Ar?NO团簇的同步辐射光电离研究

利用国家同步辐射实验室合肥光源的真空紫外同步辐射，使NO分子和Ar原子混合物的超声分子束发生光电离，测量了Ar，NO和异类团簇Ar·NO的光电离效率谱. 在谱中，在与Ar原子的共振线对应的能量区域(11.5—12.0 eV)观察到一个强的类共振结构. 这个结果表明，在异类团簇Ar·NO的内部，稀有气体Ar原子的激发能转移到与它接触的分子NO上，使分子NO发生电离. 关键词： Ar·NO团簇 同步辐射 光电离 能量转移     

Soft X-ray spectroscopic study of a gas-puff Z-pinch argon plasma

X-ray radiation characteristics of argon plasma produced by a gas-puff Z-pinch device were investigated using an X-ray crystal spectrometer, an X-ray diode, and an extreme ultraviolet (XUV) spectrometer. Using a germanium crystal we have observed spectral emission from Ar XVII produced by hot spots at the pinched stage. With the help of a 2-m grazing incidence XUV spectrometer, the spectrum of 30 to 250 Å were obtained. Strong lines from Ar VIII to Ar XIII were observed with a continuum whose peak is around 120 Å. The radiation energy in the spectral range is estimated to be about 23 joule which is about 0.6% of the electrical energy stored in capacitors     

Effect of buffer gas on the generation of eye-safe 1.54 μm radiation using the stimulated Raman scattering technique in CH4

Experimental results on the generation of 1.54 μm eye-safe radiation in pure CH₄, CH₄:He and CH₄:Ar mixtures pumped by the fundamental of an Nd:YAG laser, using the stimulated Raman scattering (SRS) technique, are described. A decrease in the energy conversion efficiency and degradation in the beam quality of S₁ was observed in pure CH₄ at high pump energies. This problem was overcome in CH₄:He and CH₄:Ar mixtures. Compared with the first Stokes (1.54 μm) energy conversion efficiency in pure CH₄, at a pump energy of 126 mJ, an enhancement of 50% in energy conversion efficiency was observed in the CH₄:Ar mixture (60% argon concentration) and as much as 100% in the CH₄:He mixture (60% helium concentration). The use of these buffer gas mixtures improved the spatial beam quality of the Stokes radiation considerably and also resulted in raising the pump threshold for optical breakdown of the Raman gain medium.     

Effect of buffer gas on the generation of eye-safe 1.54 μm radiation using the stimulated Raman scattering technique in CH4

Experimental results on the generation of 1.54 μm eye-safe radiation in pure CH₄, CH₄:He and CH₄:Ar mixtures pumped by the fundamental of an Nd:YAG laser, using the stimulated Raman scattering (SRS) technique, are described. A decrease in the energy conversion efficiency and degradation in the beam quality of S₁ was observed in pure CH₄ at high pump energies. This problem was overcome in CH₄:He and CH₄:Ar mixtures. Compared with the first Stokes (1.54 μm) energy conversion efficiency in pure CH₄, at a pump energy of 126 mJ, an enhancement of 50% in energy conversion efficiency was observed in the CH₄:Ar mixture (60% argon concentration) and as much as 100% in the CH₄:He mixture (60% helium concentration). The use of these buffer gas mixtures improved the spatial beam quality of the Stokes radiation considerably and also resulted in raising the pump threshold for optical breakdown of the Raman gain medium.     

Formation of tight plasma pinches and generation of high-power soft x-ray radiation pulses in fast Z-pinch implosions

Argon K-shell plasma radiation source experiments were carried out on the GIT-12 generator [Bugaev, S.P. et al., 1997, Russian Phys. Journal, 40, 38] for a long (300 ns) implosion regime. The performance of a shell-on-solid-fill double gas puff was characterized in the experiments with and without an external axial magnetic field. The maximum Ar K-shell radiation yield registered in the experiments without an axial magnetic field was at the level of 1100 J/cm. This yield is consistent with the theoretically predicted yield for a short (100 ns) implosion regime. The experiments showed that the initial magnetic field which provides stabilization of the shell-on-solid-fill double gas puff was lower than that required for stabilization of a single annular gas puff. Satisfactory stabilization of the double gas puff was observed at an initial axial magnetic field of 1.4 kG. The maximum Ar K-shell radiation yield registered in the experiments with the axial magnetic field did not exceed 400 J/cm. A sharp reduction of the K-shell yield cannot be explained only by taking into account the energy losses associated with the compression of the axial magnetic field. Original Text ? Astro, Ltd., 2006.     

高速CT阻滞产生X射线辐射的数值模拟研究

以Ar等离子体为例,应用一维辐射流体力学模型,对高速度、高密度的紧凑等离子体环(CT)撞击静态靶减速产生软X射线辐射的物理过程进行了数值模拟研究。利用分裂格式方法计算得到了描述碰撞物理过程的各力学量随时间的演化关系,以及固定CT动能时使停滞CT成为最有效辐射源的初始速度和质量的最优搭配。对计算过程中相关物理量的跟踪分析表明,在1%的误差范围内计算格式满足能量守恒方程。     

A new source of radiation in single-bubble sonoluminescence

An unsolved challenge of sonoluminescence phenomenon is the mechanism of light emission at the moment of collapse. In this article, by considering single-bubble sonoluminescence and based on the hydrochemical model and thermal bremsstrahlung approach, for the first time two different origins of light have numerically been studied to describe the Ar bubble radiation in water at the moment of collapse: (a) radiation from the Ar gas inside the bubble and (b) radiation from the thin layer of the surrounding fluid. The results indicate that, contrary to the previous studies, the radiation from the water shell is dominant, and it is about one order of magnitude stronger than the radiation from the gas inside the bubble. This result can decrease the difference between the theoretical results and the previous experimental data. In addition, based on the role of acoustic pressure amplitude on the characteristics of single-bubble sonoluminescence, various parameters such as degree of ionization, gas pressure, temperature and power were calculated. The results are in excellent agreement with the reported experimental measurements.     

Observation of resonant diffusive radiation in random multilayered systems

Diffusive radiation is a new type of radiation predicted to occur in randomly inhomogeneous media due to the multiple scattering of pseudophotons. This theoretical effect is now observed experimentally. The radiation is generated by the passage of electrons of energy 200 KeV-2.2 MeV through a random stack of films in the visible light region. The radiation intensity increases resonantly provided the Cerenkov condition is satisfied for the average dielectric constant of the medium. The observed angular dependence and electron resonance energy are in agreement with the theoretical predictions. These observations open a road to application of diffusive radiation in particle detection, astrophysics, soft-x-ray generation, etc.     

On the origin of visible continuum radiation in rare gas glow discharges

To prove the electron-atom bremsstrahlung origin of visible continuum radiation in rare gas medium-pressure glow discharges some new experiments and theoretical considerations were carried out.Arguments for the bremsstrahlung theory are supported by experimental results for (i) the behaviour of the radiation in ArHg mixtures; (ii) the spectral distribution in the visible and near UV range (Ne, Ar, Xe); (iii) the change of intensity during the transition from the diffuse to the constricted mode of the positive column (Ne) and (iv) the behaviour of the radiation in the Faraday dark space (He).Together with some other facts a foundation of the bremsstrahlung theory is given.     

Ar 3s, 3p satellite lines studied by fluorescence spectroscopy

The fluorescent radiation emitted by the Ar 3s, 3p satellite states (observed by photoelectron spectroscopy) has been recorded in the wavelength range between 400 and 780 Å with an energy resolution ranging from 50 to 100 mV. The fluorescence was stimulated by use of undispersed synchrotron radiation.     

Electrodeless microwave source of UV radiation

The parameters of an electrodeless microwave low-pressure discharge in an Ar + Hg vapor mixture are studied, the design of a UV radiation source for water disinfection is suggested, and its main characteristics are presented. The domestic microwave oven (f = 2.45 GHz; N = kW) is used as a microwave radiation source. The maximal UV power at wavelength λ = 254 nm amounts to 120–130 W.     

基于声辐射模态讨论声能量辐射与传递

声辐射模态表示了振动声源表面的辐射模式。基于声辐射模态讨论了振动声源表面声能量辐射和声场中声能量传递的性质,给出声能量辐射和传递的模式。采用表面声强描述振动声源表面的声能量辐射,采用声强描述声能量在声场中的传递。表面声强和声强可分解成两部分,一部分将辐射的声能量传递到远场;另一部分表现为振动声源与声场之间的能量交换。针对矩形板分析了声能量辐射和传递,数值计算结果与理论结果一致。结果表明基于声辐射模态讨论声能量辐射与传递是可行的和有效的。     

The mechanism of Vavilov-Cherenkov radiation

The mechanism of generation of Vavilov-Cherenkov radiation is discussed in this article. The developers of the theory of the Vavilov-Cherenkov effect, I.E. Tamm and I.M. Frank, attributed this effect to their discovery of a new mechanism of radiation when a charged particle moves uniformly and rectilinearly in the medium. As such a mechanism presupposes the violation of the laws of conservation of energy and momentum, they proposed the abolition of these laws to account for the Vavilov-Cherenkov radiation mechanism. This idea has received a considerably wide acceptance in the creation of other theories, for example, transition radiation theory. In this paper, the radiation mechanism for the charge constant motion is demonstrated to be incorrect, because it contradicts not only the laws of conservation of energy and momentum, but also the very definitions of uniform and rectilinear motion (Newton's First Law). A consistent explanation of the Vavilov-Cherenkov radiation microscopic mechanism that does not contradict the basic laws is proposed. It is shown that the radiation arises from the interaction of the moving charge with bound charges that are spaced fairly far away from its trajectory. The Vavilov-Cherenkov radiation mechanism bears a slowing down character, but it differs fundamentally from bremsstrahlung, primarily because the Vavilov-Cherenkov radiation onset results from a two-stage process. First, the moving particle polarizes the medium; then, the already polarized atoms radiate coherently, provided that the particle velocity exceeds the phase speed of light in the medium. If the particle velocity is less than the phase speed of light in the medium, the polarized atoms return energy to the outgoing particle. In this case, radiation is not observed. Special attention is given to the relatively constant particle velocity as the condition of the coherent composition of waves. However, its motion cannot be designated as a uniform and rectilinear one in the sense of its definition by Newton's First Law, and it also contradicts the laws of conservation of energy and momentum.     

Neutral Bremsstrahlung radiation of Ne,Ar and O

The neutral Bremsstrahlung cross-sections of Ne, Ar and atomic oxygen around the 3 and 10μ wavelength regions were measured in a high temperature plasma generated in a shock tube. The results were generally a factor of three higher than the theoretical values calculated by Geltman. Agreement with the experimental results of Taylor and Caledonia around 3μ was good except for the case of Ne. The cross-sections around 10μ are the first measurements in this wavelength region. Enhanced radiation due to atomic line emission on top of the Bremsstrahlung continuum, as predicted by Hyman was observed around 7.44μ.     

飞秒超强激光驱动太赫兹辐射特性的实验研究

强太赫兹源是太赫兹科学技术发展的关键,其中大能量强场太赫兹脉冲源在超快物态调控、新型电子加速器等领域具有重要的应用前景.超快超强激光与等离子体相互作用是近年来发展起来的一种新型的强场太赫兹辐射产生途径.本文报道了利用超强飞秒激光脉冲与金属薄膜靶作用产生太赫兹辐射的实验结果,研究了激光能量和离焦量对靶后太赫兹辐射能量的影响,并通过监测激光背向散射光谱,定性揭示了其变化规律与不同光强下的电子加热机制的相关性.实验表征了太赫兹辐射的频谱、偏振及聚焦光斑情况.测量结果表明,实验产生了脉冲能量达458μJ、聚焦场强高达GV/m量级的超宽带太赫兹辐射,为开展极端太赫兹脉冲与物质相互作用研究提供了一种新的强场太赫兹光源.     

Efficient radiation production in long implosions of structured gas-puff Z pinch loads from large initial radius

We have proposed and demonstrated successfully a new approach for generating high-yield K-shell radiation with large-diameter gas-puff Z pinches. The novel load design consists of an outer region plasma that carries the current and couples energy from the driver, an inner region plasma that stabilizes the implosion, and a high-density center jet plasma that radiates. It increased the Ar K-shell yield at 3.46 MA in 200 ns implosions from 12 cm initial diameter by a factor of 2, to 21 kJ, matching the yields obtained earlier on the same accelerator with 100 ns implosions. A new "pusher-stabilizer-radiator" physical model is advanced to explain this result.     

A study of the radiation of a Nd:YAG laser-MIG hybrid plasma

To study the coupling of a Nd:YAG laser beam and a MIG arc with the spectrum of the plasma, a new hollow probe method is used to collect radiation from specific points within the arc plasma. With the probe, the spatial distributions of the MIG arc radiation with and without the Nd:YAG laser hybrid plasma are collected and analyzed by a fiber spectrometer. Through analysis of the spectrum, radiation in the ultraviolet (Fe II dominated), visible (Fe I dominated) and infra (Ar I dominated) spectral zones are acquired for comparison of the difference between the MIG and Laser-MIG hybrid welding processes. The electronic temperature is calculated using the Boltzmann plot method and the electronic density is calculated using the Stark broadening method. The results show that the Laser-MIG hybrid welding processes cause the plasma energy to focus on the center of the welding arc and approach the welding pool. An ionizing duct abundant with Fe ions will be formed near the position of the impinging laser beam, which makes the welding arc stable. The electronic temperature of the Laser-MIG hybrid welding arc is a little higher than that of the MIG. The electronic density of Laser-MIG hybrid welding is higher than that of the MIG.     

黑体辐射中两类粒子的辐射规律

考虑到相对论效应,采用量子统计的方法,得到了满足Bose-Einstein统计分布和Fermi-Dirac统计分布的两类粒子的黑体辐射公式（包括Planck黑体辐射公式）．发现辐射谱不仅与黑体的辐射温度有关,还与辐射粒子的能量、化学势和种类有关．辐射强度与辐射粒子的能量、静质量、简并因子有关。     

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通过红外可见内窥镜诊断系统对EAST等离子体芯部逃逸电子的同步辐射功率谱进行了分析,得出低能段逃逸电子同步辐射主要在红外波段,随着逃逸电子能量的增加,同步辐射向短波方向移动进入可见光波段。在欧姆放电条件下,对逃逸电子同步辐射所产生的的红外可见光进行了成像分析,同时研究了EAST等离子体在低杂波和中性束注入加热条件下的逃逸电子行为。实验结果显示,低杂波和 NBI 的投入总体抑制电子的逃逸,但低杂波投入初期产生的快电子对逃逸电子的产生具有促进作用。     

EAST 装置等离子体逃逸电子同步辐射行为的实验研究

通过红外可见内窥镜诊断系统对EAST 等离子体芯部逃逸电子的同步辐射功率谱进行了分析,得出低能段逃逸电子同步辐射主要在红外波段,随着逃逸电子能量的增加,同步辐射向短波方向移动进入可见光波段。在欧姆放电条件下,对逃逸电子同步辐射所产生的的红外可见光进行了成像分析,同时研究了EAST 等离子体在低杂波和中性束注入加热条件下的逃逸电子行为。实验结果显示,低杂波和NBI 的投入总体抑制电子的逃逸,但低杂波投入初期产生的快电子对逃逸电子的产生具有促进作用。