Equilibrium state analysis of a nonneutral plasma under a uniform magnetic field

International Nuclear Information System (INIS)

Fernandez, J.E.; Molinari, V.G.; Sumini, M.A.

1990-01-01

By recourse to the Boltzmann H-theorem, the existence of a thermodynamic equilibrium state has been proved for a nonneutral plasma under an external magnetic field. The equation describing the density profile of ions or electrons has been found. The density equation has been numerically solved for a generic magnetic field and plasma frequency, giving a parametric limit for the confinement region. An appropriate change of variable allows to approximate the density equation whose analytical solution has been found. The approximated density closely fits the numerical solution of the original equation. (Author)

Confinement of pure electron plasmas in the Columbia Non-neutral Torus

International Nuclear Information System (INIS)

Berkery, John W.; Pedersen, Thomas Sunn; Kremer, Jason P.; Marksteiner, Quinn R.; Lefrancois, Remi G.; Hahn, Michael S.; Brenner, Paul W.

2007-01-01

The Columbia Non-neutral Torus (CNT) [T. S. Pedersen, J. P. Kremer, R. G. Lefrancois, Q. Marksteiner, N. Pomphrey, W. Reiersen, F. Dahlgreen, and X. Sarasola, Fusion Sci. Technol. 50, 372 (2006)] is a stellarator used to study non-neutral plasmas confined on magnetic surfaces. A detailed experimental study of confinement of pure electron plasmas in CNT is described here. Electrons are introduced into the magnetic surfaces by placing a biased thermionic emitter on the magnetic axis. As reported previously, the insulated rods holding this and other emitter filaments contribute to the radial transport by charging up negatively and creating ExB convective transport cells. A model for the rod-driven transport is presented and compared to the measured transport rates under a number of different conditions, finding good agreement. Neutrals also drive transport, and by varying the neutral pressure in the experiment, the effects of rod-driven and neutral-driven transport are separated. The neutral-driven electron loss rate scales linearly with neutral pressure. The neutral driven transport, presumably caused by electron-neutral collisions, is much greater than theoretical estimates for neoclassical diffusion in a classical stellarator with strong radial electric fields. In fact the confinement time is on the order of the electron-neutral collision time. Ion accumulation, electron attachment, and other effects are considered, but do not explain the observed transport rates

Numerical calculation of axisymmetric non-neutral plasma equilibria

International Nuclear Information System (INIS)

Spencer, R.L.; Rasband, S.N.; Vanfleet, R.R.

1993-01-01

Efficient techniques for computing axisymmetric non-neutral plasma equilibria are described. These equilibria may be obtained either by requiring global thermal equilibrium, by specifying the midplane radial density profile, or by specifying the radial profile of ∫n dz. Both splines and finite-differences are used, and the accuracy of the two is compared by using a new characterization of the thermal equilibrium density profile which gives a simple formula for estimating the radial and axial gradient scale lengths of thermal equilibria. It is found that for global thermal equilibrium 1% accuracy is achieved with splines if the distance between neighboring splines is about two Debye lengths while finite differences require a grid spacing of about one-half Debye length to achieve the same accuracy

Improved Temperature Diagnostic for Non-Neutral Plasmas with Single-Electron Resolution

Science.gov (United States)

Shanman, Sabrina; Evans, Lenny; Fajans, Joel; Hunter, Eric; Nelson, Cheyenne; Sierra, Carlos; Wurtele, Jonathan

2016-10-01

Plasma temperature diagnostics in a Penning-Malmberg trap are essential for reliably obtaining cold, non-neutral plasmas. We have developed a setup for detecting the initial electrons that escape from a trapped pure electron plasma as the confining electrode potential is slowly reduced. The setup minimizes external noise by using a silicon photomultiplier to capture light emitted from an MCP-amplified phosphor screen. To take advantage of this enhanced resolution, we have developed a new plasma temperature diagnostic analysis procedure which takes discrete electron arrival times as input. We have run extensive simulations comparing this new discrete algorithm to our existing exponential fitting algorithm. These simulations are used to explore the behavior of these two temperature diagnostic procedures at low N and at high electronic noise. This work was supported by the DOE DE-FG02-06ER54904, and the NSF 1500538-PHY.

Numerical study on formation process of helical nonneutral plasmas using electron injection from outside magnetic surfaces

International Nuclear Information System (INIS)

Nakamura, Kazutaka; Himura, Haruhiko; Masamune, Sadao; Sanpei, Akio; Isobe, Mitsutaka

2009-01-01

In order to investigate the formation process of helical nonneutral plasmas, we calculate the orbits of electron injected in the stochastic magnetic field when the closed helical magnetic surfaces is correspond with the equipotential surfaces. Contrary to the experimental observation, there are no electrons inward penetrating. (author)

2D Diffusion of Rods in a Nonneutral Plasma with Finite E × B Shear.

Science.gov (United States)

Jin, D. Z.; Dubin, Daniel H. E.

2000-10-01

Cross-magnetic-field collisional diffusion of test particles is discussed for a nonneutral plasma column in the 2D regime, where the diffusion is due to the E × B drift of charged rods (bounce-averaged electrons) in the random Coulomb fields of other rods. If the overall flow has a finite E × B velocity shear, the diffusion can be orders of magnitude smaller than predicted by previous calculations,(J.B. Taylor and B. McNamara, Phys. Fluids 14), 1492 (1971); J.M. Dawson, H. Okuda and R.N. Carlile, Phys. Rev. Lett. 27, 491 (1971). which are shown to hold only for a nearly shear-free plasma. Particle-in-cell and molecular dynamics simulations of the diffusion match the theory, provided that the E × B rotation frequency is monotonically decreasing as a function of radius (negative shear, the usual case in a stable nonneutral plasma column). Interestingly, when the rotation frequency is monotonically increasing (positive shear), the transport is suppressed by another order of magnitude or more. This phenomenon is related to the nonlinear dynamics of prograde point vortices in a shear flow.(David A. Schecter and Daniel H.E. Dubin, Phys. Rev. Lett. 83), 2191 (1999).

Experimental observation of fluid echoes in a non-neutral plasma

International Nuclear Information System (INIS)

Yu, Jonathan H.; Driscoll, C. Fred

2002-01-01

Experimental observation of a nonlinear fluid echo is presented which demonstrates the reversible nature of spatial Landau damping, and that non-neutral plasmas behave as nearly ideal 2D fluids. These experiments are performed on UCSD's CamV Penning-Malmberg trap with magnetized electron plasmas. An initial m i =2 diocotron wave is excited, and the received wall signal damps away in about 5 wave periods. The density perturbation filaments are observed to wrap up as the wave is spatially Landau damped. An m t =4 'tickler' wave is then excited, and this wave also Landau damps. The echo consists of a spontaneous appearance of a third m e =2 wave after the responses to the first two waves have inviscidly damped away. The appearance time of the echo agrees with theory, and data suggests the echo is destroyed at least partly due to saturation

The effect of externally applied oscillating electric fields on the l=1 and l=2 diocotron modes in non-neutral plasmas

International Nuclear Information System (INIS)

Spencer, R.L.

1990-01-01

A high-frequency oscillating electric field can change the properties of diocotron modes in non-neutral plasmas. The effect depends crucially on the azimuthal mode number, m, of the applied field. For m=0,±1 there is no effect, and for applied standing waves there is also no effect. But if the applied field has the form of a traveling wave with |m|≥2, the frequency of stable diocotron modes can be modified and for |m|≥3, the l=2 instability of hollow density profiles can be stabilized. The analytic results are verified with a nonlinear fluid simulation of an infinitely long non-neutral plasma

Finite-Length Diocotron Modes in a Non-neutral Plasma Column

Science.gov (United States)

Walsh, Daniel; Dubin, Daniel

2017-10-01

Diocotron modes are 2D distortions of a non-neutral plasma column that propagate azimuthally via E × B drifts. While the infinite-length theory of diocotron modes is well-understood for arbitrary azimuthal mode number l, the finite-length mode frequency is less developed (with some exceptions), and is naturally of relevance to experiments. In this poster, we present an approach to address finite length effects, such as temperature dependence of the mode frequency. We use a bounce-averaged solution to the Vlasov Equation, in which the Vlasov Equation is solved using action-angle variables of the unperturbed Hamiltonian. We write the distribution function as a Fourier series in the bounce-angle variable ψ, keeping only the bounce-averaged term. We demonstrate a numerical solution to this equation for a realistic plasma with a finite Debye Length, compare to the existing l = 1 theory, and discuss possible extensions of the existing theory to l ≠ 1 . Supported by NSF/DOE Partnership Grants PHY1414570 and DESC0002451.

First observations of partially neutralized and quasineutral plasmas in the Columbia Non-neutral Torus

Science.gov (United States)

Sarasola, Xabier; Brenner, Paul; Hahn, Michael; Pedersen, Thomas

2009-11-01

The Columbia Non-neutral Torus (CNT) is the first stellarator devoted to the study of pure electron, partially neutralized and positron-electron plasmas. To date, CNT usually operates with electron rich plasmas (with negligible ion density) [1], but a stellarator can also confine plasmas of arbitrary degree of neutralization. In CNT the accumulation of ions alters the equilibrium of electron plasmas and a global instability has been observed when the ion fraction exceeds 10 %. A characterization of this instability is presented in [2], analyzing its parameter dependence and spatial structure (non- resonant with rational surfaces). A new set of experiments is currently underway studying plasmas of arbitrary degree of neutralization, ranging from pure electron to quasineutral plasmas. Basic observations show that the plasma potential decouples from emitter bias when we increase the degree of the neutralization of our plasmas. Partially neutralized plasmas are also characterized by multiple mode behavior with dominant modes between 20 and 200 kHz. When the plasma becomes quasineutral, it reverts to single mode behavior. The first results on partially neutralized plasmas confined on magnetic surfaces will be presented. [1] J. Kremer, PRL 97, (2006) 095003 [2] Q. Marksteiner, PRL 100 (2008) 065002

Parameter Dependence of Inward Diffusion on Injected Electrons in Helical Non-Neutral Plasmas

International Nuclear Information System (INIS)

Wakabayashi, H.; Himura, H.; Fukao, M.; Yoshida, Z.

2003-01-01

Experimental studies on an electron injection into a helical magnetic field and characteristics of non-neutral plasmas have been performed. It is found that the space potential φs has a weak dependence on the injection angle except for a narrow 'window' region in which φs significantly drops. A calculation shows that because of the electric field Eg of the electron gun (e-gun), the emitted electrons are launched quasi-parallel to the helical magnetic field B, regardless of α. This seems to agree with the observation. The 'window' seen in the data may be attributed to an current-driven instability which might result in the insufficient electron penetration or the degradation of electron confinement in the magnetic surface

Toroidal equilibrium of a non-neutral plasma with toroidal current, inertia and pressure

International Nuclear Information System (INIS)

Bhattacharyya, S.N.; Avinash, K.

1992-01-01

Equilibrium of non-neutral clouds in a toroidal vessel with toroidal magnetic field is demonstrated in the presence of a toroidal current, finite mass and finite pressure. With a toroidal current, it is shown that in a large-aspect-ratio conducting torus the equilibrium is governed by competition between forces produced by image charges and image currents. When μ 0 ε 0 E r 2 >B θ 2 (whe re E r and B θ are the self electrostatic and self magnetic fields of the cloud), the confinement is electrostatic and plasma shifts inwards; when μ 0 ε 0 E r 2 θ 2 , the confinement is magnetic and plasma shifts outwards. For μ 0 ε 0 E r 2 = B θ 2 there is no equilibrium. With finite mass or finite pressure, it is shown, in a large-aspect-ratio approximation, that the fluid drift surfaces and equipotential surfaces are displaced with respect to each other. In both cases the fluid drift surfaces are shifted inwards from the equipotential surfaces. (author)

Simulations of the instability of the m=1 self-shielding diocotron mode in finite-length nonneutral plasmas

International Nuclear Information System (INIS)

Mason, Grant W.; Spencer, Ross L.

2002-01-01

The 'self-shielding' m=1 diocotron mode in Malmberg-Penning traps has been known for over a decade to be unstable for finite length nonneutral plasmas with hollow density profiles. Early theoretical efforts were unsuccessful in accounting for the exponential growth and/or the magnitude of the growth rate. Recent theoretical work has sought to resolve the discrepancy either as a consequence of the shape of the plasma ends or as a kinetic effect resulting from a modified distribution function as a consequence of the protocol used to form the hollow profiles in experiments. We have investigated both of these finite length mechanisms in selected test cases using a three-dimensional particle-in-cell code that allows realistic treatment of shape and kinetic effects. We find that a persistent discrepancy of a factor of 2-3 remains between simulation and experimental values of the growth rate

Simulations of the instability of the m=1 self-shielding diocotron mode in finite-length non-neutral plasmas

International Nuclear Information System (INIS)

Mason, Grant W.; Spencer, Ross L.

2002-01-01

The 'self-shielding' m=1 diocotron mode in Malmberg-Penning traps has been known for over a decade to be unstable for finite length non-neutral plasmas with hollow density profiles. Early theoretical efforts were unsuccessful in accounting for the exponential growth and/or the magnitude of the growth rate. Recent theoretical work has sought to resolve the discrepancy either as a consequence of the shape of the plasma ends or as a kinetic effect resulting from a modified distribution function as a consequence of the protocol used to form the hollow profiles in experiments. Both of these finite length mechanisms have been investigated in selected test cases using a three-dimensional particle-in-cell code that allows realistic treatment of shape and kinetic effects. A persistent discrepancy of a factor of 2-3 remains between simulation and experimental values of the growth rate. Simulations reported here are more in agreement with theoretical predictions and fail to explain the discrepancy

Laser optically pumped by laser-produced plasma

International Nuclear Information System (INIS)

Silfvast, W.T.; Wood, O.R. II.

1975-01-01

Laser solids, liquids and gases are pumped by a new technique in which the output from an efficient molecular laser, such as a CO 2 laser, ionizes a medium, such as xenon, into a generally cylindrical plasma volume, in proximity to the pumped laser body. Breakdown yields a visible and ultraviolet-radiation-emitting plasma in that volume to pump the laser body. The spectral radiance of the plasma is significantly higher than that produced by a dc-discharge-heated plasma at nearly all wavelengths in the plasma spectrum. The risetime of radiation from the laser-produced plasma can also be significantly shorter than that of a dc heated plasma. A further advantage resides in the fact that in some applications the attenuating walls needed by flashlamps may be eliminated with the result that laser threshold is more readily reached. Traveling wave excitation may be provided by oblique incidence of the pumping laser beam through the ionizable medium to create sequential ionization of portions of that medium along the length of the pumped laser body. (auth)

Laser-pulsed Plasma Chemistry: Laser-initiated Plasma Oxidation Of Niobium

OpenAIRE

Marks R.F.; Pollak R.A.; Avouris Ph.; Lin C.T.; Thefaine Y.J.

1983-01-01

We report the first observation of the chemical modification of a solid surface exposed to an ambient gas plasma initiated by the interaction of laser radiation with the same surface. A new technique, which we designate laser-pulsed plasma chemistry (LPPC), is proposed for activating heterogeneous chemical reactions at solid surfaces in a gaseous ambient by means of a plasma initiated by laser radiation. Results for niobium metal in one atmosphere oxygen demonstrate single-pulse, self-limitin...

A perspective on the contributions of Ronald C. Davidson to plasma physics

Science.gov (United States)

Wurtele, Jonathan S.

2016-10-01

Starting in the 1960s and continuing for half a century, Ronald C. Davidson made fundamental theoretical contributions to a wide range of areas of pure and applied plasma physics. Davidson was one of the founders of nonneutral plasma physics and a pioneer in developing and applying kinetic theory and nonlinear stability theorems to collective interaction processes and nonlinear dynamics of nonneutral plasmas and intense charged particle beams. His textbooks on nonneutral plasmas are the classic references for the field and educated generations of graduate students. Davidson was a strong advocate for applying the ideas of plasma theory to develop techniques that benefit other branches of science. For example, one of the major derivative fields enabled by nonneutral plasmas is the study of antimatter plasmas and the synthesis of antihydrogen. This talk will review a few highlights of Ronald Davidson's impact on plasma physics and related fields of science.

Nonneutralized charge effects on tokamak edge magnetohydrodynamic stability

International Nuclear Information System (INIS)

Zheng, Linjin; Horton, W.; Miura, H.; Shi, T.H.; Wang, H.Q.

2016-01-01

Owing to the large ion orbits, excessive electrons can accumulate at tokamak edge. We find that the nonneutralized electrons at tokamak edge can contribute an electric compressive stress in the direction parallel to magnetic field by their mutual repulsive force. By extending the Chew–Goldburger–Low theory (Chew et al., 1956 [13]), it is shown that this newly recognized compressive stress can significantly change the plasma average magnetic well, so that a stabilization of magnetohydrodynamic modes in the pedestal can result. This linear stability regime helps to explain why in certain parameter regimes the tokamak high confinement can be rather quiet as observed experimentally.

Plasma state. The universe's fire

International Nuclear Information System (INIS)

Lehner, Th.

2004-01-01

The plasma is the fourth state of matter, obtained at a very high temperature by the separation of the electrons from their nuclei. Plasma represents 99% of the visible mass of our present day universe and was the unique state of matter at its very beginning. Plasmas are present in the core of stars and in the interstellar environment. More closer to us, they are responsible of spectacular phenomena, like aurora borealis, lightning, comet queues etc.. This book makes a review of the different types of plasmas (electromagnetic, Earth's plasmas, spatial plasmas, solar plasmas, astrophysical plasmas). One chapter presents the thermonuclear fusion as future energy source. Another one treats of the chaos and turbulence inside plasmas. Some applications of plasmas are reviewed: MHD and ionic propulsion systems, MHD energy conversion and MHD generators, thermo-ionic converters, solid-state plasmas, particle accelerators, coherent radiation sources, 'Zeta' machines, X-ray lasers, isotopic separation, non-neutral plasmas and charged beams, free-electrons lasers, electrons and positrons plasmas, industrial applications (etching and cleaning, manufacturing of solar cells, flat screens, industrial reactors, waste treatment, cold plasma-assisted sterilization, effluents decontamination etc.). A last chapter makes an overview of the modern research in plasma physics. (J.S.)

Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma

Energy Technology Data Exchange (ETDEWEB)

Tong Huifeng; Yuan Hong [Institute of Fluid Physics, Chinese Academy of Engineering Physics, P.O. Box 919-101, Mianyang, Sichuan 621900 (China); Tang Zhiping [CAS Key Laboratory for Mechanical Behavior and Design of Materials, Department of Mechanics and Mechanical Engineering, University of Science and Technology of China, Hefei 230026 (China)

2013-01-28

When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times which show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.

Research briefing on contemporary problems in plasma science

International Nuclear Information System (INIS)

1991-01-01

An overview is presented of the broad perspective of all plasma science. Detailed discussions are given of scientific opportunities in various subdisciplines of plasma science. The first subdiscipline to be discussed is the area where the contemporary applications of plasma science are the most widespread, low temperature plasma science. Opportunities for new research and technology development that have emerged as byproducts of research in magnetic and inertial fusion are then highlighted. Then follows a discussion of new opportunities in ultrafast plasma science opened up by recent developments in laser and particle beam technology. Next, research that uses smaller scale facilities is discussed, first discussing non-neutral plasmas, and then the area of basic plasma experiments. Discussions of analytic theory and computational plasma physics and of space and astrophysical plasma physics are then presented

Plasma cutting or laser cutting. Plasma setsudan ka laser setsudan ka

Energy Technology Data Exchange (ETDEWEB)

Nakamura, A. (Tanaka Engineering Works Ltd., Saitama (Japan))

1991-05-01

Comparisons and discussions were made on the plasma cutting and laser cutting in sheet steel cutting, referring partly to gas cutting. Historically, the cutting has been developed from gas, plasma, and laser in that order, and currently these three methods are used mixedly. Generally, the plasma cutting is superior in cutting speed, but inferior in cut face quality, and it requires measures of dust collection. Due to high accuracy and quality in cut face, the laser cutting has been practically used for quite some time in the thin sheet industry, but medium to thick sheet cutting had a problem of unavailability of high output laser suitable for these ranges. However, the recent technologies have overcome the problem as a result of development at the authors {prime} company of a 2 kW class laser cutter capable of cutting 19 mm thick sheet. The cutter has been proven being particularly excellent in controllability. Choice of whether plasma or laser would depend upon which priority is to be taken, cost or accuracy. 15 figs., 3 tabs.

Laser beam-plasma plume interaction during laser welding

Science.gov (United States)

Hoffman, Jacek; Moscicki, Tomasz; Szymanski, Zygmunt

2003-10-01

Laser welding process is unstable because the keyhole wall performs oscillations which results in the oscillations of plasma plume over the keyhole mouth. The characteristic frequencies are equal to 0.5-4 kHz. Since plasma plume absorbs and refracts laser radiation, plasma oscillations modulate the laser beam before it reaches the workpiece. In this work temporary electron densities and temperatures are determined in the peaks of plasma bursts during welding with a continuous wave CO2 laser. It has been found that during strong bursts the plasma plume over the keyhole consists of metal vapour only, being not diluted by the shielding gas. As expected the values of electron density are about two times higher in peaks than their time-averaged values. Since the plasma absorption coefficient scales as ~N2e/T3/2 (for CO2 laser radiation) the results show that the power of the laser beam reaching the metal surface is modulated by the plasma plume oscillations. The attenuation factor equals 4-6% of the laser power but it is expected that it is doubled by the refraction effect. The results, together with the analysis of the colour pictures from streak camera, allow also interpretation of the dynamics of the plasma plume.

Efficient simulation and likelihood methods for non-neutral multi-allele models.

Science.gov (United States)

Joyce, Paul; Genz, Alan; Buzbas, Erkan Ozge

2012-06-01

Throughout the 1980s, Simon Tavaré made numerous significant contributions to population genetics theory. As genetic data, in particular DNA sequence, became more readily available, a need to connect population-genetic models to data became the central issue. The seminal work of Griffiths and Tavaré (1994a , 1994b , 1994c) was among the first to develop a likelihood method to estimate the population-genetic parameters using full DNA sequences. Now, we are in the genomics era where methods need to scale-up to handle massive data sets, and Tavaré has led the way to new approaches. However, performing statistical inference under non-neutral models has proved elusive. In tribute to Simon Tavaré, we present an article in spirit of his work that provides a computationally tractable method for simulating and analyzing data under a class of non-neutral population-genetic models. Computational methods for approximating likelihood functions and generating samples under a class of allele-frequency based non-neutral parent-independent mutation models were proposed by Donnelly, Nordborg, and Joyce (DNJ) (Donnelly et al., 2001). DNJ (2001) simulated samples of allele frequencies from non-neutral models using neutral models as auxiliary distribution in a rejection algorithm. However, patterns of allele frequencies produced by neutral models are dissimilar to patterns of allele frequencies produced by non-neutral models, making the rejection method inefficient. For example, in some cases the methods in DNJ (2001) require 10(9) rejections before a sample from the non-neutral model is accepted. Our method simulates samples directly from the distribution of non-neutral models, making simulation methods a practical tool to study the behavior of the likelihood and to perform inference on the strength of selection.

5. Laser plasma interaction

International Nuclear Information System (INIS)

Labaune, C.; Fuchs, J.; Bandulet, H.

2002-01-01

Imprint elimination, smoothing and preheat control are considerable problems in inertial fusion and their possible solution can be achieved by using low-density porous materials as a buffer in target design. The articles gathered in this document present various aspects of the laser-plasma interaction, among which we have noticed: -) numerical algorithmic improvements of the Vlasov solver toward the simulation of the laser-plasma interaction are proposed, -) the dependence of radiation temperatures and X-ray conversion efficiencies of hohlraum on the target structures and laser irradiation conditions are investigated, -) a study of laser interaction with ultra low-density (0,5 - 20 mg/cm 3 ) porous media analyzing backscattered light at incident laser frequency ω 0 and its harmonics 3*ω 0 /2 and 2*ω 0 is presented, -) investigations of laser interaction with solid targets and crater formation are carried out with the objective to determine the ablation loading efficiency, -) a self organization in an intense laser-driven plasma and the measure of the relative degree of order of the states in an open system based on the S-theorem are investigated, and -) the existence and stability of electromagnetic solitons generated in a relativistic interaction of an intense laser light with uniform under-dense cold plasma are studied

Laser-plasma interactions and applications

CERN Document Server

Neely, David; Bingham, Robert; Jaroszynski, Dino

2013-01-01

Laser-Plasma Interactions and Applications covers the fundamental and applied aspects of high power laser-plasma physics. With an internationally renowned team of authors, the book broadens the knowledge of young researchers working in high power laser-plasma science by providing them with a thorough pedagogical grounding in the interaction of laser radiation with matter, laser-plasma accelerators, and inertial confinement fusion. The text is organised such that the theoretical foundations of the subject are discussed first, in Part I. In Part II, topics in the area of high energy density physics are covered. Parts III and IV deal with the applications to inertial confinement fusion and as a driver of particle and radiation sources, respectively. Finally, Part V describes the principle diagnostic, targetry, and computational approaches used in the field. This book is designed to give students a thorough foundation in the fundamental physics of laser-plasma interactions. It will also provide readers with knowl...

The application of laser plasma in ophthalmology

International Nuclear Information System (INIS)

He Yujiang; Luo Le; Sun Yabing

2000-01-01

The production and development of laser plasma are introduced, and the contribution of laser biomedicine and laser plasma technology to ophthalmology is analyzed. The latest three progresses (laser photocoagulation, photo-refractive keratotomy and laser iridectomy) of laser plasma applications in ophthalmology are presented

Scaling of laser-plasma interactions with laser wavelength and plasma size

International Nuclear Information System (INIS)

Max, C.E.; Campbell, E.M.; Mead, W.C.; Kruer, W.L.; Phillion, D.W.; Turner, R.E.; Lasinski, B.F.; Estabrook, K.G.

1983-01-01

Plasma size is an important parameter in wavelength-scaling experiments because it determines both the threshold and potential gain for a variety of laser-plasma instabilities. Most experiments to date have of necessity produced relatively small plasmas, due to laser energy and pulse-length limitations. We have discussed in detail three recent Livermore experiments which had large enough plasmas that some instability thresholds were exceeded or approached. Our evidence for Raman scatter, filamentation, and the two-plasmon decay instability needs to be confirmed in experiments which measure several instability signatures simultaneously, and which produce more quantitative information about the local density and temperature profiles than we have today

Scaling of laser-plasma interactions with laser wavelength and plasma size

Energy Technology Data Exchange (ETDEWEB)

Max, C.E.; Campbell, E.M.; Mead, W.C.; Kruer, W.L.; Phillion, D.W.; Turner, R.E.; Lasinski, B.F.; Estabrook, K.G.

1983-01-25

Plasma size is an important parameter in wavelength-scaling experiments because it determines both the threshold and potential gain for a variety of laser-plasma instabilities. Most experiments to date have of necessity produced relatively small plasmas, due to laser energy and pulse-length limitations. We have discussed in detail three recent Livermore experiments which had large enough plasmas that some instability thresholds were exceeded or approached. Our evidence for Raman scatter, filamentation, and the two-plasmon decay instability needs to be confirmed in experiments which measure several instability signatures simultaneously, and which produce more quantitative information about the local density and temperature profiles than we have today.

Nonlinear electrostatic ion-acoustic "oscilliton" waves driven by charge non-neutrality effects

Directory of Open Access Journals (Sweden)

J. Z. G. Ma

2011-01-01

Full Text Available Nonlinear "oscilliton" structures features a low-frequency (LF solitary envelope, the amplitude of which is modulated violently by superimposed high-frequency (HF oscillations. We have studied the charge non-neutrality effects on the excitation of electrostatic ion-acoustic (IA oscillitons. A two-fluid, warm plasma model is employed, and a set of nonlinear self-similar equations is solved in a cylindrical geometry. Under charge-neutrality conditions, three conventional IA structures (namely, sinusoidal, sawtooth, and spicky/bipolar are obtained. By contrast, under charge non-neutrality conditions, oscilliton structures are excited, where the LF envelope is in the sound-wave (SW mode, while the HF ingredients include the IA mode and the ion-Langmiur (IL mode. The amplitudes of the SW wave are violently modulated by the IA oscillations, whereas the upward sides of the IA amplitudes are modulated by the IL oscillations of smaller amplitudes, and the downward sides are modulated by hybrid IA/IL oscillations. The nonlinear oscillitons are found to be dependent not only upon the input parameters (e.g., the Mach number, the Debye length, and the initial temperature of particles, but on initial conditions as well.

Collisional transport in nonneutral plasmas

International Nuclear Information System (INIS)

Dubin, D.H.E.

1999-01-01

Classical transport theory grossly underestimates collisionally-driven cross-field transport for plasmas in the parameter regime of r c D , where r c ≡ v-bar/Ω c , λ D 2 ≡ T/4πe 2 n. In current experiments operating in this regime, cross-field test particle transport is observed to be a factor of 10 larger than the prediction of classical theory. Heat conduction is enhanced by up to 300 times over classical theory, and viscosity is up to 10 4 times larger. New guiding center theories of transport due to long-range collisions have been developed that agree with the measurements. Theory also predicts that emission and absorption of plasma waves may further enhance the thermal conduction and viscosity, providing a possible mechanism for anomalous thermal conductivity in the electron channel of fusion plasmas. (author)

Influence of the laser pulse duration on laser-produced plasma properties

International Nuclear Information System (INIS)

Drogoff, B Le; Margot, J; Vidal, F; Laville, S; Chaker, M; Sabsabi, M; Johnston, T W; Barthelemy, O

2004-01-01

In the framework of laser-induced plasma spectroscopy (LIPS) applications, time-resolved characteristics of laser-produced aluminium plasmas in air at atmospheric pressure are investigated for laser pulse durations ranging from 100 fs to 270 ps. Measurements show that for delays after the laser pulse longer than ∼100 ns, the plasma temperature increases slightly with the laser pulse duration, while the electron density is independent of it. In addition, as the pulse duration increases, the plasma radiation emission lasts longer and the spectral lines arise later from the continuum emission. The time dependence of the continuum emission appears to be similar whatever the duration of the laser pulse is, while the temporal evolution of the line emission seems to be affected mainly by the plasma temperature. Finally, as far as spectrochemical applications (such as LIPS) of laser-produced plasmas are concerned, this study highlights the importance of the choice of appropriate temporal gating parameters for each laser pulse duration

Spectrochemical analysis using laser plasma excitation

International Nuclear Information System (INIS)

Radziemski, L.J.

1989-01-01

This paper reports on analyses of gases, liquids, particles, and surfaces in which laser plasma is used to vaporize and excite a material. The authors present a discussion of the interaction between laser radiation and a solid and some recent analytical results using laser plasma excitation on metals. The use of laser plasmas as an ablation source is also discussed

Progress of Laser-Driven Plasma Accelerators

International Nuclear Information System (INIS)

Nakajima, Kazuhisa

2007-01-01

There is a great interest worldwide in plasma accelerators driven by ultra-intense lasers which make it possible to generate ultra-high gradient acceleration and high quality particle beams in a much more compact size compared with conventional accelerators. A frontier research on laser and plasma accelerators is focused on high energy electron acceleration and ultra-short X-ray and Tera Hertz radiations as their applications. These achievements will provide not only a wide range of sciences with benefits of a table-top accelerator but also a basic science with a tool of ultrahigh energy accelerators probing an unknown extremely microscopic world.Harnessing the recent advance of ultra-intense ultra-short pulse lasers, the worldwide research has made a tremendous breakthrough in demonstrating high-energy high-quality particle beams in a compact scale, so called ''dream beams on a table top'', which represents monoenergetic electron beams from laser wakefield accelerators and GeV acceleration by capillary plasma-channel laser wakefield accelerators. This lecture reviews recent progress of results on laser-driven plasma based accelerator experiments to quest for particle acceleration physics in intense laser-plasma interactions and to present new outlook for the GeV-range high-energy laser plasma accelerators

Thermonuclear fusion plasma produced by lasers

International Nuclear Information System (INIS)

Yamanaka, C.; Yokoyama, M.; Nakai, S.; Sasaki, T.; Yoshida, K.; Matoba, M.; Yamabe, C.; Tschudi, T.; Yamanaka, T.; Mizui, J.; Yamaguchi, N.; Nishikawa, K.

1975-01-01

Recently, much attention has been focused on laser fusion schemes using high-density plasmas produced by implosion. Scientific-feasibility laser-fusion experiments are now in time. But the physics of interaction between laser and plasma, the high-compression technique and the development of high-power lasers are still important problems to be solved if laser fusion is to make some progress. In the field of laser-plasma coupling, experiments were carried out in which hydrogen and deuterium sticks were bombarded by laser beams; in these experiments, a glass-laser system, LETKKO-I, with an energy of 50 J in a nanosecond pulse, and a double-discharge TEA CO 2 laser system with an energy of 100 J in a 100-ns pulse were used. A decrease in reflectivity occurred at a laser intensity one order of magnitude higher than the parametric-instability threshold. Self-phase modulation of scattered light due to modulational instability was found. A Brillouin-backscattering isotope effect due to the hydrogen and deuterium plasma has also been observed in the red-side part of the SHG-light. Preliminary compression experiments have been carried out using a glass-laser system LETKKO-II, with an energy of 250-1000 J in a ns-pulse. A hologram has been used to study shock waves in the plasma due to the SHG-light converted from the main laser beam. Development of high-power lasers has been promoted, such as disc-glass lasers, E-beam CO 2 lasers and excimer lasers. (author)

Study on Laser Induced Plasma Produced in Liquid

International Nuclear Information System (INIS)

Tsuda, N.; Yamada, J.

2003-01-01

When an intense laser light is focused in liquid, a hot plasma is produced at the focal spot. The breakdown threshold and the transmittance of sodium choroids solution are observed using excimer laser or YAG laser. The breakdown threshold decreases with increasing NaCl concentration. Threshold intensity of plasma produced by YAG laser is lower than excimer laser. The behavior of plasma development is observed by a streak camera. The plasma produced by a YAG laser develops only backward. However, the plasma produced by excimer laser develops not only backward but also forward same as the plasma development in high-pressure gases

Laser plasma interactions in hohlraums

Energy Technology Data Exchange (ETDEWEB)

Kruer, W.L.

1994-10-05

Lasers plasma instabilities are an important constraint in x-ray driven inertial confinement fusion. In hohlraums irradiated with 1.06 {mu}m light on the Shiva laser, plasma instabilities were extremely deleterious, driving the program to the use of shorter wavelength light. Excellent coupling has been achieved in hohlraums driven with 0.35 {mu}m light on the Nova laser. Considerable attention is being given to the scaling of this excellent coupling to the larger hohlraums for an ignition target. Various instability control mechanisms such as large plasma wave damping and laser beam incoherence are discussed, as well as scaling experiments to check the instability levels.

Relativistic laser channeling in plasmas for fast ignition

Science.gov (United States)

Lei, A. L.; Pukhov, A.; Kodama, R.; Yabuuchi, T.; Adumi, K.; Endo, K.; Freeman, R. R.; Habara, H.; Kitagawa, Y.; Kondo, K.; Kumar, G. R.; Matsuoka, T.; Mima, K.; Nagatomo, H.; Norimatsu, T.; Shorokhov, O.; Snavely, R.; Yang, X. Q.; Zheng, J.; Tanaka, K. A.

2007-12-01

We report an experimental observation suggesting plasma channel formation by focusing a relativistic laser pulse into a long-scale-length preformed plasma. The channel direction coincides with the laser axis. Laser light transmittance measurement indicates laser channeling into the high-density plasma with relativistic self-focusing. A three-dimensional particle-in-cell simulation reproduces the plasma channel and reveals that the collimated hot-electron beam is generated along the laser axis in the laser channeling. These findings hold the promising possibility of fast heating a dense fuel plasma with a relativistic laser pulse.

Laser-plasma interactions in magnetized environment

Science.gov (United States)

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J.

2018-05-01

Propagation and scattering of lasers present new phenomena and applications when the plasma medium becomes strongly magnetized. With mega-Gauss magnetic fields, scattering of optical lasers already becomes manifestly anisotropic. Special angles exist where coherent laser scattering is either enhanced or suppressed, as we demonstrate using a cold-fluid model. Consequently, by aiming laser beams at special angles, one may be able to optimize laser-plasma coupling in magnetized implosion experiments. In addition, magnetized scattering can be exploited to improve the performance of plasma-based laser pulse amplifiers. Using the magnetic field as an extra control variable, it is possible to produce optical pulses of higher intensity, as well as compress UV and soft x-ray pulses beyond the reach of other methods. In even stronger giga-Gauss magnetic fields, laser-plasma interaction enters a relativistic-quantum regime. Using quantum electrodynamics, we compute a modified wave dispersion relation, which enables correct interpretation of Faraday rotation measurements of strong magnetic fields.

Modeling the astrophysical dynamical process with laser-plasmas

International Nuclear Information System (INIS)

Xia Jiangfan; Zhang Jun; Zhang Jie

2001-01-01

The use of the state-of-the-art laser facility makes it possible to create conditions of the same or similar to those in the astrophysical processes. The introduction of the astrophysics-relevant ideas in laser-plasma experiments is propitious to the understanding of the astrophysical phenomena. However, the great difference between the laser-produced plasmas and the astrophysical processes makes it awkward to model the latter by laser-plasma experiments. The author addresses the physical backgrounds for modeling the astrophysical plasmas by laser plasmas, connecting these two kinds of plasmas by scaling laws. Thus, allowing the creation of experimental test beds where observations and models can be quantitatively compared with laser-plasma data. Special attentions are paid on the possibilities of using home-made laser facilities to model astrophysical phenomena

Interaction of Intense Lasers with Plasmas

Science.gov (United States)

Shvets, Gennady

1995-01-01

This thesis addresses two important topics in nonlinear laser plasma physics: the interaction of intense lasers with a non thermal homogeneous plasma, the excitation of laser wakefields in hollow plasma channels, and the stability of channel guided propagation of laser pulses. In the first half of this thesis a new theoretical approach to the nonlinear interaction of intense laser pulses with underdense plasmas is developed. Unlike previous treatments, this theory is three-dimensional, relativistically covariant, and does not assume that astudied. An experimental check of this calculation is suggested, based on the predicted non-linear polarization rotation (the second harmonic is emitted polarized perpendicularly to polarization of the incident signal). The concept of renormalization is applied to the plasma and electromagnetic radiation (photons and plasmons). To the lowest order, this corresponds to relativistically correcting the electron mass for its oscillation in an intense EM field and to replacing the vacuum dispersion relation by the usual relativistic plasma dispersion relation. This renormalization procedure is then carried to higher order in epsilon=omega_sp{p} {2}a^2/[(1+a^2/2)^ {3/2}omega^2]. This yields the nonlinear modification of the index of refraction of a strong electromagnetic wave and the dispersion of a weak probe in the presence of the wave. In the second part of this thesis the stability of short laser pulses propagating through parabolic channels and the wake excitation of hollow plasma channels are studied. The stability of a channel guided short laser pulse propagation is analyzed for the first time. Perturbations to the laser pulse are shown to modify the ponderomotive pressure, which distorts the dielectric properties of the plasma channel. The channel perturbation then further distorts the laser pulse. A set of coupled mode equations is derived, and a matrix dispersion relation is obtained analytically. The ponderomotive excitation

Plasmas and intense laser light

International Nuclear Information System (INIS)

Kennedy, E.T.

1984-01-01

The present article begins with a description of the laser technology required to reach the high irradiances of interest and provides a brief outline of the more important diagnostic techniques used in investigating the plasmas. An introduction to plasma waves is given and the linear and nonlinear excitation of waves is discussed. The remainder of the article describes some of the experimental evidence supporting the interpretation of the plasma behaviour at high laser-light intensities in terms of the excitation of plasma waves and the subsequent heating of plasma by these waves. (author)

New photoionization lasers pumped by laser-induced plasma radiation

International Nuclear Information System (INIS)

Hube, M.; Dieckmann, M.; Beigang, R.; Welling, H.; Wellegehausen, B.

1988-01-01

Innershell photoionization of atomic gases and vapors by soft x rays from a laser-produced plasma is a potential method for making lasers at short wavelengths. Normally, in such experiments only a single plasma spot or plasma line is created for the excitation. This gives high excitation rates but only a short excitation length. At high excitation rates detrimental influences, such as amplified spontaneous emission, optical saturation, or quenching processes, may decrease or even destroy a possible inversion. Therefore, it seems to be more favorable to use a number of separated plasma spots with smaller excitation rates and larger excitation lengths. As a test, a three-plasma spot device was constructed and used in the well-known Cd-photoionization laser at 442 nm. With a 600-mJ Nd:YAH laser (pulse length, 8 ns) for plasma production, output energies up to 300 μJ have been measured, which is more than a doubling of so far obtained data. On innershell excitation, levels may be populated that allow direct lasers as in the case of Cd or that are metastable and cannot be directly coupled to lower levels. In this case modifications in the excitation process are necessary. Such modifications may be an optical pump process in the atom prior to the innershell photoionization or an optical pump process (population transfer process) after the innershell ionization, leading to Raman or anti-Stokes Raman-type laser emissions. With these techniques and the developed multiplasma spot excitation device a variety of new laser emissions in K and Cs ions have been achieved which are indicated in the level schemes

Diagnostics of laser ablated plasma plumes

DEFF Research Database (Denmark)

Amoruso, S.; Toftmann, B.; Schou, Jørgen

2004-01-01

The effect of an ambient gas on the expansion dynamics of laser ablated plasmas has been studied for two systems by exploiting different diagnostic techniques. First, the dynamics of a MgB2 laser produced plasma plume in an Ar atmosphere has been investigated by space-and time-resolved optical...... of the laser ablated plasma plume propagation in a background gas. (C) 2003 Elsevier B.V All rights reserved....

Stability of Non-Neutral Plasma Cylinder Consisting of Magnetized Cold Electrons and of Small Density Fraction of Ions Born at Rest: Non-Local Analysis

International Nuclear Information System (INIS)

Yeliseyev, Y. N.

2009-01-01

The non-local stability problem of the plasma cylinder, filled with 'cold' magnetized rigidly rotating electrons, and a small density fraction of ions, is solved. The ions are supposed to be born at rest by ionization of background gas. The study is based on the kinetic description of ions. The equilibrium distribution function, taking into account the peculiarity of ions birth, is used. The radial electric field is caused by space charge of non-neutral plasma. The dispersion equation for plasma eigen frequencies is obtained analytically. It is valid within the total admissible range of values of electric and magnetic fields. Normalized eigen frequencies ω'/Ω i are calculated for the basic azimuth mode m = 1(ω' ω-mω i + , ω + = (-ω ci +Ω i )/2, Ω i (ω ci 2 -4eE r /m i r) 1/2 is called the 'modified' ion cyclotron (MIC) frequency), for the density fraction of ions of atomic nitrogen f N i /n e = 0,01 and are presented in graphic form versus parameter 2ω pe 2 /ω ce 2 . The spectra of oscillations ω'/Ω i consist of the family of electron Trivel-piece--Gould (TG) modes and of the families of MIC modes. The frequencies of MIC modes are located in a small vicinity of harmonics of the MIC frequency Ω i above and below the harmonic. The TG modes in non-neutral plasma fall in the region of MIC frequencies Ω i and interact strongly with MIC modes. The slow TG modes become unstable near the crossings with non-negative harmonics of MIC frequencies. The instabilities have a resonant character. The lowest radial TG mode has a maximum growth rate at crossing with a zero harmonic of Ω i ((Im ω'/Ω i ) max ≅0,074). The growth rates of MIC modes are much lower ((Im ω'/Ω i ) max pe 2 /ω ce 2 , corresponding to strong radial electric fields (ω ci 2 r /m i r|), in which the ions are unmagnetized. The oscillations of small amplitude are seen on some frequency dependencies of MIC modes. They are similar to oscillations on dispersion curves of electron waves in

Hollow laser plasma self-confined microjet generation

Science.gov (United States)

Sizyuk, Valeryi; Hassanein, Ahmed; CenterMaterials under Extreme Environment Team

2017-10-01

Hollow laser beam produced plasma (LPP) devices are being used for the generation of the self-confined cumulative microjet. Most important place by this LPP device construction is achieving of an annular distribution of the laser beam intensity by spot. An integrated model is being developed to detailed simulation of the plasma generation and evolution inside the laser beam channel. The model describes in two temperature approximation hydrodynamic processes in plasma, laser absorption processes, heat conduction, and radiation energy transport. The total variation diminishing scheme in the Lax-Friedrich formulation for the description of plasma hydrodynamic is used. Laser absorption and radiation transport models on the base of Monte Carlo method are being developed. Heat conduction part on the implicit scheme with sparse matrixes using is realized. The developed models are being integrated into HEIGHTS-LPP computer simulation package. The integrated modeling of the hollow beam laser plasma generation showed the self-confinement and acceleration of the plasma microjet inside the laser channel. It was found dependence of the microjet parameters including radiation emission on the hole and beam radiuses ratio. This work is supported by the National Science Foundation, PIRE project.

Staging of laser-plasma accelerators

Energy Technology Data Exchange (ETDEWEB)

Steinke, S., E-mail: ssteinke@lbl.gov; Tilborg, J. van; Benedetti, C.; Geddes, C. G. R.; Gonsalves, A. J.; Nakamura, K.; Schroeder, C. B.; Esarey, E. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Daniels, J. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven (Netherlands); Swanson, K. K.; Shaw, B. H.; Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); University of California, Berkeley, California 94720 (United States)

2016-05-15

We present results of an experiment where two laser-plasma-accelerator stages are coupled at a short distance by a plasma mirror. Stable electron beams from the first stage were used to longitudinally probe the dark-current-free, quasi-linear wakefield excited by the laser of the second stage. Changing the arrival time of the electron beam with respect to the second stage laser pulse allowed reconstruction of the temporal wakefield structure, determination of the plasma density, and inference of the length of the electron beam. The first stage electron beam could be focused by an active plasma lens to a spot size smaller than the transverse wake size at the entrance of the second stage. This permitted electron beam trapping, verified by a 100 MeV energy gain.

Channeling and stability of laser pulses in plasmas

International Nuclear Information System (INIS)

Sprangle, P.; Krall, J.; Esarey, E.

1995-01-01

A laser pulse propagating in a plasma is found to undergo a combination of hose and modulation instabilities. The coupled equations for the laser beam envelope and centroid are derived and solved for a laser pulse of finite length propagating through either a uniform plasma or preformed plasma density channel. The laser envelope equation describes the pulse self-focusing and optical guiding in plasmas and is used to analyze the self-modulation instability. The laser centroid equation describes the transverse motion of the laser pulse (hosing) in plasmas. Significant coupling between the centroid and envelope motion as well as harmonic generation in the envelope can occur. In addition, the transverse profile of the generated wake field is strongly affected by the laser hose instability. Methods to reduce the laser hose instability are demonstrated. copyright 1995 American Institute of Physics

Generation conditions of CW Diode Laser Sustained Plasma

Science.gov (United States)

Nishimoto, Koji; Matsui, Makoto; Ono, Takahiro

2016-09-01

Laser sustained plasma was generated using 1 kW class continuous wave diode laser. The laser beam was focused on the seed plasma generated by arc discharge in 1 MPa xenon lamp. The diode laser has advantages of high energy conversion efficiency of 80%, ease of maintenance, compact size and availability of conventional quartz based optics. Therefore, it has a prospect of further development compared with conventional CO2 laser. In this study, variation of the plasma shape caused by laser power is observed and also temperature distribution in the direction of plasma radius is measured by optical emission spectroscopy.

Energy transport in laser produced plasmas

International Nuclear Information System (INIS)

Key, M.H.

1989-06-01

The study of energy transport in laser produced plasmas is of great interest both because it tests and develops understanding of several aspects of basic plasma physics and also because it is of central importance in major applications of laser produced plasmas including laser fusion, the production of intense X-ray sources, and X-ray lasers. The three sections cover thermal electrons (energy transport in one dimension, plane targets and lateral transport from a focal spot, thermal smoothing, thermal instabilities), hot electrons (preheating in one dimension, lateral transport from a focal spot) and radiation (preheating in one dimension, lateral transport and smoothing, instabilities). (author)

Lasers as a tool for plasma diagnostics

International Nuclear Information System (INIS)

Jahoda, F.C.

1981-01-01

Lasers can be used as non-perturbative probes to measure many plasma parameters. Plasma refractivity is primarily a function of electron density, and interferometric measurements of phase changes with either pulsed or CW lasers can determine this parameter with spatial or temporal resolution over several orders of magnitude sensitivity by using laser wavelengths from the near uv to the far infrared. Laser scattering from free electrons yields the most fundamental electron temperature measurements in the plasma parameter range where individual scattering events are uncorrelated in phase and ion temperature or plasma wave and turbulence structure in the opposite limit. Laser scattering from bound electrons can be many orders of magnitude larger if the laser is matched to appropriate resonance frequencies and can be used in specialized circumstances for measuring low-ionized impurity or dominant species neutral concentrations and velocities

Nonlinear laser-plasma interactions

Science.gov (United States)

Kaw, P. K.

2017-12-01

Soon after lasers were invented, there was tremendous curiosity on the nonlinear phenomena which would result in their interaction with a fully ionized plasma. Apart from the basic interest, it was realized that it could be used for the achievement of nuclear fusion in the laboratory. This led us to a paper on the propagation of a laser beam into an inhomogeneous fusion plasma, where it was first demonstrated that light would go up to the critical layer (where the frequency matches the plasma frequency) and get reflected from there with a reflection coefficient of order unity. The reflection coefficient was determined by collisional effects. Since the wave was expected to slow down to near zero group speed at the reflection point, the dominant collision frequency determining the reflection coefficient was the collision frequency at the reflection point. It turned out that the absorption of light was rather small for fusion temperatures. This placed a premium on investigation of nonlinear phenomena which might contribute to the absorption and penetration of the light into high-density plasma. An early investigation showed that electron jitter with respect to ions would be responsible for the excitation of decay instabilities which convert light waves into electrostatic plasma waves and ion waves near the critical frequency. These electrostatic waves would then get absorbed into the plasma even in the collisionless case and lead to plasma heating which is nonlinear. Detailed estimates of this heating were made. Similar nonlinear processes which could lead to stimulated scattering of light in the underdense region (ω >ω _p) were investigated together with a number of other workers. All these nonlinear processes need a critical threshold power for excitation. Another important process which was discovered around the same time had to do with filamentation and trapping of light when certain thresholds were exceeded. All of this work has been extensively verified in

Laser-induced gas plasma machining

Energy Technology Data Exchange (ETDEWEB)

Elhadj, Selim; Bass, Isaac Louis; Guss, Gabriel Mark; Matthews, Manyalibo J.

2017-10-17

Techniques for removing material from a substrate are provided. A laser beam is focused at a distance from the surface to be treated. A gas is provided at the focus point. The gas is dissociated using the laser energy to generate gas plasma. The substrate is then brought in contact with the gas plasma to enable material removal.

Physics of laser plasma

International Nuclear Information System (INIS)

Rubenchik, A.; Witkowski, S.

1991-01-01

This book provides a comprehensive review of laser fusion plasma physics and contains the most up-to-date information on high density plasma physics and radiation transport, useful for astrophysicists and high density physicists

Summary Report of Working Group 6: Laser-Plasma Acceleration

International Nuclear Information System (INIS)

Leemans, Wim P.; Downer, Michael; Siders, Craig

2006-01-01

A summary is given of presentations and discussions in the Laser-Plasma Acceleration Working Group at the 2006 Advanced Accelerator Concepts Workshop. Presentation highlights include: widespread observation of quasi-monoenergetic electrons; good agreement between measured and simulated beam properties; the first demonstration of laser-plasma acceleration up to 1 GeV; single-shot visualization of laser wakefield structure; new methods for measuring <100 fs electron bunches; and new methods for 'machining' laser-plasma accelerator structures. Discussion of future direction includes: developing a roadmap for laser-plasma acceleration beyond 1 GeV; a debate over injection and guiding; benchmarking simulations with improved wake diagnostics; petawatt laser technology for future laser-plasma accelerators

Trends in laser-plasma-instability experiments for laser fusion

International Nuclear Information System (INIS)

Drake, R.P.

1991-01-01

Laser-plasma instability experiments for laser fusion have followed three developments. These are advances in the technology and design of experiments, advances in diagnostics, and evolution of the design of high-gain targets. This paper traces the history of these three topics and discusses their present state. Today one is substantially able to produce controlled plasma conditions and to diagnose specific instabilities within such plasmas. Experiments today address issues that will matter for future laser facilities. Such facilities will irradiate targets with ∼1 MJ of visible or UV light pulses that are tens of nanoseconds in duration, very likely with a high degree of spatial and temporal incoherence. 58 refs., 4 figs

Laser-plasma interaction with an adaptive optics wavefront-corrected laser beam

International Nuclear Information System (INIS)

Lewis, K.

2008-12-01

The propagation of an intense laser beam trough a preformed plasma is of particular interest in order to achieve laser inertial confinement fusion. Experiments carried out with a near-diffraction limited laser beam, producing a single hot spot interacting with the plasma, delivered new results, presented in this Ph.D. dissertation. In particular the first experimental observation of the filament instability confirms the numerous theoretical and numerical studies on the subject. Beam spreading and filament-ion thresholds are studied thanks to near-field and far-field images, with respect to laser intensity, time and space, and plasma transverse velocity. Same diagnostics have been applied to the stimulated Brillouin scattered light, enabling the first observation of the transverse Brillouin activity in the plasma. (author)

A periodic plasma waveguide accelerator

International Nuclear Information System (INIS)

Cole, F.T.

1985-01-01

The increasing cost of synchrotrons and storage rings has given new interest in the search for new methods of acceleration. The primary goal of this search is very large accelerating fields, because the cost of an accelerator to reach TeV energies is dominated by costs that scale with length. Very large electric fields are possible in plasmas and in lasers and many geometries are being studied that make use of plasmas, lasers, or combinations of them. In a plasma accelerator, the plasma can have several different functions. It may act as a medium for the propagation of accelerating electric-field waves. In addition, these waves may also act as a source of the energy needed to accelerate particles. Accelerators using various waves in plasmas have been built and studied in many laboratories. The device proposed here is an attempt to separate the two functions of providing a medium and providing an energy source. A relatively low-energy electron beam is used as a non-neutral plasma only to make a slow-wave medium for the propagation of an externally generated wave. The wave is a TM electromagnetic wave and the device may be thought of as a conventional electron linear accelerator with the evacuated volume and metallic envelope replaced by the electron beam. A separate second beam, which may be electrons or heavier particles, is accelerated. The application in mind here is a single-pass collider

Laser frequency modulation with electron plasma

Science.gov (United States)

Burgess, T. J.; Latorre, V. R.

1972-01-01

When laser beam passes through electron plasma its frequency shifts by amount proportional to plasma density. This density varies with modulating signal resulting in corresponding modulation of laser beam frequency. Necessary apparatus is relatively inexpensive since crystals are not required.

Interaction of a laser-produced copper plasma jet with ambient plastic plasma

Czech Academy of Sciences Publication Activity Database

Kasperczuk, A.; Pisarczyk, T.; Badziak, J.; Borodziuk, S.; Chodukowski, T.; Gus’kov, S.Yu.; Demchenko, N. N.; Klir, D.; Kravarik, J.; Kubes, P.; Rezac, K.; Ullschmied, Jiří; Krouský, Eduard; Mašek, Karel; Pfeifer, Miroslav; Rohlena, Karel; Skála, Jiří; Pisarczyk, P.

2011-01-01

Roč. 53, č. 9 (2011), 095003-095003 ISSN 0741-3335 R&D Projects: GA MŠk(CZ) 7E09092; GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z20430508; CEZ:AV0Z10100523 Keywords : laser produced-plasma jets * PALS laser * laser ablation * copper plasma * plastic plasma Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.425, year: 2011 http://iopscience.iop.org/0741-3335/53/9/095003/pdf/0741-3335_53_9_095003.pdf

A plasma microlens for ultrashort high power lasers

Science.gov (United States)

Katzir, Yiftach; Eisenmann, Shmuel; Ferber, Yair; Zigler, Arie; Hubbard, Richard F.

2009-07-01

We present a technique for generation of miniature plasma lens system that can be used for focusing and collimating a high intensity femtosecond laser pulse. The plasma lens was created by a nanosecond laser, which ablated a capillary entrance. The spatial configuration of the ablated plasma focused a high intensity femtosecond laser pulse. This configuration offers versatility in the plasma lens small f-number for extremely tight focusing of high power lasers with no damage threshold restrictions of regular optical components.

A plasma microlens for ultrashort high power lasers

International Nuclear Information System (INIS)

Katzir, Yiftach; Eisenmann, Shmuel; Ferber, Yair; Zigler, Arie; Hubbard, Richard F.

2009-01-01

We present a technique for generation of miniature plasma lens system that can be used for focusing and collimating a high intensity femtosecond laser pulse. The plasma lens was created by a nanosecond laser, which ablated a capillary entrance. The spatial configuration of the ablated plasma focused a high intensity femtosecond laser pulse. This configuration offers versatility in the plasma lens small f-number for extremely tight focusing of high power lasers with no damage threshold restrictions of regular optical components.

The influence of laser-particle interaction in laser induced breakdown spectroscopy and laser ablation inductively coupled plasma spectrometry

International Nuclear Information System (INIS)

Lindner, Helmut; Loper, Kristofer H.; Hahn, David W.; Niemax, Kay

2011-01-01

Particles produced by previous laser shots may have significant influence on the analytical signal in laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma (LA-ICP) spectrometry if they remain close to the position of laser sampling. The effects of these particles on the laser-induced breakdown event are demonstrated in several ways. LIBS-experiments were conducted in an ablation cell at atmospheric conditions in argon or air applying a dual-pulse arrangement with orthogonal pre-pulse, i.e., plasma breakdown in a gas generated by a focussed laser beam parallel and close to the sample surface followed by a delayed crossing laser pulse in orthogonal direction which actually ablates material from the sample and produces the LIBS plasma. The optical emission of the LIBS plasma as well as the absorption of the pre-pulse laser was measured. In the presence of particles in the focus of the pre-pulse laser, the plasma breakdown is affected and more energy of the pre-pulse laser is absorbed than without particles. As a result, the analyte line emission from the LIBS plasma of the second laser is enhanced. It is assumed that the enhancement is not only due to an increase of mass ablated by the second laser but also to better atomization and excitation conditions favored by a reduced gas density in the pre-pulse plasma. Higher laser pulse frequencies increase the probability of particle-laser interaction and, therefore, reduce the shot-to-shot line intensity variation as compared to lower particle loadings in the cell. Additional experiments using an aerosol chamber were performed to further quantify the laser absorption by the plasma in dependence on time both with and without the presence of particles. The overall implication of laser-particle interactions for LIBS and LA-ICP-MS/OES are discussed.

The influence of laser-particle interaction in laser induced breakdown spectroscopy and laser ablation inductively coupled plasma spectrometry

Science.gov (United States)

Lindner, Helmut; Loper, Kristofer H.; Hahn, David W.; Niemax, Kay

2011-02-01

Particles produced by previous laser shots may have significant influence on the analytical signal in laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma (LA-ICP) spectrometry if they remain close to the position of laser sampling. The effects of these particles on the laser-induced breakdown event are demonstrated in several ways. LIBS-experiments were conducted in an ablation cell at atmospheric conditions in argon or air applying a dual-pulse arrangement with orthogonal pre-pulse, i.e., plasma breakdown in a gas generated by a focussed laser beam parallel and close to the sample surface followed by a delayed crossing laser pulse in orthogonal direction which actually ablates material from the sample and produces the LIBS plasma. The optical emission of the LIBS plasma as well as the absorption of the pre-pulse laser was measured. In the presence of particles in the focus of the pre-pulse laser, the plasma breakdown is affected and more energy of the pre-pulse laser is absorbed than without particles. As a result, the analyte line emission from the LIBS plasma of the second laser is enhanced. It is assumed that the enhancement is not only due to an increase of mass ablated by the second laser but also to better atomization and excitation conditions favored by a reduced gas density in the pre-pulse plasma. Higher laser pulse frequencies increase the probability of particle-laser interaction and, therefore, reduce the shot-to-shot line intensity variation as compared to lower particle loadings in the cell. Additional experiments using an aerosol chamber were performed to further quantify the laser absorption by the plasma in dependence on time both with and without the presence of particles. The overall implication of laser-particle interactions for LIBS and LA-ICP-MS/OES are discussed.

Stability of Non-Neutral Plasma Cylinder Consisting of Magnetized Cold Electrons and of Small Density Fraction of Ions Born at Rest: Non-Local Analysis

Science.gov (United States)

Yeliseyev, Y. N.

2009-03-01

The non-local stability problem of the plasma cylinder, filled with "cold" magnetized rigidly rotating electrons, and a small density fraction of ions, is solved. The ions are supposed to be born at rest by ionization of background gas. The study is based on the kinetic description of ions. The equilibrium distribution function, taking into account the peculiarity of ions birth, is used. The radial electric field is caused by space charge of non-neutral plasma. The dispersion equation for plasma eigen frequencies is obtained analytically. It is valid within the total admissible range of values of electric and magnetic fields. Normalized eigen frequencies ω'/Ωi are calculated for the basic azimuth mode m = 1 (ω' = ω-mωi+, ω+ = (-ωci+Ωi)/2, Ωi = (ωci2-4eEr/mir)1/2 is called the "modified" ion cyclotron (MIC) frequency), for the density fraction of ions of atomic nitrogen f = Ni/ne = 0,01 and are presented in graphic form versus parameter 2ωpe2/ωce2. The spectra of oscillations ω'/Ωi consist of the family of electron Trivel-piece—Gould (TG) modes and of the families of MIC modes. The frequencies of MIC modes are located in a small vicinity of harmonics of the MIC frequency Ωi above and below the harmonic. The TG modes in non-neutral plasma fall in the region of MIC frequencies Ωi and interact strongly with MIC modes. The slow TG modes become unstable near the crossings with non-negative harmonics of MIC frequencies. The instabilities have a resonant character. The lowest radial TG mode has a maximum growth rate at crossing with a zero harmonic of Ωi ((Im ω'/Ωi)max≈0,074). The growth rates of MIC modes are much lower ((Im ω'/Ωi)max≲0,002). Their instability has a threshold character. The instabilities of TG and MIC modes take place mainly at the values of parameter 2ωpe2/ωce2, corresponding to strong radial electric fields (ωci2≪|eEr/mir|), in which the ions are unmagnetized. The oscillations of small amplitude are seen on some frequency

Laser propagation and compton scattering in parabolic plasma channel

CERN Document Server

Dongguo, L; Yokoya, K; Hirose, T

2003-01-01

A Gaussian laser beam propagating in a parabolic plasma channel is discussed in this paper. For a weak laser, plasma density perturbation induced by interaction between the laser field and plasma is very small, the refractive index can be assumed to be constant with respect to time variable. For a parabolic plasma channel, through the static propagation equation, we obtain an analytical solution of the profile function of the Gaussian laser beam for an unmatched case and give the general condition for the matched case. As the laser intensity increases, an effect due to strong laser fields is included. We discuss how to design and select the distribution of plasma density for a certain experiment in which a plasma channel is utilized to guide a laser beam. The number of scattered photons (X-rays) generated through Compton backscattering in a plasma channel is discussed. (author)

Plasma Arc Augmented CO2 laser welding

DEFF Research Database (Denmark)

Bagger, Claus; Andersen, Mikkel; Frederiksen, Niels

2001-01-01

In order to reduce the hardness of laser beam welded 2.13 mm medium strength steel CMn 250, a plasma arc has been used simultaneously with a 2.6 kW CO2 laser source. In a number of systematic laboratory tests, the plasma arc current, plasma gas flow and distance to the laser source were varied...... with all laser parameters fixed. The welds were quality assessed and hardness measured transversely to the welding direction in the top, middle and root of the seam. In the seams welded by laser alone, hardness values between 275 and 304 HV1 were measured, about the double of the base material, 150 HV1...

Multipole traps for non-neutral plasmas

International Nuclear Information System (INIS)

Tiouririne, T.N.; Turner, L.; Lau, A.W.C.

1994-01-01

A multipolar generalization of the Penning trap is presented. The case of l=1 is that of standard Penning trap. For the case of a quadrupolar magnetic field, analytic solutions are presented for cold, confined, one-species plasmas with spheroidal or spherical boundaries; for higher l values analytic solutions are given only for spherically bounded plasmas. By virtue of the sheared flow present for solutions with l>1, the classical Brillouin ratio (stored rest energy of particles/stored magnetic energy) of unity is exceeded and attains a global limit of 2 at infinitely high l

Laser-heating of hydrogen plasma

International Nuclear Information System (INIS)

Foeldes, I.B.; Ignacz, P.N.; Kocsis, G.

1990-10-01

The possibility of creating a fully ionized hydrogen plasma to investigate the capture of slow antiprotons is discussed. Laser heating of the initially discharge-created arc or Z-pinch plasma is proposed. Within the framework of a simple 1-dimensional model based on the energy balance equation alone it is shown that plasma equilibrium can be sustained for 10 μs. A simple pulsed CO 2 laser with this pulse duration and an energy of about 10-30 J is sufficient for heating. (author) 16 refs.; 3 figs

Laser-aided plasma diagnostics

NARCIS (Netherlands)

Donne, A. J. H.; Barth, C. J.

2008-01-01

This paper will focus on two types of laser-aided diagnostics: Thomson scattering and laser-induced fluorescence. Thomson scattering is a very powerful diagnostic, which is applied at nearly every magnetic confinement device. Depending on the experimental conditions different plasma parameters can

Experimental study of laser-plasma interaction physics with short laser wavelength

International Nuclear Information System (INIS)

Labaune, C.; Amiranoff, F.; Fabre, E.; Matthieussent, G.; Rousseaux, C.; Baton, S.

1989-01-01

Many non-linear processes can affect laser-plasma coupling in fusion experiments. The interaction processes of interest involve three or more waves, including the incident electromagnetic wave and various selections of electromagnetic, electrostatic and accoustic waves. Whenever plasma waves are involved (stimulated Raman scattering, two-plasmon decay instability, parametric decay instability and others), energetic electrons are created through the various damping processes of these waves: these energetic electrons in turn deleteriously affect the compression phase in laser fusion experiments through pre-heating of the fuel core. Some parametric processes lead primarily to loss of incident laser energy (stimulated Brillouin scattering) while others, such as filamentation, lead to strongly enhanced local laser intensities through the focusing of part (or all) of the laser beam into filaments of very small dimensions with a concomitant expulsion of the plasma out of these regions. So filamentation destroys the uniformity of energy deposition in the plasma and prevents high compression efficiency of the target. These interaction effects are typically of parametric nature, with their thresholds and growth rates depending critically on plasma scale lengths. Since these scale lengths increase with available laser energy and since millimeter sized plasmas are expected from reactor targets which will be used in direct drive implosion experiments, a good understanding of these processes and their saturation mechanisms becomes imperative. We report here the results on absolute energy measurements and time-resolved spectra of SRS and SBS obtained in various types of plasmas where the major changes were the inhomogeneity scale lengths. (author) 7 refs., 7 figs

Interactions between laser and arc plasma during laser-arc hybrid welding of magnesium alloy

Science.gov (United States)

Liu, Liming; Chen, Minghua

2011-09-01

This paper presents the results of the investigation on the interactions between laser and arc plasma during laser-arc hybrid welding on magnesium alloy AZ31B using the spectral diagnose technique. By comparably analyzing the variation in plasma information (the shape, the electron temperature and density) of single tungsten inert gas (TIG) welding with the laser-arc hybrid welding, it is found that the laser affects the arc plasma through the keyhole forming on the workpiece. Depending on the welding parameters there are three kinds of interactions taking place between laser and arc plasma.

Principles of laser-plasma accelerators

International Nuclear Information System (INIS)

Malka, V.; Mora, P.

2009-01-01

The continuing development of powerful laser systems has permitted to extend the interaction of laser beams with matter far into the relativistic domain in which extremely high electric and magnetic fields are generated. Thanks to these tremendous fields, that only plasma can support and sustain, new and compact approaches for producing energetic particle beams have been recently achieved (for example the bubble regime and the colliding laser pulses scheme). The incredible progress of these laser-plasma accelerators has allowed physicists to produce high quality beams of energetic radiation and particles. These beams have interesting properties such as shortness, brightness and spatial quality, and could lend themselves to applications in many fields, including medicine (radiotherapy, proton therapy, imaging), radiation biology (short-time-scale), chemistry (radiolysis), physics and material science (radiography, electron and photon diffraction), security (material inspection), and of course accelerator science. Stimulated by the advent of compact and powerful lasers, with moderate costs and high repetition rate, this research field has witnessed considerable growth in the past few years, and the promises of laser-plasma accelerators are in tremendous progress. The recent years in particular have seen spectacular progress in the acceleration of electrons and of ions, both in terms of energy and in terms of quality of the beams. (authors)

Laser thermonuclear fusion with force confinement of hot plasma

International Nuclear Information System (INIS)

Korobkin, V.V.; Romanovsky, M.Y.

1994-01-01

The possibility of the utilization of laser radiation for plasma heating up to thermonuclear temperatures with its simultaneous confinement by ponderomotive force is investigated. The plasma is located inside a powerful laser beam with a tubelike section or inside a cavity of duct section, formed by several intersecting beams focused by cylindrical lenses. The impact of various physical processes upon plasma confinement is studied and the criteria of plasma confinement and maintaining of plasma temperature are derived. Plasma and laser beam stability is considered. Estimates of laser radiation energy necessary for thermonuclear fusion are presented

Metal surface nitriding by laser induced plasma

Science.gov (United States)

Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

1996-10-01

We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

CFD Modeling of Non-Neutral Atmospheric Boundary Layer Conditions

DEFF Research Database (Denmark)

Koblitz, Tilman

model results. A method is developed how to simulate the time-dependant non-neutral ABL flow over complex terrain: a precursor simulation is used to specify unsteady inlet boundary conditions on complex terrain domains. The advantage of the developed RANS model framework is its general applicability...... characteristics of neutral and non-neutral ABL flow. The developed ABL model significantly improves the predicted flow fields over both flat and complex terrain, when compared against neutral models and measurements....... cost than e.g. using large-eddy simulations. The developed ABL model is successfully validated using a range of different test cases with increasing complexity. Data from several large scale field campaigns, wind tunnel experiments, and previous numerical simulations is presented and compared against...

Tomography of laser fusion plasmas

International Nuclear Information System (INIS)

Ceglio, N.M.

1977-01-01

Experimental programs exist in a number of laboratories throughout the world to test the feasibility of using powerful laser systems to drive the implosion of hydrogen isotope fuel to thermonuclear burn conditions. In a typical experiment multiple laser beams are focused onto a glass microshell (typically 50 μm to 200 μm diameter) filled with an equimolar D-T gas mixture. X-ray and particle emissions from the target provide important information about the hydrodynamic implosion of the glass shell and the associated compression and heating of the D-T fuel. Standard diagnostics for imaging such emissions are the grazing incidence reflection (GIR) x-ray microscope and the pinhole camera. Recently, a particular coded imaging technique, Zone Plate Coded Imaging (ZPCI), has been successfully used for x-ray and particle microscopy of laser fusion plasmas. ZPCI is highly attractive for investigating laser produced plasmas because it possesses a tomographic capability not shared by either the GIR or pinhole imaging techniques. This presentation provides a brief discussion of the tomographic potential of ZPCI. In addition, the first tomographic x-ray images (tomographic resolution approximately 74 μm) of a laser produced plasma are presented

Plasma Science Committee (PLSC) and the Panel on Opportunities in Plasma Science and Technology (OPST)

International Nuclear Information System (INIS)

1993-01-01

The Plasma Science Committee (PLSC) of the National Research Council (NRC) is charged with monitoring the health of the field of plasma science in the United States and identifies and examines both broad and specific issues affecting the field. Regular meetings, teleconferences, briefings from agencies and the scientific community, the formation of study panels to prepare reports, and special symposia are among the mechanisms used by the PLSC to meet its charge. During July 1992, the PLSC sponsored a workshop on nonneutral plasmas in traps. Although no written report on the workshop results, was prepared for public distribution, a summary of highlights was provided to the OPST Subpanel on Nonneutral Plasmas. The PLSC also continued its follow-up briefings and discussions on the results of the results of the report Plasma Processing of materials. Scientific and Technological Opportunities. As a result of these activities, the Committee is now working with the NRC Committee on Atomic, Molecular, and Optical Sciences (CAMOS) to organize a symposium on database needs in plasma processing of materials

The use of laser beams for plasma diagnostics

International Nuclear Information System (INIS)

Gex, J.P.; Jolas, A.; Launspach, J.; Schirmann, D.

1975-01-01

The optical properties of lasers allow them to be a promising source for plasma diagnosis. The Q-switched lasers provide the opportunity to make observations in a very short time interval down to a few picoseconds. The laser space and time coherence properties allow interferometric measurements of plasma electron densities. Thus in the experiments of laser-matter interactions, the radiation obtained by frequency conversion of the Nd: glass laser emission is used for density measurements (up to 10 20 cm -3 ) in small scale plasmas (approximately equal to 1mm). Owing to the monochromaticity and high intensity of the Q-switched laser radiation, density fluctuations and microscopic instabilities of the plasma can be studied by Thompson scattering measurements. Finally, some statistically isotropic media become birefringent under the action of the strong electrical field of the laser beam radiation. This effect can be used for laser pulse duration measurements in a range not exceeding a few picoseconds [fr

Interferometric studies of laser-created plasmas using compact soft x-ray lasers

International Nuclear Information System (INIS)

Dunn, J; Nilsen, J; Moon, S; Keenan, R; Jankowska, E; Maconi, M C; Hammarsten, E C; Filevich, J; Hunter, J R; Smith, R F; Shlyaptsev, V; Rocca, J J

2003-01-01

We summarize results of several successful dense plasma diagnostics experiments realized by combining two different kinds of table-top soft x-ray lasers with an amplitude division interferometer based on diffraction grating beam splitters. In the first set of experiments this robust high throughput diffraction grating interferometer (DGI) was used with a 46.9 nm portable capillary discharge laser to study the dynamics of line focus and point focus laser-created plasmas. The measured electron density profiles, which differ significantly from those expected from a classical expansion, unveil important two-dimensional effects of the dynamics of these plasmas. A second DGI customized to operate in combination with a 14.7 nm Ni-like Pd transient gain laser was used to perform interferometry of line focus laser-created plasmas with picosecond time resolution. These measurements provide valuable new benchmarks for complex hydrodynamic codes and help bring new understanding of the dynamics of dense plasmas. The instrumentation and methodology we describe is scalable to significantly shorter wavelengths, and constitutes a promising scheme for extending interferometry to the study of very dense plasmas such as those investigated for inertial confinement fusion

Laser plasma focus produced in a ring target

International Nuclear Information System (INIS)

Saint-Hilaire, G.; Szili, Z.

1976-01-01

A new geometry for generating a laser-produced plasma is presented. A toroidal mirror is used to focus a CO 2 laser beam on the inside wall of a copper ring target. The plasma produced converges at the center of the ring where an axial plasma focus is formed. High-speed photography shows details of a plasma generated at a distance from the target surface. This new geometry could have important applications in the field of x-ray lasers

Plasma Channel Diagnostic Based on Laser Centroid Oscillations

International Nuclear Information System (INIS)

Gonsalves, Anthony; Nakamura, Kei; Lin, Chen; Osterhoff, Jens; Shiraishi, Satomi; Schroeder, Carl; Geddes, Cameron; Toth, Csaba; Esarey, Eric; Leemans, Wim

2010-01-01

A technique has been developed for measuring the properties of discharge-based plasma channels by monitoring the centroid location of a laser beam exiting the channel as a function of input alignment offset between the laser and the channel. The centroid position of low-intensity ( 14 Wcm -2 ) laser pulses focused at the input of a hydrogen-filled capillary discharge waveguide was scanned and the exit positions recorded to determine the channel shape and depth with an accuracy of a few %. In addition, accurate alignment of the laser beam through the plasma channel can be provided by minimizing laser centroid motion at the channel exit as the channel depth is scanned either by scanning the plasma density or the discharge timing. The improvement in alignment accuracy provided by this technique will be crucial for minimizing electron beam pointing errors in laser plasma accelerators.

Laser--plasma interaction in a theta-pinch geometry

International Nuclear Information System (INIS)

Armstrong, W.T.

1978-06-01

Prompt stimulated Brillouin scatter (SBS) is studied in an experiment wherein a high power, pulsed CO 2 laser irradiates an independently produced, theta-pinch plasma. SBS does not significantly affect laser heating of the plasma. Measurements of density profiles and temperature histories permitted examination of laser refraction, local heating and net absorption. Refractive containment of the CO 2 laser beam by an on-axis density minimum was observed at early times during the laser pulse. However, refractive containment was lost at late times due to the diffusive loss of the density minimum. Classical modeling of the expected heating required ''bleached'' absorption to account for the observed heating. A plasma absorptivity of approximately 46% was inferred from calorimetry measurements at 250 mtorr fill pressure. These results confirm that classical heating and refraction dominated the laser-plasma interaction

Laser surface wakefield in a plasma column

International Nuclear Information System (INIS)

Gorbunov, L.M.; Mora, P.; Ramazashvili, R.R.

2003-01-01

The structure of the wakefield in a plasma column, produced by a short intense laser pulse, propagating through a gas affected by tunneling ionization is investigated. It is shown that besides the usual plasma waves in the bulk part of the plasma column [see Andreev et al., Phys. Plasmas 9, 3999 (2002)], the laser pulse also generates electromagnetic surface waves propagating along the column boundary. The length of the surface wake wave substantially exceeds the length of the plasma wake wave and its electromagnetic field extends far outside the plasma column

Interaction of ultra-short ultra-intense laser pulses with under-dense plasmas; Interaction d'impulsions laser ultra-courtes et ultra-intenses avec des plasmas sous denses

Energy Technology Data Exchange (ETDEWEB)

Solodov, A

2000-12-15

Different aspects of interaction of ultra-short ultra-intense laser pulses with underdense plasmas are studied analytically and numerically. These studies can be interesting for laser-driven electron acceleration in plasma, X-ray lasers, high-order harmonic generation, initial confinement fusion with fast ignition. For numerical simulations a fully-relativistic particle code WAKE was used, developed earlier at Ecole Polytechnique. It was modified during the work on the thesis in the part of simulation of ion motion, test electron motion, diagnostics for the field and plasma. The studies in the thesis cover the problems of photon acceleration in the plasma wake of a short intense laser pulse, phase velocity of the plasma wave in the Self-Modulated Laser Wake-Field Accelerator (SM LWFA), relativistic channeling of laser pulses with duration of the order of a plasma period, ion dynamics in the wake of a short intense laser pulse, plasma wave breaking. Simulation of three experiments on the laser pulse propagation in plasma and electron acceleration were performed. Among the main results of the thesis, it was found that reduction of the plasma wave phase velocity in the SM LWFA is crucial for electron acceleration, only if a plasma channel is used for the laser pulse guiding. Self-similar structures describing relativistic guiding of short laser pulses in plasmas were found and relativistic channeling of initially Gaussian laser pulses of a few plasma periods in duration was demonstrated. It was shown that ponderomotive force of a plasma wake excited by a short laser pulse forms a channel in plasma and plasma wave breaking in the channel was analyzed in detail. Effectiveness of electron acceleration by the laser field and plasma wave was compared and frequency shift of probe laser pulses by the plasma waves was found in conditions relevant to the current experiments. (author)

Tritium-doping enhancement of polystyrene by ultraviolet laser and hydrogen plasma irradiation for laser fusion experiments

Energy Technology Data Exchange (ETDEWEB)

Iwasa, Yuki, E-mail: iwasa-y@ile.osaka-u.ac.jp [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Yamanoi, Kohei; Iwano, Keisuke; Empizo, Melvin John F.; Arikawa, Yasunobu; Fujioka, Shinsuke; Sarukura, Nobuhiko; Shiraga, Hiroyuki; Takagi, Masaru; Norimatsu, Takayoshi; Azechi, Hiroshi [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Noborio, Kazuyuki; Hara, Masanori; Matsuyama, Masao [Hydrogen Isotope Research Center, Organization for Promotion of Research, University of Toyama, 3190 Gofuku, Toyama 930-8555 (Japan)

2016-11-15

Highlights: • Tritium-doped polystyrene films are fabricated by the Wilzbach method with UV laser and hydrogen plasma irradiation. • The 266-nm laser-irradiated, 355-nm laser-irradiated, and hydrogen plasma-irradiated polystyrene films exhibit higher PSL intensities and specific radioactivities than the non-irradiated sample. • Tritium doping by UV laser irradiation can be largely affected by the laser wavelength because of polystyrene’s absorption. • Hydrogen plasma irradiation results to a more uniform doping concentration even at low partial pressure and short irradiation time. • UV laser and plasma irradiations can be utilized to fabricate tritium-doped polystyrene shell targets for future laser fusion experiments. - Abstract: We investigate the tritium-doping enhancement of polystyrene by ultraviolet (UV) laser and hydrogen plasma irradiation. Tritium-doped polystyrene films are fabricated by the Wilzbach method with UV laser and hydrogen plasma. The 266-nm laser-irradiated, 355-nm laser-irradiated, and hydrogen plasma-irradiated polystyrene films exhibit higher PSL intensities and specific radioactivities than the non-irradiated sample. Tritium doping by UV laser irradiation can be largely affected by the laser wavelength because of polystyrene’s absorption. In addition, UV laser irradiation is more localized and concentrated at the spot of laser irradiation, while hydrogen plasma irradiation results to a more uniform doping concentration even at low partial pressure and short irradiation time. Both UV laser and plasma irradiations can nevertheless be utilized to fabricate tritium-doped polystyrene targets for future laser fusion experiments. With a high doping rate and efficiency, a 1% tritium-doped polystyrene shell target having 7.6 × 10{sup 11} Bq g{sup −1} specific radioactivity can be obtained at a short period of time thereby decreasing tritium consumption and safety management costs.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Thresholds of surface plasma formation by the interaction of laser pulses with a metal

Science.gov (United States)

Borets-Pervak, I. Yu; Vorob'ev, V. S.

1995-04-01

An analysis is made of a model of the formation of a surface laser plasma which takes account of the heating and vaporisation of thermally insulated surface microdefects. This model is used in an interpretation of experiments in which such a plasma has been formed by irradiation of a titanium target with microsecond CO2 laser pulses. A comparison with the experimental breakdown intensities is used to calculate the average sizes of microdefects and their concentration: the results are in agreement with the published data. The dependence of the delay time of plasma formation on the total energy in a laser pulse is calculated.

Guiding of laser pulses in plasma waveguides created by linearly-polarized femtosecond laser pulses

OpenAIRE

Lemos, N.; Cardoso, L.; Geada, J.; Figueira, G.; Albert, F.; Dias, J. M.

2018-01-01

We experimentally demonstrate that plasma waveguides produced with ultra-short laser pulses (sub-picosecond) in gas jets are capable of guiding high intensity laser pulses. This scheme has the unique ability of guiding a high-intensity laser pulse in a plasma waveguide created by the same laser system in the very simple and stable experimental setup. A hot plasma column was created by a femtosecond class laser that expands into an on-axis parabolic low density profile suitable to act as a wav...

Staging laser plasma accelerators for increased beam energy

International Nuclear Information System (INIS)

Panasenko, Dmitriy; Shu, Anthony; Schroeder, Carl; Gonsalves, Anthony; Nakamura, Kei; Matlis, Nicholas; Cormier-Michel, Estelle; Plateau, Guillaume; Lin, Chen; Toth, Csaba; Geddes, Cameron; Esarey, Eric; Leemans, Wim

2008-01-01

Staging laser plasma accelerators is an efficient way of mitigating laser pump depletion in laser driven accelerators and necessary for reaching high energies with compact laser systems. The concept of staging includes coupling of additional laser energy and transporting the electron beam from one accelerating module to another. Due to laser damage threshold constraints, in-coupling laser energy with conventional optics requires distances between the accelerating modules of the order of 10m, resulting in decreased average accelerating gradient and complicated e-beam transport. In this paper we use basic scaling laws to show that the total length of future laser plasma accelerators will be determined by staging technology. We also propose using a liquid jet plasma mirror for in-coupling the laser beam and show that it has the potential to reduce distance between stages to the cm-scale.

Plasma Profile Measurements for Laser Fusion Research with the Nike KrF Laser

Science.gov (United States)

Oh, Jaechul; Weaver, J. L.; Serlin, V.; Obenschain, S. P.

2015-11-01

The grid image refractometer of the Nike laser facility (Nike-GIR) has demonstrated the capability of simultaneously measuring electron density (ne) and temperature (Te) profiles of coronal plasma. For laser plasma instability (LPI) research, the first Nike-GIR experiment successfully measured the plasma profiles in density regions up to ne ~ 4 ×1021 cm-3 (22% of the critical density for 248 nm light of Nike) using an ultraviolet probe laser (λp = 263 nm). The probe laser has been recently replaced with a shorter wavelength laser (λp = 213 nm, a 5th harmonic of the Nd:YAG laser) to diagnose a higher density region. The Nike-GIR system is being further extended to measure plasma profiles in the on-going experiment using 135°-separated Nike beam arrays for the cross-beam energy transfer (CBET) studies. We present an overview of the extended Nike-GIR arrangements and a new numerical algorithm to extract self-consistant plasma profiles with the measured quantities. Work supported by DoE/NNSA.

Coupling of laser energy into plasma channels

International Nuclear Information System (INIS)

Dimitrov, D. A.; Giacone, R. E.; Bruhwiler, D. L.; Busby, R.; Cary, J. R.; Geddes, C. G. R.; Esarey, E.; Leemans, W. P.

2007-01-01

Diffractive spreading of a laser pulse imposes severe limitations on the acceleration length and maximum electron energy in the laser wake field accelerator (LWFA). Optical guiding of a laser pulse via plasma channels can extend the laser-plasma interaction distance over many Rayleigh lengths. Energy efficient coupling of laser pulses into and through plasma channels is very important for optimal LWFA performance. Results from simulation parameter studies on channel guiding using the particle-in-cell (PIC) code VORPAL [C. Nieter and J. R. Cary, J. Comput. Phys. 196, 448 (2004)] are presented and discussed. The effects that density ramp length and the position of the laser pulse focus have on coupling into channels are considered. Moreover, the effect of laser energy leakage out of the channel domain and the effects of tunneling ionization of a neutral gas on the guided laser pulse are also investigated. Power spectral diagnostics were developed and used to separate pump depletion from energy leakage. The results of these simulations show that increasing the density ramp length decreases the efficiency of coupling a laser pulse to a channel and increases the energy loss when the pulse is vacuum focused at the channel entrance. Then, large spot size oscillations result in increased energy leakage. To further analyze the coupling, a differential equation is derived for the laser spot size evolution in the plasma density ramp and channel profiles are simulated. From the numerical solution of this equation, the optimal spot size and location for coupling into a plasma channel with a density ramp are determined. This result is confirmed by the PIC simulations. They show that specifying a vacuum focus location of the pulse in front of the top of the density ramp leads to an actual focus at the top of the ramp due to plasma focusing, resulting in reduced spot size oscillations. In this case, the leakage is significantly reduced and is negligibly affected by ramp length

Prospective application of laser plasma propulsion in rocket technology

International Nuclear Information System (INIS)

Lu Xin; Zhang Jie; Li Yingjun

2002-01-01

Interest in laser plasma propulsion is growing intensively. The interaction of high intensity short laser pulses with materials can produce plasma expansion with a velocity of hundreds of km/s. The specific impulse of ablative laser propulsion can be many tens of times greater than that of chemical rockets. The development and potential application of laser plasma propulsion are discussed

CO laser interferometer for REB-plasma experiments

International Nuclear Information System (INIS)

Burmasov, V.S.; Kruglyakov, E.P.

1996-01-01

The Michelson carbon oxide laser interferometer for measuring plasma density in studies on REB-plasma interaction is described. A detail description of the interferometer and CO laser is presented. For a selection of a single wavelength laser operation the CaF 2 prism is applied. A Ge:Au photoconductor at 77 deg K is applied as the detector. The CO laser radiation at λ 5.34 μm coincides with the detector maximum sensitivity (of the order of 1000 V/W). This increases the interferometer sensitivity about ten times with respect to the He-Ne laser (λ = 3.39 μm) used as the source of light. The typical interferogram and time evolution of plasma density obtained at GOL-M device are presented. (author). 3 figs., 5 refs

CO laser interferometer for REB-plasma experiments

Energy Technology Data Exchange (ETDEWEB)

Burmasov, V S; Kruglyakov, E P [Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation)

1997-12-31

The Michelson carbon oxide laser interferometer for measuring plasma density in studies on REB-plasma interaction is described. A detail description of the interferometer and CO laser is presented. For a selection of a single wavelength laser operation the CaF{sub 2} prism is applied. A Ge:Au photoconductor at 77 deg K is applied as the detector. The CO laser radiation at {lambda} 5.34 {mu}m coincides with the detector maximum sensitivity (of the order of 1000 V/W). This increases the interferometer sensitivity about ten times with respect to the He-Ne laser ({lambda} = 3.39 {mu}m) used as the source of light. The typical interferogram and time evolution of plasma density obtained at GOL-M device are presented. (author). 3 figs., 5 refs.

Railgun system using a laser-induced plasma armature

International Nuclear Information System (INIS)

Onozuka, M.; Oda, Y.; Azuma, K.

1996-01-01

Development of an electromagnetic railgun system that utilizes a laser-induced plasma armature formation has been conducted to investigate the application of the railgun system for high-speed pellet injection into fusion plasmas. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. The railgun system successfully accelerated the laser-induced plasma armature by an electromagnetic force that accelerated the pellet. The highest velocity of the solid hydrogen pellets, obtained so far, was 2.6 km/sec using a 2m-long railgun. copyright 1996 American Institute of Physics

Railgun system using a laser-induced plasma armature

Science.gov (United States)

Onozuka, Masanori; Oda, Yasushi; Azuma, Kingo

1996-05-01

Development of an electromagnetic railgun system that utilizes a laser-induced plasma armature formation has been conducted to investigate the application of the railgun system for high-speed pellet injection into fusion plasmas. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. The railgun system successfully accelerated the laser-induced plasma armature by an electromagnetic force that accelerated the pellet. The highest velocity of the solid hydrogen pellets, obtained so far, was 2.6 km/sec using a 2m-long railgun.

Determination of Plasma Screening Effects for Thermonuclear Reactions in Laser-generated Plasmas

Energy Technology Data Exchange (ETDEWEB)

Wu, Yuanbin; Pálffy, Adriana, E-mail: yuanbin.wu@mpi-hd.mpg.de, E-mail: Palffy@mpi-hd.mpg.de [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

2017-03-20

Due to screening effects, nuclear reactions in astrophysical plasmas may behave differently than in the laboratory. The possibility to determine the magnitude of these screening effects in colliding laser-generated plasmas is investigated theoretically, having as a starting point a proposed experimental setup with two laser beams at the Extreme Light Infrastructure facility. A laser pulse interacting with a solid target produces a plasma through the Target Normal Sheath Acceleration scheme, and this rapidly streaming plasma (ion flow) impacts a secondary plasma created by the interaction of a second laser pulse on a gas jet target. We model this scenario here and calculate the reaction events for the astrophysically relevant reaction {sup 13}C({sup 4}He, n ){sup 16}O. We find that it should be experimentally possible to determine the plasma screening enhancement factor for fusion reactions by detecting the difference in reaction events between two scenarios of ion flow interacting with the plasma target and a simple gas target. This provides a way to evaluate nuclear reaction cross-sections in stellar environments and can significantly advance the field of nuclear astrophysics.

Collisional absorption of two laser beams in plasma

International Nuclear Information System (INIS)

Mohan, M.; Acharya, R.

1977-04-01

The collisional absorption of two laser beams is considered by solving the kinetic equation for the plasma electron. Results show that the simultaneous effect of two laser beams on the heating rate is greater as compared with the individual contribution of each laser beam when the two laser beams have a difference of frequencies equal to the plasma frequency

Laser-plasma based electron acceleration studies planned at CAT, Indore

International Nuclear Information System (INIS)

Naik, P.A.; Gupta, P.D.

2005-01-01

The Laser Plasma Division at the Centre for Advanced Technology is engaged in a variety of R and D activities on laser-plasma interaction with special emphasis on laser-matter interaction at ultra-high intensities. An important aspect of our future work is studies in laser-plasma based acceleration using an elaborate infrastructural set-up of ultra-fast laser and plasma diagnostic systems and recently acquired 10 TW, 50 fs Ti: Sapphire laser system. This paper presents outline of the planned studies in this field. (author)

Laser-Plasma Modeling Using PERSEUS Extended-MHD Simulation Code for HED Plasmas

Science.gov (United States)

Hamlin, Nathaniel; Seyler, Charles

2017-10-01

We discuss the use of the PERSEUS extended-MHD simulation code for high-energy-density (HED) plasmas in modeling the influence of Hall and electron inertial physics on laser-plasma interactions. By formulating the extended-MHD equations as a relaxation system in which the current is semi-implicitly time-advanced using the Generalized Ohm's Law, PERSEUS enables modeling of extended-MHD phenomena (Hall and electron inertial physics) without the need to resolve the smallest electron time scales, which would otherwise be computationally prohibitive in HED plasma simulations. We first consider a laser-produced plasma plume pinched by an applied magnetic field parallel to the laser axis in axisymmetric cylindrical geometry, forming a conical shock structure and a jet above the flow convergence. The Hall term produces low-density outer plasma, a helical field structure, flow rotation, and field-aligned current, rendering the shock structure dispersive. We then model a laser-foil interaction by explicitly driving the oscillating laser fields, and examine the essential physics governing the interaction. This work is supported by the National Nuclear Security Administration stewardship sciences academic program under Department of Energy cooperative agreements DE-FOA-0001153 and DE-NA0001836.

Polarization spectroscopy on laser-produced plasmas and Z-pinch plasmas

Energy Technology Data Exchange (ETDEWEB)

Kim, Dong E. [POSTECH, Kyungbuk (Korea); Baronova, Elena O. [RRC Kurchatov Institute, Nuclear Fusion Institute, Moscow (Russian Federation); Jakubowski, Lech [Soltan Institute for Nuclear Studies, Swierk-Otwock (Poland)

2002-08-01

PPS experiments on laser-produced plasmas are reviewed. Polarization is interpreted in terms of the anisotropic velocity distribution of electrons due to non-local transport. The polarization of an x-ray laser, and recent results regarding the recombining plasma are also presented. X-ray polarization spectroscopy experiments on heliumlike ion lines from a vacuum spark and from a plasma focus are presented: in both cases, the resonance line of the heliumlike ions shows polarization in the direction perpendicular to the discharge axis. Two possible interpretations are suggested. (author)

Lasers plasmas and magnetic field

International Nuclear Information System (INIS)

Albertazzi, Bruno

2014-01-01

We studied the coupling between a laser produced plasmas and a magnetic field in two cases: 1) in the context of Inertial Fusion Confinement (ICF), we first studied how magnetic fields are self generated during the interaction between a target and a laser, then 2) to progress in the understanding of the large-scale shaping of astrophysical jets, we studied the influence of an externally applied magnetic field on the dynamics of a laser-produced plasma expanding into vacuum. The first part of this thesis is thus dedicated to a numerical and experimental study of the self generated magnetic fields that are produced following the irradiation of a solid target by a high power laser (having pulse duration in the nanosecond and picosecond regimes). These fields play an important role in the frame of ICF since they influence the dynamics of the electrons produced during the laser-matter interaction, and thus condition the success of ICF experiments. The second part of this thesis is a numerical and experimental study of the influence of an externally applied magnetic field on the morphology of a laser produced plasma freely otherwise expanding into vacuum. This work aims at better understanding the observed large-scale collimation of astrophysical jets which cannot be understood in the frame of existing models. We notably show that a purely axial magnetic field can force an initially isotropic laboratory flow, scaled to be representative of a flow emerging from a Young Star Object, in a re-collimation shock, from which emerges a narrow, well collimated jet. We also show that the plasma heating induced at the re-collimation point could explain the 'puzzling' observations of stationary X ray emission zones embedded within astrophysical jets. (author) [fr

Radiation sources based on laser-plasma interactions

NARCIS (Netherlands)

Jaroszynski, D.A.; Bingham, R.; Brunetti, E.; Ersfeld, B.; Gallacher, J.G.; Geer, van der S.B.; Issac, R.; Jamison, S.P.; Jones, D.; Loos, de M.J.; Lyachev, A.; Pavlov, V.M.; Reitsma, A.J.W.; Saveliev, Y.M.; Vieux, G.; Wiggins, S.M.

2006-01-01

Plasma waves excited by intense laser beams can be harnessed to produce femtosecond duration bunches of electrons with relativistic energies. The very large electrostatic forces of plasma density wakes trailing behind an intense laser pulse provide field potentials capable of accelerating charged

High-energy 4ω probe laser for laser-plasma experiments at Nova

International Nuclear Information System (INIS)

Glenzer, S.H.; Weiland, T.L.; Bower, J.; MacKinnon, A.J.; MacGowan, B.J.

1999-01-01

For the characterization of inertial confinement fusion plasmas, we implemented a high-energy 4ω probe laser at the Nova laser facility. A total energy of >50 J at 4ω, a focal spot size of order 100 μm, and a pointing accuracy of 100 μm was demonstrated for target shots. This laser provides intensities of up to 3x10 14 Wcm -2 and therefore fulfills high-power requirements for laser-plasma interaction experiments. The 4ω probe laser is now routinely used for Thomson scattering. Successful experiments were performed in gas-filled hohlraums at electron densities of n e >2x10 21 cm -3 which represents the highest density plasma so far being diagnosed with Thomson scattering. copyright 1999 American Institute of Physics

Characteristics of plasma plume in fiber laser welding of aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Gao, Ming; Chen, Cong; Hu, Ming; Guo, Lianbo; Wang, Zemin, E-mail: zmwang@mail.hust.edu.cn; Zeng, Xiaoyan

2015-01-30

Highlights: • Spectroscopic properties of fiber laser induced Al plasma plume are measured. • The plume is usually a metal vapor dominated weakly ionized plasma. • The plume is a strongly ionized plasma after laser power is higher than 5 kW. • Plasma shielding effect must be considered after laser power reaches 5 kW. • Plasma shielding effect is dominated by inverse bremsstrahlung absorption. - Abstract: To understand the laser–matter interaction in fiber laser welding of aluminum alloys, the effects of laser power on the characteristics of fiber laser induced plasma plume were studied by emission spectroscopic analysis firstly. The plasma characteristic parameters including electron temperature, electron density, ionization degree, and inverse bremsstrahlung linear absorption coefficient were computed according to the spectral data. It was found that the laser power of 5 kW is a turning point. After the laser power reaches 5 kW, the plume changes from a metal vapor dominated weakly ionized plasma to a strongly ionized plasma. The corresponding phenomena are the dramatic increase of the value of characteristic parameters and the appearance of strong plasma shielding effect. The calculation of effective laser power density demonstrated that the plasma shielding effect is dominated by inverse bremsstrahlung absorption. The finding suggested the plasma shielding effect must be considered in fiber laser welding of aluminum alloys, rather than is ignored as claimed in previous view.

Railgun system using a laser-induced plasma armature

Energy Technology Data Exchange (ETDEWEB)

Onozuka, M.; Oda, Y.; Azuma, K. [Mitsubishi Heavy Industries, Ltd., 3-3-1, Minatomirai, Nishi-ku, Yokohama 220-84 (Japan)

1996-05-01

Development of an electromagnetic railgun system that utilizes a laser-induced plasma armature formation has been conducted to investigate the application of the railgun system for high-speed pellet injection into fusion plasmas. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. The railgun system successfully accelerated the laser-induced plasma armature by an electromagnetic force that accelerated the pellet. The highest velocity of the solid hydrogen pellets, obtained so far, was 2.6 km/sec using a 2m-long railgun. {copyright} {ital 1996 American Institute of Physics.}

Absorption of turbulent laser plasma radiation

International Nuclear Information System (INIS)

Silin, V.P.

1979-02-01

Some theoretical results relating to the interaction of high-power laser radiation with a plasma are presented including the development of a theory of parametric instabilities in an inhomogeneous laser plasma which shows that the size of the spatial region in which the turbulent state develops is comparable with the characteristic dimension of a several-fold fluctuation in the plasma density close to its critical value. The conditions are identified under which parametric turbulence gives an anomalous effective collision frequency substantially greater than the normal electron-ion collision frequency. Even during the build-up of strong parametric turbulence, conditions are found for the development of anomalous dissipation which results in heating of the bulk of the electrons. Under opposite conditions, the dynamic behaviour due to the influence of the ponderomotive forces associated with the p component of the radiation field shows that under slow plasma flow conditions, a considerable proportion of the laser energy absorbed by the plasma is transferred to the fast electrons. Suppression of the Cherenkov mechanism for generation of the fast electron component is observed on transition to fast plasma flow conditions. (author)

Laser-plasma interaction physics for shock ignition

Directory of Open Access Journals (Sweden)

Goyon C.

2013-11-01

Full Text Available In the shock ignition scheme, the ICF target is first compressed with a long (nanosecond pulse before creating a convergent shock with a short (∼100 ps pulse to ignite thermonuclear reactions. This short pulse is typically (∼2.1015–1016 W/cm2 above LPI (Laser Plasma Instabilities thresholds. The plasma is in a regime where the electron temperature is expected to be very high (2–4 keV and the laser coupling to the plasma is not well understood. Emulating LPI in the corona requires large and hot plasmas produced by high-energy lasers. We conducted experiments on the LIL (Ligne d'Integration Laser, 10 kJ at 3ω and the LULI2000 (0.4 kJ at 2ω facilities, to approach these conditions and study absorption and LPI produced by a high intensity beam in preformed plasmas. After introducing the main risks associated with the short pulse propagation, we present the latest experiment we conducted on LPI in relevant conditions for shock ignition.

Soft X-Ray amplification in laser plasmas

International Nuclear Information System (INIS)

Louis-Jacquet, M.

1988-01-01

The principles, experiments and theoretical models of soft x-ray, amplification, produced in laser plasmas, are studied. In the discussion of the principles, the laser plasma medium, the definition of the gain, the population inversions, saturation and superradiance are described. The results concerning recombination and collisional excitation experiments, as well as experimental devices are shown. A complete physical simulation to design and interpret x-ray laser experiments is given. Applications of x-ray lasers in grating production techniques, in contact microscopy and holography are considered

Traveling-wave laser-produced-plasma energy source for photoionization laser pumping and lasers incorporating said

Science.gov (United States)

Sher, Mark H.; Macklin, John J.; Harris, Stephen E.

1989-09-26

A traveling-wave, laser-produced-plasma, energy source used to obtain single-pass gain saturation of a photoionization pumped laser. A cylindrical lens is used to focus a pump laser beam to a long line on a target. Grooves are cut in the target to present a surface near normal to the incident beam and to reduce the area, and hence increase the intensity and efficiency, of plasma formation.

Effect of laser peening with glycerol as plasma confinement layer

Science.gov (United States)

Tsuyama, Miho; Ehara, Naoya; Yamashita, Kazuma; Heya, Manabu; Nakano, Hitoshi

2018-03-01

The effects of controlling the plasma confinement layer on laser peening were investigated by measuring the hardness and residual stress of laser-peened stainless steels. The plasma confinement layer contributes to increasing the pressure of shock waves by suppressing the expansion of the laser-produced plasma. Most previous studies on laser peening have employed water as the plasma confinement layer. In this study, a glycerol solution is used in the context of a large acoustic impedance. It is found that this glycerol solution is superior to water in its ability to confine plasma and that suitable conditions exist for the glycerol solution to act as a plasma confinement layer to achieve efficient laser peening.

Plasma wakefields driven by an incoherent combination of laser pulses: a path towards high-average power laser-plasma accelerators

Energy Technology Data Exchange (ETDEWEB)

Benedetti, C.; Schroeder, C.B.; Esarey, E.; Leemans, W.P.

2014-05-01

he wakefield generated in a plasma by incoherently combining a large number of low energy laser pulses (i.e.,without constraining the pulse phases) is studied analytically and by means of fully-self-consistent particle-in-cell simulations. The structure of the wakefield has been characterized and its amplitude compared with the amplitude of the wake generated by a single (coherent) laser pulse. We show that, in spite of the incoherent nature of the wakefield within the volume occupied by the laser pulses, behind this region the structure of the wakefield can be regular with an amplitude comparable or equal to that obtained from a single pulse with the same energy. Wake generation requires that the incoherent structure in the laser energy density produced by the combined pulses exists on a time scale short compared to the plasma period. Incoherent combination of multiple laser pulses may enable a technologically simpler path to high-repetition rate, high-average power laser-plasma accelerators and associated applications.

Enhanced laser beam coupling to a plasma

International Nuclear Information System (INIS)

Steiger, A.D.; Woods, C.H.

1976-01-01

Density perturbations are induced in a heated plasma by means of a pair of oppositely directed, polarized laser beams of the same frequency. The wavelength of the density perturbations is equal to one half the wavelength of the laser beams. A third laser beam is linearly polarized and directed at the perturbed plasma along a line that is perpendicular to the direction of the two opposed beams. The electric field of the third beam is oriented to lie in the plane containing the three beams. The frequency of the third beam is chosen to cause it to interact resonantly with the plasma density perturbations, thereby efficiently coupling the energy of the third beam to the plasma. 10 claims, 2 figures

Plasma Modes

Science.gov (United States)

Dubin, D. H. E.

This chapter explores several aspects of the linear electrostatic normal modes of oscillation for a single-species non-neutral plasma in a Penning trap. Linearized fluid equations of motion are developed, assuming the plasma is cold but collisionless, which allow derivation of the cold plasma dielectric tensor and the electrostatic wave equation. Upper hybrid and magnetized plasma waves in an infinite uniform plasma are described. The effect of the plasma surface in a bounded plasma system is considered, and the properties of surface plasma waves are characterized. The normal modes of a cylindrical plasma column are discussed, and finally, modes of spheroidal plasmas, and finite temperature effects on the modes, are briefly described.

Diagnostics of laser-produced plasmas

Directory of Open Access Journals (Sweden)

Batani Dimitri

2016-12-01

Full Text Available We present the general challenges of plasma diagnostics for laser-produced plasmas and give a few more detailed examples: spherically bent crystals for X-ray imaging, velocity interferometers (VISAR for shock studies, and proton radiography.

The laser, measuring instrument for plasmas

International Nuclear Information System (INIS)

Anderegg, F.; Behn, R.; Paris, P.J.; Salito, S.A.; Siegrist, M.R.; Weisen, H.

1988-06-01

There are several different and in general complementary methods for the investigation of plasmas. All of them have different characteristics and properties covering a large spectrum of physical measuring techniques. Electromagnetic waves serving as 'thermometers' permit to detect the global behaviour of the plasma as well as that of the particles composing it. One of the advantages of these introspective methods is that it brings information on temporary and local conditions of the domain being interrogated. With the development of micro-wave sources and lasers after the war the principal tools of this type of plasma diagnostics are now available. In this paper the emphasis is on the lasers which are different according to the type of measurement. Their versatility in measuring plasma parameters is largely acknowledged. We illustrate the potential of measuring methods by lasers by means of the research work done at two experimental installations of CRPP. (author) 21 figs., 8 refs

Interaction of ultra-short ultra-intense laser pulses with under-dense plasmas

International Nuclear Information System (INIS)

Solodov, A.

2000-12-01

Different aspects of interaction of ultra-short ultra-intense laser pulses with underdense plasmas are studied analytically and numerically. These studies can be interesting for laser-driven electron acceleration in plasma, X-ray lasers, high-order harmonic generation, initial confinement fusion with fast ignition. For numerical simulations a fully-relativistic particle code WAKE was used, developed earlier at Ecole Polytechnique. It was modified during the work on the thesis in the part of simulation of ion motion, test electron motion, diagnostics for the field and plasma. The studies in the thesis cover the problems of photon acceleration in the plasma wake of a short intense laser pulse, phase velocity of the plasma wave in the Self-Modulated Laser Wake-Field Accelerator (SM LWFA), relativistic channeling of laser pulses with duration of the order of a plasma period, ion dynamics in the wake of a short intense laser pulse, plasma wave breaking. Simulation of three experiments on the laser pulse propagation in plasma and electron acceleration were performed. Among the main results of the thesis, it was found that reduction of the plasma wave phase velocity in the SM LWFA is crucial for electron acceleration, only if a plasma channel is used for the laser pulse guiding. Self-similar structures describing relativistic guiding of short laser pulses in plasmas were found and relativistic channeling of initially Gaussian laser pulses of a few plasma periods in duration was demonstrated. It was shown that ponderomotive force of a plasma wake excited by a short laser pulse forms a channel in plasma and plasma wave breaking in the channel was analyzed in detail. Effectiveness of electron acceleration by the laser field and plasma wave was compared and frequency shift of probe laser pulses by the plasma waves was found in conditions relevant to the current experiments. (author)

Stability Limits and Properties of Dense Nonneutral Plasmas

International Nuclear Information System (INIS)

Pollock, R. E.

2001-01-01

Developed equipment consisted of a high magnetic field solenoid with supporting instrumentation for electron plasma confinement. The solenoid was designed and delivered in year 1. In year 2, it was mapped and the trap was created and commissioned. In parallel, an ongoing program of beam-plasma interaction studies was carried out with a lower field trap developed earlier. The trap was placed in the IUCF Coolor (an intermediate-energy electron-cooled storage ring) and the effects of the beam on the plasma were investigated, including energy and angular momentum transfer. Student projects carried out within the beam-plasma group also included development of a diagnostic with high spatial resolution, and preparation for extension of the beam-plasma interaction study to much lower beam energy. This became the principal group activity during the latter part of the project

Infrared laser scattering system for plasma diagnostics

Energy Technology Data Exchange (ETDEWEB)

Muraoka, K; Hiraki, N; Kawasaki, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1975-05-01

The possibility of observing the collective scattering of infrared laser light from plasmas is discussed in terms of the laser power requirement, the necessary optical system and the detector performance, and is shown to be feasible with the present day techniques to get the ion temperature by means of a CO/sub 2/ laser on theta pinch plasmas. Based on this estimate, the construction of the TEA CO/sub 2/ laser and the preparations of the optical components have been started and some preliminary results of these are described.

Infrared laser scattering system for plasma diagnostics

International Nuclear Information System (INIS)

Muraoka, Katsunori; Hiraki, Naoji; Kawasaki, Shoji

1975-01-01

The possibility of observing the collective scattering of infrared laser light from plasmas is discussed in terms of the laser power requirement, the necessary optical system and the detector performance, and is shown to be feasible with the present day techniques to get the ion temperature by means of a CO 2 laser on theta pinch plasmas. Based on this estimate, the construction of the TEA CO 2 laser and the preparations of the optical components have been started and some preliminary results of these are described. (auth.)

Spectroscopic diagnostics of plasma during laser processing of aluminium

International Nuclear Information System (INIS)

Lober, R; Mazumder, J

2007-01-01

The role of the plasma in laser-metal interaction is of considerable interest due to its influence in the energy transfer mechanism in industrial laser materials processing. A 10 kW CO 2 laser was used to study its interaction with aluminium under an argon environment. The objective was to determine the absorption and refraction of the laser beam through the plasma during the processing of aluminium. Laser processing of aluminium is becoming an important topic for many industries, including the automobile industry. The spectroscopic relative line to continuum method was used to determine the electron temperature distribution within the plasma by investigating the 4158 A Ar I line emission and the continuum adjacent to it. The plasmas are induced in 1.0 atm pure Ar environment over a translating Al target, using f/7 and 10 kW CO 2 laser. Spectroscopic data indicated that the plasma composition and behaviour were Ar-dominated. Experimental results indicated the plasma core temperature to be 14 000-15 300 K over the incident range of laser powers investigated from 5 to 7 kW. It was found that 7.5-29% of the incident laser power was absorbed by the plasma. Cross-section analysis of the melt pools from the Al samples revealed the absence of any key-hole formation and confirmed that the energy transfer mechanism in the targets was conduction dominated for the reported range of experimental data

Spectroscopic diagnostics of plasma during laser processing of aluminium

Science.gov (United States)

Lober, R.; Mazumder, J.

2007-10-01

The role of the plasma in laser-metal interaction is of considerable interest due to its influence in the energy transfer mechanism in industrial laser materials processing. A 10 kW CO2 laser was used to study its interaction with aluminium under an argon environment. The objective was to determine the absorption and refraction of the laser beam through the plasma during the processing of aluminium. Laser processing of aluminium is becoming an important topic for many industries, including the automobile industry. The spectroscopic relative line to continuum method was used to determine the electron temperature distribution within the plasma by investigating the 4158 Å Ar I line emission and the continuum adjacent to it. The plasmas are induced in 1.0 atm pure Ar environment over a translating Al target, using f/7 and 10 kW CO2 laser. Spectroscopic data indicated that the plasma composition and behaviour were Ar-dominated. Experimental results indicated the plasma core temperature to be 14 000-15 300 K over the incident range of laser powers investigated from 5 to 7 kW. It was found that 7.5-29% of the incident laser power was absorbed by the plasma. Cross-section analysis of the melt pools from the Al samples revealed the absence of any key-hole formation and confirmed that the energy transfer mechanism in the targets was conduction dominated for the reported range of experimental data.

Free-electron laser driven by the LBNL laser-plasma accelerator

International Nuclear Information System (INIS)

Schroeder, C.B.; Fawley, W.M.; Gruner, F.; Bakeman, M.; Nakamura, K.; Robinson, K.E.; Toth, Cs.; Esarey, E.; Leemans, W.P.

2008-01-01

A design of a compact free-electron laser (FEL), generating ultra-fast, high-peak flux, XUV pulses is presented. The FEL is driven by ahigh-current, 0.5 GeV electron beam from the Lawrence Berkeley National Laboratory (LBNL) laser-plasma accelerator, whose active acceleration length is only a few centimeters. The proposed ultra-fast source (∼10 fs) would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science. Owing to the high current (>10 kA) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially greater than 10 13 photons/pulse. Devices based both on self-amplified spontaneous emission and high-harmonic generated input seeds, to reduce undulator length and fluctuations, are considered.

Measurements of laser-hole boring into overdense plasmas using x-ray laser refractometry (invited)

International Nuclear Information System (INIS)

Kodama, R.; Takahashi, K.; Tanaka, K.A.; Kato, Y.; Murai, K.; Weber, F.; Barbee, T.W.; DaSilva, L.B.

1999-01-01

We developed a 19.6 nm laser x-ray laser grid-image refractometer (XRL-GIR) to diagnose laser-hole boring into overdense plasmas. The XRL-GIR was optimized to measure two-dimensional electron density perturbation on a scale of a few tens of μm in underdense plasmas. Electron density profiles of laser-produced plasmas were obtained for 10 20 - 10 22 cm -3 with the XRL-GIR and for 10 19 - 10 20 cm -3 from an ultraviolet interferometer, the profiles of which were compared with those from hydrodynamic simulation. By using this XRL-GIR, we directly observed laser channeling into overdense plasmas accompanied by a bow shock wave showing a Mach cone ascribed to supersonic propagation of the channel front. copyright 1999 American Institute of Physics

LASER PLASMA AND LASER APPLICATIONS: Plasma transparency in laser absorption waves in metal capillaries

Science.gov (United States)

Anisimov, V. N.; Kozolupenko, A. P.; Sebrant, A. Yu

1988-12-01

An experimental investigation was made of the plasma transparency to heating radiation in capillaries when absorption waves propagated in these capillaries as a result of interaction with a CO2 laser pulse of 5-μs duration. When the length of the capillary was in excess of 20 mm, total absorption of the radiation by the plasma was observed at air pressures of 1-100 kPa. When the capillary length was 12 mm, a partial recovery of the transparency took place. A comparison was made with the dynamics and recovery of the plasma transparency when breakdown of air took place near the free surface.

Laser-plasma booster for ion post acceleration

Directory of Open Access Journals (Sweden)

Satoh D.

2013-11-01

Full Text Available A remarkable ion energy increase is demonstrated for post acceleration by a laser-plasma booster. An intense short-pulse laser generates a strong current by high-energy electrons accelerated, when this intense short-pulse laser illuminates a plasma target. The strong electric current creates a strong magnetic field along the high-energy electron current in plasma. During the increase phase in the magnetic field, a longitudinal inductive electric field is induced for the forward ion acceleration by the Faraday law. Our 2.5-dimensional particle-in-cell simulations demonstrate a remarkable increase in ion energy by several tens of MeV.

Hydrodynamic simulation of X-UV laser-produced plasmas

International Nuclear Information System (INIS)

Fajardo, M.; Zeitoun, P.; Gauthier, J.C.

2004-01-01

With the construction of novel X-UV sources, such as V-UV FEL's (free-electron lasers), X-UV laser-matter interaction will become available at ultra-high intensities. But even table-top facilities such as X-UV lasers or High Harmonic Generation, are starting to reach intensities high enough to produce dense plasmas. X-UV laser-matter interaction is studied by a 1-dimensional hydrodynamic Lagrangian code with radiative transfer for a range of interesting X-UV sources. Heating is found to be very different for Z=12-14 elements having L-edges around the X-UV laser wavelength. Possible absorption mechanisms were investigated in order to explain this behaviour, and interaction with cold dense matter proved to be dominant. Plasma sensitivity to X-UV laser parameters such as energy, pulse duration, and wavelength was also studied, covering ranges of existing X-UV lasers. We found that X-UV laser-produced plasmas could be studied using table-top lasers, paving the way for future V-UV-FEL high intensity experiments. (authors)

Numerical investigation of three-dimensional single-species plasma equilibria on magnetic surfaces

International Nuclear Information System (INIS)

Lefrancois, Remi G.; Pedersen, Thomas Sunn; Boozer, Allen H.; Kremer, Jason P.

2005-01-01

Presented for the first time are numerical solutions to the three-dimensional nonlinear equilibrium equation for single-species plasmas confined on magnetic surfaces and surrounded by an equipotential boundary. The major-radial shift of such plasmas is found to be outward, qualitatively similar to the Shafranov shift of quasineutral plasmas confined on magnetic surfaces. However, this is the opposite of what occurs in the pure toroidal field equilibria of non-neutral plasmas (i.e., in the absence of magnetic surfaces). The effect of varying the number of Debye lengths in the plasma for the three-dimensional (3D) model is in agreement with previous 2D calculations: the potential varies significantly on magnetic surfaces for plasmas with few Debye lengths (a d ), and tends to be constant on surfaces when many Debye lengths are present (a > or approx. 10λ d ). For the case of a conducting boundary that does not conform to the outer magnetic surface, the plasma is shifted towards the conductor and the potential varies significantly on magnetic surfaces near the plasma edge. Debye shielding effects are clearly demonstrated when a nonuniform bias is applied to the boundary. Computed equilibrium profiles are presented for the Columbia Non-Neutral Torus [T. S. Pedersen, A. H. Boozer, J. P. Kermer, R. Lefrancois, F. Dahlgren, N. Pomphrey, W. Reiersen, and W. Dorland, Fusion Sci. Technol. 46, 200 (2004)], a stellarator designed to confine non-neutral plasmas

Laser-plasma interaction physics in the context of fusion

International Nuclear Information System (INIS)

Labaune, C.; Fuchs, J.; Depierreux, S.; Tikhonchuk, V.T.; Baldis, H.A.; Pesme, D.; Myatt, J.; Huller, S.; Laval, G.; Tikhonchuk, V.T.

2000-01-01

Of vital importance for Inertial Confinement Fusion (ICF) are the understanding and control of the nonlinear processes which can occur during the propagation of the laser pulses through the underdense plasma surrounding the fusion capsule. The control of parametric instabilities has been studied experimentally, using LULI six-beam laser facility, and also theoretically and numerically. New results based on the direct observation of plasma waves with Thomson scattering of a short wavelength probe beam have revealed the occurrence of the Langmuir decay instability. This secondary instability may play an important role in the saturation of stimulated Raman scattering. Another mechanism for inducing the growth of the scattering instabilities is the so-called 'plasma-induced incoherence'. Namely, recent theoretical studies have shown that the propagation of laser beams through the underdense plasma can increase their spatial and temporal incoherence. This plasma-induced beam smoothing can reduce the levels of parametric instabilities. One signature of this process is a large increase of the spectral width of the laser light after propagation through the plasma. Comparison of the experimental results with numerical propagation through the plasma. Comparison of the experimental results with numerical simulations shows an excellent agreement between the observed and calculated time-resolved spectra of the transmitted laser light at various laser intensities. (authors)

Non-Neutralizing Antibodies Directed against HIV and Their Functions

Directory of Open Access Journals (Sweden)

Luzia M. Mayr

2017-11-01

Full Text Available B cells produce a plethora of anti-HIV antibodies (Abs but only few of them exhibit neutralizing activity. This was long considered a profound limitation for the enforcement of humoral immune responses against HIV-1 infection, especially since these neutralizing Abs (nAbs are extremely difficult to induce. However, increasing evidence shows that additional non-neutralizing Abs play a significant role in decreasing the viral load, leading to partial and sometimes even total protection. Mechanisms suspected to participate in protection are numerous. They involve the Fc domain of Abs as well as their Fab part, and consequently the induced Ab isotype will be determinant for their functions, as well as the quantity and quality of the Fc-receptors (FcRs expressed on immune cells. Fc-mediated inhibitory functions, such as Ab-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, aggregation, and even immune activation have been proposed. However, as for nAbs, the non-neutralizing activities are limited to a subset of anti-HIV Abs. An improved in-depth characterization of the Abs displaying these functional responses is required for the development of new vaccination strategies, which aim to selectively trigger the B cells able to induce the right functional Ab combinations both at the right place and at the right time. This review summarizes our current knowledge on non-neutralizing functional inhibitory Abs and discusses the potential benefit of inducing them via vaccination. We also provide new insight into the roles of the FcγR-mediated Ab therapeutics in clinical trials for HIV diseases.

Interaction between laser-produced plasma and guiding magnetic field

International Nuclear Information System (INIS)

Hasegawa, Jun; Takahashi, Kazumasa; Ikeda, Shunsuke; Nakajima, Mitsuo; Horioka, Kazuhiko

2013-01-01

Transportation properties of laser-produced plasma through a guiding magnetic field were examined. A drifting dense plasma produced by a KrF laser was injected into an axisymmetric magnetic field induced by permanent ring magnets. The plasma ion flux in the guiding magnetic field was measured by a Faraday cup at various distances from the laser target. Numerical analyses based on a collective focusing model were performed to simulate plasma particle trajectories and then compared with the experimental results. (author)

Laser produced plasma density measurement by Mach-Zehnder interferometry

International Nuclear Information System (INIS)

Vaziri, A.; Kohanzadeh, Y.; Mosavi, R.K.

1976-06-01

This report describes an optical interferometric method of measuring the refractive index of the laser-produced plasma, giving estimates of its electron density. The plasma is produced by the interaction of a high power pulsed CO 2 laser beam with a solid target in the vacuum. The time varying plasma has a transient electron density. This transient electron density gives rise to a changing plasma refractive index. A Mach-Zehnder ruby laser interferometer is used to measure this refractive index change

Laser plasma acceleration of electrons with multi-PW laser beams in the frame of CILEX

Energy Technology Data Exchange (ETDEWEB)

Cros, B., E-mail: brigitte.cros@u-psud.fr [LPGP, CNRS and Université Paris Sud, Orsay (France); Paradkar, B.S. [LPGP, CNRS and Université Paris Sud, Orsay (France); Davoine, X. [CEA DAM DIF, Arpajon F-91297 (France); Chancé, A. [CEA IRFU-SACM, Gif-Sur-Yvette (France); Desforges, F.G. [LPGP, CNRS and Université Paris Sud, Orsay (France); Dobosz-Dufrénoy, S. [CEA DSM-IRAMIS-SPAM, Gif-sur-Yvette (France); Delerue, N. [LAL, CNRS and Universit Paris Sud, Orsay (France); Ju, J.; Audet, T.L.; Maynard, G. [LPGP, CNRS and Université Paris Sud, Orsay (France); Lobet, M.; Gremillet, L. [CEA DAM DIF, Arpajon F-91297 (France); Mora, P. [CPhT, CNRS and Ecole Polytechnique, Palaiseau (France); Schwindling, J.; Delferrière, O. [CEA IRFU-SACM, Gif-Sur-Yvette (France); Bruni, C.; Rimbault, C.; Vinatier, T. [LAL, CNRS and Universit Paris Sud, Orsay (France); Di Piazza, A. [Max-Planck-Institut für Kernphysik, Heidelberg (Germany); Grech, M. [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, Palaiseau (France); and others

2014-03-11

Laser plasma acceleration of electrons has progressed along with advances in laser technology. It is thus expected that the development in the near-future of multi-PW-class laser and facilities will enable a vast range of scientific opportunities for laser plasma acceleration research. On one hand, high peak powers can be used to explore the extremely high intensity regime of laser wakefield acceleration, producing for example large amounts of electrons in the GeV range or generating high energy photons. On the other hand, the available laser energy can be used in the quasi-linear regime to create accelerating fields in large volumes of plasma and study controlled acceleration in a plasma stage of externally injected relativistic particles, either electrons or positrons. In the frame of the Centre Interdisciplinaire de la Lumière EXtrême (CILEX), the Apollon-10P laser will deliver two beams at the 1 PW and 10 PW levels, in ultra-short (>15fs) pulses, to a target area dedicated to electron acceleration studies, such as the exploration of the non-linear regimes predicted theoretically, or multi-stage laser plasma acceleration.

Simulation of QED effects in ultrahigh intensity laser-plasma interaction

International Nuclear Information System (INIS)

Kostyukov, I.; Nerush, E.

2010-01-01

Complete text of publication follows. Due to an impressive progress in laser technology, laser pulses with peak intensity of nearly 2 x 10 22 W/cm 2 are now available in laboratory. When the matter is irradiated by so intense laser pulses high energy density plasma is produced. Besides of fundamental interest such plasma is the efficient source of particles and radiation with extreme parameters that opens bright perspectives in developments of advanced particle accelerators, next generation of radiation sources, laboratory modelling of astrophysics phenomena etc. Even high laser intensity the radiation reaction and QED effects become important. One of the QED effects, which recently attracts much attention, is the electron-positron plasma creation in strong laser field. The plasma can be produced via electromagnetic cascades: the seeded charged particles is accelerated in the field of counter-propagating laser pulses, then they emit energetic photons, the photons by turn decay in the laser field and create electron-positron pairs. The pair particles accelerated in the laser field produce new generation of the photons and pairs. For self-consistent study of the electron-positron plasma dynamics in the laser field we develop 2D code based on particle-in-cell and Monte-Carlo methods. The electron, positron and photon dynamics as well as evolution of the plasma and laser fields are calculated by PIC technique while photon emission and pair production are calculated by Monte-Carlo method. We simulate pair production in the field of counter-propagating linearly polarized laser pulses. It is shown that for the laser intensity above threshold the plasma production becomes so intense that the laser pulse are strongly absorbed in the plasma. The laser intensity threshold and the rate of laser field absorption are calculated. Acknowledgements. This work has been supported by federal target 'The scientific and scientific-pedagogical personnel of innovation in Russia' and by

Plasma production and heating by a laser TEA-CO2

International Nuclear Information System (INIS)

Goes, L.C.S.; Sudano, J.P.; Rodrigues, N.A.S.

1987-01-01

Preliminary experiments of plasma production and heating by laser irradiation of gases and solid targets have been performed with a laser TEA-CO 2 (1 MW, 80 ns, monomode), developed and built at the IEAv/Laser Laboratory. The laser beam was focused in the interior of a vacuum chamber (100 1) with a base pressure of 10 1 torr, and recolimated by a system of confocal lenses. The breakdown theresholds for nitrogen gas was investigated by varying the laser power, the neutral gas density and the focal lenght of the lenses. Plasma breakdown observed in the range of pressures between 100-720 torr was in good agreement with calculations of cascade ionization theory and classical absorption by inverse-Bremsstrahlung. The laser absorption was inferred by measuring the power transmitted in the presence and absence of plasma. The light emitted by the plasma was detected by a fast photo-diode, indicating that the plasma expansion phase lasted for several microseconds. These investigations have been applied in the development of plasma shutters for laser pulse compression. (author) [pt

QC operator’s nonneutral posture against musculoskeletal disorder’s (MSDs) risks

Science.gov (United States)

Kautsar, F.; Gustopo, D.; Achmadi, F.

2018-04-01

Musculoskeletal disorders refer to a gamut of inflammatory and degenerative disorders aggravated largely by the performance of work. It is the major cause of pain, disability, absenteeism and reduced productivity among workers worldwide. Although it is not fatal, MSDs have the potential to develop into serious injuries in the musculoskeletal system if ignored. QC operators work in nonneutral body posture. This cross-sectional study was condusted in order to investigate correlation between risk assessment results of QEC and body posture calculation of mannequin pro. Statistical analysis was condusted using SPSS version 16.0. Validity test, Reliability test and Regression analysis were conducted to compare the risk assessment output of applied method and nonneutral body posture simulation. All of QEC’s indicator classified as valid and reliable. The result of simple regression anlysis are back (0.3264.32), wrist/hand (4.86 >4.32) and neck (1.298 <4.32). Result of this study shows that there is an influence between nonneutral body posture of the QC operator during work with risk of musculoskeletal disorders. The potential risk of musculoskeletal disorders is in the shoulder/arm and wrist/hand of the QC operator, whereas the back and neck are not affected.

Bernstein modes in a non-neutral plasma column

Science.gov (United States)

Walsh, Daniel; Dubin, Daniel H. E.

2018-05-01

This paper presents theory and numerical calculations of electrostatic Bernstein modes in an inhomogeneous cylindrical plasma column. These modes rely on finite Larmor radius effects to propagate radially across the column until they are reflected when their frequency matches the upper hybrid frequency. This reflection sets up an internal normal mode on the column and also mode-couples to the electrostatic surface cyclotron wave (which allows the normal mode to be excited and observed using external electrodes). Numerical results predicting the mode spectra, using a novel linear Vlasov code on a cylindrical grid, are presented and compared to an analytical Wentzel Kramers Brillouin (WKB) theory. A previous version of the theory [D. H. E. Dubin, Phys. Plasmas 20(4), 042120 (2013)] expanded the plasma response in powers of 1/B, approximating the local upper hybrid frequency, and consequently, its frequency predictions are spuriously shifted with respect to the numerical results presented here. A new version of the WKB theory avoids this approximation using the exact cold fluid plasma response and does a better job of reproducing the numerical frequency spectrum. The effect of multiple ion species on the mode spectrum is also considered, to make contact with experiments that observe cyclotron modes in a multi-species pure ion plasma [M. Affolter et al., Phys. Plasmas 22(5), 055701 (2015)].

Confinement of laser plasma by solenoidal field for laser ion source

International Nuclear Information System (INIS)

Okamura, M.; Kanesue, T.; Kondo, K.; Dabrowski, R.

2010-01-01

A laser ion source can provide high current, highly charged ions with a simple structure. However, it was not easy to control the ion pulse width. To provide a longer ion beam pulse, the plasma drift length, which is the distance between laser target and extraction point, has to be extended and as a result the plasma is diluted severely. Previously, we applied a solenoid field to prevent reduction of ion density at the extraction point. Although a current enhancement by a solenoid field was observed, plasma behavior after a solenoid magnet was unclear because plasma behavior can be different from usual ion beam dynamics. We measured a transverse ion distribution along the beam axis to understand plasma motion in the presence of a solenoid field.

Diagnostics of ytterbium/aluminium laser plasmas

International Nuclear Information System (INIS)

Bailey, J.; Lee, R.W.; Landen, O.L.; Kilkenny, J.D.; Lewis, C.L.; Busquet, M.

1986-11-01

Microdot spectroscopy was used to study the x-ray emission from laser-produced plasmas consisting of 10% ytterbium, 90% aluminium. Spectra were recorded with a space-resolving flat crystal (PET) mini-spectrometer in the 4.0-8.0 A range. The Janus research laser at LLNL irradiated the targets with green (0.53 μm) light in a 1 nsec pulse. The power density was varied between 4x10 13 and 3x10 14 W/cm 2 . The plasma electron density and temperature were determined from the aluminium XI, XII and XIII line emission. By examining correlations between changes in the plasma conditions with changes in the ytterbium spectra, we will determine the potential for using ytterbium line emission as a plasma diagnostic

Three dimensional imaging technique for laser-plasma diagnostics

International Nuclear Information System (INIS)

Jiang Shaoen; Zheng Zhijian; Liu Zhongli

2001-01-01

A CT technique for laser-plasma diagnostic and a three-dimensional (3D) image reconstruction program (CT3D) have been developed. The 3D images of the laser-plasma are reconstructed by using a multiplication algebraic reconstruction technique (MART) from five pinhole camera images obtained along different sight directions. The technique has been used to measure the three-dimensional distribution of X-ray of laser-plasma experiments in Xingguang II device, and the good results are obtained. This shows that a CT technique can be applied to ICF experiments

Three dimensional imaging technique for laser-plasma diagnostics

Energy Technology Data Exchange (ETDEWEB)

Shaoen, Jiang; Zhijian, Zheng; Zhongli, Liu [China Academy of Engineering Physics, Chengdu (China)

2001-04-01

A CT technique for laser-plasma diagnostic and a three-dimensional (3D) image reconstruction program (CT3D) have been developed. The 3D images of the laser-plasma are reconstructed by using a multiplication algebraic reconstruction technique (MART) from five pinhole camera images obtained along different sight directions. The technique has been used to measure the three-dimensional distribution of X-ray of laser-plasma experiments in Xingguang II device, and the good results are obtained. This shows that a CT technique can be applied to ICF experiments.

Characteristics of X-ray photons in tilted incident laser-produced plasma

International Nuclear Information System (INIS)

Wang Ruirong; Chen Weimin; Xie Dongzhu

2008-01-01

Characteristics of X-ray and spout direction of heat plasma flow were studied on Shenguang-II laser facility. Using of pinhole X-ray camera, X-ray photons from the plasma of aluminum (Al) irradiated by 1.053 μm laser, was measured and analysed. It is observed that the spatial distribution of X-ray photons in Al plasma for tilted irradiation is symmetic at the center of the target. The spout direction of heat plasma flow is inferred by the distribution contour of X-ray photons. the experimental results show that the spout direction of heat plasma flow is normal to target plane and the output intensity of X-ray photons does not increase significantly for tilted laser incidence. Uniformity of laser energy deposition is improved by superposing tilted incident and laser perpendicularly incident laser. At the same time, it is found that the conversion efficiency from the tilted incident laser energy to X-ray photons of laser-produced plasma is decreased. (authors)

Dynamics of intense laser channel formation in an underdense plasma

International Nuclear Information System (INIS)

Davis, J.; Petrov, G.M.; Velikovich, A.L.

2005-01-01

Efficient guiding and propagation of multi-keV x-rays in plasmas can be achieved by dynamically modifying the media through plasma channel formation. The dynamics of plasma channel formation is studied in preformed underdense plasma irradiated by a high intensity laser. This is done by a two-dimensional model coupling laser propagation to a relativistic particle-in-cell model. For laser intensity of 10 20 W/cm 2 and a laser beam width of 5 μm the channel formation proceeds on a time scale of 60-70 fs in uniform plasma with density 10 18 cm -3 . The channel closes shortly after the rear of the laser pulse has passed due to Coulomb attraction from the ion core. Electron cavitation occurs only if the laser intensity is above a certain threshold intensity and the laser pulse duration exceeds 100 fs. X-ray generation and propagation is feasible for ultrarelativistic laser pulses with small beam width, less than ∼20 μm, and duration of more than 100 fs

Topics in high-intensity laser plasma interaction

International Nuclear Information System (INIS)

Leemans, W.P.

1991-01-01

The interaction of high intensity laser pulses with pre-formed and laser-produced plasmas is studied. Through experiments and simulations we have investigated stimulated Compton scattering in preformed plasmas and the plasma physics aspects of tunnel-ionized gases. A theoretical study is presented on the nonlinear dynamics of relativistic plasma waves driven by colinear optical mixing. The electron density-fluctuation spectra induced by stimulated Compton scattering have been directly observed for the first time. A CO2 laser was focused into pre-formed plasmas with densities n(e) varied from 0.4-6 x 10(exp 16) cu cm. The fluctuations corresponding to backscatter were probed using Thomson scattering. At low n(e), the scattered spectra peak at a frequency shift Delta omega is approximately kv e and appears to be in a linear regime. At the highest n(e), a nonlinear saturation of the SCS instability is observed due to a self-induced perturbation of the electron distribution function. Tunnel-ionized plasmas have been studied through experiments and particle simulations. Experimentally, qualitative evidence for plasma temperature control by varying the laser polarization was obtained by the measurement of stimulated Compton scattering fluctuation spectra and x-ray emission from such plasmas. A higher parallel temperature than expected from the single-particle tunneling model was observed. Simulations indicate that stochastic heating and the Weibel instability play an important role in plasma heating in all directions and isotropization. The non-linear dynamics associated with beatwave (Delta omega, Delta k) excited long wavelength plasma waves in the presence of strong, short wavelength density ripple have been examined, using the relativistic Lagrangian oscillator model. This model shows period doubling that roughly follows Feigenbaum scaling, and a transition to chaos

Plasma wave amplitude measurement created by guided laser wakefield

International Nuclear Information System (INIS)

Wojda, Franck

2010-01-01

The interaction of an intense laser pulse of short duration with a plasma produces a plasma wave with large amplitude in its wake, which is associated with a longitudinal electric field. It can be used to accelerate relativistic electrons injected into the wave to energies in the GeV range over distances of the order of a few centimeters, short compared to acceleration lengths in conventional accelerators. The control of the electron beam characteristics during the acceleration process is fundamental for achieving a usable laser-plasma acceleration stage. The main result of this thesis is the creation and characterization of a plasma wave in a weakly nonlinear regime over a length of several centimeters. Capillary tubes are used to guide the laser beam over these distances, while maintaining a large enough intensity (∼ 10 17 W/cm 2 ). The guided laser beam ionizes the gas in the tube and creates the plasma wave. A diagnostic based on the modification of the laser pulse spectrum was used to determine the amplitude of the plasma wave along the tube. The amplitude of the plasma wave was studied as a function of gas filling pressure, length of the capillary and laser energy. Experimental results are compared; they are in excellent agreement with analytical results and modeling. They show that the electric field associated with the plasma wave is between 1 and 10 GV/m over a length of up to 8 cm. This work has demonstrated the ability to create a controlled plasma wave in a weakly nonlinear regime. (author)

Qualitative analysis of plasma created by shock laser

International Nuclear Information System (INIS)

Grevey, D.; Maiffredy, L.; Vannes, A.B.; Gobin, P.F.

1987-01-01

The origin of effects observed of the surface of metals treated by lasers was studied. High speed cinematography (20,000 frames/sec) was used to follow the evolution of plasma shape from start to finish. An Nd glass laser and FeNi targets were used. The irradiated surface was examined using optical and scanning electron-microscopes. The phenomenology of plasma formation, and plasma expansion are summarized. Liquid spattering and concentric waves on the target surface are revealed. Results suggest that the main agent of the effects in laser-target interactions is the plasma, which creates compression waves inside the target. These waves quickly become a shock wave which can modify the microstructure of the target [fr

Measurement of Debye length in laser-produced plasma.

Science.gov (United States)

Ehler, W.

1973-01-01

The Debye length of an expanded plasma created by placing an evacuated chamber with an entrance slit in the path of a freely expanding laser produced plasma was measured, using the slab geometry. An independent measurement of electron density together with the observed value for the Debye length also provided a means for evaluating the plasma electron temperature. This temperature has applications in ascertaining plasma conductivity and magnetic field necessary for confinement of the laser produced plasma. Also, the temperature obtained would be useful in analyzing electron-ion recombination rates in the expanded plasma and the dynamics of the cooling process of the plasma expansion.

179th International School of Physics "Enrico Fermi" : Laser-Plasma Acceleration

CERN Document Server

Gizzi, L A; Faccini, R

2012-01-01

Impressive progress has been made in the field of laser-plasma acceleration in the last decade, with outstanding achievements from both experimental and theoretical viewpoints. Closely exploiting the development of ultra-intense, ultrashort pulse lasers, laser-plasma acceleration has developed rapidly, achieving accelerating gradients of the order of tens of GeV/m, and making the prospect of miniature accelerators a more realistic possibility. This book presents the lectures delivered at the Enrico Fermi International School of Physics and summer school: "Laser-Plasma Acceleration" , held in Varenna, Italy, in June 2011. The school provided an opportunity for young scientists to experience the best from the worlds of laser-plasma and accelerator physics, with intensive training and hands-on opportunities related to key aspects of laser-plasma acceleration. Subjects covered include: the secrets of lasers; the power of numerical simulations; beam dynamics; and the elusive world of laboratory plasmas. The object...

Laser-aided diagnostics of plasmas and gases

CERN Document Server

Muraoka, K

2000-01-01

Updated and expanded from the original Japanese edition, Laser-Aided Diagnostics of Gases and Plasmas takes a unique approach in treating laser-aided diagnostics. The book unifies the subject by joining applications instead of describing each application as a totally separate system. In taking this approach, it highlights the relative strengths of each method and shows how they can complement each other in the study of gases and plasmas.The first part of the book presents a general introduction to the laser-aided study of gases and plasmas, including the various principles and hardware needed for each method, while the second part describes the applications of each general system in detail.Beneficial to a wide spectrum of academic and industrial researchers, this book provides a solid examination of the various options and methods available when involved in the analysis and diagnostics of gases and plasmas.

Magnetic confinement of laser produced LiH plasma in LITE

International Nuclear Information System (INIS)

Ard, W.B.; Stufflebeam, J.H.; Tomlinson, R.G.

1976-01-01

In the LITE experiment, a hot, dense plasma produced by laser heating of an approximately 100 μ dia LiH particle is used to fill a minimum-B baseball coil mirror magnetic containment field. The confined laser produced plasma subsequently serves as the target for an energetic neutral hydrogen beam in experiments to investigate the target plasma buildup approach for creating and sustaining an equilibrium, steady state mirror fusion plasma. In the experiments, the LiH particle is positioned in vacuum at the laser beam focus by a feedback particle suspension system and heated by two sided irradiation with the focused dual beam, 50 j, 7 nsec output of a Q-switched Nd-glass laser. The energy density of the laser produced plasma is initially much greater than that of the surrounding magnetic field and the plasma expands, converting its internal energy into expansion kinetic energy and displacement of the magnetic field. As the energy density falls below that of the magnetic field, the expansion is stopped and the plasma becomes trapped, making the transition to a low beta, mirror confined plasma. This report is concerned with the properties and behavior of the plasma in the confinement stage

Research on imploded plasma heating by short pulse laser for fast ignition

International Nuclear Information System (INIS)

Kodama, R.; Kitagawa, Y.; Mima, K.

2001-01-01

Since the peta watt module (PWM) laser was constructed in 1995, investigated are heating processes of imploded plasmas by intense short pulse lasers. In order to heat the dense plasma locally, a heating laser pulse should be guided into compressed plasmas as deeply as possible. Since the last IAEA Fusion Conference, the feasibility of fast ignition has been investigated by using the short pulse GEKKO MII glass laser and the PWM laser with GEKKO XII laser. We found that relativistic electrons are generated efficiently in a preformed plasma to heat dense plasmas. The coupling efficiency of short pulse laser energy to a solid density plasma is 40% when no plasmas are pre-formed, and 20% when a large scale plasma is formed by a long pulse laser pre-irradiation. The experimental results are confirmed by numerical simulations using the simulation code 'MONET' which stands for the Monte-Carlo Electron Transport code developed at Osaka. In the GEKKO XII and PWM laser experiments, intense heating pulses are injected into imploded plasmas. As a result of the injection of heating pulse, it is found that high energy electrons and ions could penetrate into imploded core plasmas to enhance neutron yield by factor 3∼5. (author)

Hose-Modulation Instability of Laser Pulses in Plasmas

International Nuclear Information System (INIS)

Sprangle, P.; Krall, J.; Esarey, E.

1994-01-01

A laser pulse propagating in a uniform plasma or a preformed plasma density channel is found to undergo a combination of hose and modulation instabilities, provided the pulse centroid has an initial tilt. Coupled equations for the laser centroid and envelope are derived and solved for a finite-length laser pulse. Significant coupling between the centroid and the envelope, harmonic generation in the envelope, and strong modification of the wake field can occur. Methods to reduce the growth rate of the laser hose instability are demonstrated

Effect of laser spot size on energy balance in laser induced plasmas

International Nuclear Information System (INIS)

Pant, H.C.; Sharma, S.; Bhawalkar, D.D.

1980-01-01

The effect of the laser spot size on laser light absorption in laser induced plasmas from solid targets was studied. It was found that at a constant laser intensity on the target, reduction in the laser spot size enhances the net laser energy absorption. It was also observed that the laser light reflection from the target becomes more diffused when the focal spot size is reduced

Paul trap experiment to simulate intense nonneutral beam propagation through a periodic focusing field configuration

CERN Document Server

Davidson, R C; Majeski, R; Qin, H; Shvets, G

2001-01-01

This paper describes the design concept for a compact Paul trap experimental configuration that fully simulates the collective processes and nonlinear transverse dynamics of an intense charged particle beam that propagates over large distances through a periodic quadrupole magnetic field. To summarize, a long nonneutral plasma column (L>=r sub p) is confined axially by applied DC voltages V[circ]=const. on end cylinders at z=+-L, and transverse confinement is provided by segmented cylindrical electrodes (at radius r sub w) with applied oscillatory voltages +-V sub 0 (t) over 90 deg. segments. Because the transverse focusing force is similar in waveform to that produced by a discrete set of periodic quadrupole magnets in a frame moving with the beam, the Paul trap configuration offers the possibility of simulating intense beam propagation in a compact experimental facility. The nominal operating parameters in the experimental design are: barium ions (A=137); plasma column length 2L=2 m; wall radius r sub w =10...

Electron acceleration by femtosecond laser interaction with micro-structured plasmas

Science.gov (United States)

Goers, Andy James

Laser-driven accelerators are a promising and compact alternative to RF accelerator technology for generating relativistic electron bunches for medical, scientific, and security applications. This dissertation presents three experiments using structured plasmas designed to advance the state of the art in laser-based electron accelerators, with the goal of reducing the energy of the drive laser pulse and enabling higher repetition rate operation with current laser technology. First, electron acceleration by intense femtosecond laser pulses in He-like nitrogen plasma waveguides is demonstrated. Second, significant progress toward a proof of concept realization of quasi-phasematched direct acceleration (QPM-DLA) is presented. Finally, a laser wakefield accelerator at very high plasma density is studied, enabling relativistic electron beam generation with ˜10 mJ pulse energies. Major results from these experiments include: • Acceleration of electrons up to 120 MeV from an ionization injected wakefield accelerator driven in a 1.5 mm long He-like nitrogen plasma waveguide • Guiding of an intense, quasi-radially polarized femtosecond laser pulse in a 1 cm plasma waveguide. This pulse provides a strong drive field for the QPM-DLA concept. • Wakefield acceleration of electrons up to ˜10 MeV with sub-terawatt, ˜10 mJ pulses interacting with a thin (˜200 mum), high density (>1020 cm-3) plasma. • Observation of an intense, coherent, broadband wave breaking radiation flash from a high plasma density laser wakefield accelerator. The flash radiates > 1% of the drive laser pulse energy in a bandwidth consistent with half-cycle (˜1 fs) emission from violent unidirectional acceleration of electron bunches from rest. These results open the way to high repetition rate (>˜kHz) laser-driven generation of relativistic electron beams with existing laser technology.

Coherent nonlinear backscattering by laser-plasma interactions

International Nuclear Information System (INIS)

Anderson, D.; Wilhelmsson, H.

1974-01-01

A theoretical analysis is carried out for the problem of coherent nonlinear backscattering of laser radiation by a high density plasma. A number of effects of direct interest to the DT-pellet fusion research is investigated. A simple physical description is introduced, which relies on a nonlinear potential formulation of the scattering equations. The simplicity and the unified nature of the approach enables one to evaluate and compare the influence on the radiation reflectivity of different effects, such as e.g. inhomogeneities, blow-off velocities, temperature gradients, laser band width and relativistic oscillatory velocities. The understanding of the role played by the various phenomena has consequently improved and it is thought that this approach should be useful for the interpretation of laser-plasma data obtained by computer simulation or laboratory experiments. The results may also be utilized to estimate how and to what extent one may avoid undesired anomalous reflection when planning new laser-plasma devices. (Auth.)

Laser-heated emissive plasma probe.

Science.gov (United States)

Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K

2008-08-01

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.

Laser-heated emissive plasma probe

International Nuclear Information System (INIS)

Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K.

2008-01-01

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge

Laser-heated emissive plasma probe

Science.gov (United States)

Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K.

2008-08-01

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808nm wavelength and an output power up to 50W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.

The interaction of intense subpicosecond laser pulses with underdense plasmas

Energy Technology Data Exchange (ETDEWEB)

Coverdale, Christine Ann [Univ. of California, Davis, CA (United States)

1995-05-11

Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10¹⁶ W/cm² laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L_plasma ≥ 2L_Rayleigh > cτ. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n_o ≤ 0.05n_cr). Specifically, the parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in ω-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered.

Precedent Research on Compact Laser-plasma based Gantry for Cancer Therapy

International Nuclear Information System (INIS)

Hee, Park Seong; Jeong, Young Uk; Lee, Ki Tae; Kim, Kyung Nam; Cha, Young Ho

2012-03-01

This is the precedent R and D to develop the technology of next generation compact particle cancer treatment system based on laser-plasma interaction and to deduce a big project. The subject of this project are the survey of application technology of laser-plasma based particle beam and the design of compact laser-plasma based gantry. The survey of characteristic of particle beam for cancer therapy and present status can be adapted to develop new system. The comparison between particle beams from the existing system and new one based on laser-plasma acceleration will be important to new design and design optimization. The project includes design of multi-dimensional laser transfer beamline, minimization of laser-plasma acceleration chamber, design of effective energy separation/selection system, and radiation safety and local shielding

Diagnosing high density, fast-evolving plasmas using x-ray lasers

International Nuclear Information System (INIS)

Cauble, R.; Da Silva, L.B.; Barbee, T.W. Jr.

1994-09-01

As x-ray laser (XRL) research has matured, it has become possible to reliably utilize XRLs for applications in the laboratory. Laser coherence, high brightness and short pulse duration all make the XRL a unique tool for the diagnosis of laboratory plasmas. The high brightness of XRLs makes them well-suited for imaging and for interferometry when used in conjunction with multilayer mirrors and beamsplitters. We have utilized a soft x-ray laser in such an imaging system to examine laser-produced plasmas using radiography, moire deflectometry, and interferometry. Radiography experiments yield 100-200 ps snapshots of laser driven foils at a resolution of 1-2 μm. Moire deflectometry with an XRL has been used to probe plasmas at higher density than by optical means. Interferograms, which allow direct measurement of electron density in laser plasmas, have been obtained with this system

Study of laser plasma interactions in the relativistic regime

International Nuclear Information System (INIS)

Umstadter, D.

1997-01-01

We discuss the first experimental demonstration of electron acceleration by a laser wakefield over instances greater than a Rayleigh range (or the distance a laser normally propagates in vacuum). A self-modulated laser wakefield plasma wave is shown to have a field gradient that exceeds that of an RF linac by four orders of magnitude (E => 200 GV/m) and accelerates electrons with over 1-nC of charge per bunch in a beam with space-charge-limited emittance (1 mm-mrad). Above a laser power threshold, a plasma channel, created by the intense ultrashort laser pulse (I approx. 4 x1018 W/CM2, gamma = 1 micron, r = 400 fs), was found to increase the laser propagation distance, decrease the electron beam divergence, and increase the electron energy. The plasma wave, directly measured with coherent Thomson scattering is shown to damp-due to beam loading-in a duration of 1.5 ps or approx. 100 plasma periods. These results may have important implications for the proposed fast ignitor concept

Hybrid 3D model for the interaction of plasma thruster plumes with nearby objects

Science.gov (United States)

Cichocki, Filippo; Domínguez-Vázquez, Adrián; Merino, Mario; Ahedo, Eduardo

2017-12-01

This paper presents a hybrid particle-in-cell (PIC) fluid approach to model the interaction of a plasma plume with a spacecraft and/or any nearby object. Ions and neutrals are modeled with a PIC approach, while electrons are treated as a fluid. After a first iteration of the code, the domain is split into quasineutral and non-neutral regions, based on non-neutrality criteria, such as the relative charge density and the Debye length-to-cell size ratio. At the material boundaries of the former quasineutral region, a dedicated algorithm ensures that the Bohm condition is met. In the latter non-neutral regions, the electron density and electric potential are obtained by solving the coupled electron momentum balance and Poisson equations. Boundary conditions for both the electric current and potential are finally obtained with a plasma sheath sub-code and an equivalent circuit model. The hybrid code is validated by applying it to a typical plasma plume-spacecraft interaction scenario, and the physics and capabilities of the model are finally discussed.

[Study of enhancement effect of laser-induced crater on plasma radiation].

Science.gov (United States)

Chen, Jin-Zhong; Zhang, Xiao-Ping; Guo, Qing-Lin; Su, Hong-Xin; Li, Guang

2009-02-01

Single pulses exported from high-energy neodymium glass laser were used to act on the same position of soil sample surface repeatedly, and the plasma emission spectra generated from sequential laser pulse action were collected by spectral recording system. The experimental results show that the laser-induced soil plasma radiation was enhanced continuously under the confinement effect of the crater walls, and the line intensities and signal-to-background ratios both had different improvements along with increasing the number of acting pulses. The photographs of the plasma image and crater appearance were taken to study the plasma shape, laser-induced crater appearance, and the mass of the ablated sample. The internal mechanism behind that laser-induced crater enhanced plasma radiation was researched. Under the sequential laser pulse action, the forming plasma as a result enlarges gradually first, leading to distortion at the trail of plasma plume, and then, its volume diminishes slowly. And also, the color of the plasma changes from buff to white gradually, which implies that the temperature increases constantly. The laser-induced crater had a regular shape, that is, the diameter increased from its bottom to top gradually, thus forming a taper. The mass of the laser-ablated substance descends along with increasing the amount of action pulse. Atomization degree of vaporized substance was improved in virtue of the crater confinement effect, Fresnel absorption produced from the crater walls reflection, and the inverse bremsstrahlung, and the plasma radiation intensity was enhanced as a result.

Plasma conditions for non-Maxwellian electron distributions in high current discharges and laser-produced plasmas

International Nuclear Information System (INIS)

Whitney, K.G.; Pulsifer, P.E.

1993-01-01

Results from the standard quasilinear theory of ion-acoustic and Langmuir plasma microturbulence are incorporated into the kinetic theory of the electron distribution function. The theory is then applied to high current discharges and laser-produced plasmas, where either the current flow or the nonlinear laser-light absorption acts, respectively, as the energy source for the microturbulence. More specifically, the theory is applied to a selenium plasma, whose charge state is determined under conditions of collisional-radiative equilibrium, and plasma conditions are found under which microturbulence strongly influences the electron kinetics. In selenium, we show that this influence extends over a wide range of plasma conditions. For ion-acoustic turbulence, a criterion is derived, analogous to one previously obtained for laser heated plasmas, that predicts when Ohmic heating dominates over electron-electron collisions. This dominance leads to the generation of electron distributions with reduced high-energy tails relative to a Maxwellian distribution of the same temperature. Ion-acoustic turbulence lowers the current requirements needed to generate these distributions. When the laser heating criterion is rederived with ion-acoustic turbulence included in the theory, a similar reduction in the laser intensity needed to produce non-Maxwellian distributions is found. Thus we show that ion-acoustic turbulence uniformly (i.e., by the same numerical factor) reduces the electrical and heat conductivities, as well as the current (squared) and laser intensity levels needed to drive the plasma into non-Maxwellian states

7. Lasers and plasmas forum - ILP 2015 Forum. Book of abstracts

International Nuclear Information System (INIS)

Mora, P.; Le Marec, A.; Ferri, S.; Corde, S.; Ceccotti, T.; Dozieres, M.; Pariente, G.; Azamoum, Y.; Cheriaux, G.; Baccou, C.; Romagnani, L.; Ravasio, A.; Masson-Laborde, P.E.; Laffite, S.; Neuville, C.; Casner, A.; Debayle, A.; Lobet, M.; Cosse, P.; Falize, E.; Taieb, R.; Rozmus, W.; Colaitis, A.; Boutoux, G.; Llor Aisa, E.; Ducret, J.E.; Le Pennec, M.; Barbrel, B.; Rouan, D.; Smets, R.; Seisson, G.; Boyer, S.; Massacrier, G.; Harmand, M.; Jacquemot, S.; Adam, J.C.; Boutoux, G.; Busquet, M.; Bychenkov, V. Yu.; Castan, A.; Chatagnier, A.; Chiaramello, M.; Debayle, A.; Deschaud, Basil; Do, A.; Fedeli, L.; Ferri, J.; Gangolf, T.; Gilles, D.; Vallet, A.; D'Humieres, E.; Khiar, B.; Grassi, A.; Hadj-Bachir, M.; Lee, P.; Lobet, M.; Loiseau, P.; Maitrallain, A.; Masson-Laborde, P.E.; Mollica, F.; Moreau, J.G.; Nicolas, Loic; Pain, J.-C.; Penninckx, D.; Riconda, C.; Ruyer, C.; Soleilhac, A.; Van Box Som, L.

2015-06-01

List of oral presentation abstracts: Effect of XUV lasers partial coherence on the characterization of their spectral properties; Study of ionization potential lowering and other statistical properties of coupled plasmas using numerical simulation and classical molecular dynamics; Plasma acceleration by particle beam; Electron acceleration by surface wave resonant excitation in relativistic regime; Optimization of a laser-generated X Ka source (Ti:Sa 10 TW - 100 Hz); Apollon 10 PW: description and status; The future of the research federation and of power laser facilities; Inertial confinement fusion and operation of 'rugby'-shape hohlraums; Chronometry and efficiency of direct attack implosion at OMEGA facility; Laser-plasma interaction physics in beam crossing configuration; NIF Discovery Science experiments for the study of the strongly nonlinear regime of the ablative Rayleigh-Taylor instability; X opacity measurements in mid-Z dense plasmas with a new target design of indirect heating; Photoionization dynamics: Transition and scattering delays; Ion acceleration induced by laser-produced electrostatic shocks; Electron Transport and Related Non-equilibrium Distribution Functions in Hot Large Scale ICF Plasmas; Rate optimization of neutron-less fusion reactions initiated by laser-accelerated protons; Nonlinear laser-plasma interactions modeling at hydrodynamic scales: application to beam crossing energy exchange; Evolution of a Sedov-Taylor blast-wave: radiative, nonlocal heat transport and field effects; Measuring ultra-intense laser beams in space time; A few applications of the radiative and quantum electrodynamics effects in future extreme-intensity laser-matter experiments; X-rays imaging diagnostics for PETAL; Laboratory Astrophysics with High Power Lasers; Femto-second electron dynamics in the Warm dense Matter; The extra-solar planets; Study of HEDP magnetic reconnection; Opacity of solar-type stars inside: what (un)certainties?; Validation of solar

Overview and future prospects of laser plasma propulsion technology

International Nuclear Information System (INIS)

Zheng Zhiyuan; Lu Xin; Zhang Jie

2003-01-01

Due to its high cost, low efficiency, complex operation and unsatisfactory recycling, traditional rocket propulsion by chemical fuels has hindered the exploration of outer space to further limits. With the rapid development of laser and space technology, the new technology of laser propulsion exhibits unique advantages and prospects. The mechanism and current development of laser plasma propulsion are reviewed, with mention of the technical problems and focus issues of laser plasma in micro-flight propulsion

Evolution of plasma double layers in laser-ablation plumes

International Nuclear Information System (INIS)

Gurlui, S.; Sanduloviciu, M.; Mihesan, C.; Ziskind, M.; Focsa, C.

2005-01-01

The double layers (DLs) are one of the most complex problems of the plasma physics. These layers are apparently important not only in laboratory plasmas and laser-ablation plasma plumes but also in natural phenomena, e.g. the aurora and fire balls.This work studies the dynamics of the double layers in a laser ablation plume from different targets irradiated by a Nd: YAG 10 ns pulsed laser. The plasma formation was studied by means of both Langmuir probe and mass spectrometry methods using an experimental set-up developed for the study of environmental or technological interest samples. The ionic current distribution in plasma plume formation was recorded in different experimental conditions. We have found that it depends on the laser energy, the pressure of the buffer gas and the probe position. The periodical oscillations recorded in different experimental conditions prove that these plasma formations (DLs) are local physical systems able to accumulate and release energy. Acting as storing and releasing energy elements, the DLs can sustain periodical or non-periodical variations of the current or of the other global parameters of the plasma. (author)

Propagation Characteristics of High-Power Vortex Laguerre-Gaussian Laser Beams in Plasma

Directory of Open Access Journals (Sweden)

Zhili Lin

2018-04-01

Full Text Available The propagation characteristics of high-power laser beams in plasma is an important research topic and has many potential applications in fields such as laser machining, laser-driven accelerators and laser-driven inertial confined fusion. The dynamic evolution of high-power Laguerre-Gaussian (LG beams in plasma is numerically investigated by using the finite-difference time-domain (FDTD method based on the nonlinear Drude model, with both plasma frequency and collision frequency modulated by the light intensity of laser beam. The numerical algorithms and implementation techniques of FDTD method are presented for numerically simulating the nonlinear permittivity model of plasma and generating the LG beams with predefined parameters. The simulation results show that the plasma has different field modulation effects on the two exemplified LG beams with different cross-sectional patterns. The self-focusing and stochastic absorption phenomena of high-power laser beam in plasma are also demonstrated. This research also provides a new means for the field modulation of laser beams by plasma.

Transition between laser absorption dominated regimes in carbon-based plasma

Directory of Open Access Journals (Sweden)

K. Hajisharifi

2017-09-01

Full Text Available In this work, we investigate the energy absorption enhancement of a laser by adding a variety of light ion species to a primarily carbon-based plasma during the high-power laser interaction with the finite size targets. A developed Particle-In-Cell simulation code is used to study the reduction of laser reflectivity (stimulated backward scatterings in both Brillouin- and Raman-dominated regimes. The simulation is performed in various Carbon-light ion plasmas such as Carbon-Hydrogen, Carbon-Helium, Carbon-Deuterium, and Carbon-Tritium. The results show that, in the optimized condition, the inclusion of light Hydrogen ions into the Carbon-based plasma up to 50%-50% mixture enhances the laser absorption exceeding 20% in the Brillouin regime due to the suppression of laser reflectivity in contract to 4% in the Raman-dominated regime. Moreover, the absorption dominated regime switches from Raman to Brillouin regime by adding 50% of Hydrogen ions to a purely carbon target. The results of this investigation will be applicable to the laser-plasma experiments so long as the laser energy absorption in the Carbon plasma target, the most readily available material in laboratory, is concerned.

Self-focusing of laser beam crossing a laser plasma

International Nuclear Information System (INIS)

Bakos, J.S.; Foeldes, I.B.; Ignacz, P.N.; Soerlei, Zs.

1983-03-01

A crossed-beam experiment was performed to clarify the mechanism of self-focusing in a laser produced spark. The plasma was created by one beam and self-focusing was observed in the weak probe beam which crossed the plasma. Experimental results show that the cause of self-focusing is the nonuniform heating mechanism. (author)

Dynamics expansion of laser produced plasma with different materials in magnetic field

Energy Technology Data Exchange (ETDEWEB)

Rabia Qindeel; Noriah Bte Bidin; Yaacob Mat daud [Laser Technology Laboratory, Physics Department, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia)], E-mail: plasmaqindeel@yahoo.com

2008-12-01

The dynamics expansion of the plasma generated by laser ablation of different materials has been investigated. The dynamics and confinement of laser generated plasma plumes are expanding across variable magnetic fields. A Q-switched neodymium-doped yttrium aluminum garnet laser with 1064 nm, 8 ns pulse width and 0.125 J laser energy was used to generate plasma that was allowed to expand across variable magnetic within 0.1 - 0.8 T. The expansions of laser-produced plasma of different materials are characterized by using constant laser power. CCD video camera was used to visualize and record the activities in the focal region. The plasma plume length, width and area were measured by using Matrox Inpector 2.1 and video Test 0.5 software. Spectrums of plasma beam from different materials are studied via spectrometer. The results show that the plasma generated by aluminum target is the largest than Brass and copper. The optical radiation from laser generated plasma beam spectrums are obtained in the range of UV to visible light.

Advanced diagnostics for laser plasma interaction studies and some recent experiments

International Nuclear Information System (INIS)

Chaurasia, S.; Munda, D.S.; Dhareshwar, L.J.

2008-10-01

The complete characterization of Laser plasma interaction studies related to inertial confinement fusion laser and Equation of state (EOS) studies needs many diagnostics to explain the several physical phenomena occurring simultaneously in the laser produced plasma. This involves many on ion emission are important to understand physical phenomena which are responsible for generation of laser plasma as well as its interaction with an intense laser. In this report we describe the development of various x-ray diagnostics which are used in determining temporal, spatial and spectral properties of x-rays radiated from laser produced plasma. Diagnostics which have been used in experiments for investigation of laser-produced plasma as a source of ions are also described. Techniques using an optical streak camera and VISAR which are being used in the Equation of States (EOS) studies of various materials, which are important for material science, astrophysics as well as ICF is described in details. (author)

Laser-plasma interactions for fast ignition

Science.gov (United States)

Kemp, A. J.; Fiuza, F.; Debayle, A.; Johzaki, T.; Mori, W. B.; Patel, P. K.; Sentoku, Y.; Silva, L. O.

2014-05-01

In the electron-driven fast-ignition (FI) approach to inertial confinement fusion, petawatt laser pulses are required to generate MeV electrons that deposit several tens of kilojoules in the compressed core of an imploded DT shell. We review recent progress in the understanding of intense laser-plasma interactions (LPI) relevant to FI. Increases in computational and modelling capabilities, as well as algorithmic developments have led to enhancement in our ability to perform multi-dimensional particle-in-cell simulations of LPI at relevant scales. We discuss the physics of the interaction in terms of laser absorption fraction, the laser-generated electron spectra, divergence, and their temporal evolution. Scaling with irradiation conditions such as laser intensity are considered, as well as the dependence on plasma parameters. Different numerical modelling approaches and configurations are addressed, providing an overview of the modelling capabilities and limitations. In addition, we discuss the comparison of simulation results with experimental observables. In particular, we address the question of surrogacy of today's experiments for the full-scale FI problem.

Measurements of Electron Temperature and Density Profiles of Plasmas Produced by Nike KrF Laser for Laser Plasma Instability (LPI) Research

Science.gov (United States)

Oh, Jaechul; Weaver, J. L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Karasik, M.; Chan, L.-Y.; Serlin, V.; Phillips, L.

2012-10-01

ExperimentsfootnotetextJ. Oh, et al, GO5.4, APS DPP (2010).^,footnotetextJ. L. Weaver, et al, GO5.3, APS DPP (2010). using Nike KrF laser observed LPI signatures from CH plasmas at the laser intensities above ˜1x10^15 W/cm^2. Knowing spatial profiles of temperature (Te) and density (ne) in the underdense coronal region (0 Nike LPI experiment, a side-on grid imaging refractometer (GIR)footnotetextR. S. Craxton, et al, Phys. Fluids B 5, 4419 (1993). is being deployed for measuring the underdense plasma profiles. The GIR will resolve Te and ne in space taking a 2D snapshot of probe laser (λ= 263 nm, δt = 10 psec) beamlets (50μm spacing) refracted by the plasma at a selected time during the laser illumination. Time-resolved spectrometers with an absolute-intensity-calibrated photodiode array and a streak camera will simultaneously monitor light emission from the plasma in spectral ranges relevant to Raman (SRS) and two plasmon decay (TDP) instabilities. The experimental study of effects of the plasma profiles on the LPI initiation will be presented.

The x-ray laser as a tool for imaging plasmas

International Nuclear Information System (INIS)

Libby, S.B.; Da Silva, L.B.; Barbee, T.W. Jr.

1995-07-01

The x-ray laser is now being used at LLNL as a tool for measuring the behaviors of hot dense plasmas. In particular, we have used the 155 Angstrom yttrium laser to study transient plasmas by both radiography and moire deflectrometry. These techniques have been used to probe long scale length plasmas at electron densities exceeding 10 22 cm -3 . Recent advances in multilayer technology have made it possible to directly image ion densities in directly driven thin foils to an accuracy of 1--2 μm. In addition, we have constructed an x-ray laser Mach-Zehnder interferometer using multilayer beam-splitters. This interferometer yields direct 2D projections of electron densities in plasmas with micron spatial resolution. In addition, this interferometer can be used to measure spectral line shapes to high accuracy. Among the subject plasmas under study are laser irradiated planar targets, gold hohlraums, and x-ray lasers themselves

Dynamics of plasma ions motion in ultra-intense laser-excited plasma wakes

International Nuclear Information System (INIS)

Zhou Suyun; Li Jing

2013-01-01

The effects of heavy ions and protons motion in an ultra-intense laser-driven plasma wake are compared by rebuilding a plasma wake model. It is shown that with the same laser and plasma background electron density n 0 , the heavy ions' motion suppresses wake-field resonant excitation less than the protons' motion in their own plasma wake. Though heavy ions obtain more kinetic energy from the plasma wake, its energy density is less than that of the protons due to the ion density being far less than the proton density. As a result, the total energy of heavy ions obtained from the wake-field is far less than that of protons. The dependence of the kinetic energy and the energy density of protons and heavy ions on n 0 is discussed. (paper)

Mid-infrared lasers for energy frontier plasma accelerators

Directory of Open Access Journals (Sweden)

I. V. Pogorelsky

2016-09-01

Full Text Available Plasma wake field accelerators driven with solid-state near-IR lasers have been considered as an alternative to conventional rf accelerators for next-generation TeV-class lepton colliders. Here, we extend this study to the mid-IR spectral domain covered by CO_{2} lasers. We conclude that the increase in the laser driver wavelength favors the regime of laser wake field acceleration with a low plasma density and high electric charge. This regime is the most beneficial for gamma colliders to be converted from lepton colliders via inverse Compton scattering. Selecting a laser wavelength to drive a Compton gamma source is essential for the design of such a machine. The revealed benefits from spectral diversification of laser drivers for future colliders and off-spring applications validate ongoing efforts in advancing the ultrafast CO_{2} laser technology.

Laser and Plasma Technology Division annual report 1993

International Nuclear Information System (INIS)

Venkatramani, N.; Verma, R.L.

1994-01-01

This report describes the activities of the Laser and Plasma Technology Division during the year 1993. This Division is engaged in the research and development of high power beams namely laser, plasma and electron beams, which are characterized by high power density, normally in excess of 1 kW/mm 2 . Laser and Plasma Technology Division has strived to establish indigenous capability to cater to the requirements of the Department of Atomic Energy. The broad programme objectives of the Division are : (1) Development and technology readiness studies of laser, plasma and electron beam devices, (2) Studies on related physical phenomena with a view to gain better understanding of the devices, and (3) Improvements in technology and exploration of new areas. This report covers the activities of the Division during 1993 and describes how successfully the objectives have been met. The activities described in the report are diverse in nature. The report has been compiled from individual reports of various groups/sections with marginal editing. (author). refs., tabs., figs

Laser and Plasma Technology Division annual report 1993

Energy Technology Data Exchange (ETDEWEB)

Venkatramani, N; Verma, R L [eds.; Bhabha Atomic Research Centre, Bombay (India). Laser and Plasma Technology Div.

1994-12-31

This report describes the activities of the Laser and Plasma Technology Division during the year 1993. This Division is engaged in the research and development of high power beams namely laser, plasma and electron beams, which are characterized by high power density, normally in excess of 1 kW/mm{sup 2}. Laser and Plasma Technology Division has strived to establish indigenous capability to cater to the requirements of the Department of Atomic Energy. The broad programme objectives of the Division are : (1) Development and technology readiness studies of laser, plasma and electron beam devices, (2) Studies on related physical phenomena with a view to gain better understanding of the devices, and (3) Improvements in technology and exploration of new areas. This report covers the activities of the Division during 1993 and describes how successfully the objectives have been met. The activities described in the report are diverse in nature. The report has been compiled from individual reports of various groups/sections with marginal editing. (author). refs., tabs., figs.

Self-focusing and guiding of short laser pulses in ionizing gases and plasmas

International Nuclear Information System (INIS)

Esarey, E.; Sprangle, P.; Krall, J.; Ting, A.

1997-01-01

The propagation of intense laser pulses in gases and plasmas is relevant to a wide range of applications, including laser-driven accelerators, laser-plasma channeling, harmonic generation, supercontinuum generation, X-ray lasers, and laser-fusion schemes. Here, several features of intense, short-pulse (≤1 ps) laser propagation in gases undergoing ionization and in plasmas are reviewed, discussed, and analyzed. The wave equations for laser pulse propagation in a gas undergoing ionization and in a plasma are derived. The source-dependent expansion method is discussed, which is a general method for solving the paraxial wave equation with nonlinear source terms. In gases, the propagation of high-power (near the critical power) laser pulses is considered including the effects of diffraction, nonlinear self-focusing, ionization, and plasma generation. Self-guided solutions and the stability of these solutions are discussed. In plasmas, optical guiding by relativistic effects, ponderomotive effects, and preformed density channels is considered. The self-consistent plasma response is discussed, including plasma wave effects and instabilities such as self-modulation. Recent experiments on the guiding of laser pulses in gases and in plasmas are briefly summarized

En Route: next-generation laser-plasma-based electron accelerators; En Route: Elektronenbeschleuniger der naechsten Generation auf Laser-Plasma-Basis

Energy Technology Data Exchange (ETDEWEB)

Hidding, Bernhard

2008-05-15

Accelerating electrons to relativistic energies is of fundamental interest, especially in particle physics. Today's accelerator technology, however, is limited by the maximum electric fields which can be created. This thesis presents results on various mechanisms aiming at exploiting the fields in focussed laser pulses and plasma waves for electron acceleration, which can be orders of magnitude higher than with conventional accelerators. With relativistic, underdense laser-plasma-interaction, quasimonoenergetic electron bunches with energies up to {approx}50 MeV and normalized emittances of the order of 5mmmrad have been generated. This was achieved by focussing the {approx}80 fs, 1 J pulses of the JETI-laser at the FSU Jena to intensities of several 10{sup 19}W=cm{sup 2} into gas jets. The experimental observations could be explained via 'bubble acceleration', which is based on self-injection and acceleration of electrons in a highly nonlinear breaking plasma wave. For the rst time, this bubble acceleration was achieved explicitly in the self-modulated laser wakefield regime (SMLWFA). This quasimonoenergetic SMLWFA-regime stands out by relaxing dramatically the requirements on the driving laser pulse necessary to trigger bubble acceleration. This is due to self-modulation of the laser pulse in high-density gas jets, leading to ultrashort laser pulse fragments capable of initiating bubble acceleration. Electron bunches with durations laser pulse fragment can be powerful enough to drive a bubble. Distinct double peaks have been observed in the electron spectra, indicating that two quasimonoenergetic electron bunches separated by only few tens of fs have formed. This is backed up by PIC-Simulations (Particle-in-Cell). These results underline the feasibility of the construction of small table

Propagation of Gaussian laser beam in cold plasma of Drude model

International Nuclear Information System (INIS)

Wang Ying; Yuan Chengxun; Zhou Zhongxiang; Li Lei; Du Yanwei

2011-01-01

The propagation characters of Gaussian laser beam in plasmas of Drude model have been investigated by complex eikonal function assumption. The dielectric constant of Drude model is representative and applicable in describing the cold unmagnetized plasmas. The dynamics of ponderomotive nonlinearity, spatial diffraction, and collision attenuation is considered. The derived coupling equations determine the variations of laser beam and irradiation attenuation. The modified laser beam-width parameter F, the dimensionless axis irradiation intensity I, and the spatial electron density distribution n/n 0 have been studied in connection with collision frequency, initial laser intensity and beam-width, and electron temperature of plasma. The variations of laser beam and plasma density due to different selections of parameters are reasonably explained, and results indicate the feasible modification of the propagating characters of laser beam in plasmas, which possesses significance to fast ignition, extended propagation, and other applications.

Characterization of Electron Temperature and Density Profiles of Plasmas Produced by Nike KrF Laser for Laser Plasma Instability (LPI) Research

Science.gov (United States)

Oh, Jaechul; Weaver, J. L.; Phillips, L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Chan, L.-Y.; Serlin, V.

2011-10-01

Previous experiments with Nike KrF laser (λ = 248 nm , Δν ~ 1 THz) observed LPI signatures near quarter critical density (nc / 4) in CH plasmas, however, detailed measurement of the temperature (Te) and density (ne) profiles was missing. The current Nike LPI campaign will perform experimental determination of the plasma profiles. A side-on grid imaging refractometer (GIR) is the main diagnostic to resolve Te and ne in space taking 2D snapshots of probe laser (λ = 266 nm , Δt = 8 psec) beamlets (50 μm spacing) refracted by the plasma at laser peak time. Ray tracing of the beamlets through hydrodynamically simulated (FASTRAD3D) plasma profiles estimates the refractometer may access densities up to ~ 0 . 2nc . With the measured Te and ne profiles in the plasma corona, we will discuss analysis of light data radiated from the plasmas in spectral ranges relevant to two plasmon decay and convective Raman instabilities. Validity of the (Te ,ne) data will also be discussed for the thermal transport study. Work supported by DoE/NNSA and ONR and performed at NRL.

First Laser-Plasma Interaction and Hohlraum Experiments on NIF

International Nuclear Information System (INIS)

Dewald, E L; Glenzer, S H; Landen, O L; Suter, L J; Jones, O S; Schein, J; Froula, D; Divol, L; Campbell, K; Schneider, M S; McDonald, J W; Niemann, C; Mackinnon, A J

2005-01-01

Recently the first hohlraum experiments have been performed at the National Ignition Facility (NIF) in support of indirect drive Inertial Confinement Fusion (ICF) designs. The effects of laser beam smoothing by spectral dispersion (SSD) and polarization smoothing (PS) on the beam propagation in long scale gas-filled pipes has been studied at plasma scales as found in indirect drive gas filled ignition hohlraum designs. The long scale gas-filled target experiments have shown propagation over 7 mm of dense plasma without filamentation and beam break up when using full laser smoothing. Vacuum hohlraums have been irradiated with laser powers up to 6 TW, 1-9 ns pulse lengths and energies up to 17 kJ to activate several diagnostics, to study the hohlraum radiation temperature scaling with the laser power and hohlraum size, and to make contact with hohlraum experiments performed at the NOVA and Omega laser facilities. Subsequently, novel long laser pulse hohlraum experiments have tested models of hohlraum plasma filling and long pulse hohlraum radiation production. The validity of the plasma filling assessment in analytical models and in LASNEX calculations has been proven for the first time. The comparison of these results with modeling will be discussed

Confinement of laser plasma expansion with strong external magnetic field

Science.gov (United States)

Tang, Hui-bo; Hu, Guang-yue; Liang, Yi-han; Tao, Tao; Wang, Yu-lin; Hu, Peng; Zhao, Bin; Zheng, Jian

2018-05-01

The evolutions of laser ablation plasma, expanding in strong (∼10 T) transverse external magnetic field, were investigated in experiments and simulations. The experimental results show that the magnetic field pressure causes the plasma decelerate and accumulate at the plasma-field interface, and then form a low-density plasma bubble. The saturation size of the plasma bubble has a scaling law on laser energy and magnetic field intensity. Magnetohydrodynamic simulation results support the observation and find that the scaling law (V max ∝ E p /B 2, where V max is the maximum volume of the plasma bubble, E p is the absorbed laser energy, and B is the magnetic field intensity) is effective in a broad laser energy range from several joules to kilo-joules, since the plasma is always in the state of magnetic field frozen while expanding. About 15% absorbed laser energy converts into magnetic field energy stored in compressed and curved magnetic field lines. The duration that the plasma bubble comes to maximum size has another scaling law t max ∝ E p 1/2/B 2. The plasma expanding dynamics in external magnetic field have a similar character with that in underdense gas, which indicates that the external magnetic field may be a feasible approach to replace the gas filled in hohlraum to suppress the wall plasma expansion and mitigate the stimulated scattering process in indirect drive ignition.

Collimation of laser-produced plasmas using axial magnetic field

Czech Academy of Sciences Publication Activity Database

Roy, Amitava; Harilal, S.S.; Hassan, S.M.; Endo, Akira; Mocek, Tomáš; Hassanein, A.

2015-01-01

Roč. 33, č. 2 (2015), s. 175-182 ISSN 0263-0346 R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143; GA MŠk EE2.3.30.0057 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143; OP VK 4 POSTDOK(XE) CZ.1.07/2.3.00/30.0057 Institutional support: RVO:68378271 Keywords : laser-produced plasma * optical emission spectroscopy * plasma-B field interaction * plasma temperature and density * tin plasma Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.649, year: 2015

Double pulse laser ablation and plasma: Laser induced breakdown spectroscopy signal enhancement

International Nuclear Information System (INIS)

Babushok, V.I.; DeLucia, F.C.; Gottfried, J.L.; Munson, C.A.; Miziolek, A.W.

2006-01-01

A review of recent results of the studies of double laser pulse plasma and ablation for laser induced breakdown spectroscopy applications is presented. The double pulse laser induced breakdown spectroscopy configuration was suggested with the aim of overcoming the sensitivity shortcomings of the conventional single pulse laser induced breakdown spectroscopy technique. Several configurations have been suggested for the realization of the double pulse laser induced breakdown spectroscopy technique: collinear, orthogonal pre-spark, orthogonal pre-heating and dual pulse crossed beam modes. In addition, combinations of laser pulses with different wavelengths, different energies and durations were studied, thus providing flexibility in the choice of wavelength, pulse width, energy and pulse sequence. The double pulse laser induced breakdown spectroscopy approach provides a significant enhancement in the intensity of laser induced breakdown spectroscopy emission lines up to two orders of magnitude greater than a conventional single pulse laser induced breakdown spectroscopy. The double pulse technique leads to a better coupling of the laser beam with the plasma plume and target material, thus providing a more temporally effective energy delivery to the plasma and target. The experimental results demonstrate that the maximum effect is obtained at some optimum separation delay time between pulses. The optimum value of the interpulse delay depends on several factors, such as the target material, the energy level of excited states responsible for the emission, and the type of enhancement process considered. Depending on the specified parameter, the enhancement effects were observed on different time scales ranging from the picosecond time level (e.g., ion yield, ablation mass) up to the hundred microsecond level (e.g., increased emission intensity for laser induced breakdown spectroscopy of submerged metal target in water). Several suggestions have been proposed to explain

Line intensities for diagnosing laser-produced plasmas

International Nuclear Information System (INIS)

Kauffman, R.L.; Matthews, D.L.; Lee, R.W.; Whitten, B.L.; Kilkenny, J.D.

1983-01-01

We have measured relative line intensities of the K x-ray spectra of Si, Cl, and Ca from laser-produced plasmas to assess their usefulness as a plasma diagnostic. The different elements are added at low concentrations to CH disks which are irradiated at 5 x 10 14 W/cm 2 with a 0.53 μm laser pulse of 20 Joules at 1 nsec. The concentration of each element is kept low in order not to change the Z of the plasma, and therefore the plasma dynamics. The various spectra are measured with a time-resolved spectrograph to obtain line intensities as a function of time over the length of the laser pulse. These relative intensities of various He-like and H-like lines are compared with calculations from a steady-state level population code. The results give good consistency among the various line ratios. Agreement is not as good for analysis of the Li-like satellite lines. Modelling of the Li-like lines need further investigation. 10 references, 9 figures

Radiative processes in a laser-fusion plasma

International Nuclear Information System (INIS)

Campbell, P.M.; Kubis, J.J.; Mitrovich, D.

1976-01-01

Plasmas compressed and heated by an intense laser pulse offer promise for the ignition of propagating thermonuclear burn and, ultimately, for use in fusion reactors. It is evident theoretically that the emission and absorption of x-rays by the plasma has a significant effect on the dynamics of the laser compression process. In order to achieve densities high enough for efficient thermonuclear burn, the fusion pellet must be compressed along a low adiabat. This will not be possible if the compressed region of the pellet is significantly preheated by x-rays originating in the hot outer regions. A satisfactory model of compression hydrodynamics must, therefore, include a comprehensive treatment of radiation transport based on a non-LTE model of the plasma. The model must be valid for Fermi-Dirac statistics, since high compression along a low adiabat will, in general, produce degenerate electron distributions. This report is concerned with the plasma model and the corresponding radiation emission and absorption coefficients, including nonthermal processes which occur in the laser deposition region

Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

International Nuclear Information System (INIS)

Ma, Guangjin; Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo; Krausz, Ferenc; Yu, Wei

2015-01-01

We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach

Laser treatment of plasma sprayed HA coatings

NARCIS (Netherlands)

Khor, KA; Vreeling, A; Dong, ZL; Cheang, P

1999-01-01

Laser treatment was conducted on plasma sprayed hydroxyapatite (HA) coatings using a Nd-YAG pulse laser. Various laser parameters were investigated. The results showed that the HA surface melted when an energy level of greater than or equal to 2 J and a spot size of 2 mm was employed during

Ion Beam Analysis applied to laser-generated plasmas

Czech Academy of Sciences Publication Activity Database

Cutroneo, Mariapompea; Macková, Anna; Havránek, Vladimír; Malinský, Petr; Torrisi, L.; Kormunda, M.; Barchuk, M.; Ullschmied, Jiří; Dudžák, Roman

2016-01-01

Roč. 11, APR (2016), C04011 ISSN 1748-0221. [Conference on Plasma Physics by Laser and Applications (PPLA). Frascati, 05.10.2015-07.10.2015] R&D Projects: GA MŠk(CZ) LM2011019; GA ČR GA15-01602S; GA MŠk LM2015073 Institutional support: RVO:61389021 ; RVO:61389005 Keywords : accelerator applications * lasers * plasma diagnostics Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders; BL - Plasma and Gas Discharge Physics (UFP-V) Impact factor: 1.220, year: 2016

Boundary asymptotics for a non-neutral electrochemistry model with small Debye length

Science.gov (United States)

Lee, Chiun-Chang; Ryham, Rolf J.

2018-04-01

This article addresses the boundary asymptotics of the electrostatic potential in non-neutral electrochemistry models with small Debye length in bounded domains. Under standard physical assumptions motivated by non-electroneutral phenomena in oxidation-reduction reactions, we show that the electrostatic potential asymptotically blows up at boundary points with respect to the bulk reference potential as the scaled Debye length tends to zero. The analysis gives a lower bound for the blow-up rate with respect to the model parameters. Moreover, the maximum potential difference over any compact subset of the physical domain vanishes exponentially in the zero-Debye-length limit. The results mathematically confirm the physical description that electrolyte solutions are electrically neutral in the bulk and are strongly electrically non-neutral near charged surfaces.

Infrared laser scattering system for the plasma diagnostics: CO/sub 2/ laser characteristics

Energy Technology Data Exchange (ETDEWEB)

Hiraki, N; Kawasaki, S; Muraoka, K

1975-08-01

A detailed study was conducted of the operating characteristics of a double discharge infrared TEA carbon dioxide laser used for scattering measurements of plasmas. The discharge condition, the laser output energy and power, the beam profile and divergence, the emission spectral line width, the time lag and jitter of the output from the discharge trigger, have been established. It is concluded that the carbon dioxide oscillator can deliver the allowable beam divergence and spectral line width for the measurement of ion temperature in light scattering studies of theta pinch plasmas. The results presented might be applicable to laser fusion experiments using carbon dioxide lasers.

Anisotropic instability in a laser heated plasma

International Nuclear Information System (INIS)

Sangam, A.; Morreeuw, J.-P.; Tikhonchuk, V. T.

2007-01-01

The theory of the Weibel instability induced by the inverse Bremsstrahlung absorption of a laser light in an underdense plasma is revisited. It is shown that previous analyses have strongly overestimated the effect by neglecting the stabilizing term related to the interaction of the generated quasistatic magnetic field with the laser-heated electrons. The revised model leads to a reduction of the growth rate by more than a factor of 10, to strong reduction of the domain of unstable modes and to inversion of the direction of the unstable wave vectors in the long wavelength limit. The consequences of this instability on the laser plasma interaction are also discussed

Tunable Laser Plasma Accelerator based on Longitudinal Density Tailoring

Energy Technology Data Exchange (ETDEWEB)

Gonsalves, Anthony; Nakamura, Kei; Lin, Chen; Panasenko, Dmitriy; Shiraishi, Satomi; Sokollik, Thomas; Benedetti, Carlo; Schroeder, Carl; Geddes, Cameron; Tilborg, Jeroen van; Osterhoff, Jens; Esarey, Eric; Toth, Csaba; Leemans, Wim

2011-07-15

Laser plasma accelerators have produced high-quality electron beams with GeV energies from cm-scale devices and are being investigated as hyperspectral fs light sources producing THz to {gamma}-ray radiation and as drivers for future high-energy colliders. These applications require a high degree of stability, beam quality and tunability. Here we report on a technique to inject electrons into the accelerating field of a laser-driven plasma wave and coupling of this injector to a lower-density, separately tunable plasma for further acceleration. The technique relies on a single laser pulse powering a plasma structure with a tailored longitudinal density profile, to produce beams that can be tuned in the range of 100-400 MeV with percent-level stability, using laser pulses of less than 40 TW. The resulting device is a simple stand-alone accelerator or the front end for a multistage higher-energy accelerator.

Betatron radiation from a laser-plasma accelerator

International Nuclear Information System (INIS)

Schnell, Michael

2014-01-01

The presented thesis investigates the processes which lead to the generation of highenergetic X-ray radiation, also known as ''betatron radiation'', by means of a relativistic laser-plasma interaction. The generated betatron radiation has been extensively characterized by measuring its radiated intensity, energy distribution, far-field beam profile, and source size. It was shown for the first time that betatron radiation can be used as a non-invasive diagnostic tool to retrieve very subtle information on the electron acceleration dynamics within the plasma wave. Furthermore, a compact polarimeter setup has been developed in a unique experiment in which the polarization state of the laser-plasma generated betatron radiation was measured in single-shot mode. This lead to a detailed study of the orientation of the electron trajectory within the plasma interaction. By controlling the injection of the electrons into the plasma wave it was demonstrated that one can tune the polarization state of the emitted X-rays. This result is very promising for further applications, particularly for feeding the electrons into an additional conventional accelerator or a permanent magnet based undulator for the production of intense X-ray beams. During this work, the experimental setup for accelerating electrons and generating high-energy X-ray beams was consistently improved: to enhance both its reliability and stability. Subsequently, the betatron radiation was used as a reliable diagnostic tool of the electron dynamics within the plasma. Parallel to the experimental work, 3-Dimensional Particle-In-Cell (3D-PlC) simulations were performed together with colleagues from the University of Duesseldorf. The simulations included the electron acceleration and the X-ray generation processes together with the recoil force acting on an accelerating electron caused by the emitted radiation during which one can also ascertain its polarization state. The simulations proved to be in good agreement

Investigation of relativistic laser-plasmas using nuclear diagnostics

International Nuclear Information System (INIS)

Guenther, Marc M.

2011-01-01

The present work explores with the development of a novel nuclear diagnostic method for the investigation of the electron dynamics in relativistic laser-plasma interactions. An additional aim of this work was the determination of the real laser peak intensity via the interaction of an intense laser short-pulse with a solid target. The nuclear diagnostics is based on a photo-neutron disintegration nuclear activation method. The main constituent of the nuclear diagnostic are novel pseudoalloic activation targets as a kind of calorimeter to measure the high-energy bremsstrahlung produced by relativistic electrons. The targets are composed of several stable isotopes with different (γ,xn)-reaction thresholds. The activated nuclides were identified via the characteristic gamma-ray decay spectrum by using high-resolution gamma spectroscopy after the laser irradiation. Via the gamma spectroscopy the (γ,xn)-reaction yields were determined. The high-energy bremsstrahlung spectrum has been deconvolved using a novel analysis method based on a modified Penfold-Leiss method. This facilitates the reconstruction of the spectrum of bremsstrahlung photons without any anticipated fit procedures. Furthermore, the characterization of the corresponding bremsstrahlung electrons in the interaction zone is accessible immediately. The consolidated findings about the properties of the relativistic electrons were used to determine the real peak intensity at the laser-plasma interaction zone. In the context of this work, experiments were performed at three different laser facilities. First Experiments were carried out at the 100 TW laser facility at Laboratoire pour l'Utilisation des Lasers Intense (LULI) in France and supplementary at the Vulcan laser facility at Rutherford Appleton Laboratory (RAL) in United Kingdom. The main part of the activation experiments were performed at the PHELIX laser facility (Petawatt High Energy Laser for heavy Ion EXperiments) at GSI-Helmholtzzentrum fuer

Dynamics of a multiple-pulse-driven x-ray laser plasma

International Nuclear Information System (INIS)

Wan, A.S.; Da Silva, L.B.; Moreno, J.C.; Cauble, R.; Celliers, P.; Dalhed, H.E. Jr.; Koch, J.A.; Nilsen, J.

1996-01-01

In this paper we describe experimental and computational studies of multiple-pulse-driven laser plasma, which is the gain medium for a neon-like yttrium x-ray laser. Near-field emission profiles have been measured both with and without reinjection of the x-ray laser photons to couple with the amplifying medium created by later pulses using an external multilayer mirror. From the temporal and spatial evolution of the near-field emission profiles we can examine the pulse-to-pulse variation of the x-ray laser plasma due to changes in the hydrodynamics, laser deposition, and the injecting of x-ray laser photons back into an amplifying x-ray laser plasma. Using a combination of radiation hydrodynamics, atomic kinetics, and ray propagation codes, reasonable agreement has been obtained between simulations and the experimental results. copyright 1996 American Institute of Physics

Transient Plasma Photonic Crystals for High-Power Lasers.

Science.gov (United States)

Lehmann, G; Spatschek, K H

2016-06-03

A new type of transient photonic crystals for high-power lasers is presented. The crystal is produced by counterpropagating laser beams in plasma. Trapped electrons and electrically forced ions generate a strong density grating. The lifetime of the transient photonic crystal is determined by the ballistic motion of ions. The robustness of the photonic crystal allows one to manipulate high-intensity laser pulses. The scheme of the crystal is analyzed here by 1D Vlasov simulations. Reflection or transmission of high-power laser pulses are predicted by particle-in-cell simulations. It is shown that a transient plasma photonic crystal may act as a tunable mirror for intense laser pulses. Generalizations to 2D and 3D configurations are possible.

The physics of megajoule, large-scale, and ultrafast short-scale laser plasmas

International Nuclear Information System (INIS)

Campbell, E.M.

1992-01-01

Recent advances in laser science and technology have opened new possibilities for the study of high energy density plasma physics. The advances include techniques to control the laser spatial and temporal coherence, and the development of laser architectures and optical materials that have led to the demonstration of compact, short pulse (τ≤10 -12 sec) high brightness lasers, capable of irradiating plasmas with intensities ≥10 18 W/cm 2 . Experiments with reduced laser coherence have shown a substantial decrease in laser-driven parametric instabilities and have extended the parameter range where inverse bremsstrahlung absorption is the dominant coupling process. Beam smoothing with short wavelength lasers should result in inverse bremsstrahlung dominated coupling in the irradiance parameter regimes of the millimeter scale-length plasmas envisioned for the megajoule class lasers for ignition and gain in inertial fusion. In addition new regimes of laser--plasma coupling will become experimentally accessible when plasmas are irradiated with I≥10 18 W/cm 2 . Relativistic effects, extreme profile modification, and electrons heated to energies exceeding 1 MeV are several of the phenomena that are expected. Numerous applications in basic and applied plasma physics will result from these new capabilities

Laser-induced incandescence applied to dusty plasmas

NARCIS (Netherlands)

van de Wetering, F.M.J.H.; Oosterbeek, W.; Beckers, J.; Nijdam, S.; Kovacevic, E.; Berndt, J.

2016-01-01

This paper reports on the laser heating of nanoparticles (diameters ≤1 μm) confined in a reactive plasma by short (150 ps) and intense (~63 mJ) UV (355 nm) laser pulses (laser-induced incandescence, LII). Important parameters such as the particle temperature and radius follow from analysis of the

Laser-Hole Boring into Overdense Plasmas Measured with Soft X-Ray Laser Probing

Energy Technology Data Exchange (ETDEWEB)

Takahashi, K [Institute of Laser Engineering, Osaka University, Yamada Oka 2-6, Suita, Osaka 565-0871, (Japan); Kodama, R [Institute of Laser Engineering, Osaka University, Yamada Oka 2-6, Suita, Osaka 565-0871, (Japan); Tanaka, K A [Institute of Laser Engineering, Osaka University, Yamada Oka 2-6, Suita, Osaka 565-0871, (Japan); Hashimoto, H [Institute of Laser Engineering, Osaka University, Yamada Oka 2-6, Suita, Osaka 565-0871, (Japan); Kato, Y [Institute of Laser Engineering, Osaka University, Yamada Oka 2-6, Suita, Osaka 565-0871, (Japan); Mima, K [Institute of Laser Engineering, Osaka University, Yamada Oka 2-6, Suita, Osaka 565-0871, (Japan); Weber, F A [University of California, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Barbee, Jr, T W [University of California, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Da Silva, L B [University of California, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States)

2000-03-13

A laser self-focused channel formation into overdense plasmas was observed using a soft x-ray laser probe system with a grid image refractometry (GIR) technique. 1.053 {mu}m laser light with a 100 ps pulse duration was focused onto a preformed plasma at an intensity of 2x10{sup 17} W /cm{sup 2} . Cross sections of the channel were obtained which show a 30 {mu}m diameter in overdense plasmas. The channel width in the overdense region was kept narrow as a result of self-focusing. Conically diverging density ridges were also observed along the channel, indicating a Mach cone created by a shock wave due to the supersonic propagation of the channel front. (c) 2000 The American Physical Society.

Laser-Hole Boring into Overdense Plasmas Measured with Soft X-Ray Laser Probing

International Nuclear Information System (INIS)

Takahashi, K.; Kodama, R.; Tanaka, K. A.; Hashimoto, H.; Kato, Y.; Mima, K.; Weber, F. A.; Barbee, T. W. Jr.; Da Silva, L. B.

2000-01-01

A laser self-focused channel formation into overdense plasmas was observed using a soft x-ray laser probe system with a grid image refractometry (GIR) technique. 1.053 μm laser light with a 100 ps pulse duration was focused onto a preformed plasma at an intensity of 2x10 17 W /cm 2 . Cross sections of the channel were obtained which show a 30 μm diameter in overdense plasmas. The channel width in the overdense region was kept narrow as a result of self-focusing. Conically diverging density ridges were also observed along the channel, indicating a Mach cone created by a shock wave due to the supersonic propagation of the channel front. (c) 2000 The American Physical Society

Plasma satellites of X-ray lines of ions in a picosecond laser plasma

International Nuclear Information System (INIS)

Belyaev, V.S.; Vinogradov, V.I.; Kurilov, A.S.; Matafonov, A.P.; Lisitsa, V.S.; Gavrilenko, V. P.; Faenov, A.Ya.; Pikuz, T.A.; Skobelev, I.Yu.; Magunov, A.I.; Pikuz, S.A. Jr.

2004-01-01

We present the results of our measurements of the spectra for multicharged ions in a plasma produced by moderately intense (about 10 17 W cm -2 ) picosecond laser pulses. They suggest the existence of intense plasma oscillations with a frequency appreciably lower than the frequency of the laser radiation. The observed spectrum for the plasma satellites of the Lyman Ly α doublet of the hydrogenic F IX ion in a dense plasma was modeled theoretically. The resulting doublet profile was shown to have a complex structure that depends nontrivially both on the plasma density and on the frequency and amplitude of the plasma oscillations. The positions of the satellites and their separations allowed them to be associated with intense electrostatic oscillations with an amplitude of (4-6) x 10 8 V cm -1 and a frequency near (0.7-1) x 10 15 s -1 . Assuming the oscillation frequency to be determined by the strength of the magnetic field B generated in the plasma, we obtained an estimate of B that is in reasonable agreement with other measurements and estimates of this quantity. Our theoretical analysis allowed explanation of the emission spectra observed when flat fluoroplastic targets were heated by intense picosecond laser pulses

Local thermodynamic equilibrium considerations in powerchip laser-induced plasmas

Energy Technology Data Exchange (ETDEWEB)

Merten, Jonathan A., E-mail: jmerten@astate.edu; Smith, Benjamin W., E-mail: bwsmith@chem.ufl.edu; Omenetto, Nicoló, E-mail: omenetto@chem.ufl.edu

2013-05-01

Time-resolved emission experiments are reported in the fast-decaying transient plasma induced by a microchip laser on an aluminum target in three different cover gases, i.e., air, argon and helium. The laser operates at 532 nm, with a repetition frequency of 1 kHz and a pulse width of less than 0.5 ns. The overall persistence of plasma emission is of the order of 100 ns. We examine the existence of local thermodynamic equilibrium (LTE) by evaluating the temporal criteria required (in addition to the McWhirter criterion), as recommended by Cristoforetti et al. (Spectrochim. Acta Part B 65, 2010, 86–95). The temporal criteria examine the evolution of temperature and electron number density and compare their rate of change to the rate at which electron collisions can thermalize the change. These considerations are used to determine time windows in which LTE may be present. Our results suggest that calibration-free LIBS measurements with these lasers may be possible for some elements at early times, especially under argon. - Highlights: ► Powerchip laser-induced plasma evolution is affected by cover gas. ► Plasma often out of LTE, despite fulfilling the McWhirter criterion ► Calibration-free LIBS may be possible with powerchip laser plasmas.

Local thermodynamic equilibrium considerations in powerchip laser-induced plasmas

International Nuclear Information System (INIS)

Merten, Jonathan A.; Smith, Benjamin W.; Omenetto, Nicoló

2013-01-01

Time-resolved emission experiments are reported in the fast-decaying transient plasma induced by a microchip laser on an aluminum target in three different cover gases, i.e., air, argon and helium. The laser operates at 532 nm, with a repetition frequency of 1 kHz and a pulse width of less than 0.5 ns. The overall persistence of plasma emission is of the order of 100 ns. We examine the existence of local thermodynamic equilibrium (LTE) by evaluating the temporal criteria required (in addition to the McWhirter criterion), as recommended by Cristoforetti et al. (Spectrochim. Acta Part B 65, 2010, 86–95). The temporal criteria examine the evolution of temperature and electron number density and compare their rate of change to the rate at which electron collisions can thermalize the change. These considerations are used to determine time windows in which LTE may be present. Our results suggest that calibration-free LIBS measurements with these lasers may be possible for some elements at early times, especially under argon. - Highlights: ► Powerchip laser-induced plasma evolution is affected by cover gas. ► Plasma often out of LTE, despite fulfilling the McWhirter criterion ► Calibration-free LIBS may be possible with powerchip laser plasmas

Characterization of X-ray emission from laser generated plasma

Science.gov (United States)

Cannavò, Antonino; Torrisi, Lorenzo; Ceccio, Giovanni; Cutroneo, Mariapompea; Calcagno, Lucia; Sciuto, Antonella; Mazzillo, Massimo

2018-01-01

X-ray emission from laser generated plasma was studied at low (1010 W/cm2) and high (1018 W/cm2) intensity using ns and fs laser, respectively. Plasma characteristics were controlled trough the laser parameters, the irradiation conditions and the target properties. The X-ray spectra were acquired using fast detection technique based on SiC diodes with different active regions. The X-ray yield increases with the atomic number of the target, both at low and high intensity, and a similar empirical law has been obtained. The X-ray emission mechanisms from plasma are correlated to the plasma temperature and density and to the Coulomb charge particle acceleration, due to the charge separation effects produced in the non-equilibrium plasma. Functional dependences, theoretical approaches and interpretation of possible mechanism will be presented and discussed.

Characterization of X-ray emission from laser generated plasma

Directory of Open Access Journals (Sweden)

Cannavò Antonino

2018-01-01

Full Text Available X-ray emission from laser generated plasma was studied at low (1010 W/cm2 and high (1018 W/cm2 intensity using ns and fs laser, respectively. Plasma characteristics were controlled trough the laser parameters, the irradiation conditions and the target properties. The X-ray spectra were acquired using fast detection technique based on SiC diodes with different active regions. The X-ray yield increases with the atomic number of the target, both at low and high intensity, and a similar empirical law has been obtained. The X-ray emission mechanisms from plasma are correlated to the plasma temperature and density and to the Coulomb charge particle acceleration, due to the charge separation effects produced in the non-equilibrium plasma. Functional dependences, theoretical approaches and interpretation of possible mechanism will be presented and discussed.

Hot and dense plasma probing by soft X-ray lasers

Czech Academy of Sciences Publication Activity Database

Krůs, Miroslav; Kozlová, Michaela; Nejdl, Jaroslav; Rus, B.

2018-01-01

Roč. 13, č. 1 (2018), č. článku C01004. ISSN 1748-0221. [International Symposium on Laser-Aided Plasma Diagnostics/18./. Prague, 24.09.2017-28.09.2017] R&D Projects: GA MŠk LM2010014; GA MŠk(CZ) LM2015083 Institutional support: RVO:61389021 Keywords : Plasma diagnostics - interferometry * spectroscopy and imaging * Plasma diagnostics - probes * Plasma generation (laser-produced, RF, x ray-produced) Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: 2.11 Other engineering and technologies Impact factor: 1.220, year: 2016 http://iopscience.iop.org/article/10.1088/1748-0221/13/01/C01004

Sapphire capillaries for laser-driven wakefield acceleration in plasma. Fs-laser micromachining and characterization

International Nuclear Information System (INIS)

Schwinkendorf, Jan-Patrick

2012-05-01

Plasma wakefields are a promising approach for the acceleration of electrons with ultrahigh (10 to 100 GV/m) electric fields. Nowadays, high-intensity laser pulses are routinely utilized to excite these large-amplitude plasma waves. However, several detrimental effects such as laser diffraction, electron-wake dephasing and laser depletion may terminate the acceleration process. Two of these phenomena can be mitigated or avoided by the application of capillary waveguides, e.g. fabricated out of sapphire for longevity. Capillaries may compensate for laser diffraction like a fiber and allow for the creation of tapered gas-density profiles working against the dephasing between the accelerating wave and the particles. Additionally, they offer the possibility of controlled particle injection. This thesis is reporting on the set up of a laser for fs-micromachining of capillaries of almost arbitrary shapes and a test stand for density-profile characterization. These devices will permit the creation of tailored gas-density profiles for controlled electron injection and acceleration inside plasma.

Sapphire capillaries for laser-driven wakefield acceleration in plasma. Fs-laser micromachining and characterization

Energy Technology Data Exchange (ETDEWEB)

Schwinkendorf, Jan-Patrick

2012-08-15

Plasma wakefields are a promising approach for the acceleration of electrons with ultrahigh (10 to 100 GV/m) electric fields. Nowadays, high-intensity laser pulses are routinely utilized to excite these large-amplitude plasma waves. However, several detrimental effects such as laser diffraction, electron-wake dephasing and laser depletion may terminate the acceleration process. Two of these phenomena can be mitigated or avoided by the application of capillary waveguides, e.g. fabricated out of sapphire for longevity. Capillaries may compensate for laser diffraction like a fiber and allow for the creation of tapered gas-density profiles working against the dephasing between the accelerating wave and the particles. Additionally, they offer the possibility of controlled particle injection. This thesis is reporting on the set up of a laser for fs-micromachining of capillaries of almost arbitrary shapes and a test stand for density-profile characterization. These devices will permit the creation of tailored gas-density profiles for controlled electron injection and acceleration inside plasma.

Temporally asymmetric laser pulse for magnetic-field generation in plasmas

Energy Technology Data Exchange (ETDEWEB)

Singh, Mamta; Gopal, Krishna; Gupta, Devki Nandan, E-mail: dngupta@physics.du.ac.in

2016-04-01

Of particular interest in this article, the case study of an asymmetric laser pulse interaction with a plasma for magnetic field enhancement has been investigated. The strong ponderomotive force due to the short leading edge of the propagating laser pulse drives a large nonlinear current, producing a stronger quasistatic magnetic field. An analytical expression for the magnetic field is derived and the strength of the magnetic field is estimated for the current laser-plasma parameters. The theoretical results are validated through the particle-in-cell (PIC) simulations and are in very close agreement with the simulation based estimations. This kind of magnetic field can be useful in the plasma based accelerators as well as in the laser-fusion based experiments. - Highlights: • We employ an asymmetric laser pulse to enhance the magnetic field strength in a plasma. • Short leading front of the pulse drives a strong ponderomotive force. • An analytical expression for the magnetic field is derived. • The strength of the magnetic field is estimated for the current laser–plasma parameters.

Temporally asymmetric laser pulse for magnetic-field generation in plasmas

International Nuclear Information System (INIS)

Singh, Mamta; Gopal, Krishna; Gupta, Devki Nandan

2016-01-01

Of particular interest in this article, the case study of an asymmetric laser pulse interaction with a plasma for magnetic field enhancement has been investigated. The strong ponderomotive force due to the short leading edge of the propagating laser pulse drives a large nonlinear current, producing a stronger quasistatic magnetic field. An analytical expression for the magnetic field is derived and the strength of the magnetic field is estimated for the current laser-plasma parameters. The theoretical results are validated through the particle-in-cell (PIC) simulations and are in very close agreement with the simulation based estimations. This kind of magnetic field can be useful in the plasma based accelerators as well as in the laser-fusion based experiments. - Highlights: • We employ an asymmetric laser pulse to enhance the magnetic field strength in a plasma. • Short leading front of the pulse drives a strong ponderomotive force. • An analytical expression for the magnetic field is derived. • The strength of the magnetic field is estimated for the current laser–plasma parameters.

Angular distribution of laser ablation plasma

International Nuclear Information System (INIS)

Kondo, K.; Kanesue, T.; Dabrowski, R.; Okamura, M.

2010-01-01

An expansion of a laser induced plasma is fundamental and important phenomena in a laser ion source. To understand the expanding direction, an array of Langmuir probes were employed. The chosen ion for the experiment was Ag 1+ which was created by a second harmonics of a Nd-YAG laser. The obtained angular distribution was about ±10 degree. This result also indicates a proper positioning of a solenoid magnet which enhances ion beam current.

Self-phase modulation of laser light in laser produced plasma

International Nuclear Information System (INIS)

Yamanaka, C.; Yamanaka, T.; Mizui, J.; Yamaguchi, N.

1975-02-01

A spectrum broadening due to the self-phase modulation of a laser light was observed in the laser produced deuterium and hydrogen plasma. Qualitative treatments of the density modulation due to the self-focusing process and the modulational instability were discussed. The theoretical estimation of spectrum broadening fairly accorded with the experimental results. (auth.)

DEVICE FOR INVESTIGATION OF MAGNETRON AND PULSED-LASER PLASMA

Directory of Open Access Journals (Sweden)

A. P. Burmakov

2012-01-01

Full Text Available Various modifications of complex pulsed laser and magnetron deposition thin-film structures unit are presented. They include joint and separate variants of layer deposition. Unit realizes the plasma parameters control and enhances the possibility of laser-plasma and magnetron methods of coatings deposition.

Electron acceleration using laser produced plasmas

CERN Multimedia

CERN. Geneva; Landua, Rolf

2005-01-01

Low density plasmas have long been of interest as a potential medium for particle acceleration since relativistic plasma waves are capable of supporting electric fields greater than 100 GeV/m. The physics of particle acceleration using plasmas will be reviewed, and new results will be discussed which have demonstrated that relatively narrow energy spread (<3%) beams having energies greater than 100 MeV can be produced from femtosecond laser plasma interactions. Future experiments and potential applications will also be discussed.

effect of the plasma ion channel on self-focusing of a Gaussian laser pulse in underdense plasma

Directory of Open Access Journals (Sweden)

Sh Irani

2013-09-01

Full Text Available  We have considered the self-focusing of a Gaussian laser pulse in unmagnetized plasma. High-intensity electromagnetic fields cause the variation of electron density in plasma. These changes in the special conditions cause the acceleration of electrons to the higher energy and velocities. Thus the equation of plasma density evolution was obtained considering the electrons ponderomotive force. Then, an equation for the width of laser pulse with a relativistic mass correction term and the effect of ion channel were derived and the propagation of high-intensity laser pulse in an underdense plasma with weak relativistic approximation was investigated. It is shown that the ratio of ion channel radius to spot size could result in different forms of self focusing for the laser pulse in plasma.

Plasma turbulence imaging using high-power laser Thomson scattering

Science.gov (United States)

Zweben, S. J.; Caird, J.; Davis, W.; Johnson, D. W.; Le Blanc, B. P.

2001-01-01

The two-dimensional (2D) structure of plasma density turbulence in a magnetically confined plasma can potentially be measured using a Thomson scattering system made from components of the Nova laser of Lawrence Livermore National Laboratory. For a plasma such as the National Spherical Torus Experiment at the Princeton Plasma Physics Laboratory, the laser would form an ≈10-cm-wide plane sheet beam passing vertically through the chamber across the magnetic field. The scattered light would be imaged by a charge coupled device camera viewing along the direction of the magnetic field. The laser energy required to make 2D images of density turbulence is in the range 1-3 kJ, which can potentially be obtained from a set of frequency-doubled Nd:glass amplifiers with diameters in the range of 208-315 mm. A laser pulse width of ⩽100 ns would be short enough to capture the highest frequency components of the expected density fluctuations.

Stimulated Brillouin backscattering and magnetic field generation in laser-produced plasmas

International Nuclear Information System (INIS)

Bawa'aneh, M.S.

1999-01-01

This thesis is concerned with aspects of laser-plasma interactions related to fusion reactions; in particular thermoelectric magnetic field generation around a hole dug in plasma by intense laser beams, and stimulated Brillouin back scattering (SBBS) from plasmas containing hot spots. A hole, of the size of the laser focal spot, is dug in the plasma when illuminated by intense laser if the laser pressure exceeds the plasma thermal pressure. This hole is found to have steep, radial density gradients. My first concern arose from the prediction that magnetic fields might be generated around the hole-plasma interface in places where the steep density gradients overlap with the non-aligned temperature gradients. When a high-power laser beam is focused on a solid pellet, plasma is formed at the surface. In order to create conditions for thermonuclear reactions in the interior of the pellet, an effective deposition of the laser energy to thermal energy of the pellet via laser-plasma coupling is necessary. When light irradiates a plasma collective processes occur, which can either enhance or reduce the light absorption. For a better understanding of the fusion problem a knowledge of the nature of these collective processes and of the fraction of light reflected from the plasma modes is required. Local hot spots seen experimentally lead to higher gain levels of scattered light. These local temperature inhomogeneities could lead to non-equilibrium distributions, which result in a free energy leading to some interesting phenomena in plasma. In the second part of the thesis stimulated Brillouin back scattering from an ion acoustic mode in a hot spot is studied. Temperature inhomogeneities lead to an ion acoustic instability, and to higher levels of SBBS gain, which leads to lower thresholds for the same electron to ion temperature ratios. This could be the answer for the observed high levels of scattering from hot spots. (author)

Studies of intense-laser plasma instabilities

Czech Academy of Sciences Publication Activity Database

Láska, Leoš; Krása, Josef; Badziak, J.; Jungwirth, Karel; Krouský, Eduard; Margarone, Daniele; Parys, P.

2013-01-01

Roč. 272, May (2013), 94-98 ISSN 0169-4332 R&D Projects: GA MŠk(CZ) 7E09092; GA MŠk(CZ) LC528; GA AV ČR IAA100100715 Institutional research plan: CEZ:AV0Z10100523 Keywords : laser plasma instabilities * self-generated magnetic field * longitudinal structure of the expanding plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.538, year: 2013

Waves and instabilities in noneutral plasmas

International Nuclear Information System (INIS)

Davidson, R.C.

1989-01-01

This paper presents a survey of the equilibrium, stability and collective oscillation properties of magnetically-confined nonneutral plasmas. Emphasis is placed on summarizing several of the technical advances that have occurred in both theory and experiment since the early 1970's. 97 refs., 26 figs

Plasma dynamics from laser ablated solid lithium

Indian Academy of Sciences (India)

b; 52.25.-b; 52.70.-m. 1. Introduction. Pulsed laser ablation of a solid sample generates a dense plasma emission in the shape of ... The multichannel analyser plate of the ICCD was gated for as less as 4 ns using ... to explain the atomic collision processes [4]. .... Within duration of laser pulse, there occurs laser-solid interac-.

Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

Science.gov (United States)

Chen, Jikun; Stender, Dieter; Pichler, Markus; Döbeli, Max; Pergolesi, Daniele; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas

2015-10-01

Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially 18O substituted La0.6Sr0.4MnO3 target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

Laser and Plasma Technology Division, Annual Reports 1996 and 1997

International Nuclear Information System (INIS)

Venkatramani, N.

1999-04-01

This report describes the activity of the Laser and Plasma Technology Division of Bhabha Atomic Research Centre during the two year period 1996- 1997. This division is engaged in the research and development of high power beams mainly laser, plasma and electron beams. Laser and Plasma Technology Division has strived to establish indigenous capability to cater to the requirements of Department of Atomic Energy. This involves development and technology readiness study of laser, plasma and electron beam devices. In addition, studies are also carried out on related physical phenomenon with a view to gain better understanding of the devices. This report has been compiled from individual reports of various groups/sections working in the division. A list of publications by the several members of the division is also included. (author)

Infrared laser scattering system for the plasma diagnostics

International Nuclear Information System (INIS)

Hiraki, Naoji; Kawasaki, Shoji; Muraoka, Katsunori

1975-01-01

As the results of the parametric studies of the double discharge TEA CO 2 laser, the required properties on the laser system for the scattering diagnostics of plasmas are shown to be realized with our CO 2 laser. The direction of the future improvements of the laser performance is also discussed. (auth.)

Optical characteristics of a gallium laser plasma

International Nuclear Information System (INIS)

Shuaibov, A.K.; Shimon, L.L.; Dashchenko, A.I.; Shevera, I.V.; Chuchman, M.P.

2001-01-01

Results are presented from studies of the emission from an erosion gallium laser plasma at a moderate intensity (W = (1-5) x 10 8 W/cm 2 ) of a 1.06-μm laser radiation. It is shown that, under these conditions, the lower excited states of gallium atoms are populated most efficiently. Among the ions, only the most intense GaII lines are observed in the emission spectrum. The populations of GaI and GaII excited states are not related to direct electron excitation, but are determined by the recombination of gallium ions with slow electrons. The recombination times of GaIII and GaII ions in the core of the plasma jet are determined from the waveforms of emission in the GaII and GaI spectral lines and are equal to 10 and 140 ns, respectively. The results obtained are of interest for spectroscopic diagnostics of an erosion plasma produced from gallium-containing layered crystals during the laser deposition of thin films

MED101: a laser-plasma simulation code. User guide

International Nuclear Information System (INIS)

Rodgers, P.A.; Rose, S.J.; Rogoyski, A.M.

1989-12-01

Complete details for running the 1-D laser-plasma simulation code MED101 are given including: an explanation of the input parameters, instructions for running on the Rutherford Appleton Laboratory IBM, Atlas Centre Cray X-MP and DEC VAX, and information on three new graphics packages. The code, based on the existing MEDUSA code, is capable of simulating a wide range of laser-produced plasma experiments including the calculation of X-ray laser gain. (author)

Laser and Plasma Technology Division : annual report 1991

International Nuclear Information System (INIS)

1992-01-01

A brief account of the research and development (R and D) activities carried out by Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Bombay during 1991 is presented. The R and D activities are reported under the headings (1) Laser Activities, (2) Thermal Plasma Activities, (3) Electron Beam Activities and (4) Divisional Workshop Activities. List of publications is given at the end of each activity heading

Laser-produced aluminum plasma expansion inside a plastic plasma envelope

Czech Academy of Sciences Publication Activity Database

Kasperczuk, A.; Pisarczyk, T.; Chodukowski, T.; Kalinowska, Z.; Parys, P.; Renner, Oldřich; Gus´kov, S.Y.; Demchenko, N. N.; Ullschmied, Jiří; Krouský, Eduard; Pfeifer, Miroslav; Rohlena, Karel; Skála, Jiří

2012-01-01

Roč. 19, č. 9 (2012), s. 1-8 ISSN 1070-664X R&D Projects: GA MŠk(CZ) 7E09092; GA MŠk(CZ) LC528; GA ČR GAP205/10/0814 Grant - others:7FP LASERLAB-EUROPE(XE) 228334 Program:FP7 Institutional research plan: CEZ:AV0Z10100523; CEZ:AV0Z20430508 Keywords : laser-mater interaction * plasma jets production * x-ray spectroscopy * particle plasma diagnosis * ion charge density * plasma temperature Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.376, year: 2012

Plasma discreteness effects in the presence of an intense, ultrashort laser pulse

Energy Technology Data Exchange (ETDEWEB)

Savchenko, V.I.; Fisch, N.J.

1996-03-01

Discrete effects of the plasma irradiated by an ultrashort, intense laser pulse are investigated. Although, for most plasmas of interest, the damping of the laser pulse is due to collective plasma effects, in certain regimes the energy absorbed in the plasma microfields can be important. A scattering matrix is derived for an electron scattering off an ion in the presence of an intense laser field.

Plasma discreteness effects in the presence of an intense, ultrashort laser pulse

International Nuclear Information System (INIS)

Savchenko, V.I.; Fisch, N.J.

1996-03-01

Discrete effects of the plasma irradiated by an ultrashort, intense laser pulse are investigated. Although, for most plasmas of interest, the damping of the laser pulse is due to collective plasma effects, in certain regimes the energy absorbed in the plasma microfields can be important. A scattering matrix is derived for an electron scattering off an ion in the presence of an intense laser field

Excitation of Accelerating Plasma Waves by Counter-propagating Laser Beams

International Nuclear Information System (INIS)

Gennady Shvets; Nathaniel J. Fisch; Alexander Pukhov

2001-01-01

Generation of accelerating plasma waves using two counter-propagating laser beams is considered. Colliding-beam accelerator requires two laser pulses: the long pump and the short timing beam. We emphasize the similarities and differences between the conventional laser wakefield accelerator and the colliding-beam accelerator (CBA). The highly nonlinear nature of the wake excitation is explained using both nonlinear optics and plasma physics concepts. Two regimes of CBA are considered: (i) the short-pulse regime, where the timing beam is shorter than the plasma period, and (ii) the parametric excitation regime, where the timing beam is longer than the plasma period. Possible future experiments are also outlined

Motion of the plasma critical layer during relativistic-electron laser interaction with immobile and comoving ion plasma for ion acceleration

International Nuclear Information System (INIS)

Sahai, Aakash A.

2014-01-01

We analyze the motion of the plasma critical layer by two different processes in the relativistic-electron laser-plasma interaction regime (a 0 >1). The differences are highlighted when the critical layer ions are stationary in contrast to when they move with it. Controlling the speed of the plasma critical layer in this regime is essential for creating low-β traveling acceleration structures of sufficient laser-excited potential for laser ion accelerators. In Relativistically Induced Transparency Acceleration (RITA) scheme, the heavy plasma-ions are fixed and only trace-density light-ions are accelerated. The relativistic critical layer and the acceleration structure move longitudinally forward by laser inducing transparency through apparent relativistic increase in electron mass. In the Radiation Pressure Acceleration (RPA) scheme, the whole plasma is longitudinally pushed forward under the action of the laser radiation pressure, possible only when plasma ions co-propagate with the laser front. In RPA, the acceleration structure velocity critically depends upon plasma-ion mass in addition to the laser intensity and plasma density. In RITA, mass of the heavy immobile plasma-ions does not affect the speed of the critical layer. Inertia of the bared immobile ions in RITA excites the charge separation potential, whereas RPA is not possible when ions are stationary

Laser beam trapping and propagation in cylindrical plasma columns

International Nuclear Information System (INIS)

Feit, M.D.; Fleck, J.A. Jr.

1976-01-01

An analysis of the scheme to heat magnetically confined plasma columns to kilovolt temperatures with a laser beam requires consideration of two propagation problems. The first question to be answered is whether stable beam trapping is possible. Since the laser beam creates its own density profile by heating the plasma, the propagation of the beam becomes a nonlinear phenomenon, but not necessarily a stable one. In addition, the electron density at a given time depends on the preceding history of both the medium and the laser pulse. A self-consistent time dependent treatment of the beam propagation and the medium hydrodynamics is consequently required to predict the behavior of the laser beam. Such calculations have been carried out and indicate that propagation of a laser beam in an initially uniform plasma can form a stable filament which alternately focuses and defocuses. An additional question that is discussed is whether diffractive losses associated with long propagation paths are significant

Modeling of plasma plume induced during laser welding

International Nuclear Information System (INIS)

Moscicki, T.; Hoffman, J.; Szymanski, Z.

2005-01-01

During laser welding, the interaction of intense laser radiation with a work-piece leads to the formation of a long, thin, cylindrical cavity in a metal, called a keyhole. Generation of a keyhole enables the laser beam to penetrate into the work-piece and is essential for deep welding. The keyhole contains ionized metal vapour and is surrounded by molten material called the weld pool. The metal vapour, which flows from the keyhole mixes with the shielding gas flowing from the opposite direction and forms a plasma plume over the keyhole mouth. The plasma plume has considerable influence on the processing conditions. Plasma strongly absorbs laser radiation and significantly changes energy transfer from the laser beam to a material. In this paper the results of theoretical modelling of plasma plume induced during welding with CO 2 laser are presented. The set of equations consists of equation of conservation of mass, energy, momentum and the diffusion equation: ∂ρ/∂t + ∇·(ρ ρ ν =0; ∂(ρE)/∂t + ∇·( ρ ν (ρE + p)) = ∇ (k eff ∇T - Σ j h j ρ J j + (τ eff · ρ ν )) + Σ i κ i I i - R; ∂/∂t(ρ ρ ν ) + ∇· (ρ ρ ν ρ ν ) = - ∇p + ∇(τ) + ρ ρ g + ρ F, where τ is viscous tensor τ = μ[(∇ ρ ν + ∇ ρT ν )-2/3∇· ρ ν I]; ∂/∂t(ρY i ) + ∇·(ρ ρ ν Y i ) = ∇·ρD i,m ∇T i ; where μ ν denotes velocity vector, E - energy, ρ mass density; k - thermal conductivity, T- temperature, κ - absorption coefficient, I i local laser intensity, R - radiation loss function, p - pressure, h j enthalpy, J j - diffusion flux of j component, ν g - gravity, μ F - external force, μ - dynamic viscosity, I - unit tensor, Y i - mass fraction of iron vapor in the gas mixture, D i,m - mass diffusion coefficient. The terms k eff and τ eff contain the turbulent component of the thermal conductivity and the viscosity, respectively. All the material functions are functions of the temperature and mass fraction only. The equations

Proceedings of the 13th international symposium on laser-aided plasma diagnostics

International Nuclear Information System (INIS)

Kawahata, Kazuo

2007-09-01

The 9th international symposium on LASER-AIDED PLASMA DIAGNOSTICS was held from 18th November to 21st September, 2007 at Takayama, Japan. This symposium was organized by the National Institute for Fusion Science, Toki, Japan. The topics of the symposium include laser diagnostics and diagnostics aided by lasers for fusion plasmas, industrial process plasmas, environmental plasmas as well as for other plasma applications and processes related to plasmas. Hardware development related to laser-aided plasma diagnostics is another topic. Over 80 participants attended this international symposium. 1 Akazaki lecture, 10 general talks, 10 topical talks, 12 short oral talks and 45 posters were presented. This issue is the collection of the papers presented at the title symposium. The 41 of the presented papers are indexed individually. (J.P.N.)

Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

Energy Technology Data Exchange (ETDEWEB)

Chen, Jikun; Stender, Dieter; Pichler, Markus; Pergolesi, Daniele; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas, E-mail: thomas.lippert@psi.ch [General Energy Research Department, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Döbeli, Max [Ion Beam Physics, ETH Zurich, CH-8093 Zurich (Switzerland)

2015-10-28

Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially {sup 18}O substituted La{sub 0.6}Sr{sub 0.4}MnO{sub 3} target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

Experimental studies of laser guiding and wake excitation in plasma channels

International Nuclear Information System (INIS)

Volfbeyn, P.; Lawrence Berkeley National Lab., CA

1998-06-01

This thesis presents results of experimental investigations of laser guiding in plasma channels. A new technique for plasma channel creation, the Ignitor-Heater scheme was proposed and experimentally tested in hydrogen and nitrogen. It made use of two laser pulses. The Ignitor, an ultrashort ( 17 W/cm 2 , 75fs laser pulse. The guiding properties and transmission and coupling efficiency were studied as a function of relative position of the channel and the injection pulse focus. Whereas entrance coupling efficiency into the channel was lower than expected, channel coupling to continuum losses were found to be in good agreement with analytical predictions. The authors speculate that increased coupling efficiency can be achieved through better mode matching into the channel. Analytic and numerical one dimensional (1-D), nonrelativistic theory of laser pulse propagation in underdense plasma was presented, in the context of laser wakefield acceleration. The relation between the laser pulse energy depletion, longitudinal laser pulse shape distortion, and changes in the group velocity and center wavelength was explored. 1-D theory was extended to treat the case of a laser exciting a wake in a hollow plasma channel, by making use of an energy conservation argument. Based on the results of this theory, a laser wakefield diagnostic was proposed where, by measuring the changes in phase or spectrum of the driving laser pulse, it is possible to infer the amplitude of the plasma wake

Measurements of Electron Density Profiles of Plasmas Produced by Nike KrF Laser for Laser Plasma Instability (LPI) Research

Science.gov (United States)

Oh, Jaechul; Weaver, J. L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Karasik, M.; Chan, L.-Y.; Serlin, V.; Phillips, L.

2013-10-01

Knowing spatial profiles of electron density (ne) in the underdense coronal region (n Nike LPI experiment, a side-on grid imaging refractometer (GIR) was deployed for measuring the underdense plasma profiles. Plasmas were produced from flat CH targets illuminated by Nike KrF laser with total energies up to 1 kJ of 0.5 ~ 1 nsec FWHM pulses. The GIR resolved ne up to 3 ×1021 /cm3 in space taking 2D snapshot images of probe laser (λ = 263 nm, Δt = 10 ps) beamlets (50 μm spacing) refracted by the plasma at a selected time during the laser illumination. The individual beamlet transmittances were also measured for Te estimation. Time-resolved spectrometers with an absolute-intensity-calibrated photodiode array and a streak camera simultaneously detected light emission from the plasma in spectral ranges relevant to Raman (SRS) and two plasmon decay instabilities. The measured spatial profiles are compared with simulation results from the FAST3D radiation hydrocode and their effects on the LPI observations are investigated. Work supported by DoE/NNSA and performed at Naval Research Laboratory.

Measurement of Laser Plasma Instability (LPI) Driven Light Scattering from Plasmas Produced by Nike KrF Laser

Science.gov (United States)

Oh, Jaechul; Weaver, J. L.; Phillips, L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Serlin, V.; Lehmberg, R. H.; McLean, E. A.; Manka, C. K.

2010-11-01

With short wavelength (248 nm), large bandwidth (1˜3 THz), and ISI beam smoothing, Nike KrF laser provides unique research opportunities and potential for direct-drive inertial confinement fusion. Previous Nike experiments observed two plasmon decay (TPD) driven signals from CH plasmas at the laser intensities above ˜2x10^15 W/cm^2 with total laser energies up to 1 kJ of ˜350 ps FWHM pulses. We have performed a further experiment with longer laser pulses (0.5˜4.0 ns FWHM) and will present combined results of the experiments focusing on light emission data in spectral ranges relevant to the Raman (SRS) and TPD instabilities. Time- or space-resolved spectral features of TPD were detected at different viewing angles and the absolute intensity calibrated spectra of thermal background were used to obtain blackbody temperatures in the plasma corona. The wave vector distribution in k-space of the participating TPD plasmons will be also discussed. These results show promise for the proposed direct-drive designs.

Modeling and application of plasma charge current in deep penetration laser welding

International Nuclear Information System (INIS)

Zhang, Xudong; Chen, Wuzhu; Jiang, Ping; Guo, Jing; Tian, Zhiling

2003-01-01

Plasma charge current distribution during deep penetration CO 2 laser welding was analyzed theoretically and experimentally. The laser-induced plasma above the workpiece surface expands up to the nozzle, driven by the particle concentration gradient, forming an electric potential between the workpiece and the nozzle due to the large difference between the diffusion velocities of the ions and the electrons. The plasma-induced current obtained by electrically connecting the nozzle and the workpiece can be increased by adding a negative external voltage. For a fixed set of welding conditions, the plasma charge current increases with the external voltage to a saturation value. The plasma charge current decreases as the nozzle-to-workpiece distance increases. Therefore, closed-loop control of the nozzle-to-workpiece distance for laser welding can be based on the linear relationship between the plasma charge current and the distance. In addition, the amount of plasma above the keyhole can be reduced by a transverse magnetic field, which reduces the attenuation of the incident laser power by the plasma so as to increase the laser welding thermal efficiency

Editorial: Focus on Laser- and Beam-Driven Plasma Accelerators

Science.gov (United States)

Joshi, Chan; Malka, Victor

2010-04-01

The ability of short but intense laser pulses to generate high-energy electrons and ions from gaseous and solid targets has been well known since the early days of the laser fusion program. However, during the past decade there has been an explosion of experimental and theoretical activity in this area of laser-matter interaction, driven by the prospect of realizing table-top plasma accelerators for research, medical and industrial uses, and also relatively small and inexpensive plasma accelerators for high-energy physics at the frontier of particle physics. In this focus issue on laser- and beam-driven plasma accelerators, the latest advances in this field are described. Focus on Laser- and Beam-Driven Plasma Accelerators Contents Slow wave plasma structures for direct electron acceleration B D Layer, J P Palastro, A G York, T M Antonsen and H M Milchberg Cold injection for electron wakefield acceleration X Davoine, A Beck, A Lifschitz, V Malka and E Lefebvre Enhanced proton flux in the MeV range by defocused laser irradiation J S Green, D C Carroll, C Brenner, B Dromey, P S Foster, S Kar, Y T Li, K Markey, P McKenna, D Neely, A P L Robinson, M J V Streeter, M Tolley, C-G Wahlström, M H Xu and M Zepf Dose-dependent biological damage of tumour cells by laser-accelerated proton beams S D Kraft, C Richter, K Zeil, M Baumann, E Beyreuther, S Bock, M Bussmann, T E Cowan, Y Dammene, W Enghardt, U Helbig, L Karsch, T Kluge, L Laschinsky, E Lessmann, J Metzkes, D Naumburger, R Sauerbrey, M. Scḧrer, M Sobiella, J Woithe, U Schramm and J Pawelke The optimum plasma density for plasma wakefield excitation in the blowout regime W Lu, W An, M Zhou, C Joshi, C Huang and W B Mori Plasma wakefield acceleration experiments at FACET M J Hogan, T O Raubenheimer, A Seryi, P Muggli, T Katsouleas, C Huang, W Lu, W An, K A Marsh, W B Mori, C E Clayton and C Joshi Electron trapping and acceleration on a downward density ramp: a two-stage approach R M G M Trines, R Bingham, Z Najmudin

Laser plasma instability experiments with KrF lasers

International Nuclear Information System (INIS)

Weaver, J. L.; Karasik, M.; Serlin, V.; Obenschain, S.; Chan, L-Y.; Kehne, D.; Schmitt, A. J.; Colombant, D.; Velikovich, A.; Oh, J.; Lehmberg, R. H.; Afeyan, B.; Phillips, L.; Seely, J.; Brown, C.; Feldman, U.; Aglitskiy, Y.; Mostovych, A. N.; Holland, G.

2007-01-01

Deleterious effects of laser-plasma instability (LPI) may limit the maximum laser irradiation that can be used for inertial confinement fusion. The short wavelength (248 nm), large bandwidth, and very uniform illumination available with krypton-fluoride (KrF) lasers should increase the maximum usable intensity by suppressing LPI. The concomitant increase in ablation pressure would allow implosion of low-aspect-ratio pellets to ignition with substantial gain (>20) at much reduced laser energy. The proposed KrF-laser-based Fusion Test Facility (FTF) would exploit this strategy to achieve significant fusion power (150 MW) with a rep-rate system that has a per pulse laser energy well below 1 MJ. Measurements of LPI using the Nike KrF laser are presented at and above intensities needed for the FTF (I∼2x10 15 W/cm 2 ). The results to date indicate that LPI is indeed suppressed. With overlapped beam intensity above the planar, single beam intensity threshold for the two-plasmon decay instability, no evidence of instability was observed via measurements of (3/2)ω o and (1/2)ω o harmonic emissions

Research progress of laser welding process dynamic monitoring technology based on plasma characteristics signal

Directory of Open Access Journals (Sweden)

Teng WANG

2017-02-01

Full Text Available During the high-power laser welding process, plasmas are induced by the evaporation of metal under laser radiation, which can affect the coupling of laser energy and the workpiece, and ultimately impact on the reliability of laser welding quality and process directly. The research of laser-induced plasma is a focus in high-power deep penetration welding field, which provides a promising research area for realizing the automation of welding process quality inspection. In recent years, the research of laser welding process dynamic monitoring technology based on plasma characteristics is mainly in two aspects, namely the research of plasma signal detection and the research of laser welding process modeling. The laser-induced plasma in the laser welding is introduced, and the related research of laser welding process dynamic monitoring technology based on plasma characteristics at home and abroad is analyzed. The current problems in the field are summarized, and the future development trend is put forward.

Wave function of free electron in a strong laser plasma

International Nuclear Information System (INIS)

Zhu Shitong; Shen Wenda; Guo Qizhi

1993-01-01

The wave function of free electron in a strong laser plasma is obtained by solving exactly the Dirac equation in a curved space-time with optical metric for the laser plasma. When the laser field is diminished to zero, the wave function is naturally reduced to relativistic wave function of free electron. The possible application of the wave function is discussed

Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations

International Nuclear Information System (INIS)

Gonsalves, Anthony; Nakamura, Kei; Lin, Chen; Osterhoff, Jens; Shiraishi, Satomi; Schroeder, Carl; Geddes, Cameron; Toth, Csaba; Esarey, Eric; Leemans, Wim

2011-01-01

A technique has been developed to accurately align a laser beam through a plasma channel by minimizing the shift in laser centroid and angle at the channel outptut. If only the shift in centroid or angle is measured, then accurate alignment is provided by minimizing laser centroid motion at the channel exit as the channel properties are scanned. The improvement in alignment accuracy provided by this technique is important for minimizing electron beam pointing errors in laser plasma accelerators.

Design of a free-electron laser driven by the LBNL laser-plasma-accelerator

International Nuclear Information System (INIS)

Schroeder, C.B.; Fawley, W.M.; Montgomery, A.L.; Robinson, K.E.; Gruner, F.; Bakeman, M.; Leemans, W.P.

2007-01-01

We discuss the design and current status of a compact free-electron laser (FEL), generating ultra-fast, high-peak flux, VUV pulses driven by a high-current, GeV electron beam from the existing Lawrence Berkeley National Laboratory (LBNL) laser-plasma accelerator, whose active acceleration length is only a few cm. The proposed ultra-fast source would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science with pulse lengths of tens of fs. Owing to the high current ( and 10 kA) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially greater than 1013 photons/pulse. Devices based both on SASE and high-harmonic generated input seeds, to reduce undulator length and fluctuations, are considered

The Validity of a Paraxial Approximation in the Simulation of Laser Plasma Interactions

International Nuclear Information System (INIS)

Hyole, E. M.

2000-01-01

The design of high-power lasers such as those used for inertial confinement fusion demands accurate modeling of the interaction between lasers and plasmas. In inertial confinement fusion, initial laser pulses ablate material from the hohlraum, which contains the target, creating a plasma. Plasma density variations due to plasma motion, ablating material and the ponderomotive force exerted by the laser on the plasma disrupt smooth laser propagation, undesirably focusing and scattering the light. Accurate and efficient computational simulations aid immensely in developing an understanding of these effects. In this paper, we compare the accuracy of two methods for calculating the propagation of laser light through plasmas. A full laser-plasma simulation typically consists of a fluid model for the plasma motion and a laser propagation model. These two pieces interact with each other as follows. First, given the plasma density, one propagates the laser with a refractive index determined by this density. Then, given the laser intensities, the calculation of one time step of the plasma motion provides a new density for the laser propagation. Because this procedure repeats over many time steps, each piece must be performed accurately and efficiently. In general, calculation of the light intensities necessitates the solution of the Helmholtz equation with a variable index of refraction. The Helmholtz equation becomes extremely difficult and time-consuming to solve as the problem size increases. The size of laser-plasma problems of present interest far exceeds current capabilities. To avoid solving the full Helmholtz equation one may use a partial approximation. Generally speaking the partial approximation applies when one expects negligible backscattering of the light and only mild scattering transverse to the direction of light propagation. This approximation results in a differential equation that is first-order in the propagation direction that can be integrated

Nonneutral plasma diagnostic commissioning for the ALPHA Antihydrogen experiment

Science.gov (United States)

Konewko, S.; Friesen, T.; Tharp, T. D.; Alpha Collaboration

2017-10-01

The ALPHA experiment at CERN creates antihydrogen by mixing antiproton and positron plasmas. Diagnostic measurements of the precursor plasmas are performed using a diagnostic suite, colloquially known as the ``stick.'' This stick has a variety of sensors and is able to move to various heights to align the desired diagnostic with the beamline. A cylindrical electrode, a faraday cup, an electron gun, and a microchannel-plate detector (MCP) are regularly used to control and diagnose plasmas in ALPHA. We have designed, built, and tested a new, upgraded stick which includes measurement capabilities in both beamline directions.

Current new applications of laser plasmas

International Nuclear Information System (INIS)

Hauer, A.A.; Forslund, D.W.; McKinstrie, C.J.; Wark, J.S.; Hargis, P.J. Jr.; Hamil, R.A.; Kindel, J.M.

1988-09-01

This report describes several new applications of laser-produced plasmas that have arisen in the last few years. Most of the applications have been an outgrowth of the active research in laser/matter interaction inspired by the pursuit of laser fusion. Unusual characteristics of high-intensity laser/matter interaction, such as intense x-ray and particle emission, were noticed early in the field and are now being employed in a significant variety of applications outside the fusion filed. Applications range from biology to materials science to pulsed-power control and particle accelerators. 92 refs., 23 figs., 4 tabs

On the mutual interaction between laser beams in plasmas

International Nuclear Information System (INIS)

Ren, C.; Duda, B.J.; Evans, R.G.; Fonseca, R.A.; Hemker, R.G.; Mori, W.B.

2002-01-01

The nonlinear interaction between light beams in a plasma is studied. In particular, nonlinearities due to relativistic mass corrections and density modulations from a plasma wave wake are considered; but the results can be generalized for other nonlinearities. A simple physical picture using the nonlinear phase velocity of the light wave in a plasma is developed to show that when two laser beams are coherent, the force can be repulsive or attractive, depending on their relative phase. When the two laser beams are polarized in mutually perpendicular directions, the force is always attractive. Using a variational method, a simple analytical expression for this attractive force is derived for Gaussian beams. The centers of the lasers move analogously to point masses under this attractive force with the laser power playing the role of the mass. Under an attractive force, solutions exist where the two lasers can spiral around each other. It is also shown that the plasma wave wake can cause the two spiraling lasers to become intertwined forming a braided pattern. The braiding is common to any nonlinearity which is not instantaneous. The analytical results concerning attraction, repulsion, and braiding have been confirmed using three dimensional particle-in-cell simulations. The simulations also show that angular momentum can radiate away leading to the coalescence of the remaining energy

Laser propagation and soliton generation in strongly magnetized plasmas

Energy Technology Data Exchange (ETDEWEB)

Feng, W.; Li, J. Q.; Kishimoto, Y. [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

2016-03-15

The propagation characteristics of various laser modes with different polarization, as well as the soliton generation in strongly magnetized plasmas are studied numerically through one-dimensional (1D) particle-in-cell (PIC) simulations and analytically by solving the laser wave equation. PIC simulations show that the laser heating efficiency substantially depends on the magnetic field strength, the propagation modes of the laser pulse and their intensities. Generally, large amplitude laser can efficiently heat the plasma with strong magnetic field. Theoretical analyses on the linear propagation of the laser pulse in both under-dense and over-dense magnetized plasmas are well confirmed by the numerical observations. Most interestingly, it is found that a standing or moving soliton with frequency lower than the laser frequency is generated in certain magnetic field strength and laser intensity range, which can greatly enhance the laser heating efficiency. The range of magnetic field strength for the right-hand circularly polarized (RCP) soliton formation with high and low frequencies is identified by solving the soliton equations including the contribution of ion's motion and the finite temperature effects under the quasi-neutral approximation. In the limit of immobile ions, the RCP soliton tends to be peaked and stronger as the magnetic field increases, while the enhanced soliton becomes broader as the temperature increases. These findings in 1D model are well validated by 2D simulations.

Ultraviolet versus infrared: Effects of ablation laser wavelength on the expansion of laser-induced plasma into one-atmosphere argon gas

International Nuclear Information System (INIS)

Ma Qianli; Motto-Ros, Vincent; Laye, Fabrice; Yu Jin; Lei Wenqi; Bai Xueshi; Zheng Lijuan; Zeng Heping

2012-01-01

Laser-induced plasma from an aluminum target in one-atmosphere argon background has been investigated with ablation using nanosecond ultraviolet (UV: 355 nm) or infrared (IR: 1064 nm) laser pulses. Time- and space-resolved emission spectroscopy was used as a diagnostics tool to have access to the plasma parameters during its propagation into the background, such as optical emission intensity, electron density, and temperature. The specific feature of nanosecond laser ablation is that the pulse duration is significantly longer than the initiation time of the plasma. Laser-supported absorption wave due to post-ablation absorption of the laser radiation by the vapor plume and the shocked background gas plays a dominant role in the propagation and subsequently the behavior of the plasma. We demonstrate that the difference in absorption rate between UV and IR radiations leads to different propagation behaviors of the plasma produced with these radiations. The consequence is that higher electron density and temperature are observed for UV ablation. While for IR ablation, the plasma is found with lower electron density and temperature in a larger and more homogenous axial profile. The difference is also that for UV ablation, the background gas is principally evacuated by the expansion of the vapor plume as predicted by the standard piston model. While for IR ablation, the background gas is effectively mixed to the ejected vapor at least hundreds of nanoseconds after the initiation of the plasma. Our observations suggest a description by laser-supported combustion wave for the propagation of the plasma produced by UV laser, while that by laser-supported detonation wave for the propagation of the plasma produced by IR laser. Finally, practical consequences of specific expansion behavior for UV or IR ablation are discussed in terms of analytical performance promised by corresponding plasmas for application with laser-induced breakdown spectroscopy.

Lack of protection following passive transfer of polyclonal highly functional low-dose non-neutralizing antibodies.

Directory of Open Access Journals (Sweden)

Anne-Sophie Dugast

Full Text Available Recent immune correlates analysis from the RV144 vaccine trial has renewed interest in the role of non-neutralizing antibodies in mediating protection from infection. While neutralizing antibodies have proven difficult to induce through vaccination, extra-neutralizing antibodies, such as those that mediate antibody-dependent cellular cytotoxicity (ADCC, are associated with long-term control of infection. However, while several non-neutralizing monoclonal antibodies have been tested for their protective efficacy in vivo, no studies to date have tested the protective activity of naturally produced polyclonal antibodies from individuals harboring potent ADCC activity. Because ADCC-inducing antibodies are highly enriched in elite controllers (EC, we passively transferred highly functional non-neutralizing polyclonal antibodies, purified from an EC, to assess the potential impact of polyclonal non-neutralizing antibodies on a stringent SHIV-SF162P3 challenge in rhesus monkeys. Passive transfer of a low-dose of ADCC inducing antibodies did not protect from infection following SHIV-SF162P3 challenge. Passively administered antibody titers and gp120-specific, but not gp41-specific, ADCC and antibody induced phagocytosis (ADCP were detected in the majority of the monkeys, but did not correlate with post infection viral control. Thus these data raise the possibility that gp120-specific ADCC activity alone may not be sufficient to control viremia post infection but that other specificities or Fc-effector profiles, alone or in combination, may have an impact on viral control and should be tested in future passive transfer experiments.

Free-electron laser with a plasma wave wiggler propagating through a magnetized plasma channel

International Nuclear Information System (INIS)

Jafari, S; Jafarinia, F; Mehdian, H

2013-01-01

A plasma eigenmode has been employed as a wiggler in a magnetized plasma channel for the generation of laser radiation in a free-electron laser. The short wavelength of the plasma wave allows a higher radiation frequency to be obtained than from conventional wiggler free-electron lasers. The plasma can significantly slow down the radiation mode, thereby relaxing the beam energy requirement considerably. In addition, it allows a beam current in excess of the vacuum current limit via charge neutralization. This configuration has a higher tunability by controlling the plasma density in addition to the γ-tunability of the standard FEL. The laser gain has been calculated and numerical computations of the electron trajectories and gain are presented. Four groups (I–IV) of electron orbits have been found. It has been shown that by increasing the cyclotron frequency, the gain for orbits of group I and group III increases, while a decrease in gain has been obtained for orbits of group II and group IV. Similarly, the effect of plasma density on gain has been exhibited. The results indicate that with increasing plasma density, the orbits of all groups shift to higher cyclotron frequencies. The effects of beam self-fields on gain have also been demonstrated. It has been found that in the presence of beam self-fields the sensitivity of the gain increases substantially in the vicinity of gyroresonance. Here, the gain enhancement and reduction are due to the paramagnetic and diamagnetic effects of the self-magnetic field, respectively. (paper)

Application of escape probability to line transfer in laser-produced plasmas

International Nuclear Information System (INIS)

Lee, Y.T.; London, R.A.; Zimmerman, G.B.; Haglestein, P.L.

1989-01-01

In this paper the authors apply the escape probability method to treat transfer of optically thick lines in laser-produced plasmas in plan-parallel geometry. They investigate the effect of self-absorption on the ionization balance and ion level populations. In addition, they calculate such effect on the laser gains in an exploding foil target heated by an optical laser. Due to the large ion streaming motion in laser-produced plasmas, absorption of an emitted photon occurs only over the length in which the Doppler shift is equal to the line width. They find that the escape probability calculated with the Doppler shift is larger compared to the escape probability for a static plasma. Therefore, the ion streaming motion contributes significantly to the line transfer process in laser-produced plasmas. As examples, they have applied escape probability to calculate transfer of optically thick lines in both ablating slab and exploding foil targets under irradiation of a high-power optical laser

Subsurface plasma in beam of continuous CO2-laser

Science.gov (United States)

Danytsikov, Y. V.; Dymshakov, V. A.; Lebedev, F. V.; Pismennyy, V. D.; Ryazanov, A. V.

1986-03-01

Experiments performed at the Institute of Atomic Energy established the conditions for formation of subsurface plasma in substances by laser radiation and its characteristics. A quasi-continuous CO2 laser emitting square pulses of 0.1 to 1.0 ms duration and 1 to 10 kW power as well as a continuous CO2 laser served as radiation sources. Radiation was focused on spots 0.1 to 0.5 mm in diameter and maintained at levels ensuring constant power density during the interaction time, while the temperature of the target surface was measured continuously. Metals, graphite and dielectric materials were tested with laser action taking place in air N2 + O2 mixtures, Ar or He atmosphere under pressures of 0.01 to 1.0 atm. Data on radiation intensity thresholds for evaporation and plasma formation were obtained. On the basis of these thresholds, combined with data on energy balance and the temperature profile in plasma layers, a universal state diagram was constructed for subsurface plasma with nonquantified surface temperature and radiation intensity coordinates.

Plasma diagnostics using laser-excited coupled and transmission ring resonators

International Nuclear Information System (INIS)

Haas, R.A.

1976-01-01

In this paper a simple two-level laser model is used to investigate the frequency response of coupled-cavity laser interferometers. It is found that under certain circumstances, often satisfied by molecular gas lasers, the frequency response exhibits a resonant behavior. This behavior severely complicates the interpretation of coupled-cavity laser interferometer measurements of rapidly varying plasmas. To circumvent this limitation a new type of laser interferometer plasma diagnostic with significantly improved time response was developed. In this interferometer the plasma is located in one arm of a transmission ring resonator cavity that is excited by an externally positioned laser. Thus, the laser is decoupled from the interferometer cavity and the time response of the interferometer is then limited by the Q of the ring resonator cavity. This improved time response is acquired without loss of spatial resolution, but requires a more sensitive signal detector since the laser is no longer used as a detector as it is in conventional coupled-cavity laser interferometers. Thus, the new technique incorporates the speed of the Mach--Zender interferometer and the sensitivity of the coupled-cavity laser interferometer. The basic operating principles of this type of interferometer have been verified using a CO 2 laser

Laser plasma interaction in rugby-shaped hohlraums

Science.gov (United States)

Masson-Laborde, P.-E.; Philippe, F.; Tassin, V.; Monteil, M.-C.; Gauthier, P.; Casner, A.; Depierreux, S.; Seytor, P.; Teychenne, D.; Loiseau, P.; Freymerie, P.

2014-10-01

Rugby shaped-hohlraum has proven to give high performance compared to a classical similar-diameter cylinder hohlraum. Due to this performance, this hohlraum has been chosen as baseline ignition target for the Laser MegaJoule (LMJ). Many experiments have therefore been performed during the last years on the Omega laser facility in order to study in details the rugby hohlraum. In this talk, we will discuss the interpretation of these experiments from the point of view of the laser plasma instability problem. Experimental comparisons have been done between rugby, cylinder and elliptical shape rugby hohlraums and we will discuss how the geometry differences will affect the evolution of laser plasma instabilities (LPI). The efficiency of laser smoothing techniques on these instabilities will also be discussed as well as gas filling effect. The experimental results will be compared with FCI2 hydroradiative calculations and linear postprocessing with Piranah. Experimental Raman and Brillouin spectrum, from which we can infer the location of the parametric instabilities, will be compared to simulated ones, and will give the possibility to compare LPI between the different hohlraum geometries.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Characteristics of the evolution of a plasma formed by cw and pulse-periodic CO2 laser radiation in various gases

Science.gov (United States)

Kanevskiĭ, M. F.; Stepanova, M. A.

1990-06-01

An investigation was made of the interaction between high-power cw and pulse-periodic CO2 laser radiation and a low-threshold optical breakdown plasma near a metal surface. Characteristics of the breakdown plasma were studied as a function of the experimental conditions. A qualitative analysis was made of the results using a simple one-dimensional model for laser combustion waves.

High Power Laser Laboratory at the Institute of Plasma Physics and Laser Microfusion: equipment and preliminary research

Directory of Open Access Journals (Sweden)

Zaraś-Szydłowska Agnieszka

2015-06-01

Full Text Available The purpose of this paper is to present the newly-opened High Power Laser Laboratory (HPLL at the Institute of Plasma Physics and Laser Microfusion (IPPLM. This article describes the laser, the main laboratory accessories and the diagnostic instruments. We also present preliminary results of the first experiment on ion and X-ray generation from laser-produced plasma that has been already performed at the HPLL.

Space-Time Characterization of Laser Plasma Interactions in the Warm Dense Matter Regime

Energy Technology Data Exchange (ETDEWEB)

Cao, L F; Uschmann, I; Forster, E; Zamponi, F; Kampfer, T; Fuhrmann, A; Holl, A; Redmer, R; Toleikis, S; Tschentsher, T; Glenzer, S H

2008-04-30

Laser plasma interaction experiments have been performed using a fs Titanium Sapphire laser. Plasmas have been generated from planar PMMA targets using single laser pulses with 3.3 mJ pulse energy, 50 fs pulse duration at 800 nm wavelength. The electron density distributions of the plasmas in different delay times have been characterized by means of Nomarski Interferometry. Experimental data were compared with hydrodynamic simulation. First results to characterize the plasma density and temperature as a function of space and time are obtained. This work aims to generate plasmas in the warm dense matter (WDM) regime at near solid-density in an ultra-fast laser target interaction process. Plasmas under these conditions can serve as targets to develop x-ray Thomson scattering as a plasma diagnostic tool, e.g., using the VUV free-electron laser (FLASH) at DESY Hamburg.

Construction of a nitrogen laser for plasma diagnostics

International Nuclear Information System (INIS)

Ishiekwene, G.C.

1994-07-01

The challenge faced in finding new sources of energy to bridge the gap between the availability and demand of energy is difficult to be overemphasized. Nuclear fusion seems to provide a potentially limitless source of energy which offers a bright prospect for solving this problem. Although an elaborate programme in fusion may be beyond the economic reach of most third world countries, some modest experiments are necessary to provide an indigenous expertise capable of enhancing international fusion studies. In order to initiate experimental research sufficient for plasma studies at an affordable cost to developing countries, this paper illustrates the construction of a simple, low cost, high power nitrogen laser and investigates some of its performance characteristics. Also, the laser is utilized as a source of illumination in the techniques of shadowgraphy. A series of shadowgrams depicting the temporal development of the plasma discharge is presented. The constructed laser is found to be cost-effective and useful in small-scale researches in laser-plasma diagnostics. (author). 6 refs, 5 figs

Laser-induced breakdown spectroscopy of tantalum plasma

International Nuclear Information System (INIS)

Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan–ul-Haq

2013-01-01

Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO 2 : N 2 : He), O 2 , N 2 , and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis

Laser-induced breakdown spectroscopy of tantalum plasma

Energy Technology Data Exchange (ETDEWEB)

Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan–ul-Haq [Centre for Advanced Studies in Physics, GC University, Lahore (Pakistan)

2013-07-15

Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO{sub 2}: N{sub 2}: He), O{sub 2}, N{sub 2}, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis.

Femtosecond self-reconfiguration of laser-induced plasma patterns in dielectrics

Science.gov (United States)

Déziel, Jean-Luc; Dubé, Louis J.; Messaddeq, Sandra H.; Messaddeq, Younès; Varin, Charles

2018-05-01

Laser-induced modification of transparent solids by intense femtosecond laser pulses allows fast integration of nanophotonic and nanofluidic devices with controlled optical properties. Experimental observations suggest that the local and dynamic nature of the interactions between light and the transient plasma plays an important role during fabrication. Current analytical models neglect these aspects and offer limited coverage of nanograting formation on dielectric surfaces. In this paper, we present a self-consistent dynamic treatment of the plasma buildup and its interaction with light within a three-dimensional electromagnetic framework. The main finding of this work is that local light-plasma interactions are responsible for the reorientation of laser-induced periodic plasma patterns with respect to the incident light polarization, when a certain energy density threshold is reached. Plasma reconfiguration occurs within a single laser pulse, on a femtosecond time scale. Moreover, we show that the reconfigured subwavelength plasma structures actually grow into the bulk of the sample, which agrees with the experimental observations of self-organized volume nanogratings. We find that mode coupling of the incident and transversely scattered light with the periodic plasma structures is sufficient to initiate the growth and self-organization of the pattern inside the medium with a characteristic half-wavelength periodicity.

NON-NEUTRALIZED ELECTRIC CURRENT PATTERNS IN SOLAR ACTIVE REGIONS: ORIGIN OF THE SHEAR-GENERATING LORENTZ FORCE

International Nuclear Information System (INIS)

Georgoulis, Manolis K.; Titov, Viacheslav S.; Mikić, Zoran

2012-01-01

Using solar vector magnetograms of the highest available spatial resolution and signal-to-noise ratio, we perform a detailed study of electric current patterns in two solar active regions (ARs): a flaring/eruptive and a flare-quiet one. We aim to determine whether ARs inject non-neutralized (net) electric currents in the solar atmosphere, responding to a debate initiated nearly two decades ago that remains inconclusive. We find that well-formed, intense magnetic polarity inversion lines (PILs) within ARs are the only photospheric magnetic structures that support significant net current. More intense PILs seem to imply stronger non-neutralized current patterns per polarity. This finding revises previous works that claim frequent injections of intense non-neutralized currents by most ARs appearing in the solar disk but also works that altogether rule out injection of non-neutralized currents. In agreement with previous studies, we also find that magnetically isolated ARs remain globally current-balanced. In addition, we confirm and quantify the preference of a given magnetic polarity to follow a given sense of electric currents, indicating a dominant sense of twist in ARs. This coherence effect is more pronounced in more compact ARs with stronger PILs and must be of sub-photospheric origin. Our results yield a natural explanation of the Lorentz force, invariably generating velocity and magnetic shear along strong PILs, thus setting a physical context for the observed pre-eruption evolution in solar ARs.

Ion acceleration by laser hole-boring into plasmas

International Nuclear Information System (INIS)

Pogorelsky, I. V.; Dover, N. P.; Babzien, M.; Bell, A. R.; Dangor, A. E.; Horbury, T.; Palmer, C. A. J.; Polyanskiy, M.; Schreiber, J.; Schwartz, S.; Shkolnikov, P.; Yakimenko, V.; Najmudin, Z.

2012-01-01

By experiment and simulations, we study the interaction of an intense CO 2 laser pulse with slightly overcritical plasmas of fully ionized helium gas. Transverse optical probing is used to show a recession of the front plasma surface with an initial velocity >10 6 m/s driven by hole-boring by the laser pulse and the resulting radiation pressure driven electrostatic shocks. The collisionless shock propagates through the plasma, dissipates into an ion-acoustic solitary wave, and eventually becomes collisional as it slows further. These observations are supported by PIC simulations which prove the conclusion that monoenergetic protons observed in our earlier reported experiment with a hydrogen jet result from ion trapping and reflection from a shock wave driven through the plasma.

Calculation of high-pressure argon plasma parameters produced by excimer laser

International Nuclear Information System (INIS)

Tsuda, Norio; Yamada, Jun

2000-01-01

When a XeCl excimer laser light was focused in a high-pressure argon gas up to 150 atm, a dense plasma developed not only backward but also forward. It is important to study on the electron density and temperature of the laser-induced plasma in the high-pressure gas. The electron density and temperature in high-pressure argon plasma produced by XeCl excimer laser has been calculated and compared with the experimental data. (author)

PREFACE: Plasma Physics by Laser and Applications 2013 Conference (PPLA2013)

Science.gov (United States)

Nassisi, V.; Giulietti, D.; Torrisi, L.; Delle Side, D.

2014-04-01

The ''Plasma Physics by Laser and Applications'' Conference (PPLA 2013) is a biennial meeting in which the National teams involved in Laser-Plasma Interaction at high intensities communicate their late results comparing with the colleagues from the most important European Laser Facilities. The sixth appointment has been organized in Lecce, Italy, from 2 to 4 October 2013 at the Rector Palace of the University of Salento. Surprising results obtained by laser-matter interaction at high intensities, as well as, non-equilibrium plasma generation, laser-plasma acceleration and related secondary sources, diagnostic methodologies and applications based on lasers and plasma pulses have transferred to researchers the enthusiasm to perform experiments ad maiora. The plasma generated by powerful laser pulses produces high kinetic particles and energetic photons that may be employed in different fields, from medicine to microelectronics, from engineering to nuclear fusion, from chemistry to environment. A relevant interest concerns the understanding of the fundamental physical phenomena, the employed lasers, plasma diagnostics and their consequent applications. For this reason we need continuous updates, meetings and expertise exchanges in this field in order to follow the evolution and disclose information, that has been done this year in Lecce, discussing and comparing the experiences gained in various international laboratories. The conference duration, although limited to just 3 days, permitted to highlight important aspects of the research in the aforementioned fields, giving discussion opportunities about the activities of researchers of high international prestige. The program consisted of 10 invited talks, 17 oral talks and 17 poster contributions for a total of 44 communications. The presented themes covered different areas and, far from being exhaustive gave updates, stimulating useful scientific discussions. The Organizers belong to three Italian Universities

Active-passively mode-locked dye laser for diagnosis of laser-produced plasmas

International Nuclear Information System (INIS)

Teng, Y.L.; Fedosejevs, R.; Sigel, R.

1981-03-01

In this report an active-passively mode-locked, flashlamp-pumped dye laser for diagnosis of laser-produced plasmas is described. This dye laser system used as a pulsed light source for high-speed photography of laser-target experiments was synchronized to the ASTERIX III iodine laser pulse with better than 100 ps accuracy. The single pulse energy was 10 μJ, pulse duration less than 10 ps. In 111 shots clear shadowgrams were obtained during a total of 151 target shots, i.e. the system worked well in 74% of the shots. (orig.)

Interplay between parametric instabilities in fusion - relevant laser plasmas

International Nuclear Information System (INIS)

Huller, St.

2003-01-01

The control of parametric instabilities plays an important role in laser fusion. They are driven by the incident laser beams in the underdense plasma surrounding a fusion capsule and hinder the absorption process of incident laser light which is necessary to heat the fusion target. Due to its high intensity and power, the laser light modifies the plasma density dynamically, such that two or more parametric instabilities compete, in particular stimulated Brillouin scattering and the filamentation instability. The complicated interplay between these parametric instabilities is studied in detail by developing an adequate model accompanied by numerical simulations with multidimensional codes. The model is applied to generic and to smoothed laser beams, which are necessary to limit parametric instabilities, with parameters close to experimental conditions. (author)

Plasma plume induced during laser welding of Magnesium alloys

International Nuclear Information System (INIS)

Hoffman, J.; Szymanski, Z.; Azharonok, V.

2005-01-01

The laser welding process is influenced by the plasma produced by laser irradiation. When the pressure of the metal vapour reaches 1 atm and the plasma temperature is 10-15 kK then the electron density is about 2-3x10 23 m -3 . Under these conditions the absorption coefficient can reach several cm -1 . This means that dense plasma over the keyhole can block the laser radiation within the path of a few millimetres. Knowledge of plasma parameters helps to control technological process. The emission spectra were registered during laser welding of magnesium alloy using of a CCD camera connected to a spectrograph of focal length 1.3 m. The entrance slit of the spectrograph was perpendicular to the metal surface, so that successive tracks of the detector recorded the radiation from the plasma slices situated at different distances (heights) from the metal surface. The space-averaged electron densities are determined from the Stark broadening of the 5528.41 A Mg I spectral line and 4481.16 A Mg II line. The Stark widths of magnesium lines are taken from other paper. It has been found that the plasma density reaches 1x10 23 m -3 . Experimentally measured line broadening is obtained from the profiles of the spectral lines integrated along the line of sight (plasma diameter) and does not correspond to the maximum plasma density. Since the plasma is non-uniform, both the electron densities and temperatures obtained from spatially integrated line profiles are lower than their maximum values in the plasma centre. This effect is much stronger for the atomic line because its intensity reaches the maximum on the plasma periphery while the maximum intensity of the ionic line originates from the plasma centre. Therefore, the absorption of the laser beam evaluated from the space-averaged plasma parameters is underestimated. To find the maximum plasma density and temperature the radial temperature distribution in the plasma plume has to be reproduced. This has been done numerically by

Influence of the laser parameters on the space and time characteristics of an aluminum laser-induced plasma

International Nuclear Information System (INIS)

Barthelemy, O.; Margot, J.; Chaker, M.; Sabsabi, M.; Vidal, F.; Johnston, T.W.; Laville, S.; Le Drogoff, B.

2005-01-01

In this work, an aluminum laser plasma produced in ambient air at atmospheric pressure by laser pulses at a fluence of 10 J/cm 2 is characterized by time- and space-resolved measurements of electron density and temperature. Varying the laser pulse duration from 6 ns to 80 fs and the laser wavelength from ultraviolet to infrared only slightly influences the plasma properties. The temperature exhibits a slight decrease both at the plasma edge and close to the target surface. The electron density is found to be spatially homogeneous in the ablation plume during the first microsecond. Finally, the plasma expansion is in good agreement with the Sedov's model during the first 500 ns and it becomes subsonic, with respect to the velocity of sound in air, typically 1 μs after the plasma creation. The physical interpretation of the experimental results is also discussed to the light of a one-dimensional fluid model which provides a good qualitative agreement with measurements

Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Geohegan, D.B.

1994-09-01

Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

International Nuclear Information System (INIS)

Geohegan, D.B.

1994-01-01

Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume

Saturation of Langmuir waves in laser-produced plasmas

International Nuclear Information System (INIS)

Baker, K.L.

1996-04-01

This dissertation deals with the interaction of an intense laser with a plasma (a quasineutral collection of electrons and ions). During this interaction, the laser drives large-amplitude waves through a class of processes known as parametric instabilities. Several such instabilities drive one type of wave, the Langmuir wave, which involves oscillations of the electrons relative to the nearly-stationary ions. There are a number of mechanisms which limit the amplitude to which Langmuir waves grow. In this dissertation, these mechanisms are examined to identify qualitative features which might be observed in experiments and/or simulations. In addition, a number of experiments are proposed to specifically look for particular saturation mechanisms. In a plasma, a Langmuir wave can decay into an electromagnetic wave and an ion wave. This parametric instability is proposed as a source for electromagnetic emission near half of the incident laser frequency observed from laser-produced plasmas. This interpretation is shown to be consistent with existing experimental data and it is found that one of the previous mechanisms used to explain such emission is not. The scattering version of the electromagnetic decay instability is shown to provide an enhanced noise source of electromagnetic waves near the frequency of the incident laser

Study of multicharged ions in the laser-produced plasmas

International Nuclear Information System (INIS)

Jaegle, P.; Carillon, A.; Jamelot, G.; Wehenkel, C.; Sureau, A.; Guennou, H.

1980-01-01

With respect to hot plasmas, laser induced plasmas have an especially high density, with a steep partial gradient and a fast temporal variation of temperature and density. The study of multicharged ion radiation, wich is necessary to perform diagnostics of plasma parameters, opens a new field for atomic physics investigations, including identification of peculiar lines, which are not observed in other conditions, large changes in line profiles due to radiative transfer and to both shift and broadening by Stark effect. Departure from population equilibrium takes place in these plasmas, going possibly so far as population inversion between ionic levels in an energy range covering EUV and soft X-rays. Experimental and theoretical study of these phenomena are in progress and needs to find solutions for complicated problems. Here, recent works performed with the laser of the GRECO 'Interaction Laser-Matiere' are briefly presented [fr

Time-Resolved Emission Spectroscopic Study of Laser-Induced Steel Plasmas

International Nuclear Information System (INIS)

Shah, M. L.; Pulhani, A. K.; Suri, B. M.; Gupta, G. P.

2013-01-01

Laser-induced steel plasma is generated by focusing a Q-switched Nd:YAG visible laser (532 nm wavelength) with an irradiance of ∼ 1 × 10 9 W/cm 2 on a steel sample in air at atmospheric pressure. An Echelle spectrograph coupled with a gateable intensified charge-coupled detector is used to record the plasma emissions. Using time-resolved spectroscopic measurements of the plasma emissions, the temperature and electron number density of the steel plasma are determined for many times of the detector delay. The validity of the assumption by the spectroscopic methods that the laser-induced plasma (LIP) is optically thin and is also in local thermodynamic equilibrium (LTE) has been evaluated for many delay times. From the temporal evolution of the intensity ratio of two Fe I lines and matching it with its theoretical value, the delay times where the plasma is optically thin and is also in LTE are found to be 800 ns, 900 ns and 1000 ns.

Laser Thomson scattering diagnostics of non-equilibrium high pressure plasmas

International Nuclear Information System (INIS)

Muraoka, K.; Uchino, K.; Bowden, M.D.; Noguchi, Y.

2001-01-01

For various applications of non-equilibrium high pressure plasmas, knowledge of electron properties, such as electron density, electron temperature and/or electron energy distribution function (eedf), is prerequisite for any rational approach to understanding physical and chemical processes occurring in the plasmas. For this purpose, laser Thomson scattering has been successfully applied for the first time to measure the electron properties in plasmas for excimer laser pumping and in microdischarges. Although this diagnostic technique is well established for measurements in high temperature plasmas, its applications to these glow discharge plasmas have had various inherent difficulties, such as a presence of high density neutral particles (>10 21 m -3 ) in the excimer laser pumping discharges and an extremely small plasma size (<0.1 mm) and the presence of nearby walls for microdischarges. These difficulties have been overcome and clear signals have been obtained. The measured results are presented and their implications in the respective discharge phenomena are discussed

III International Conference on Laser and Plasma Researches and Technologies

Science.gov (United States)

2017-12-01

A.P. Kuznetsov and S.V. Genisaretskaya III Conference on Plasma and Laser Research and Technologies took place on January 24th until January 27th, 2017 at the National Research Nuclear University "MEPhI" (NRNU MEPhI). The Conference was organized by the Institute for Laser and Plasma Technologies and was supported by the Competitiveness Program of NRNU MEPhI. The conference program consisted of nine sections: • Laser physics and its application • Plasma physics and its application • Laser, plasma and radiation technologies in industry • Physics of extreme light fields • Controlled thermonuclear fusion • Modern problems of theoretical physics • Challenges in physics of solid state, functional materials and nanosystems • Particle accelerators and radiation technologies • Modern trends of quantum metrology. The conference is based on scientific fields as follows: • Laser, plasma and radiation technologies in industry, energetic, medicine; • Photonics, quantum metrology, optical information processing; • New functional materials, metamaterials, “smart” alloys and quantum systems; • Ultrahigh optical fields, high-power lasers, Mega Science facilities; • High-temperature plasma physics, environmentally-friendly energetic based on controlled thermonuclear fusion; • Spectroscopic synchrotron, neutron, laser research methods, quantum mechanical calculation and computer modelling of condensed media and nanostructures. More than 250 specialists took part in the Conference. They represented leading Russian scientific research centers and universities (National Research Centre "Kurchatov Institute", A.M. Prokhorov General Physics Institute, P.N. Lebedev Physical Institute, Troitsk Institute for Innovation and Fusion Research, Joint Institute for Nuclear Research, Moscow Institute of Physics and Tecnology and others) and leading scientific centers and universities from Germany, France, USA, Canada, Japan. We would like to thank heartily all of

Optically pumped FIR lasers and their application in plasma diagnostics

International Nuclear Information System (INIS)

Bakos, J.S.

1986-06-01

The pysics and the construction of the far infrared lasers (FIRL) and of the infrared lasers pumping them are reviewed. The details of the construction, resonating and pumping systems, spectral and power characteristics of the FIRLs are discussed. Recently more than 1000 laser lines are known and used in the 27-80 mm wavelength range, but in many cases the laser kinetics are not fully understood, and some instability phenomena cannot be prevented. New nonlinear processes were found: two-photon pumping, hyper Raman laser tuning and relaxation phenomena. A broad application field, the plasma diagnostics by far infrared lasers is described. Scattering of infrared laser radiation can give new interesting information on the not understood effect of the anomalous transport in the high temperature plasma. (D.Gy.)

Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds

Energy Technology Data Exchange (ETDEWEB)

Tamura, Jun, E-mail: jtamura@post.j-parc.jp [J-PARC Center, Japan Atomic Energy Agency, Ibaraki 319-1195 (Japan); Kumaki, Masafumi [Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Kondo, Kotaro [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo 152-8550 (Japan); Kanesue, Takeshi; Okamura, Masahiro [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2016-02-15

We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe{sup 21+}) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe{sup 19+}). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

Collaborative Research: Tomographic imaging of laser-plasma structures

Energy Technology Data Exchange (ETDEWEB)

Downer, Michael [University of Texas at Austin

2018-01-18

The interaction of intense short laser pulses with ionized gases, or plasmas, underlies many applications such as acceleration of elementary particles, production of energy by laser fusion, generation of x-ray and far-infrared “terahertz” pulses for medical and materials probing, remote sensing of explosives and pollutants, and generation of guide stars. Such laser-plasma interactions create tiny electron density structures (analogous to the wake behind a boat) inside the plasma in the shape of waves, bubbles and filaments that move at the speed of light, and evolve as they propagate. Prior to recent work by the PI of this proposal, detailed knowledge of such structures came exclusively from intensive computer simulations. Now “snapshots” of these elusive, light-velocity structures can be taken in the laboratory using dynamic variant of holography, the technique used to produce ID cards and DVDs, and dynamic variant of tomography, the technique used in medicine to image internal bodily organs. These fast visualization techniques are important for understanding, improving and scaling the above-mentioned applications of laser-plasma interactions. In this project, we accomplished three things: 1) We took holographic pictures of a laser-driven plasma-wave in the act of accelerating electrons to high energy, and used computer simulations to understand the pictures. 2) Using results from this experiment to optimize the performance of the accelerator, and the brightness of x-rays that it emits. These x-rays will be useful for medical and materials science applications. 3) We made technical improvements to the holographic technique that enables us to see finer details in the recorded pictures. Four refereed journal papers were published, and two students earned PhDs and moved on to scientific careers in US National Laboratories based on their work under this project.

High speed photography diagnostics in laser-plasma interaction experiments

International Nuclear Information System (INIS)

Andre, M.L.

1988-01-01

The authors report on their effort in the development of techniques involved in laser-plasma experiments. This includes not only laser technology but also diagnostics studies and targets design and fabrication. Among the different kind of diagnostics currently used are high speed streak cameras, fast oscilloscopes and detectors sensitive in the i.r., visible, the u.v. region and the x-rays. In this presentation the authors describe the three high power lasers which are still in operation (P 102, OctAL and PHEBUS) and the main diagnostics used to characterize the plasma

Long-time dynamics of laser-cooled ions in the TSR storage ring

International Nuclear Information System (INIS)

Mudrich, M.

2000-01-01

This diploma thesis studies experimentally the long-time dynamics of laser-cooled 9 Be + -beams at the TSR under different cooling conditions. The goal is to enlarge the understanding of ultra-cold, non-neutral plasma at high center-of-mass energies. By means of improved measurement capabilities one can now for the first time monitor the entire phase-space over a long time. This makes it possible to quantitatively analyse the possibilities and limitations of laser cooling at a storage ring. Under optimum cooling conditions a regime of high phase-space density is reached, close to the region where influences of Coulomb coupling are expected. Furthermore, a Monte-Carlo model is worked out that qualitatively describes the beam dynamics. The model includes the influence of transverse-longitudinal coupling due to intra beam scattering on the longitudinal phase-space distribution. At high phase-space density a sudden disappearance of intra beam collisions is observed experimentally and possible interpretations are given. (orig.)

En Route: next-generation laser-plasma-based electron accelerators

International Nuclear Information System (INIS)

Hidding, Bernhard

2008-05-01

Accelerating electrons to relativistic energies is of fundamental interest, especially in particle physics. Today's accelerator technology, however, is limited by the maximum electric fields which can be created. This thesis presents results on various mechanisms aiming at exploiting the fields in focussed laser pulses and plasma waves for electron acceleration, which can be orders of magnitude higher than with conventional accelerators. With relativistic, underdense laser-plasma-interaction, quasimonoenergetic electron bunches with energies up to ∼50 MeV and normalized emittances of the order of 5mmmrad have been generated. This was achieved by focussing the ∼80 fs, 1 J pulses of the JETI-laser at the FSU Jena to intensities of several 10 19 W=cm 2 into gas jets. The experimental observations could be explained via ''bubble acceleration'', which is based on self-injection and acceleration of electrons in a highly nonlinear breaking plasma wave. For the rst time, this bubble acceleration was achieved explicitly in the self-modulated laser wakefield regime (SMLWFA). This quasimonoenergetic SMLWFA-regime stands out by relaxing dramatically the requirements on the driving laser pulse necessary to trigger bubble acceleration. This is due to self-modulation of the laser pulse in high-density gas jets, leading to ultrashort laser pulse fragments capable of initiating bubble acceleration. Electron bunches with durations < or similar 5 fs can thus be created, which is at least an order of magnitude shorter than with conventional accelerator technology. In addition, more than one laser pulse fragment can be powerful enough to drive a bubble. Distinct double peaks have been observed in the electron spectra, indicating that two quasimonoenergetic electron bunches separated by only few tens of fs have formed. This is backed up by PIC-Simulations (Particle-in-Cell). These results underline the feasibility of the construction of small table-top accelerators, while at the

EUV laser produced and induced plasmas for nanolithography

Science.gov (United States)

Sizyuk, Tatyana; Hassanein, Ahmed

2017-10-01

EUV produced plasma sources are being extensively studied for the development of new technology for computer chips production. Challenging tasks include optimization of EUV source efficiency, producing powerful source in 2 percentage bandwidth around 13.5 nm for high volume manufacture (HVM), and increasing the lifetime of collecting optics. Mass-limited targets, such as small droplet, allow to reduce contamination of chamber environment and mirror surface damage. However, reducing droplet size limits EUV power output. Our analysis showed the requirement for the target parameters and chamber conditions to achieve 500 W EUV output for HVM. The HEIGHTS package was used for the simulations of laser produced plasma evolution starting from laser interaction with solid target, development and expansion of vapor/plasma plume with accurate optical data calculation, especially in narrow EUV region. Detailed 3D modeling of mix environment including evolution and interplay of plasma produced by lasers from Sn target and plasma produced by in-band and out-of-band EUV radiation in ambient gas, used for the collecting optics protection and cleaning, allowed predicting conditions in entire LPP system. Effect of these conditions on EUV photon absorption and collection was analyzed. This work is supported by the National Science Foundation, PIRE project.

Characterization of thermal plasmas by laser light scattering

International Nuclear Information System (INIS)

Snyder, S.C.; Lassahn, G.D.; Reynolds, L.D.; Fincke, J.R.

1993-01-01

Characterization of an atmospheric pressure free-burning arc discharge and a plasma jet by lineshape analysis of scattered laser light is described. Unlike emission spectroscopy, this technique provides direct measurement of plasma gas temperature, electron temperature and electron density without the assumption of local thermodynamic equilibrium (LTE). Plasma gas velocity can also be determined from the Doppler shift of the scattered laser light. Radial gas temperature, electron temperature and electron density profiles are presented for an atmospheric pressure argon free-burning arc discharge. These results show a significant departure from LTE in the arc column, contradicting results obtained from emission spectroscopy. Radial gas temperature and gas velocity profiles in the exit plane of a subsonic atmospheric pressure argon plasma jet are also presented. In this case, the results show the plasma jet is close to LTE in the center, but not in the fringes. The velocity profile is parabolic

Initiation of an early-stage plasma during picosecond laser ablation of solids

International Nuclear Information System (INIS)

Mao, Samuel S.; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

2000-01-01

Picosecond time-resolved images of plasma initiation were recorded during pulsed-laser ablation of metal targets in an air atmosphere. An early-stage plasma was observed to form before the release of a material vapor plume. Close to the target surface, interferometry measurements indicate that the early-stage plasma has an electron number density on the order of 10 20 cm -3 . The longitudinal expansion of the ionization front for this plasma has a velocity 10 9 cm/s, during the laser pulse. In contrast, a material--vapor plume forms approximately 200 ps after the laser pulse, and it moves away from the target at 10 6 cm/s. The experimental observations of the early-stage plasma were simulated by using a theoretical model based on a two-fluids description of laser plasmas. The results indicate that the initiation of the plasma is due to air breakdown assisted by electron emission from the target

Laser Interaction and Related Plasma Phenomena: 13th International Conference. Proceedings

International Nuclear Information System (INIS)

Miley, G.H.; Campbell, E.M.; Hogan, W.J.; Maille-Petersen, C.; Coppedge, H.; Montoya, E.

1997-01-01

These proceedings contain papers presented at the Thirteenth International Conference on Laser Interaction and Related Plasma Phenomena held in Monterey, California in April, 1997. Topics covered in the conference included laser design, alternate concepts in volume ignition and advance fuels, beam/plasma interactions, nuclear-pumped lasers, alternate fast ignitors, heavy ion fusions, laser-ion beam interactions, extreme short-pulse interactions, high-energy-density plasma physics, and hydrodynamic instabilities. The conference was sponsored in part by the Lawrence Livermore National Laboratory of the United States Department of Energy. There were 80 papers presented and 23 have been abstracted for the Energy Science and Technology database

Plasma effects in attosecond pulse generation from ultra-relativistic laser-plasma interactions

International Nuclear Information System (INIS)

Boyd, T.J.M.

2010-01-01

Complete text of publication follows. Particle-in-cell simulations were performed to examine the influence of plasma effects on high harmonic spectra from the interaction of ultra-intense p-polarized laser pulses with overdense plasma targets. Furthermore, a theoretical model is proposed to explain the radiation mechanism that leads to attosecond pulse generation in the reflected field. It is shown that plasma harmonic emission affects the spectral characteristics, causing deviations in the harmonic power decay as compared with the so-called universal 8/3-decay. These deviations may occur, in a varying degree, as a consequence of the extent to which the plasma line and its harmonics affect the emission. It is also found a strong correlation of the emitted attosecond pulses with electron density structures within the plasma, responsible to generate intense localised electrostatic fields. A theoretical model based on the excitation of Langmuir waves by the re-entrant Brunel electron beams in the plasma and their electromagnetic interaction with the laser field is proposed to explain the flatter power spectral emission - described by a weaker 5/3 index and observed in numerical simulations - than that of the universal decay.

Characteristics of Droplets Ejected from Liquid Propellants Ablated by Laser Pulses in Laser Plasma Propulsion

International Nuclear Information System (INIS)

Zheng Zhiyuan; Gao Hua; Fan Zhenjun; Xing Jie

2014-01-01

The angular distribution and pressure force of droplets ejected from liquid water and glycerol ablated by nanosecond laser pulses are investigated under different viscosities in laser plasma propulsion. It is shown that with increasing viscosity, the distribution angles present a decrease tendency for two liquids, and the angular distribution of glycerol is smaller than that of water. A smaller distribution leads to a higher pressure force generation. The results indicate that ablation can be controlled by varying the viscosity of liquid propellant in laser plasma propulsion

How much laser power can propagate through fusion plasma?

International Nuclear Information System (INIS)

Lushnikov, Pavel M; Rose, Harvey A

2006-01-01

Propagation of intense laser beams is crucial for inertial confinement fusion, which requires precise beam control to achieve the compression and heating necessary to ignite the fusion reaction. The National Ignition Facility (NIF), where fusion will be attempted, is now under construction. Control of intense beam propagation may be ruined by laser beam self-focusing. We have identified the maximum laser beam power that can propagate through fusion plasma without significant self-focusing and have found excellent agreement with recent experimental data. This maximum is determined by the collective forward stimulated Brillouin scattering instability which suggests a way to increase the maximum power by appropriate choice of plasma composition with implication for NIF designs. Our theory also leads to the prediction of anti-correlation between beam spray and backscatter and therefore raises the possibility of indirect control of backscatter through manipulation of plasma ionization state or acoustic damping. We find a simple expression for laser intensity at onset of enhanced beam angular divergence (beam spray)

Plasma Density Tapering for Laser Wakefield Acceleration of Electrons and Protons

International Nuclear Information System (INIS)

Ting, A.; Gordon, D.; Kaganovich, D.; Sprangle, P.; Helle, M.; Hafizi, B.

2010-01-01

Extended acceleration in a Laser Wakefield Accelerator can be achieved by tailoring the phase velocity of the accelerating plasma wave, either through profiling of the density of the plasma or direct manipulation of the phase velocity. Laser wakefield acceleration has also reached a maturity that proton acceleration by wakefield could be entertained provided we begin with protons that are substantially relativistic, ∼1 GeV. Several plasma density tapering schemes are discussed. The first scheme is called ''bucket jumping'' where the plasma density is abruptly returned to the original density after a conventional tapering to move the accelerating particles to a neighboring wakefield period (bucket). The second scheme is designed to specifically accelerate low energy protons by generating a nonlinear wakefield in a plasma region with close to critical density. The third scheme creates a periodic variation in the phase velocity by beating two intense laser beams with laser frequency difference equal to the plasma frequency. Discussions and case examples with simulations are presented where substantial acceleration of electrons or protons could be obtained.

Laser plasma X-ray for non-destructive inspection

International Nuclear Information System (INIS)

Yagi, T.; Kusama, H.

1995-01-01

External electric field is applied to the laser produced plasma, and its found that plasma shape in soft X-ray region is changed due to the penetrating electric field. The plasma emits strong hard X-ray, which can be used as a compact light source for non-destructive inspection. (author)

Laser dynamics in transversely inhomogeneous plasma and its relevance to wakefield acceleration

Science.gov (United States)

Pathak, V. B.; Vieira, J.; Silva, L. O.; Nam, Chang Hee

2018-05-01

We present full set of coupled equations describing the weakly relativistic dynamics of a laser in a plasma with transverse inhomogeneity. We apply variational principle approach to obtain these coupled equations governing laser spot-size, transverse wavenumber, curvature, transverse centroid, etc. We observe that such plasma inhomogeneity can lead to stronger self-focusing. We further discuss the guiding conditions of laser in parabolic plasma channels. With the help of multi-dimensional particle in cell simulations the study is extended to the blowout regime of laser wakefield acceleration to show laser as well as self-injected electron bunch steering in plasma to generate unconventional particle trajectories. Our simulation results demonstrate that such transverse inhomogeneities due to asymmetric self focusing lead to asymmetric bubble excitation, thus inducing off-axis self-injection.

Laser and Plasma Technology Division annual report 1994

International Nuclear Information System (INIS)

Venkatramani, N.; Verma, R.L.

1995-01-01

A brief account of the research and development (R and D) activities carried out by Laser and Plasma Technology Division of Bhabha Atomic Research Centre, Bombay during the period 1994 is presented. The activities are reported under the headings: 1) laser activities, 2) thermal plasma activities, 3) electron beam activity. At the end of each section, a list of publications by the staff members in the field indicated by the title of the section is given. (author). refs., tabs., figs

Laser and Plasma Technology Division annual report 1994

Energy Technology Data Exchange (ETDEWEB)

Venkatramani, N; Verma, R L [eds.; Bhabha Atomic Research Centre, Bombay (India). Laser and Plasma Technology Div.

1996-12-31

A brief account of the research and development (R and D) activities carried out by Laser and Plasma Technology Division of Bhabha Atomic Research Centre, Bombay during the period 1994 is presented. The activities are reported under the headings: (1) laser activities, (2) thermal plasma activities, (3) electron beam activity. At the end of each section, a list of publications by the staff members in the field indicated by the title of the section is given. (author). refs., tabs., figs.

Bright X-ray source from a laser-driven micro-plasma-waveguide

CERN Document Server

Yi, Longqing

2016-01-01

Bright tunable x-ray sources have a number of applications in basic science, medicine and industry. The most powerful sources are synchrotrons, where relativistic electrons are circling in giant storage rings. In parallel, compact laser-plasma x-ray sources are being developed. Owing to the rapid progress in laser technology, very high-contrast femtosecond laser pulses of relativistic intensities become available. These pulses allow for interaction with micro-structured solid-density plasma without destroying the structure by parasitic pre-pulses. The high-contrast laser pulses as well as the manufacturing of materials at micro- and nano-scales open a new realm of possibilities for laser interaction with photonic materials at the relativistic intensities. Here we demonstrate, via numerical simulations, that when coupling with a readily available 1.8 Joule laser, a micro-plasma-waveguide (MPW) may serve as a novel compact x-ray source. Electrons are extracted from the walls by the laser field and form a dense ...

A laser plasma beatwave accelerator experiment

International Nuclear Information System (INIS)

Ebrahim, N.A.

1987-03-01

An experiment to test the laser plasma beatware accelerator concept is outlined. A heuristic estimate of the relevant experimental parameters is obtained from fluid theory and considerations of wave-particle interactions. Acceleration of 10 MeV electrons to approximately 70 MeV over a plasma length of 3 cm appears to be feasible. This corresponds to an accelerating gradient of approximately 2.5 GeV/m

Study on the effects of ion motion on laser-induced plasma wakes

International Nuclear Information System (INIS)

Zhou Suyun; Yu Wei; Yuan Xiao; Xu Han; Cao, L. H.; Cai, H. B.; Zhou, C. T.

2012-01-01

A 2D analytical model is presented for the generation of plasma wakes (or bubbles) with an ultra-intense laser pulse by taking into account the response of plasma ions. It is shown that the effect of ion motion becomes significant at the laser intensity exceeding 10 21 W/cm 2 and plasma background density below 10 19 cm −3 . In this regime, ion motion tends to suppress the electrostatic field induced by charge separation and makes the electron acceleration less effective. As a result, the assumption of immobile ions overestimates the efficiency of laser wake-field acceleration of electrons. Based on the analytical model, the dynamics of plasma ions in laser-induced wake field is investigated. It is found that only one bubble appears as the plasmas background density exceeds the resonant density and the deposited laser energy is concentrated into the bubble, resulting in the generation of an ion bunch with extremely high energy density.

Particle-in-cell modeling of laser Thomson scattering in low-density plasmas at elevated laser intensities

Science.gov (United States)

Powis, Andrew T.; Shneider, Mikhail N.

2018-05-01

Incoherent Thomson scattering is a non-intrusive technique commonly used for measuring local plasma density. Within low-density, low-temperature plasmas and for sufficient laser intensity, the laser may perturb the local electron density via the ponderomotive force, causing the diagnostic to become intrusive and leading to erroneous results. A theoretical model for this effect is validated numerically via kinetic simulations of a quasi-neutral plasma using the particle-in-cell technique.

Laser and Plasma Technology Division annual report 1992

International Nuclear Information System (INIS)

Venkatramani, N.; Verma, R.L.

1993-01-01

The report describes the research and development (R and D) activities of Laser and Plasma technology Division, Bhabha Atomic Research Centre, Bombay during 1992. The broad programme objectives of the Division are: (1) development and technology readiness studies of laser, plasma and electron beam devices, (2) studies on related physical phenomena with a view to gain better understanding of the devices, and (3) improvements in technology and exploration of new areas. The R and D activities are reported under the sections entitled: (1) Laser Activities, (2) Thermal Plasma Activities, and (3) Electron Beam Activities. At the end of each section, a list of publications by the staff members in the field indicated by the title of the section is given. Some of the highlights of R and D work during 1992 are:(1) fabrication of an electron beam sustained CO 2 laser, (2) commissioning of a 6.5 m high LMMHD (Liquid Metal Magneto-hydrodynamic) generator loaded with 1.5 tons of mercury, (3) fabrication of electron beam processing equipment, and (4) study of the magnetic properties of vanadium nitride films produced by reactive sputtering in an indigenously developed DC magnetron sputtering equipment. (author). 56 figs., 6 tabs

Influence of irradiation conditions on plasma evolution in laser-surface interaction

Science.gov (United States)

Hermann, J.; Boulmer-Leborgne, C.; Dubreuil, B.; Mihailescu, I. N.

1993-09-01

The plasma plume induced by pulsed CO2 laser irradiation of a Ti target at power densities up to 4×108 W cm-2 was studied by emission spectroscopy. Time- and space-resolved measurements were performed by varying laser intensity, laser temporal pulse shape, ambient gas pressure, and the nature of the ambient gas. Experimental results are discussed by comparison with usual models. We show that shock wave and plasma propagation depend critically on the ratio Ivap/Ii, Ivap being the intensity threshold for surface vaporization and Ii the plasma ignition threshold of the ambient gas. Spectroscopic diagnostics of the helium breakdown plasma show maximum values of electron temperature and electron density in the order of kTe˜10 eV and ne=1018 cm-3, respectively. The plasma cannot be described by local thermodynamic equilibrium modeling. Nevertheless, excited metal atoms appear to be in equilibrium with electrons, hence, they can be used like a probe to measure the electron temperature. In order to get information on the role of the plasma in the laser-surface interaction, Ti surfaces were investigated by microscopy after irradiation. Thus an enhanced momentum transfer from the plasma to the target due to the recoil pressure of the breakdown plasma could be evidenced.

Analytical calculations of intense Gaussian laser beam propagating in plasmas with relativistic collision correction

International Nuclear Information System (INIS)

Wang Ying; Yuan Chengxun; Gao Ruilin; Zhou Zhongxiang

2012-01-01

Theoretical investigations of a Gaussian laser beam propagating in relativistic plasmas have been performed with the WKB method and complex eikonal function. We consider the relativistic nonlinearity induced by intense laser beam, and present the relativistically generalized forms of the plasma frequency and electron collision frequency in plasmas. The coupled differential equations describing the propagation variations of laser beam are derived and numerically solved. The obtained simulation results present the similar variation tendency with experiments. By changing the plasma density, we theoretically analyze the feasibility of using a plasmas slab of a fixed thickness to compress the laser beam-width and acquire the focused laser intensity. The present work complements the relativistic correction of the electron collision frequency with reasonable derivations, promotes the theoretical approaching to experiments and provides effective instructions to the practical laser-plasma interactions.

High resolution X-ray spectromicroscopy of laser produced plasmas

Energy Technology Data Exchange (ETDEWEB)

Faenov, A.Ya. [Multi-charged Ions Spectra Data Center of VNIIFTRI (MISDC), Mendeleevo, Moscow region, (Russian Federation)

2000-01-01

In recent years new classes of X-ray spectroscopic instruments possessing both dispersive and focusing properties have been manufactured. Their principal advantage over more traditional instruments is that they combine very high luminosity with high spatial resolution, while preserving the highest possible spectral resolution of their dispersive elements. These instruments opened up the registration of plasmas in new regimes and surroundings. The measurements delivered new information about the properties of even previously studied traditional plasma objects (e.g. ns-laser produced plasmas). Also the detailed investigation of relatively new plasma laboratory sources with very small dimensions and low energy content (e.g. mJ fs-laser pulses) became possible. The purpose of this report is to give a short review of the experimental and theoretical results obtained in the past few years by MISDC (Multi-charged Ions Spectra Data Center) research team in the field of X-ray spectroscopy of a laser-produced plasma. Experimental spectra have been obtained at various laser installations with nanosecond, sub-nanosecond, picosecond and sub-picosecond pulses interacting with solid, gaseous or cluster targets in collaborations with research teams from Russia, USA, Germany, France, Poland, Belgium, Italy, China and Israel. Practically all results have been obtained with the help of spectrographs with spherically bent mica crystals operating in FSSR-1D, 2D schemes. (author)

Simultaneous streak and frame interferometry for electron density measurements of laser produced plasmas

Energy Technology Data Exchange (ETDEWEB)

Quevedo, H. J., E-mail: hjquevedo@utexas.edu; McCormick, M.; Wisher, M.; Bengtson, Roger D.; Ditmire, T. [Center for High Energy Density Science, Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

2016-01-15

A system of two collinear probe beams with different wavelengths and pulse durations was used to capture simultaneously snapshot interferograms and streaked interferograms of laser produced plasmas. The snapshots measured the two dimensional, path-integrated, electron density on a charge-coupled device while the radial temporal evolution of a one dimensional plasma slice was recorded by a streak camera. This dual-probe combination allowed us to select plasmas that were uniform and axisymmetric along the laser direction suitable for retrieving the continuous evolution of the radial electron density of homogeneous plasmas. Demonstration of this double probe system was done by measuring rapidly evolving plasmas on time scales less than 1 ns produced by the interaction of femtosecond, high intensity, laser pulses with argon gas clusters. Experiments aimed at studying homogeneous plasmas from high intensity laser-gas or laser-cluster interaction could benefit from the use of this probing scheme.

First observations of acceleration of injected electrons in a laser plasma beatwave experiment

International Nuclear Information System (INIS)

Ebrahim, N.A.; Martin, F.; Bordeur, P.; Heighway, E.A.; Matte, J.P.; Pepin, H.; Lavigne, P.

1986-01-01

The first experimental observations of acceleration of injected electrons in a laser driven plasma beatwave are presented. The plasma waves were excited in an ionized gas jet, using a short pulse high intensity CO 2 laser with two collinearly propagating beams (at λ = 9.6 μm and 10.6 μm) to excite a fast wave (v/sub p/ = c). The source of electrons was a laser plasma produced on an aluminum slab target by a third, synchronized CO 2 laser beam. A double-focusing dipole magnet was used to energy select and inject electrons into the beatwave, and a second magnetic spectrograph was used to analyze the accelerated electrons. Electron acceleration was only observed when the appropriate resonant plasma density was produced (∼ 10 17 cm -3 ), the two laser lines were incident on the plasma, and electrons were injected into this plasma from an external source

Laser pulse guiding and electron acceleration in the ablative capillary discharge plasma

International Nuclear Information System (INIS)

Kameshima, T.; Kotaki, H.; Kando, M.; Daito, I.; Kawase, K.; Fukuda, Y.; Homma, T.; Esirkepov, T. Zh.; Chen, L. M.; Kondo, S.; Bobrova, N. A.; Sasorov, P. V.; Bulanov, S. V.

2009-01-01

The results of experiments are presented for the laser electron acceleration in the ablative capillary discharge plasma. The plasma channel is formed by the discharge inside the ablative capillary. The intense short laser pulse is guided over a 4 cm length. The generated relativistic electrons show both the quasimonoenergetic and quasi-Maxwellian energy spectra, depending on laser and plasma parameters. The analysis of the inner walls of the capillaries that underwent several tens of shots shows that the wall deformation and blistering resulted from the discharge and laser pulse effects.

Laser and Plasma Technology Division annual report 1995

International Nuclear Information System (INIS)

Venkatramani, N.

1996-01-01

This report describes the activity of the Laser and Plasma Technology Division of Bhabha Atomic Research Centre, Mumbai during the period 1995. This division is engaged in the research and development of high power beams namely lasers, plasma and electron beams which are characterized by high power density. This division has strived to establish indigenous capability to cater to the requirements of the Department of Atomic Energy. The broad program objectives of the division are (1) development and technology readiness studies of laser, plasma and electron beam devices; (2) studies on related physical phenomena with a view to gain better understanding of the devices and (3) improvements in technology and exploration of new areas. This report has been compiled from individual reports of various groups/sections with marginal editing. At the end of each section; a list of publications by the staff members in the field indicated by the title of the section is given. refs., figs., tabs

Summary Report of Working Group: Laser-Plasma Acceleration

International Nuclear Information System (INIS)

Esarey, Eric; Schroeder, Carl B.; Tochitsky, Sergei; Milchberg, Howard M.

2004-01-01

A summary is given on the work presented and discussed in the Laser-Plasma Acceleration Working Group at the 2004 Advanced Accelerator Concepts Workshop, including the Plasma Acceleration Subgroup (Group-Leader: Eric Esarey; Co-Group-Leader: Sergei Tochitsky) and the Plasma Guiding Subgroup (Group-Leader: Howard Milchberg; Co-Group-Leader: Carl Schroeder)

Multistage Coupling of Laser-Wakefield Accelerators with Curved Plasma Channels

Science.gov (United States)

Luo, J.; Chen, M.; Wu, W. Y.; Weng, S. M.; Sheng, Z. M.; Schroeder, C. B.; Jaroszynski, D. A.; Esarey, E.; Leemans, W. P.; Mori, W. B.; Zhang, J.

2018-04-01

Multistage coupling of laser-wakefield accelerators is essential to overcome laser energy depletion for high-energy applications such as TeV-level electron-positron colliders. Current staging schemes feed subsequent laser pulses into stages using plasma mirrors while controlling electron beam focusing with plasma lenses. Here a more compact and efficient scheme is proposed to realize the simultaneous coupling of the electron beam and the laser pulse into a second stage. A partly curved channel, integrating a straight acceleration stage with a curved transition segment, is used to guide a fresh laser pulse into a subsequent straight channel, while the electrons continue straight. This scheme benefits from a shorter coupling distance and continuous guiding of the electrons in plasma while suppressing transverse beam dispersion. Particle-in-cell simulations demonstrate that the electron beam from a previous stage can be efficiently injected into a subsequent stage for further acceleration while maintaining high capture efficiency, stability, and beam quality.

Expansion of laser-produced plasmas into vacuum and ambient gases

International Nuclear Information System (INIS)

Williams, T.

2001-01-01

Presented in this thesis are observations recorded using optical absorption spectroscopy, laser induced fluorescence imaging and Langmuir probe techniques for a low temperature laser-produced plasma. The plasma was generated using a KrF (248 nm, 30ns) excimer laser system focused onto a solid target surface (Ti, Mg) housed within a vacuum chamber. Plasma studies were made within vacuum (x10 -5 mTorr) and low pressure ( 2 and Ar ambient gas environments. Experimental results from a volumetric integration technique for plasma species number densities are used to yield total plume content for a laser-produced plasma in vacuum. This was used to determine the threshold power density for titanium neutral species formation. Temporally resolved electron number densities were determined using a Langmuir probe technique, for a titanium plasma generated under 532 nm and 248 nm ablation, for similar power densities and spot geometries. In this case the ablation thresholds for titanium are determined in terms of average power density and peak power density. Plume opacity problems which limit OAS and LIF diagnostic techniques are minimised using novel ablations configurations. Both techniques used, the 'composite target' and the 'plasma-jet' configurations, rely on reducing the optical thickness of the plume. The plasma-jets produced were allowed to interact with an ambient argon background and the ion/neutral ratio of the plasma-jet determined. Laser-produced plasma interactions with a d.c. biased copper mesh ∼15 mm in front of the target surface are observed. Self-emission studies of plume interactions with the mesh are monitored for positive and negative biases. Also ground-state neutral and ion interactions with the mesh are observed using OAS and LIF techniques to study individual species effects. A simple model was used to predict the perturbations to charged species distributions resulting from positive and negative applied potentials, but more complex interaction

The study of waves, instabilities, and turbulence using Thomson scattering in laser plasmas

International Nuclear Information System (INIS)

Drake, R.P.

1995-01-01

Much basic work in plasma physics has been devoted to the study of wave properties in plasmas, one of the nonlinear development of driven waves, and of the instabilities in which such waves may participate. The use of laser-plasma techniques has allowed one to extend such studies into new regimes. Such techniques and their results are the subject here. Once one chooses a physical problem within this subject area, it is now possible to design a laser-plasma experiment that is optimized for the study of that problem. The plasma can be designed to have a variety of density and flow-velocity profiles, the damping of ion acoustic waves and of electron plasma waves can be independently controlled, and the waves can be driven weakly or strongly. By using Nd-glass lasers and their harmonics one can non-invasively drive and diagnose the waves, using separate laser beams to produce the plasma, drive the waves, and diagnose their properties. The author uses as examples some recent work with his collaborators, including the first experimental detection of ion plasma waves and the first direct observation of the plasma wave driven by the acoustic decay of laser light

Extending laser plasma accelerators into the mid-IR spectral domain with a next-generation ultra-fast CO2 laser

Science.gov (United States)

Pogorelsky, I. V.; Babzien, M.; Ben-Zvi, I.; Polyanskiy, M. N.; Skaritka, J.; Tresca, O.; Dover, N. P.; Najmudin, Z.; Lu, W.; Cook, N.; Ting, A.; Chen, Y.-H.

2016-03-01

Expanding the scope of relativistic plasma research to wavelengths longer than the λ/≈   0.8-1.1 μm range covered by conventional mode-locked solid-state lasers would offer attractive opportunities due to the quadratic scaling of the ponderomotive electron energy and critical plasma density with λ. Answering this quest, a next-generation mid-IR laser project is being advanced at the BNL ATF as a part of the user facility upgrade. We discuss the technical approach to this conceptually new 100 TW, 100 fs, λ  =   9-11 μm CO2 laser BESTIA (Brookhaven Experimental Supra-Terawatt Infrared at ATF) that encompasses several innovations applied for the first time to molecular gas lasers. BESTIA will enable new regimes of laser plasma accelerators. One example is shock-wave ion acceleration (SWA) from gas jets. We review ongoing efforts to achieve stable, monoenergetic proton acceleration by dynamically shaping the plasma density profile from a hydrogen gas target with laser-produced blast waves. At its full power, 100 TW BESTIA promises to achieve proton beams at an energy exceeding 200 MeV. In addition to ion acceleration in over-critical plasma, the ultra-intense mid-IR BESTIA will open up new opportunities in driving wakefields in tenuous plasmas, expanding the landscape of laser wakefield accelerator (LWFA) studies into the unexplored long-wavelength spectral domain. Simple wavelength scaling suggests that a 100 TW CO2 laser beam will be capable of efficiently generating plasma ‘bubbles’ a thousand times greater in volume compared with a near-IR solid state laser of an equivalent power. Combined with a femtosecond electron linac available at the ATF, this wavelength scaling will facilitate the study of external seeding and staging of LWFAs.

Effect of laser beam filamentation on plasma wave localization and stimulated Raman scattering

International Nuclear Information System (INIS)

Purohit, Gunjan; Sharma, R. P.

2013-01-01

This paper presents the effect of laser beam filamentation on the localization of electron plasma wave (EPW) and stimulated Raman scattering (SRS) in unmagnitized plasma when both relativistic and ponderomotive nonlinearities are operative. The filamentary dynamics of laser beam is studied and the splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. The localization of electron plasma wave takes place due to nonlinear coupling between the laser beam and EPW. Stimulated Raman scattering of this EPW is studied and backreflectivity has been calculated. The localization of EPW also affects the eigenfrequency and damping of plasma wave; consequently, mismatch and modified enhanced Landau damping lead to the disruption of SRS process and a substantial reduction in the backreflectivity. The new enhanced damping of the plasma wave has been calculated and it is found that the SRS process gets suppressed due to the localization of plasma wave in laser beam filamentary structures. For typical laser beam and plasma parameters with wavelength λ (=1064 nm), power flux (=10 16 W/cm 2 ) and plasma density (n/n cr ) = 0.2; the SRS back reflectivity is found to be suppressed by a factor of around 5%. (author)

XUV laser-produced plasma sheet beam and microwave agile mirror

International Nuclear Information System (INIS)

Shen, W.; Scharer, J.E.; Porter, B.; Lam, N.T.

1994-01-01

An excimer-laser (λ = 193 nm) produced plasma in an organic gas (TMAE) has been generated and studied. These studies have determined the ion-electron recombination coefficient and the photon absorption cross-section, of the neutral gas. The dependences of wave transmission, reflection and absorption on plasma density are obtained. A new optical system with an array of cylindrical XUV coated lenses has been implemented to form a plasma sheet to study its usage as agile mirror microwave reflector. The lens system expands the incident laser beam in X direction and compresses it in Y direction to form a sheet beam. The expanded beam then passes through a vacuum chamber filled with TMAE at 50--500 nTorr to produce the plasma sheet. Space-time measurements of the plasma density and temperature as measured by a Langmuir probe are presented. XUV optical measurements of the laser beam as measured by a photodiode are presented. Initial experiments have generated a plasma sheet of 5--10 mm x 11 cm with peak plasma density of 5 x 10 13 cm -3 . A microwave source will be utilized to study the agile mirror character of the plasma sheet. Modeling of the microwave reflection from the plasma profile will also be discussed

Nonlinear plasma wave models in 3D fluid simulations of laser-plasma interaction

Science.gov (United States)

Chapman, Thomas; Berger, Richard; Arrighi, Bill; Langer, Steve; Banks, Jeffrey; Brunner, Stephan

2017-10-01

Simulations of laser-plasma interaction (LPI) in inertial confinement fusion (ICF) conditions require multi-mm spatial scales due to the typical laser beam size and durations of order 100 ps in order for numerical laser reflectivities to converge. To be computationally achievable, these scales necessitate a fluid-like treatment of light and plasma waves with a spatial grid size on the order of the light wave length. Plasma waves experience many nonlinear phenomena not naturally described by a fluid treatment, such as frequency shifts induced by trapping, a nonlinear (typically suppressed) Landau damping, and mode couplings leading to instabilities that can cause the plasma wave to decay rapidly. These processes affect the onset and saturation of stimulated Raman and Brillouin scattering, and are of direct interest to the modeling and prediction of deleterious LPI in ICF. It is not currently computationally feasible to simulate these Debye length-scale phenomena in 3D across experimental scales. Analytically-derived and/or numerically benchmarked models of processes occurring at scales finer than the fluid simulation grid offer a path forward. We demonstrate the impact of a range of kinetic processes on plasma reflectivity via models included in the LPI simulation code pF3D. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Numerical simulation of laser filamentation in underdense plasma

International Nuclear Information System (INIS)

Yu Lichun; Chen Zhihua; Tu Qinfen

2000-01-01

Developing process of filamentation and effect of characteristic parameters in underdense plasma have been studied using numerical simulation method. Production and development of two-dimensional cylinder filamentation instability were presented clearly. The results indicate incidence laser intensity and plasma background density are important factors affecting convergent intensity. At the same time, it was showed that different laser wavelength or different electron background density could affect filamentation process. The results are consistent with theory and experiments of alien reports. It can provide reference for restraining filamentation

Interaction of a CO2 laser beam with a shock-tube plasma

International Nuclear Information System (INIS)

Box, S.J.C.; John, P.K.; Byszewski, W.W.

1977-01-01

The results of experimental investigations of the interaction of a CO 2 laser beam with plasma produced in an electromagnetic shock tube are presented. The interaction was investigated in two different configurations: with the laser beam perpendicular to the direction of propagation of the shock wave and with the laser beam parallel to the direction of the shock wave. The laser energy was 0.3 J in a 180-nsec pulse. The plasma density was in the range 10 17 --10 18 cm -3 and temperature was around 2 eV. Spectroscopic methods were used in the measurement of density and temperature. Direct observation of the path of the laser beam through the plasma was made by an image-convertor camera in conjunction with a narrow-band interference filter. The propagation of the laser through the plasma and energy absorption are discussed. The observed maximum increase in electron temperature due to the laser in the first configuration was 0.4 eV and the estimated temperature increase in the second configuration was about 2 eV

Late-time particle emission from laser-produced graphite plasma

Energy Technology Data Exchange (ETDEWEB)

Harilal, S. S.; Hassanein, A.; Polek, M. [School of Nuclear Engineering, Center for Materials Under Extreme Environment, Purdue University, West Lafayette, Indiana 47907 (United States)

2011-09-01

We report a late-time ''fireworks-like'' particle emission from laser-produced graphite plasma during its evolution. Plasmas were produced using graphite targets excited with 1064 nm Nd: yttrium aluminum garnet (YAG) laser in vacuum. The time evolution of graphite plasma was investigated using fast gated imaging and visible emission spectroscopy. The emission dynamics of plasma is rapidly changing with time and the delayed firework-like emission from the graphite target followed a black-body curve. Our studies indicated that such firework-like emission is strongly depended on target material properties and explained due to material spallation caused by overheating the trapped gases through thermal diffusion along the layer structures of graphite.

Late-time particle emission from laser-produced graphite plasma

International Nuclear Information System (INIS)

Harilal, S. S.; Hassanein, A.; Polek, M.

2011-01-01

We report a late-time ''fireworks-like'' particle emission from laser-produced graphite plasma during its evolution. Plasmas were produced using graphite targets excited with 1064 nm Nd: yttrium aluminum garnet (YAG) laser in vacuum. The time evolution of graphite plasma was investigated using fast gated imaging and visible emission spectroscopy. The emission dynamics of plasma is rapidly changing with time and the delayed firework-like emission from the graphite target followed a black-body curve. Our studies indicated that such firework-like emission is strongly depended on target material properties and explained due to material spallation caused by overheating the trapped gases through thermal diffusion along the layer structures of graphite.

Preliminary design of experiment high power density laser beam interaction with plasmas and development of a cold cathode electron beam laser amplifier

International Nuclear Information System (INIS)

Mosavi, R.K.; Kohanzadeh, Y.; Taherzadeh, M.; Vaziri, A.

1976-01-01

This experiment is designed to produce plasma by carbon dioxide pulsed laser, to measure plasma parameters and to study the interaction of the produced plasma with intense laser beams. The objectives of this experiment are the following: 1. To set up a TEA CO 2 laser oscillator and a cold cathode electron beam laser amplifier together as a system, to produce high energy optical pulses of short duration. 2. To achieve laser intensities of 10 11 watt/cm 2 or more at solid targets of polyethylene (C 2 H 4 )n, lithium hydride (LiH), and lithium deuteride in order to produce high temperature plasmas. 3. To design and develop diagnostic methods for studies of laser-induced plasmas. 4. To develop a high power CO 2 laser amplifier for the purpose of upgrading the optical energy delivered to the targets

Final Technical Report: Magnetic Reconnection in High-Energy Laser-Produced Plasmas

Energy Technology Data Exchange (ETDEWEB)

Germaschewski, Kai [Univ. of New Hampshire, Durham, NH (United States); Fox, William [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Bhattacharjee, Amitava [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

2017-04-06

This report describes the final results from the DOE Grant DE-SC0007168, “Fast Magnetic Reconnection in HED Laser-Produced Plasmas.” The recent generation of laboratory high-energy-density physics facilities has opened significant physics opportunities for experimentally modeling astrophysical plasmas. The goal of this proposal is to use these new tools to study fundamental problems in plasma physics and plasma astrophysics. Fundamental topics in this area involve study of the generation, amplification, and fate of magnetic fields, which are observed to pervade the plasma universe and govern its evolution. This project combined experiments at DOE laser facilities with kinetic plasma simulation to study these processes. The primary original goal of the project was to study magnetic reconnection using a new experimental platform, colliding magnetized laser-produced plasmas. However through a series of fortuitous discoveries, the work broadened out to allow significant advancement on multiple topics in laboratory astrophysics, including magnetic reconnection, Weibel instability, and collisionless shocks.

Laser light scatter experiments on plasma focus plant

International Nuclear Information System (INIS)

Wenzel, N.

1985-01-01

The plasma focus plant is an experiment on nuclear fusion, which is distinguished by a high neutron yield. Constituting an important method of diagnosis in plasma focussing, the laser light scatter method makes it possible, apart from finding the electron temperature and density, to determine the ion temperature resolved according to time and place and further, to study the occurrence of micro-turbulent effects. Starting from the theoretical basis, this dissertation describes light scatter measurements with ruby lasers on the POSEIDON plasma focus. They are given, together with earlier measurements on the Frascati 1 MJ plant and the Heidelberg 12 KJ plant. The development of the plasma parameters and the occurrence of superthermal light scatter events are discussed in connection with the dynamics of the plasma and the neutron emission characteristics of the individual plants. The results support the view that the thermo-nuclear neutron production at the plasma focus is negligible. Although the importance of micro-turbulent mechanisms in producing neutrons cannot be finally judged, important guidelines are given for the spatial and time relationships with plasma dynamics, plasma parameters and neutron emission. The work concludes with a comparison of all light scatter measurements at the plasma focus described in the literature. (orig.) [de

Molecular signatures in femtosecond laser-induced organic plasmas: comparison with nanosecond laser ablation.

Science.gov (United States)

Serrano, Jorge; Moros, Javier; Laserna, J Javier

2016-01-28

During the last few years, laser-induced breakdown spectroscopy (LIBS) has evolved significantly in the molecular sensing area through the optical monitoring of emissions from organic plasmas. Large efforts have been made to study the formation pathways of diatomic radicals as well as their connections with the bonding framework of molecular solids. Together with the structural and chemical-physical properties of molecules, laser ablation parameters seem to be closely tied to the observed spectral signatures. This research focuses on evaluating the impact of laser pulse duration on the production of diatomic species that populate plasmas of organic materials. Differences in relative intensities of spectral signatures from the plasmas of several organic molecules induced in femtosecond (fs) and nanosecond (ns) ablation regimes have been studied. Beyond the abundance and origin of diatomic radicals that seed the plasma, findings reveal the crucial role of the ablation regime in the breakage pattern of the molecule. The laser pulse duration dictates the fragments and atoms resulting from the vaporized molecules, promoting some formation routes at the expense of other paths. The larger amount of fragments formed by fs pulses advocates a direct release of native bonds and a subsequent seeding of the plasma with diatomic species. In contrast, in the ns ablation regime, the atomic recombinations and single displacement processes dominate the contribution to diatomic radicals, as long as atomization of molecules prevails over their progressive decomposition. Consequently, fs-LIBS better reflects correlations between strengths of emissions from diatomic species and molecular structure as compared to ns-LIBS. These new results entail a further step towards the specificity in the analysis of molecular solids by fs-LIBS.

Complementary ion and extreme ultra-violet spectrometer for laser-plasma diagnosis.

Science.gov (United States)

Ter-Avetisyan, S; Ramakrishna, B; Doria, D; Sarri, G; Zepf, M; Borghesi, M; Ehrentraut, L; Stiel, H; Steinke, S; Priebe, G; Schnürer, M; Nickles, P V; Sandner, W

2009-10-01

Simultaneous detection of extreme ultra-violet (XUV) and ion emission along the same line of sight provides comprehensive insight into the evolution of plasmas. This type of combined spectroscopy is applied to diagnose laser interaction with a spray target. The use of a micro-channel-plate detector assures reliable detection of both XUV and ion signals in a single laser shot. The qualitative analysis of the ion emission and XUV spectra allows to gain detailed information about the plasma conditions, and a correlation between the energetic proton emission and the XUV plasma emission can be suggested. The measured XUV emission spectrum from water spray shows efficient deceleration of laser accelerated electrons with energies up to keV in the initially cold background plasma and the collisional heating of the plasma.

Complementary ion and extreme ultra-violet spectrometer for laser-plasma diagnosis

International Nuclear Information System (INIS)

Ter-Avetisyan, S.; Ramakrishna, B.; Doria, D.; Sarri, G.; Zepf, M.; Borghesi, M.; Ehrentraut, L.; Stiel, H.; Steinke, S.; Schnuerer, M.; Nickles, P. V.; Sandner, W.; Priebe, G.

2009-01-01

Simultaneous detection of extreme ultra-violet (XUV) and ion emission along the same line of sight provides comprehensive insight into the evolution of plasmas. This type of combined spectroscopy is applied to diagnose laser interaction with a spray target. The use of a micro-channel-plate detector assures reliable detection of both XUV and ion signals in a single laser shot. The qualitative analysis of the ion emission and XUV spectra allows to gain detailed information about the plasma conditions, and a correlation between the energetic proton emission and the XUV plasma emission can be suggested. The measured XUV emission spectrum from water spray shows efficient deceleration of laser accelerated electrons with energies up to keV in the initially cold background plasma and the collisional heating of the plasma.

Dual-wavelength differential spectroscopic imaging for diagnostics of laser-induced plasma

Energy Technology Data Exchange (ETDEWEB)

Motto-Ros, V., E-mail: vincent.motto-ros@univ-lyon1.fr [Universite de Lyon, F-69622, Lyon, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France); Ma, Q.L. [Universite de Lyon, F-69622, Lyon, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France); Gregoire, S. [CRITT Matriaux Alsace, 19 rue de St Junien, 67300 Schiltigheim (France); Lei, W.Q.; Wang, X.C. [Universite de Lyon, F-69622, Lyon, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France); Pelascini, F.; Surma, F. [CRITT Matriaux Alsace, 19 rue de St Junien, 67300 Schiltigheim (France); Detalle, V. [Laboratoire de Recherche des Monuments Historiques, 29 rue de Paris, 77420 Champs-sur-Marne (France); Yu, J. [Universite de Lyon, F-69622, Lyon, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France)

2012-08-15

A specific configuration for plasma fast spectroscopic imaging was developed, where a pair of narrowband filters, one fitting an emission line of a species to be studied and the other out of its emission line, allowed double images to be taken for a laser-induced plasma. A dedicated software was developed for the subtraction between the double images. The result represents therefore the monochromatic emission image of the species in the plasma. We have shown in this work that such configuration is especially efficient for the monitoring of a plasma generated under the atmospheric pressure at very short delays after the impact of the laser pulse on the target, when a strong continuum emission is observed. The efficiency of the technique has been particularly demonstrated in the study of laser-induced plasma on a polymer target. Molecular species, such as C{sub 2} and CN, as well as atomic species, such as C and N, were imaged starting from 50 ns after the laser impact. Moreover space segregation of different species, atomic or molecular, inside of the plasma was clearly observed. - Highlights: Black-Right-Pointing-Pointer Imaging to study species with time and space resolution in laser induced plasma. Black-Right-Pointing-Pointer Image display of multiple species is proposed based on RGB color model. Black-Right-Pointing-Pointer Molecular emission (CN and C{sub 2}) is observed at very short delays (50 ns). Black-Right-Pointing-Pointer Segregation of different species inside the plasma is clearly established.

Experimental study of the behavior of two laser produced plasmas in air

Energy Technology Data Exchange (ETDEWEB)

Yang, Zefeng; Wei, Wenfu; Han, Jiaxun; Wu, Jian, E-mail: jxjawj@gmail.com; Li, Xingwen; Jia, Shenli [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Shaanxi 710049 (China)

2015-07-15

The interactions among two laser ablated Al plasmas and their shock wave fronts (SWFs) induced by double laser pulses in air were studied experimentally. The evolution processes, including the expansion and interaction of the two plasmas and their shocks, were investigated by laser shadowgraphs, schlieren images, and interferograms. Remarkably, the distribution of the compressed air and the laser plasmas during the colliding process was clearly obtained using the Mach-Zehnder interferometer. From the refractive index profiles, typical plasmas density and gas density behind the shock front were estimated as ∼5.2 × 10{sup 18 }cm{sup −3} and ∼2.4 × 10{sup 20 }cm{sup −3}. A stagnation layer formed by the collision of gas behind the shock front is observed. The SWFs propagated, collided, and reflected with a higher velocity than plasmas. The results indicated that the slower plasma collided at middle, leading to the formation of the soft stagnation.

Concept of a staged FEL enabled by fast synchrotron radiation cooling of laser-plasma accelerated beam by solenoidal magnetic fields in plasma bubble

Science.gov (United States)

Seryi, Andrei; Lesz, Zsolt; Andreev, Alexander; Konoplev, Ivan

2017-03-01

A novel method for generating GigaGauss solenoidal fields in a laser-plasma bubble, using screw-shaped laser pulses, has been recently presented. Such magnetic fields enable fast synchrotron radiation cooling of the beam emittance of laser-plasma accelerated leptons. This recent finding opens a novel approach for design of laser-plasma FELs or colliders, where the acceleration stages are interleaved with laser-plasma emittance cooling stages. In this concept paper, we present an outline of what a staged plasma-acceleration FEL could look like, and discuss further studies needed to investigate the feasibility of the concept in detail.

Radiation transfer effects on the spectra of laser-generated plasmas

Czech Academy of Sciences Publication Activity Database

Renner, Oldřich; Kerr, F.M.; Wolfrum, E.; Hawreliak, J.; Chambers, D.; Rose, S. J.; Wark, J. S.; Scott, H.A.; Patel, P.

2006-01-01

Roč. 96, č. 18 (2006), 185002/1-185002/4 ISSN 0031-9007 R&D Projects: GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z10100523 Keywords : laser-produced plasma * spectral line shapes * plasma modeling * radiative transfer effects Subject RIV: BH - Optics, Masers, Lasers Impact factor: 7.072, year: 2006

Hot electron spatial distribution under presence of laser light self-focusing in over-dense plasmas

International Nuclear Information System (INIS)

Tanimoto, T; Yabuuchi, T; Habara, H; Kondo, K; Kodama, R; Mima, K; Tanaka, K A; Lei, A L

2008-01-01

In fast ignition for laser thermonuclear fusion, an ultra intense laser (UIL) pulse irradiates an imploded plasma in order to fast-heat a high-density core with hot electrons generated in laser-plasma interactions. An UIL pulse needs to make plasma channel via laser self-focusing and to propagate through the corona plasma to reach close enough to the core. Hot electrons are used for heating the core. Therefore the propagation of laser light in the high-density plasma region and spatial distribution of hot electron are important in issues in order to study the feasibility of this scheme. We measure the spatial distribution of hot electron when the laser light propagates into the high-density plasma region by self-focusing

CO2 laser interaction with magnetically confined plasmas. Annual report

International Nuclear Information System (INIS)

Vlases, G.C.; Pietrzyk, Z.A.

1977-08-01

The experimental program involves two basic experimental configurations termed the slow (or steady) solenoid, and the fast solenoid. In the former, the field is essentially steady during the experiment lifetime, the gas (plasma) remains in contact with the wall, and all the heating is done by the laser. In the fast solenoid, the field rises on a timescale comparable to the laser pulse length, removing the plasma from the wall, and contributing to the plasma energy content via compression work. In the slow solenoid, preionization is generally not used, and the laser both creates the plasma and heats it. In the fast solenoid, the preionization technique is relatively critical as it must create conditions leading to a true particle minimum on axis in order to insure favorable refraction of the laser beam (''trapping''). Substantial progress has been made in both experiments this year, particularly with respect to diagnostic capabilities. In addition, the theoretical effort has expanded considerably. Highlights of this year's program are listed and details are contained in the balance of the report

Adventures in Laser Produced Plasma Research

Energy Technology Data Exchange (ETDEWEB)

Key, M

2006-01-13

In the UK the study of laser produced plasmas and their applications began in the universities and evolved to a current system where the research is mainly carried out at the Rutherford Appleton Laboratory Central Laser Facility ( CLF) which is provided to support the universities. My own research work has been closely tied to this evolution and in this review I describe the history with particular reference to my participation in it.

Plasma shape control by pulsed solenoid on laser ion source

International Nuclear Information System (INIS)

Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

2015-01-01

A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS

Plasma shape control by pulsed solenoid on laser ion source

Science.gov (United States)

Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

2015-09-01

A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

Plasma shape control by pulsed solenoid on laser ion source

Energy Technology Data Exchange (ETDEWEB)

Sekine, M. [Tokyo Institute of Technology, Meguro-ku, Tokyo 2-12-1 (Japan); RIKEN, Wako, Saitama 351-0198 (Japan); Ikeda, S. [Tokyo Institute of Technology, Yokohama, Kanagawa 226-8502 (Japan); RIKEN, Wako, Saitama 351-0198 (Japan); Romanelli, M. [Cornell University, Ithaca, NY 14850 (United States); Kumaki, M. [RIKEN, Wako, Saitama 351-0198 (Japan); Waseda University, Shinjuku, Tokyo 169-0072 (Japan); Fuwa, Y. [RIKEN, Wako, Saitama 351-0198 (Japan); Kyoto University, Uji, Kyoto 611-0011 (Japan); Kanesue, T. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Hayashizaki, N. [Tokyo Institute of Technology, Meguro-ku, Tokyo 2-12-1 (Japan); Lambiase, R. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Okamura, M. [RIKEN, Wako, Saitama 351-0198 (Japan); Brookhaven National Laboratory, Upton, NY 11973 (United States)

2015-09-21

A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

Fine Structure of a Laser-Plasma Filament in Air

International Nuclear Information System (INIS)

Eisenmann, Shmuel; Pukhov, Anatoly; Zigler, Arie

2007-01-01

The ability to select and stabilize a single filament during propagation of an ultrashort high-intensity laser pulse in air makes it possible to examine the longitudinal structure of the plasma channel left in its wake. We present detailed measurements of plasma density variations along laser propagation. Over the length of the filament, electron density variations of 3 orders of magnitude are measured. They display evidence of a meter-long postionization range, along which a self-guided structure is observed coupled with a low plasma density, corresponding to ∼3 orders of magnitude decrease from the peak density level

Fine Structure of a Laser-Plasma Filament in Air

Science.gov (United States)

Eisenmann, Shmuel; Pukhov, Anatoly; Zigler, Arie

2007-04-01

The ability to select and stabilize a single filament during propagation of an ultrashort high-intensity laser pulse in air makes it possible to examine the longitudinal structure of the plasma channel left in its wake. We present detailed measurements of plasma density variations along laser propagation. Over the length of the filament, electron density variations of 3 orders of magnitude are measured. They display evidence of a meter-long postionization range, along which a self-guided structure is observed coupled with a low plasma density, corresponding to ˜3 orders of magnitude decrease from the peak density level.

Plasma channels during filamentation of a femtosecond laser pulse with wavefront astigmatism in air

Energy Technology Data Exchange (ETDEWEB)

Dergachev, A A; Kandidov, V P; Shlenov, S A [Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation); Ionin, A A; Mokrousova, D V; Seleznev, L V; Sinitsyn, D V; Sunchugasheva, E S; Shustikova, A P [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2014-12-31

We have demonstrated experimentally and numerically the possibility of controlling parameters of plasma channels formed during filamentation of a femtosecond laser pulse by introducing astigmatism in the laser beam wavefront. It is found that weak astigmatism increases the length of the plasma channel in comparison with the case of aberration-free focusing and that strong astigmatism can cause splitting of the plasma channel into two channels located one after another on the filament axis. (interaction of laser radiation with matter. laser plasma)

Controlling Plasma Channels through Ultrashort Laser Pulse Filamentation

Science.gov (United States)

Ionin, Andrey; Seleznev, Leonid; Sunchugasheva, Elena

2013-09-01

A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding long electric discharges is discussed. The research was supported by RFBR Grants 11-02-12061-ofi-m and 11-02-01100, and EOARD Grant 097007 through ISTC Project 4073 P

Mechanism of laser beam reentry into a laser breakdown plasma

International Nuclear Information System (INIS)

Savic, P.; Kekez, M.M.; Makomaski, A.H.

1975-01-01

It is shown that the focus-directed filament often observed in streak photographs of CO 2 -laser produced gas breakdown can be explained by the lateral expansion and consequent cooling of the plasma behind the radiation supported shock. A simple analysis and more detailed numerical calculations show a temperature maximum developing in the plasma, which travels either towards or away from the light source, depending on the nature of the gas. Thus, the locus of the cutoff temperature also travels along the beam, allowing it to reenter the plasma at a velocity which may attain the speed of light. (Auth.)

Efficient Modeling of Laser-Plasma Accelerators with INF&RNO

Energy Technology Data Exchange (ETDEWEB)

Benedetti, C.; Schroeder, C. B.; Esarey, E.; Geddes, C. G. R.; Leemans, W. P.

2010-06-01

The numerical modeling code INF&RNO (INtegrated Fluid& paRticle simulatioN cOde, pronounced"inferno") is presented. INF&RNO is an efficient 2D cylindrical code to model the interaction of a short laser pulse with an underdense plasma. The code is based on an envelope model for the laser while either a PIC or a fluid description can be used for the plasma. The effect of the laser pulse on the plasma is modeled with the time-averaged poderomotive force. These and other features allow for a speedup of 2-4 orders of magnitude compared to standard full PIC simulations while still retaining physical fidelity. The code has been benchmarked against analytical solutions and 3D PIC simulations and here a set of validation tests together with a discussion of the performances are presented.

In situ measurement of plasma and shock wave properties inside laser-drilled metal holes

Science.gov (United States)

Brajdic, Mihael; Hermans, Martin; Horn, Alexander; Kelbassa, Ingomar

2008-10-01

High-speed imaging of shock wave and plasma dynamics is a commonly used diagnostic method for monitoring processes during laser material treatment. It is used for processes such as laser ablation, cutting, keyhole welding and drilling. Diagnosis of laser drilling is typically adopted above the material surface because lateral process monitoring with optical diagnostic methods inside the laser-drilled hole is not possible due to the hole walls. A novel method is presented to investigate plasma and shock wave properties during the laser drilling inside a confined environment such as a laser-drilled hole. With a novel sample preparation and the use of high-speed imaging combined with spectroscopy, a time and spatial resolved monitoring of plasma and shock wave dynamics is realized. Optical emission of plasma and shock waves during drilling of stainless steel with ns-pulsed laser radiation is monitored and analysed. Spatial distributions and velocities of shock waves and of plasma are determined inside the holes. Spectroscopy is accomplished during the expansion of the plasma inside the drilled hole allowing for the determination of electron densities.