摘要:

In this review the possibility of hollow cathode discharge for depth profile analysis is demonstrated for several new materials: planar optical waveguides fabricated by Ag+‐Na+ion exchange process in glasses, SnO2thin films for gas sensors modified by hexamethildisilazane after rapid thermal annealing, W‐ and WC‐ CVD layers deposited on Co‐metalloceramics and WO3‐ CVD thin films deposited on glass. The results are compared with different standard techniques. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843521

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The present status and future prospects of the laser fusion research and related laser plasma physics are reviewed. In laser fusion research, giant lasers for ignition and burn by imploding DT fuel pellets are under construction at LLNL (Lawrence Livermore National Laboratory) and CEA, France. In Japan , the Gekko XII and the Peta Watt laser system have been operated to investigate the implosion hydrodynamics, fast ignition, and the relativistic laser plasma interactions and a new project; FIREX( Fast Ignition Realization Experiment) had started toward the ignition and burn at the Institute of laser Engineering of Osaka University. Recently, heating experiments with cone shell target have been carried out. The thermal neutron yield is found to increase by three orders of magnitude by the peta watt laser injection to the cone shell target. The FIREX‐I is planned according to this experimental results, where multi 10kJ peta watt laser is used to heat compressed DT fuel to the ignition temperature. The FIREX‐II will follow for demonstrating ignition and burn, in which the implosion laser and heating laser are up‐graded. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843522

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Recent X‐ray observations of microquasars and Seyfert galaxies reveal broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Simulations indicate that at low inclination angle the line is measured by a distant observer as characteristic two‐peak profile. However, at high inclination angles (> 850) two additional peaks arise. This phenomenon was discovered by Matt et al. (1993) using the Schwarzschild black hole metric to analyze such effect. They assumed that the effect is applicable to a Kerr metric far beyond the range of parameters that they exploited. We check and confirm their hypothesis about such a structure of the spectral line shape for the Kerr metric case. We use no astrophysical assumptions about the physical structure of the emission region except the assumption that the region should be narrow enough. Positions and heights of these extra peaks drastically depend on both the radial coordinate of the emitting region (annuli) and the inclination angle. It was found that these extra peaks arise due to gravitational lens effect in the strong gravitational field, namely they are formed by photons with some number of revolutions around black hole. This conclusion is based only on relativistic calculations without any assumption about physical parameters of the accretion disc like X‐ray surface emissivity etc. We discuss how analysis of the iron spectral line shapes could give an information about an upper limit of magnetic field near black hole horizon. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843523

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Protontherapy is a well‐established approach to treat cancer due to the favorable ballistic properties of proton beams. The specific dependence of proton energy losses in biological tissues (the Bragg peak) promotes the solution of one of the main problems of radiation therapy, namely, the irradiation of a malignant tumor with a sufficiently strong and homogeneous dose, ensuring that the irradiation of the surrounding healthy tissues and organs is minimal. Nevertheless, this treatment is today only possible with large scale accelerator facilities which are very difficult to install at existing hospitals. In present talk we discuss the feasibility of using laser plasma as a source of high‐energy ions for the purposes of proton therapy. The proposal is based on the efficient ion acceleration theoretically predicted and observed in recent laboratory and numerical experiments on the interaction of high‐power laser radiation with solid targets. In the scheme proposed, a beam of fast ions accelerated by a laser pulse can be integrated in the installations intended for proton therapy. These applications require charged particle beams of high quality (i.e., such that the ratio of the energy width of the beam to its mean energy is small). In order to produce beams with controlled quality, it is proposed to use double‐layer targets in which the first layer consists of heavy multicharged ions and the second layer (thin and narrow in the transverse direction) consists of protons. We also discuss the possibility of the ion acceleration up to energies needed for the hadron therapy with the usage of the high repetition rate, moderate intensity lasers. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843524

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Charged‐particle beams are employed for a number of scientific and technological applications. The conventional description of their collective behavior is usually given in terms of the Vlasov equation. In the last 15 years some alternative descriptions have been developed in terms of a nonlinear Schro¨dinger equation governing the collective dynamics of the beam while interacting with the surrounding medium. This approach gives new insights, providing an alternative “key of reading” of the charged‐particle beam dynamics, and have been applied to a number of physical problems concerning conventional particle accelerating machines as well as plasma‐based accelerator schemes. Remarkably, it is based on a mathematical formalism fully similar to those used for the propagation of e.m. radiation beams in nonlinear media a well as the nonlinear dynamics of the Bose‐Einsten condensates.In this paper, a presentation of some significant nonlinear collective effects of a charged‐particle beam in particle accelerators, that have been recently investigated in the framework of the above Schro¨dinger‐like descriptions, is given. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843525

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This paper reports the results of several experiments performed at the LULI laboratory (Palaiseau, France) concerning the propagation of large relativistic currents in matter from ultra‐high‐intensity laser pulse interaction with target. We present our results according to the type of diagnostics used in the experiments: 1) K&agr; emission and K&agr; imaging, 2) study of target rear side emission in the visible region, 3) time resolved optical shadowgraphy. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843526

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

In the spectra of many Oe and Be stars we observe complex profiles in the lines of many ions. The observed features are the composition of a number of absorption components. This fact is interpreted by the existence of independent density formations in the region, where a specific ion line is created. These density regions rotate and move radially with different velocities and so they create components with different widths and radial shifts. We name these components Satellite Absorption Components (SACs or DACs). In this paper we present the model proposed by Danezis et al. (2003), which describes the structure of these density regions. With this method we can calculate the apparent rotational (Vrot) and expansion/contraction radial velocities (Vexp) of these density regions, as well as an expression of the optical depth (&xgr;). Also we present three applications to the spectra of hot emission stars. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843527

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Full three dimensional Particle‐in‐Cell (PIC) simulations are performed in order to investigate effects of field‐aligned (parallel) ion flow shears on low‐frequency plasma instabilities. It is shown that the parallel ion flow velocity shear can induce the ion‐acoustic instability, even when the ion flow velocity is so small that the instability can not take place. Simulation results are consistent with the analysis based on the local theory. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843528

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A brief review of the occurrence of amplitude modulated structures in space and laboratory plasmas is provided, followed by a theoretical analysis of the mechanism of carrier wave (self‐) interaction, with respect to electrostatic plasma modes. A generic collisionless unmagnetized fluid model is employed. Both cold‐(zero‐temperature) and warm‐(finite temperature) fluid descriptions are considered and compared. The weakly nonlinear oscillation regime is investigated by applying a multiple scale (reductive perturbation) technique and a Nonlinear Schro¨dinger Equation (NLSE) is obtained, describing the evolution of the slowly varying wave amplitude in time and space. The amplitude’s stability profile reveals the possibility ofmodulational instabilityto occur under the influence of external perturbations. The NLSE admits exact localized envelope (solitary wave) solutions of bright (pulses) or dark (holes, voids) type, whose characteristics depend on intrinsic plasma parameters. The role of perturbation obliqueness (with respect to the propagation direction), finite temperature and — possibly — defect (dust) concentration is explicitly considered. The relevance of this description with respect to known electron‐ion (e‐i) as well asdusty(complex) plasma modes is briefly discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843529

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Here we will present some spectroscopic methods for emission gas research in the emission line region of Active Galactic Nuclei (AGNs): (1) We will demonstrate the possibility to use the Boltzmann‐plot method to estimate the physical conditions in the broad line regions (BLRs); (2) We will discuss the applicability of so called “Gaussian method” for spectral line shape investigation of narrow line regions (NLRs) and BLRs; (3) We will present a method to fit the line profiles with a kinematically complex model. We apply a two‐component model assuming that the line wings originate in a very broad line region (VBLR) and the line core in an intermediate line region (ILR) of AGNs. The VBLR is assumed to be an accretion disk and the ILR a spherical emission region; (4) Also, a model for fitting of the broad absorption lines in quasars will be discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1843530

出版商:AIP    

年代:1904

数据来源: AIP