Generation of dual pulses of the runaway electron beam current during the subnanosecond breakdown of atomic and molecular gases

With a diaphragm placed behind the anode foil, dual runaway electron beams have been provided in helium, hydrogen, nitrogen, and air under a pressure of several torrs to several dozen torrs and a high-voltage pulse amplitude of about 250 kV. These beams consist of two pulses with commensurable amplitudes with a time interval between them of several dozen picoseconds to several hundred picoseconds. It has been shown that the breakdown of the interelectrode gap at pressures from several torrs to several dozen torrs may occur in different regimes and dual pulses of the electron beam current are registered when the initial current through the gap is below 1 kA. It has been found that a supershort avalanche electron beam that consists of one pulse is generated when the delay of breakdown equals several hundred picoseconds. It has been shown that, when the gas pressure reaches several hundred Torr, including atmospheric pressure, the runaway electrons are detected behind the foil after the termination of the supershort avalanche electron beam pulse.     

静电放电电磁脉冲的实验研究

 利用单极子天线对静电放电产生的电磁脉冲进行了实验研究。测量表明, 静电放电电磁脉冲辐射场为脉冲持续时间百纳秒的窄脉冲,但在距离放电源几米以内,其场强很大,典型值可达千伏每米量级, 其频谱主要分布在几十到几百兆赫,典型的频谱上限值可以达到几个吉赫。     

Submillimetre laser spectroscopy of intensely absorbing liquids

The submillimetre spectra of several intensely absorbing liquids have been measured with a tunable submillimetre laser at several spot frequencies in the range from about 20 to 200cm^?1. The spot frequency measurements enable us to check the accuracy of broadband power absorption spectra obtained by Michelson interferometry under a range of conditions and for several different types of heavily absorbing liquids, including aqueous solutions of current interest.     

高能闪光照相光源位置测量

介绍了一种高能闪光照相系统的光源位置重复性测量方法。相同客体不同次实验图像的位置可以反映闪光照相系统的光源位置重复性。首先从球形客体实验图像中检测出客体的钨飞层外界面,然后利用界面数据拟合得到对应的圆心位置。多次照相图像圆心位置的重复性反映了光源位置的重复性。实验测量了闪光照相系统的光源位置重复性,实验结果表明,某闪光照相系统光源位置的重复性好于0.1 mm。     

Low-energy electron beam source

Experimental results of research into a ferroelectric-plasma-source-assisted hollow anode (HA) discharge as a source of low-energy electron beams are presented. To generate electron beams, the HA auto-bias negative voltage was achieved by the discharge current flowing through the resistor connecting the HA and the grounded electrode. It is shown that this method allows reliable and reproducible generation of low-energy electron beams with electron energy of several hundreds of eV, electron current density up to several A/cm² and pulse duration of several tens of microseconds.     

Anisotropy of optical,electrical, and photoelectrical properties of amorphous hydrogenated silicon films modified by femtosecond laser irradiation

Two types of independent anisotropic structures have been formed simultaneously in amorphous hydrogenated films by applying a femtosecond laser pulse to them, i.e., a structure with a period of several micrometers to several tens of micrometers and a structure with a period of several hundred nanometers. The formation mechanisms of these strictures are different, which allows us to orient them relative to each other in a desirable way. Both structures independently influence the optical properties of the modified films, which causes the diffraction of transmitted light and making the films polarization-sensitive. The conductivity of the modified films correlates with the mutual orientation of the anisotropic structures, whereas no interrelation between the photoconductivity and optical performance of the modified films has been observed.     

Dynamics of slip lines on the surface of polycrystalline copper

Tunneling microscopy is used to study the geometry and dynamics of slip lines on the surface of cold-rolled polished copper during steady-state creep at room temperature. Dislocation sources in a 200-to 300-nm-thick surface layer are found to be initially activated under stresses. As a result, a large number of lines are formed whose lengths vary from several tens to several hundreds of nanometers. Then, dislocation sources located in deeper layers become operative, which results in the formation of slip lines as long as ≈8–9 μm. The formation, evolution, and disappearance of slip lines are caused by the motion of bands having a width of several nanometers. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 11, 2004, pp. 1996–1999. Original Russian Text Copyright ? 2004 by Vettegren, Svetlov.     

Rayleigh-Taylor不稳定性背光照相实验背光源初步理论研究

为开展中等功率激光器上Rayleigh-Taylor不稳定性背光照相实验,对多种背光源靶材料及其发射的K、L、M带X光谱强度作了数值模拟计算。计算结果表明,用数百焦耳倍频激光来产生能量为2keV左右的X光背光源是可能的。     

Speculations on quark observation

Results of non-perturbative calculations in several models of relativistic quantum field theory lead to the concept of a stable particle whose mass is not well defined. Assuming that quarks are such particles, we propose several possible methods of quark observation.     

Switching of the electrical conductivity of plasticized PVC films under uniaxial pressure

The jumplike switching of the electrical conductivity in wide-band-gap polymer (antistatic plasticized polyvinylchloride) films under uniaxial pressure is studied. In various plasticized PVC materials, the uniaxial pressure inducing a conductivity jump by four orders of magnitude or higher changes from several to several hundreds of bars, and this effect is retained at a film thickness of several hundred microns, which is two orders of magnitude larger than the critical film thicknesses known for other wide-band-gap polymers. In addition to the earlier interpretation of the conductivity anomalies in plasticized PVC, we proposed a phenomenological electron-molecular dynamic nanotrap model, in which local charge transfer is provided by mobile molecule segments in a plasticized polymer.     

Design of a Common Ellipsoidal Mirror for the Focalization of Several Radioastronomic Bands: New Method and Application to Three Bands

The design of a common ellipsoidal mirror for the focalization of several radioastronomic bands, by means of a straightforward method, is presented. Three bands centered at 100, 80 and 45 GHz are chosen for the validation of the method. Quasi-optics theory is used to design an optical system that can focalize several bands with the minimum possible optic elements, and also to share the maximum of them. Lenses, mirrors, feeder dimensions and the distances among each component necessaries for the focalization in each band are calculated. The simultaneous design in several radioastronomic observation bands reduces the cost of manufacturing, the total number of optic elements and the density of optical elements on the receiver cabin.     

Nonadditivity of quantum capacity for multiparty communication channels

We investigate multiparty communication scenarios where information is sent from several senders to several receivers. We establish a relation between the quantum capacity of multiparty communication channels and their distillability properties, which enables us to show that the quantum capacity of such channels is not additive.     

New aspects of dynamic electron diffraction in a crystal

An analytical theory of three-wave dynamic interaction of electrons with a crystal, which is valid in a wide range of electron energies (from several hundreds of eV to several MeV), and a quantum-dynamic concept of propagation of electron waves in a nonabsorbing crystal, which takes into account their dispersion and decay of the interference effects, are presented.     

Multi-state Quantum Teleportation via One Entanglement State

A multi-sender-controlled quantum teleportation scheme is proposed to teleport several secret quantum states from different senders to a distance receiver based on only one Einstein-Podolsky-Rosen (EPR) pair with controlled-NOT (CNOT) gates. In the present scheme, several secret single-qubit quantum states are encoded into a multi-qubit entangled quantum state. Two communication modes, i.e., the detecting mode and the message mode, are employed so that the eavesdropping can be detected easily and the teleported message may be recovered efficiently. It has an advantage over teleporting several different quantum states for one scheme run with more efficiency than the previous quantum teleportation schemes.     

Observation of phase defects in quasi-two-dimensional Bose-Einstein condensates

We have observed phase defects in quasi-2D Bose-Einstein condensates close to the condensation temperature. Either a single or several equally spaced condensates are produced by selectively evaporating the sites of a 1D optical lattice. When several clouds are released from the lattice and allowed to overlap, dislocation lines in the interference patterns reveal nontrivial phase defects.     

UHV-SEM observations of cleaning process and step formation on silicon (111) surfaces by annealing

The cleaning process and step formation by high temperature annealing up to 1250°C on the Si(111) surface are observed by an ultra-high-vacuum scanning electron microscope (UHV-SEM). The clean surface is composed of alternate planes of terraces and step bands with widths of several μm and 1 μm, respectively, in the 〈1?1?2〉 direction. Both planes are inclined by about 10° to each other. The surface steps are not only monolayer steps, but also higher steps comprising several monolayers. Monolayer steps join to form a high step, and 70–80 steps of several monolayers high form a step band by bunching in an average distance of several hundred A toward the 〈1?10〉 direction. The step structure depends on the annealing temperature and on the angle at which the cutting plane is off from the exact 〈111〉 orientation. In several studies of high energy reflection electron microscopy under small grazing angle incidence monolayer steps were observed on the terrace, but no rough structures like the step bands and high steps could be discerned. The step structure observed by the present experiment is compared with those observed by previous workers.     

Sonophoresis in transdermal drug deliverys

Transdermal drug delivery (TDD) has several significant advantages compared to oral drug delivery, including elimination of pain and sustained drug release. However, the use of TDD is limited by low skin permeability due to the stratum corneum (SC), the outermost layer of the skin. Sonophoresis is a technique that temporarily increases skin permeability such that various medications can be delivered noninvasively. For the past several decades, various studies of sonophoresis in TDD have been performed focusing on parameter optimization, delivery mechanism, transport pathway, or delivery of several drug categories including hydrophilic and high molecular weight compounds. Based on these various studies, several possible mechanisms of sonophoresis have been suggested. For example, cavitation is believed to be the predominant mechanism responsible for drug delivery in sonophoresis. This review presents details of various studies on sonophoresis including the latest trends, delivery of various therapeutic drugs, sonophoresis pathways and mechanisms, and outlook of future studies.     

Multiphoton polymerization with the holographic control of femtosecond and continuous laser radiation

A unit in which two lasers, one with femtosecond and the other continuous radiation, were used was designed and manufactured. Both lasers worked under holographic control conditions provided by two spatial optic modulators. Experiments with creating several polymer structures by several femtosecond optical “traps” simultaneously were performed. The possibility of the production of one polymer article by simultaneous displacement of several femtosecond optical traps was demonstrated. A polymer article was also prepared by several femtosecond traps and manipulated with the use of several continuous traps. The possibility of focusing femtosecond radiation onto an extended object (“thread” 13 μm long) and the preparation of a polymer object by controlling a femtosecond optical trap in three-dimensional space was demonstrated.     

玻璃转变研究进展

玻璃转变是凝聚态物理基础理论中的一个重要问题和难题，是涉及动力学和热力学的众多前沿问题．玻璃转变的理论一直在不断的发展和更新．从20世纪50年代出现的自由体积理论到现在还在不断完善的模态耦合理论及其他众多理论，都只能解决玻璃转变中的某些问题．一个完整的玻璃转变理论仍需要人们作艰苦的努力．为了澄清混淆不清的玻璃转变概念，文章就玻璃转变的概念、研究内容和有关理论的发展进行简述．在分析了几个占主导地位的玻璃转变理论后，阐述了玻璃转变中需要进一步深入研究的问题．