 35 ml · min^?1?55 ml · min^?1 with an interval of 5 ml · min^?1, the partial emission line of the Cr element in the laser plasma is measured, and the Boltzmann oblique line is drawn after the integrated intensity obtained. We calculate the evolution characteristics of the laser-plasma electron temperature with experimental parameters. The results show that the electron temperature values obtained from the intensity of the spectral lines of different elements are consistent with each other, indicating the reliability of the experimental measurement data. The range of electron temperature is obtained from the intensity of the Cr element line in the plasma range from 4071.0 K to 5628.4 K. As the flow rate continues to increase, the plasma electron temperature also increases but gradually becomes gentle. We select Cr 357.87 nm as the analytical line in the experiment and measure the particle density ratios of the Cr element in the ground state at different ICCD gate delays and sample flow rates. It provides experimental parameter support for further LIBS quantitative analysis of trace heavy metal elements in a liquid matrix.

     

Observation of transitions involving core-excited states in Ar III and Ar IV and high-lying singly excited states in Ar I–Ar IV

In this paper we present a comprehensive analysis of beam-foil and beam-gas excited spectrum of argon observed in small wavelength region, 2965–3090 Å, using Ar^+/2+ ions in the energy range 200–650 keV. The comparison of beam-foil spectrum (BFS) at different incident beam energy and with that of beam-gas spectrum (BGS), one can find solution for blending problem in beam-foil spectroscopy. Many new transitions were identified on the basis of calculated wavelength from the accurately known energy levels of Ar I, Ar II, Ar III and Ar V. The transitions of Ar I originate from highly excited states (10p to 17p and 10f to 17f). Based on TOPbase estimates using close-coupling approximation five transitions involving core-excited states and nine transitions originating from highly excited states in the spectrum of Ar III and Ar IV were also identified. Radiative life time of two core excited quintet states (3s3p⁴(⁴P)6d ⁵D and 3s3p⁴(⁴P)8f⁵F^o) of Ar III were measured and found to be in ‘good’ agreement with that of the calculated value using close-coupling approximation.     

Spectroscopic Diagnostics of Pulsed arc Plasmas for Particle Generation

Pulsed arc plasmas were diagnosed by means of emission spectroscopy. A capacitor was discharged through argon and hydrogen leading to a few cycles of damped current oscillation with ≈120 μs period and 5‐12 kA maximum current. Spectroscopic measurements in the visible range were carried out in order to characterise the electron temperature and density in the arc channel as well as electron and gas temperatures in the afterglow plasmas. Spectra were integrated over 10 μs time windows and shifted in time from pulse to pulse. The plasmas also contained substantial fractions of electrode material (brass), namely copper and zinc. The electron density was measured in the conventional way from the broadening of H_β or from the Ar I Stark width. In the arc channel, it ranged from about 3 · 10²² to 2 · 10²³ m^–3. The broadening of Zn II lines could also be used. Ratios of Ar I to Ar II and of Zn I to Zn II line intensities were analysed for the electron temperature. Line pairs were found which lay conveniently close in one frame of the spectrometer allowing automatic on‐line analysis without relying on reproducibility. Atomic physics models including opacity were developed for Ar II and Zn II in order to check the existence of a Boltzmann distribution of their excited states. These calculations showed that the observed levels were in fact close to thermodynamic equilibrium, in particular, if the resonance lines were optically thick. Electron temperature measurements yielded values between 14000 K and 21000 K. The gas temperature in the afterglow, where particles should have formed, was derived from the rotational and vibrational temperatures of C₂ molecular bands. Ratios between Cu I line intensities yielded the electron temperatures. Both were found to be a few 1000 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of multiple impurity seeding effect using SONIC integrated divertor code for JT-60SA plasma prediction

In order to study the potential impurity seeding operation regime of the future fusion devices, the first application of the integrated divertor code SONIC to the Ar + Ne mixed-impurity seeding operation of JT-60SA steady-state high-β plasma has been carried out. In the case, Ne is added to Ar-only seeding, the separatrix electron density has fell into the desired low separatrix electron density of the scenario. This is mainly because the D⁺ flow velocity towards the inner divertor has been increased by the Ne seeding. The resultant friction force transports Ar impurities towards the inner divertor region, while impurities are stagnated in the top of scrape-off layer (SOL) in the Ar-only seeding case. The higher impurity radiation power in the divertor regions and lower one in the SOL region above the X point have been obtained in mixed-impurity seeding cases, which show similar tendency as the Ar + Ne mixed-impurity seeding experiment in JT-60 U. At the core edge, Z_eff has been slightly increased and the radiation power has been decreased as the Ne seeding rate increases. The core plasma/impurity transport has been also evaluated by the TOPICS code using the impurity density at the core edge computed by the SONIC as a boundary parameter. The results show lower Z_eff and radiation power, and higher electron temperature in the core in the mixed-impurity seeding cases. Above possible contributors to the better energy confinement indicate that the mixed-impurity seeding operation might be more effective than Ar-only seeding operation.     

Distribution Radiale de la Densité des Atomes Métastables dans les Plasmas Produits par un Champ Electrique Continu ou de Haute-Fréquence

The radial density distribution of metastable Ar(³P₂) and resonant Ar(¹P₁) atoms is determined experimentally in two types of electrical discharges of cylindrical shape: the positive column plasma of a DC discharge and the plasma produced by an electromagnetic surface wave. The exitation and deexcitation rates for Ar(³P₂) by electron collisions are determined as a function of radius from the measured radial population density profile using a population density balance equation. These rate coefficients are obtained for various electron density values on the axis. The published values for these coefficients in the positive column plasma assume that they are independent of the discharge current. In this work, it is shown that these coefficients actually decrease as the electron density increases. In a more general way, the results obtained indicate that the examination of the radial density distributions of exited atoms is a powerful method for determining the kinetics of their creation and destruction.     

X-ray spectroscopy from variable,Z laser-produced plasmas

We have investigated the sensitivity of X-ray line intensities as a laser-plasma diagnostic by seeding Si in CH and PbO plasmas. The Si K X-ray spectrum is measured using both time-integrating and time-resolving spectrographs to investigate the effect of time averaging on the line intensities. The measured intensities are compared with theoretical estimates for an isothermal, isodensity plasma. Si line intensities vary with the Z of the plasma, as expected from simple scaling models, indicating the Si lines can be a good plasma diagnostic. The line intensities do not predict a unique temperature and density, but, instead, the inferred temperature and density vary, depending on the line ratio used. These variations are attributed to large spatial gradients of temperature and density in the plasmas. Problems in interpretation are discussed, as well as possible directions for future experiments.     

“碰撞-辐射”模型在Z箍缩等离子体K壳层线辐射谱分析中的应用

介绍了由K壳层谱线强度比估算等离子体状态参数的"碰撞-辐射"模型的基本原理.详细描述了自行研制的基于该模型的Z箍缩等离子体K壳层线辐射谱分析程序——ZSPEC的基本情况.给出了氖等离子体的计算结果,包括不同电离态离子的相对含量随电子温度的变化曲线和K壳层谱线强度比在"电子密度-电子温度"平面内的等高线分布图.该程序已在"阳"加速器Z箍缩实验结果分析中得到应用,将椭圆晶体谱仪测得的氖等离子体K壳层谱线强度比与ZSPEC程序计算结果相比较,得出在该发实验 关键词： 碰撞-辐射模型 K壳层线辐射谱')" href="#">K壳层线辐射谱 氖气喷气Z箍缩 阳加速器     

X-ray absorption lines: Signature for preheat level in non-explosive laser implosions

The measured X-ray spectrum from thick glass shells imploded with two TW six-beam laser pulses displayed absorption by transitions of Si ions. This indicates the existence around the time of peak compression of a cooler (? 200 eV) layer surrounding the hot innermost glass layer, of density times thickness ?ΔR ～ 0.6 × 10^-3 g/cm². This temperature is indicative of the preheat level earlier in the implosion.     

A 90° laser scattering experiment for measuring temperature and density of ions and electrons in a cold dense theta pinch plasma

In a 90° scattering experiment performed on a plasma with a density of some 10¹⁷cm^?3 and a temperature of some eV a scattering spectrum is expected which consists essentially of an intense central part and two very weak satellite peaks. In this investigation the spectrum of the central part (ion line) was resolved. From the ion line alone which was in good agreement with calculated spectra, the ion temperature, electron temperature and electron density were determined. At some plasma parameters only a few particles were included in the Debye volume. Also in these cases no deviations from calculated spectra have been observed. In addition the position and half-width of the satellites were measured. The position of the satellites yields an independent value of the electron density which agrees very well with that determined from the ion line. The half-width of the satellites was much broader than expected theoretically due to fluctuations of the electron density within the scattering volume. The measurement was performed on a theta pinch plasma. The energy of the condensor bank was 7.5 kJ, the voltage 18 kV. As a light source aQ-switch laser was used with a power of about 100 MW. Because of beam stops to prevent stray light only a fourth of the whole power reached the plasma.     

An experimental investigation of partial LTE for lower excited levels of Ar(I) in a wall-confined,argon arc plasma

This paper contains experimental results on partial LTE in the lower excited levels of Ar(I). The experiments were performed in a well-confined argon arc source. The population densities were obtained from self-absorption measurements of the lines. Plasma parameters were determined spectroscopically; measurements included the electron density (from the H_β line width) and the electron temperature (from the Boltzmann plot for higher excited levels of Ar(I)). The results show that the levels 1s₅ to 1s₅ are in Saha-Boltzmann equilibrium for electron densities above 3 × 10¹⁶ cm^-3.     

Theoretical study of the MgAr molecule and its ion Mg<Superscript>+</Superscript>Ar: potential energy curves and spectroscopic constants

The adiabatic potential energy curves of the low-lying electronic states of the MgAr molecule dissociating into Mg (3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p)+Ar have been investigated. The electronic structure of the Mg-Ar molecule is calculated using [Mg²⁺] and [Ar] core pseudopotentials complemented by the core polarization operators for both atoms, considering the molecule to be a two-electron system. The derived spectroscopic constants of the ground state and lower excited states are in good agreement with available experimental and theoretical work. In addition, for the purpose of checking the pseudopotential accuracy on a simpler related system, low lying potential energy curves of the single active electron Mg⁺Ar ion are also reported and the corresponding molecular constants are compared with those in the existing literature.