Electron bunch compression and acceleration in the laser wakefield

The compression and acceleration of an external electron bunch into the laser wakefield is studied using 3D modeling with the LAPLAC code and compared to analytical predictions. It is shown, for a laser propagating in a plasma channel, that the nonlinear laser pulse dynamics together with the finite laser spot size influence the electron bunch compression and acceleration due to the reduction of the laser pulse group velocity. The transverse bunch dynamics and loading effect determine the final bunch charge and density and restrict the compressed sizes of the trapped and accelerated electron bunch. The dynamics of the electron bunch are illustrated with a set of parameters where the accelerated bunch acquires an energy of the order of 2 GeV, and 1% energy spread with sub-micron sizes.     

One GeV acceleration with laser wakefield in the linear regime

We derive an expression for the maximum energy gain of an accelerated electron, in the limit that the plasma wave created by a laser wake is linear both along the longitudinal direction and in the transverse plane, and with a maximum laser power lower than the critical power for relativistic self-focusing. With an available power of 300 TW, the energy gain is of 1 GeV.     

Criteria for the optimization of parameters of a multibunch scheme of wakefield acceleration

We propose criteria for the optimization of a wakefield acceleration scheme in a dielectric-lined waveguide structure, which is aimed at increasing the efficiency of energy transfer from the driving to witness (driven) electron bunches with simultaneous increase in the accelerating field gradient. It is suggested to use a multimode acceleration structure excited by a train of short electron bunches profiled in a special manner. The proposed scheme provides for a maximum energy transformer ratio simultaneously with an increase in the wakefield as compared to the values typical of the traditional linear acceleration scheme.     

Inverse free electron lasers and laser wakefield acceleration driven by CO2 lasers

The staged electron laser acceleration (STELLA) experiment demonstrated staging between two laser-driven devices, high trapping efficiency of microbunches within the accelerating field and narrow energy spread during laser acceleration. These are important for practical laser-driven accelerators. STELLA used inverse free electron lasers, which were chosen primarily for convenience. Nevertheless, the STELLA approach can be applied to other laser acceleration methods, in particular, laser-driven plasma accelerators. STELLA is now conducting experiments on laser wakefield acceleration (LWFA). Two novel LWFA approaches are being investigated. In the first one, called pseudo-resonant LWFA, a laser pulse enters a low-density plasma where nonlinear laser/plasma interactions cause the laser pulse shape to steepen, thereby creating strong wakefields. A witness e-beam pulse probes the wakefields. The second one, called seeded self-modulated LWFA, involves sending a seed e-beam pulse into the plasma to initiate wakefield formation. These wakefields are amplified by a laser pulse following shortly after the seed pulse. A second e-beam pulse (witness) follows the seed pulse to probe the wakefields. These LWFA experiments will also be the first ones driven by a CO(2) laser beam.     

Laser Interferometer Gravitational-wave Observatories: An Overview

Abstract

The quest to detect gravitational radiation is on the threshold of a new era. Technological developments in the 1980s have led to the point where it is now possible to design an instrument based on the Michelson interferometer which should not only be able to detect gravity waves but should function as an astronomical observatory. Stimulated by the need for a southern hemisphere facility, the Australian National University in collaboration with the University of Western Australia is poised to enter this exciting field. Here, we will briefly describe the principle of operation of these giant laser interferometers and examine performance limits imposed by the Heisenberg uncertainty principle.     

Laser applications to chemical and environmental analysis: introduction to the feature issue

This issue of Applied Optics features 16 papers describing chemical and environmental measurements made possible by lasers. Many of these contributions were presented at the Optical Society of America Topical Meeting on Laser Applications to Chemical and Environmental Analysis, held in Orlando, Florida, 9-11 March 1998.     

Laser applications to chemical and environmental analysis: introduction to the feature issue

This issue of Applied Optics features 14 papers that describe recent advances of laser techniques, including instrumentation, application in combustion research, and detection of pollutants. Most of these contributions were presented at the Eighth Optical Society of America Topical Meeting on Laser Applications to Chemical and Environmental Analysis (8th LACEA), held in Boulder, Colorado, 7-10 February, 2002.     

Laser applications to chemical and environmental analysis: introduction to the feature issue

This issue of Applied Optics features 15 papers that describe laser techniques for measurements in chemical and environmental analysis. Many of these contributions were presented at the Optical Society of America Topical Meeting on Laser Applications to Chemical and Environmental Analysis, held in Santa Fe, New Mexico, 11-13 February 2000.     

An acceleration method for the BEM-based cooling simulation of injection molding

Mold cooling process in injection molding is of great importance and most cooling analyses are based on the boundary element (BEM) approach. The BEM leads to dense influence matrices, which greatly affect the computational efficiency and scale. In this paper, an acceleration method is presented to speed up the solution procedure. In this method, the dense BEM matrix is split into a sparse dominant matrix and a dense residual matrix. The residual item is transformed from the inner iteration to the outer iteration, and the dominant item can be stored in the RAM memory so that the resulting system of equations will be solved much more quickly. Numerical experiments show that this developed approach is a cost-effective method for BEM-based simulation of injection mold cooling.     

One GeV acceleration with laser wakefield in the linear regime

We derive an expression for the maximum energy gain of an accelerated electron, in the limit that the plasma wave created by a laser wake is linear both along the longitudinal direction and in the transverse plane, and with a maximum laser power lower than the critical power for relativistic self-focusing. With an available power of 300 TW, the energy gain is of 1 GeV.     

Superhard phases of simple substances and binary compounds of the B-C-N-O system: from diamond to the latest results (a Review)

The basic known and hypothetic one- and two-element phases of the B-C-N-O system (both superhard phases having diamond and boron structures and precursors to synthesize them) are described. The attention has been given to the structure, basic mechanical properties, and methods to identify and characterize the materials. For some phases that have been recently described in the literature the synthesis conditions at high pressures and temperatures are indicated.     

Metals and incinerators: The latest regulatory phase

Recent regulations in the United States controlling emissions of metals and halogen acid gases from boilers and industrial furnaces (BIFs) burning regu     

North American Symposium on Laser Induced Breakdown Spectroscopy (NASLIBS): introduction to feature issue

This feature issue highlights the topics of the 2011 North American Symposium on Laser Induced Breakdown Spectroscopy (NASLIBS). These include LIBS application to Security and Forensic, Biomedical and Environmental, Liquid Analysis and Fundamentals of LIBS, Instrumentation/Commercialization, Fusion with LIBS, and New Frontiers.     

Light and color in the open air: introduction to the feature issue.

This special feature of Applied Optics reports the results of new experimental and theoretical research concerning a number of naked-eye optical phenomena, including ice-crystal halo displays, mirages, rainbows, glories, optical caustics, clear-sky phenomena, cloud coronas, cloud iridescence, and the extinction of skylight.     

Laser induced deflection technique for absolute thin film absorption measurement: optimized concepts and experimental results

Using experimental results and numerical simulations, two measuring concepts of the laser induced deflection (LID) technique are introduced and optimized for absolute thin film absorption measurements from deep ultraviolet to IR wavelengths. For transparent optical coatings, a particular probe beam deflection direction allows the absorption measurement with virtually no influence of the substrate absorption, yielding improved accuracy compared to the common techniques of separating bulk and coating absorption. For high-reflection coatings, where substrate absorption contributions are negligible, a different probe beam deflection is chosen to achieve a better signal-to-noise ratio. Various experimental results for the two different measurement concepts are presented.     

The control of major accident hazards: the land-use planning issue.

Land-Use Planning with respect to major accident hazards constitutes one of the new requirements of the 'Seveso II Directive'. The paper discusses the rationale and the requirements set by the Directive for the operators of the plants and the planning authorities to take into account the major accident hazards in the land-use planning procedure. Then, the paper focuses on approaches and criteria applied in the European Union, and gives information on procedures in other countries, wherever available. The approaches analysed are grouped into three broad categories, namely, establishing 'generic distances', 'consequence based', and 'risk based'. Finally, two illustrative examples facilitate understanding and comparison of the analysed approaches.