In-line and following-up tests of perspective fusion-reactor materials in plasma focus devices

The paper presents results of recent experiments, as performed with the PF-1000 and PF-6 Plasma-Focus facilities, which were aimed at investigation of the correlation between processes of the irradiation of different materials of fusion devices and results of this irradiation. Among the irradiated samples there were pure tungsten, tantalum, copper, aluminum, and alloys, based on these metals, various steels, carbon and carbon-based materials, which are designed for plasma facing components or constructional parts of future thermonuclear reactors of the inertial- and magnetic-confinement types. The corpuscular radiation consisted of high-energy (E _D>100 keV) deuterium ion beams and fast (v _str ≥ 10⁷ cm/s) deuterium-plasma streams. They were investigated by a number of methods with spatial and temporal resolution. Particular attention was paid to the verification of diagnostic techniques, which might be used for time- and space-resolved studies of the interaction process. Correlation of these data with information obtained from subsequent analytical investigation of some of the irradiated specimens, as performed by means of a number of methods typical for material sciences, gives possibility to deduce physical mechanisms of the deuterium implantation and radiation damage of the investigated materials in dependence on the conditions of their irradiation.     

用于等离子体焦点装置的强流装置

研制了用于稠密等离子体焦点的强流装置,该装置采用八台低电感低内阻脉冲电容器和八个低感大电流、可控触发高压开关并联组成初级储能模块,高压开关同步击穿后产生μs级强电流经平行板传输线加载到负载。脉冲电容器和高压开关采用一体化设计,结构紧凑,使脉冲电容器与高压开关间的连接电感尽可能小;平板传输线为扇形结构,一个扇形平板传输线连接一个高压开关,平行板传输线可以将电感做得较小,有利于大电流回路的传输。在脉冲电容器充电20 kV时,假负载上可以得到500 kA的电流,电流上升时间约为3.7 μs。     

A high-neutron-output dense plasma focus

A 1.4 kJ ultra-clean Mather-type dense plasma focus has produced 14 MeV neutrons on over 600 consecutive shots without a misfire and without purging the gas. The D-T neutron output decreased from (3.4 ± 0.7) × 10⁹ to (2.1±0.6) × 10⁹. After 650 shots, the original D-T neutron output was restored by purging hydrogen and helium gas.     

Microinstabilities in the plasma focus

Experimentally observed suprathermal microwave emission correlated to soft X-rays emitted with high anisotropy are indicating the existence of current driven microinstabilities in the plasma focus.     

Effect of plasma sheath structure in plasma focus

The development of plasma sheath in the run-down phase and pinch phase in a plasma focus is studied with laser interferometry. The time-resolved interferograms show that the structures of plasma sheaths in the run-down phase are different at low and high pressures of filling gas. This leads to a distinct plasma pattern above the anode. At low pressure the plasma sheath in the run-down phase has clear boundaries, resulting in better compression in the pinch phase and a higher X-ray yield. At high pressure the plasma sheath is turbulent at the back side and become disordered in the pinch phase, giving little or no X-ray emission. The effect of a ceiling, i.e., a metal plate placed above the anode, is investigated. With the ceiling the reproducibility of X-ray emission is much improved     

Many-particle quantum theory for a class of free-electron devices

The small signal, cold beam regime of a wide class of free-electron lasers including magnetic and optical helical wigglers and stimulated Cerenkov radiation is discussed based on the many-particle fully quantized Bambini-Renieri Hamiltonian. The central topic is the photon statistics under various conditions and the significance of cooperative effects.     

稠密等离子体焦点装置研制

研制了一台用作脉冲中子源的稠密等离子体焦点装置(DPF),其放电室为Mather型结构。介绍了整个装置的工作原理及系统组成,详细论述了放电室的设计方法。实验结果表明,在550~600 Pa充氘压力范围下,当储能电容充电电压大于19 kV时,装置的平均中子产额大于5.0×10⁸(D-D)中子/脉冲,中子脉冲宽度(FWHM)为(40±5) ns。该装置能用于中子、伽马辐射诊断中探测系统灵敏度实验研究,也可用于开展快中子照相、中子活化分析以及单粒子效应等方面的研究工作。     

Two-dimensional theory of microwave O-type devices

Conclusions

1. 1.
   Integral equations are formulated that describe the processes occurring in O-type devices within the framework of a two-dimensional linear theory.     
   
   

Collimated soft X-rays from the plasma focus

Highly anisotropic soft X-ray emission with a quantum energy of approximately 1 keV has been observed at a plasma focus device. Typical beam divergence is 50 mrad as confirmed by different experimental methods.     

Effect of targets on plasma focus dynamics

Shadowgraphs were taken of a 3-kJ plasma focus in the presence of a flat disc target placed downstream of the anode and a 1-mm wire target inserted along the axis at the anode. It was found that: (i) the flat disc target does not affect the dynamics of the focus proper when it is placed downstream at a distance greater than the anode radius; (ii) the current sheet moves over the disc and forms a pinch beyond it as though the disc had become a new anode; and (iii) the plasma focuses strongly onto a 1-mm wire on-axis. These observations may be used to design beam-target experiments in a plasma focus machine. They indicate the possibility of focus-fiber experiments, and also raise the possibility of and indicate the guidelines for designing a sequential focus device     

Measurements referring to plasma focus scaling laws

In order to establish scaling laws and characteristic curves of a plasma focus device, the neutron output was measured as a function of the deuterium filling pressure, accelerator length and capacitor energy.     

TiAlN coatings synthesised using a dense plasma focus system and varied focus shots

TiAlN coatings were synthesised by a 2.3 kJ pulsed plasma focus system. The effect of focus shots on crystallography, microstructure, surface morphology, roughness and hardness was investigated. The coating's crystallography and microstructure were investigated using X-ray diffraction (XRD) characterisation. The XRD data showed that TiAlN coatings were crystallised in the cubic NaCl B1 structure with orientations in the (111), (200), (220) and (311) crystallographic planes. Texture coefficients showed a competition between (111) and (200) planes. The coatings surface morphology and thickness analyses were carried out using scanning electron microscopy (SEM). SEM micrographs showed dense and uniformly spread film with fine-grained morphology with hardly any pit, hole and crater. The surface roughness and hardness of TiAlN coatings were investigated by atomic force microscopy and Vickers microhardness tester. Grain size and roughness were found to decrease, whereas thickness and hardness were found to increase, with increasing focus shots.     

The theory of magnetic shocks in collisionless plasma

Summary The fundamental physics which leads to the formation of either a laminar or a turbulent shock in a collisionless plasma is reviewed. Magnetosonic and whistler waves play important roles in determining the fine structure of a shock, such as the bow shock formed ahead of the Earth's magnetosphere.

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Riassunto Si rivede la fisica fondamentale che conduce alla formazione sia di un urto laminare che di un urto turbolento in un plasma senza collisione. Le onde magnetosoniche e fischianti svolgono un ruolo importante nel determinare la struttura fine di un urto, così come l'onda d'urto formata al di fuori della magnetosfera della Terra.

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Резюме Анализируется фундаментальная физка, которая приводит к образованию либо ламинарноай турбулентной уларной волны в бесстолкновителыной. плазме. Магнитозвуковые волны и свистящие атмосферики играют важну№ роль в определении тонкой структуры ударной волны, такой как ударная волна сжатия, образованная перед Эемной магнитосферой.

     

Relativistic Boltzmann theory for a plasma: I. The entropy production

An expression for the entropy production has been derived on the basis of which it is argued that the choice of reference frame as proposed by Landau and Lifshitz is to be preferred rather than any other possibility.     

Operatorial form of the theory of polarization optical devices: I. Spectral theory of the basic devices

While the theory of operators in quantum mechanics is expressed nowadays in a pure operatorial form (wrapped mostly in Dirac's symbolic language), in optics the polarization device operators and their action are analyzed yet in the old matrix (Jones or Muller) formalism. The theory of polarization device operators has not taken systematically advantage of the very general, fundamental and deep results of the spectral theory of operators, on the basis of which it can be structured in an elegant deductive and physically expressive form. In this paper we apply the spectral theorem to the polarization device operators, we calculate their expansions in a pure operatorial Dirac-dyadic form and give some examples which illustrate the advantages from the physical insight viewpoint of such an approach. We are concerning here only with the basic polarization devices, to which correspond normal operators.     

纳米器件电流噪声的散射理论统一模型研究

传统散射理论在研究器件噪声特性时,并没有考虑非相干输运和库仑作用对散粒噪声的抑制,而在实际纳米器件中这两种效应不可忽略.本文基于散射区等效接触端模型推导了考虑上述两种效应的电流噪声散射理论统一模型,该模型适用于从相干输运到非相干输运的整个输运区,并同时考虑了泡利不相容原理和库仑作用对散粒噪声的抑制.本文也提出了一种基于统一模型的电流噪声数值模拟方法,该方法所得散射区特性与散射区等效接触端模型特性一致. 关键词： 电流噪声 散射理论 统一模型