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1

Dynamics and stability of relativistic GRB blast waves

In gamma-ray-bursts (GRB), ultra-relativistic blast waves are ejected into\\u000athe circumburst medium. We analyse in unprecedented detail the deceleration of\\u000aa self-similar Blandford-McKee blast wave from a Lorentz factor 25 to the\\u000anonrelativistic Sedov phase. Our goal is to determine the stability properties\\u000aof its frontal shock. We carried out a grid-adaptive relativistic 2D\\u000ahydro-simulation at extreme resolving power, following

Z. Meliani; R. Keppens

2010-01-01

2

Synchrotron signature of a relativistic blast wave with decaying microturbulence

NASA Astrophysics Data System (ADS)

Microphysics of weakly magnetized relativistic collisionless shock waves, corroborated by recent high performance numerical simulations, indicates the presence of a microturbulent layer of large magnetic field strength behind the shock front, which must decay beyond some hundreds of skin depths. This paper discusses the dynamics of such microturbulence, borrowing from these same numerical simulations, and calculates the synchrotron signature of a power law of shock accelerated particles. The decaying microturbulent layer is found to leave distinct signatures in the spectro-temporal evolution of the spectrum F? ? t-??-? of a decelerating blast wave, which are potentially visible in early multiwavelength follow-up observations of gamma-ray bursts. This paper also discusses the influence of the evolving microturbulence on the acceleration process, with particular emphasis on the maximal energy of synchrotron afterglow photons, which falls in the GeV range for standard gamma-ray burst parameters. Finally, this paper argues that the evolving microturbulence plays a key role in shaping the spectra of recently observed gamma-ray bursts with extended GeV emission, such as GRB 090510.

Lemoine, M.

2013-01-01

3

Dynamics and stability of relativistic gamma-ray-bursts blast waves

Aims: In gamma-ray-bursts (GRBs), ultra-relativistic blast waves are ejected into the circumburst medium. We analyse in unprecedented detail the deceleration of a self-similar Blandford-McKee blast wave from a Lorentz factor 25 to the nonrelativistic Sedov phase. Our goal is to determine the stability properties of its frontal shock. Methods: We carried out a grid-adaptive relativistic 2D hydro-simulation at extreme resolving

Z. Meliani; R. Keppens

2010-01-01

4

Dynamics and stability of relativistic gamma-ray-bursts blast waves

NASA Astrophysics Data System (ADS)

Aims: In gamma-ray-bursts (GRBs), ultra-relativistic blast waves are ejected into the circumburst medium. We analyse in unprecedented detail the deceleration of a self-similar Blandford-McKee blast wave from a Lorentz factor 25 to the nonrelativistic Sedov phase. Our goal is to determine the stability properties of its frontal shock. Methods: We carried out a grid-adaptive relativistic 2D hydro-simulation at extreme resolving power, following the GRB jet during the entire afterglow phase. We investigate the effect of the finite initial jet opening angle on the deceleration of the blast wave, and identify the growth of various instabilities throughout the coasting shock front. Results: We find that during the relativistic phase, the blast wave is subject to pressure-ram pressure instabilities that ripple and fragment the frontal shock. These instabilities manifest themselves in the ultra-relativistic phase alone, remain in full agreement with causality arguments, and decay slowly to finally disappear in the near-Newtonian phase as the shell Lorentz factor drops below 3. From then on, the compression rate decreases to levels predicted to be stable by a linear analysis of the Sedov phase. Our simulations confirm previous findings that the shell also spreads laterally because a rarefaction wave slowly propagates to the jet axis, inducing a clear shell deformation from its initial spherical shape. The blast front becomes meridionally stratified, with decreasing speed from axis to jet edge. In the wings of the jetted flow, Kelvin-Helmholtz instabilities occur, which are of negligible importance from the energetic viewpoint. Conclusions: Relativistic blast waves are subject to hydrodynamical instabilities that can significantly affect their deceleration properties. Future work will quantify their effect on the afterglow light curves.

Meliani, Z.; Keppens, R.

2010-09-01

5

Gamma-ray burst afterglows from trans-relativistic blast wave simulations

We present a study of the intermediate regime between ultra-relativistic and\\u000anonrelativistic flow for gamma-ray burst afterglows. The hydrodynamics of\\u000aspherically symmetric blast waves is numerically calculated using the AMRVAC\\u000aadaptive mesh refinement code. Spectra and light curves are calculated using a\\u000aseparate radiation code that, for the first time, links a parametrisation of\\u000athe microphysics of shock acceleration, synchrotron

H. J. van Eerten; K. Leventis; Z. Meliani; R. A. M. J. Wijers; R. Keppens

2009-01-01

6

NASA Astrophysics Data System (ADS)

The distance radiation waves that supersonically propagate in optically thick, diffusive media are energy sensitive. A blast wave can form in a material when the initially diffusive, supersonic radiation wave becomes transonic. Under specific conditions, the blast wave is visible with radiography as a density perturbation. [Peterson et al., Phys. Plasmas 13, 056901 (2006)] showed that the time-integrated drive energy can be measured using blast wave positions with uncertainties less than 10% at the Z Facility. In some cases, direct measurements of energy loss through diagnostic holes are not possible with bolometric and x-ray radiometric diagnostics. Thus, radiography of high compression blast waves can serve as a complementary technique that provides time-integrated energy loss through apertures. In this paper, we use blast waves to characterize the energy emerging through a 2.4 mm aperture and show experimental results in comparison to simulations.

Tierney, Thomas E.; Tierney, Heidi E.; Idzorek, George C.; Watt, Robert G.; Peterson, Robert R.; Peterson, Darrell L.; Fryer, Christopher L.; Lopez, Mike R.; Jones, Michael C.; Sinars, Daniel; Rochau, Gregory A.; Bailey, James E.

2008-10-01

7

We present results of experimental studies of spherical blast waves in seasonally frozen soils with different physical and mechanical properties at different temperatures. A comparison with results in [i, 2] shows that the wave parameters depend strongly on the characteristics of the soil in the initial unfrozen state and on the temperature. When the temperature falls, the maximum stresses and

G. M. Lyakhov; G. B. Frash

1983-01-01

8

Neutrinos from a channelled blast wave in jets of AGN

Based on a recently published model for gamma-ray production by a collimated, relativistic blast wave cf. Pohl and Schlickeiser (2000), we have calculated the neutrino production resulting from the proton-proton collisions in the highly relativistic plasma in jets of AGN. It is shown that neutrino emission is correlated with the emission of TeV gamma-rays. The search for neutrino emissions from

C. Schuster; M. Pohl; R. Schlickeiser

2001-01-01

9

Gamma-ray burst afterglows from transrelativistic blast wave simulations

We present a study of the intermediate regime between ultrarelativistic and non-relativistic flow for gamma-ray burst afterglows. The hydrodynamics of spherically symmetric blast waves is numerically calculated using the AMRVAC adaptive mesh refinement code. Spectra and light curves are calculated using a separate radiation code that, for the first time, links a parametrization of the microphysics of shock acceleration, synchrotron

H. J. van Eerten; K. Leventis; Z. Meliani; R. A. M. J. Wijers; R. Keppens

2010-01-01

10

Recent numerical work on multidimensional relativistic outflows relevant to GRB afterglow observations are presented. Special relativistic hydrodynamical simulations using adaptive mesh refinement (AMR) allow for resolving the multidimensional dynamics of GRB blast waves. We present models of jetted relativistic blast waves making the transition to non-relativistic flow.

Andrew MacFadyen

2004-01-01

11

Gamma-ray burst afterglows from transrelativistic blast wave simulations

NASA Astrophysics Data System (ADS)

We present a study of the intermediate regime between ultrarelativistic and non-relativistic flow for gamma-ray burst afterglows. The hydrodynamics of spherically symmetric blast waves is numerically calculated using the AMRVAC adaptive mesh refinement code. Spectra and light curves are calculated using a separate radiation code that, for the first time, links a parametrization of the microphysics of shock acceleration, synchrotron self-absorption and electron cooling to a high-performance hydrodynamic simulation. For the dynamics, we find that the transition to the non-relativistic regime generally occurs later than expected, the Sedov-Taylor solution overpredicts the late-time blast wave radius and the analytical formula for the blast wave velocity from Huang, Dai & Lu overpredicts the late-time velocity by a factor of 4/3. Also, we find that the lab frame density directly behind the shock front divided by the fluid Lorentz factor squared remains very close to four times the unshocked density, while the effective adiabatic index of the shock changes from relativistic to non-relativistic. For the radiation, we find that the flux may differ up to an order of magnitude depending on the equation of state that is used for the fluid and that the counterjet leads to a clear rebrightening at late times for hard-edged jets. Simulating GRB 030329 using predictions for its physical parameters from the literature leads to spectra and light curves that may differ significantly from the actual data, emphasizing the need for very accurate modelling. Predicted light curves at low radio frequencies for a hard-edged jet model of GRB 030329 with opening angle 22° show typically two distinct peaks, due to the combined effect of jet break, non-relativistic break and counterjet. Spatially resolved afterglow images show a ring-like structure.

van Eerten, H. J.; Leventis, K.; Meliani, Z.; Wijers, R. A. M. J.; Keppens, R.

2010-03-01

12

Large amplitude relativistic plasma waves

NASA Astrophysics Data System (ADS)

Relativistic, longitudinal plasma oscillations are studied for the case of a simple water bag distribution of electrons having cylindrical symmetry in momentum space with the axis of the cylinder parallel to the velocity of wave propagation. The plasma is required to obey the relativistic Vlasov-Poisson equations, and solutions are sought in the wave frame. An exact solution for the plasma density as a function of the electrostatic field is derived. The maximum electric field is presented in terms of an integral over the known density. It is shown that when the perpendicular momentum is neglected, the maximum electric field approaches infinity as the wave phase velocity approaches the speed of light. It is also shown that for any nonzero perpendicular momentum, the maximum electric field will remain finite as the wave phase velocity approaches the speed of light. The relationship to previously published solutions is discussed as is some recent controversy regarding the proper modeling of large amplitude relativistic plasma waves.

Coffey, Timothy

2010-05-01

13

Blast-wave characteristics near Site 300

The blast-wave overpressures propagating in the atmosphere near the Lawrence Livermore National Laboratory (LLNL) Site 300 have been measured at selected locations to determine whether the Site 300 blast operations will be hindered by the proposed construction of a residential development adjacent to its border.We tested high-explosives (HE) weights ranging from 14 to 545 lb under various weather conditions. Although more tests should be conducted before a definitive statement can be made on the blast propagation near Site 300, we offer the following preliminary interpretation of the results obtained to date. The readings at the closest locations show that the blast-wave overpressures exceed the 126-decibel (dB) level established by LLNL at about 250 lb of HE detonation. The weather conditions do not materially affect the pressure levels at these locations. Insufficient test data exist along the Corral Hollow Road perimeter, making it difficult to reasonably predict HE blast effects along the southern border. Therefore, we recommend that additional measurements be made along this and other boundaries in future tests, to provide more comprehensive data to help determine the blast-wave propagation characteristics in the proposed development areas. Blast-wave focusing may occur in the proposed residential development area under certain weather conditions. We recommend that this possibility should be addressed for its potentially adverse impact on the proposed residential area. Because the testing ground controlled by Physics International, Inc. (PI) is adjacent to Site 300, it is important to be aware of PI`s detonation activities. Peak overpressure measurements near PI`s Corral Hollow Road entrance reveal that PI shots over 25 lb HE have exceeded 126 dB, the limit established by LLNL for safe operations.

Kang, Sang-Wook; Kleiber, J.C. Jr.

1993-08-01

14

Swift GRBs and the blast wave model

NASA Astrophysics Data System (ADS)

The complex structure of the light curves of Swift GRBs has made their interpretation and that of the blast wave caused by the burst, more difficult than in the pre-Swift era. We aim to constrain the blast wave parameters: electron energy distribution, p, density profile of the circumburst medium, k, and the continued energy injection index, q. We do so by comparing the observed multi-wavelength light curves and X-ray spectra of a Swift sample to the predictions of the blast wave model. We can successfully interpret all of the bursts in our sample of 10, except two, within the framework of the blast wave model, and we can estimate with confidence the electron energy distribution index for 6 of the sample. Furthermore we identify jet breaks in half of the bursts. A statistical analysis of the distribution of p reveals that, even in the most conservative case of least scatter, the values are not consistent with a single, universal value. The values of k suggest that the circumburst density profiles are not drawn from only one of the constant density or wind-like media populations.

Curran, P. A.; van der Horst, A. J.; Starling, R. L. C.; Wijers, R. A. M. J.

2009-05-01

15

The Stability of Plane Blast Waves.

National Technical Information Service (NTIS)

The stability of a plane blast wave to surface perturbations is examined. It is found possible by making a 'thin' sheet approximation to the geometry, to obtain a set of ordinary differential equations which describe the sheet motion. These equations are ...

R. Gerwin R. B. Hall

1968-01-01

16

ERIC Educational Resources Information Center

|The Lorentz transformation applies directly to the kinematics of moving particles viewed as geometric points. Wave propagation, on the other hand, involves moving planes which are extended objects defined by simultaneity. By treating a plane wave as a geometric object moving at the phase velocity, novel results are obtained that illustrate the…

Houlrik, Jens Madsen

2009-01-01

17

Reactive Blast Waves from Composite Charges

Investigated here is the performance of composite explosives - measured in terms of the blast wave they drive into the surrounding environment. The composite charge configuration studied here was a spherical booster (1\\/3 charge mass), surrounded by aluminum (Al) powder (2\\/3 charge mass) at an initial density of = 0.604 g\\/cc. The Al powder acts as a fuel but does

A L Kuhl; J B Bell; V E Beckner

2009-01-01

18

Blast waves and how they interact with structures.

The paper defines and describes blast waves, their interaction with a structure and its subsequent response. Explosions generate blast waves, which need not be due to explosives. A blast wave consists of two parts: a shock wave and a blast wind. The paper explains how shock waves are formed and their basic properties. The physics of blast waves is non-linear and therefore non-intuitive. To understand how an explosion generates a blast wave a numerical modelling computer code, called a hydrocode has to be employed. This is briefly explained and the cAst Eulerian hydrocode is used to illustrate the formation and propagation of the blast wave generated by a 1 kg sphere of TNT explosive detonated 1 m above the ground. The paper concludes with a discussion of the response of a structure to a blast wave and shows that this response is governed by the structures natural frequency of vibration compared to the duration of the blast wave. The basic concepts introduced are illustrated in a second simulation that introduces two structures into the blast field of the TNT charge. PMID:11307674

Cullis, I G

2001-02-01

19

Biologic response to complex blast waves

Small, bare charges were detonated inside an M59 armored personnel carrier (APC) in an attempt to simulate the complex blast waves generated by the jets from shaped-charge warheads penetrating into armored vehicles. Anesthetized sheep were placed inside the APC at 92- and 122-cm ranges from 57- or 113-g pentolite charges. Pressure-time was measured by pressure transducers either mounted on the animals or free standing at comparable ranges on the opposite side of the vehicle. In general, the waveforms were characterized by an initial shock wave of less than 1-msec duration followed by repeated reflections of decreasing magnitude. No deaths nor lung hemorrhages were observed, but all the animals sustained severe ear injury. Animals subjected to peak overpressures of 1.2 to 2.3 bar from the 113-g explosions also received slight non-auditory blast injuries to the upper respiratory and gastrointestinal tracts; those exposed to peak overpressures of just under 1 bar from the 57-g charges did not. The non-auditory blast injuries inside the APC were more severe than those sustained by sheep at comparable distances from 113-g charges in the open. The results suggested that the biological consequences of a complex wave of the type encountered in this study can be equated approximately to a Friedlander wave with a peak overpressure equal to that of the complex wave and with a total impulse equal to the impulse over the first 2 to 3 msec of the complex wave. 9 refs., 7 figs., 1 tab.

Richmond, D.R.; Yelverton, J.T.; Fletcher, E.R.; Phillips, Y.Y.

1985-01-01

20

Motion of cylindrically-symmetrical relativistic shock waves

NASA Astrophysics Data System (ADS)

Some observed astrophysical phenomena such as the blast of a supernova suggest the necessity of study of the motion of shock waves in a relativistic fluid flow in the presence of a magnetic field. This paper deals with the motion of special relativistic shock wave which propagates from the center line outwardly after an explosion with the assumption that the magnetic field has an axial component only. Similarity solutions which depend on the parameter ? = r/t are constructed. Two special cases are then studied in detail. In the first case, there is an ultra-relativistic fluid in front of the shock and in the second case, there is a cold fluid in front of the shock.

Shi, Chang Chun

1986-12-01

21

Langmuir wave in weakly inhomogeneous relativistic plasma

The evolution of a Langmuir wave in a weakly inhomogeneous relativistic plasma with a positive density gradient is considered. It is shown that, at relativistic phase velocities, the wave evolution even at the tail of the electron distribution, where it is close to linear in the nonrelativistic case, results in the wave transformation into a hybrid of two waves with different spatial periods. Nonlinear dispersion relations for different stages of the wave evolution are derived.

Matveev, A. I. [South Federal University, Institute of Technology (Russian Federation)

2008-11-15

22

Transverse relativistic effects in paraxial wave interference

NASA Astrophysics Data System (ADS)

We consider relativistic deformations of interfering paraxial waves moving in the transverse direction. Owing to superluminal transverse phase velocities, noticeable deformations of the interference patterns arise when the waves move with respect to each other with non-relativistic velocities. Similar distortions also appear on a mutual tilt of the interfering waves, which causes a phase delay analogous to the relativistic time delay. We illustrate these observations by the interference between a vortex wave beam and a plane wave, which exhibits a pronounced deformation of the radial fringes into a fork-like pattern (relativistic Hall effect). Furthermore, we describe an additional relativistic motion of the interference fringes (a counter-rotation in the vortex case), which becomes noticeable at the same non-relativistic velocities.

Bliokh, Konstantin Y.; Izdebskaya, Yana V.; Nori, Franco

2013-04-01

23

Direct Initiation of Detonation by Non-Ideal Blast Waves.

National Technical Information Service (NTIS)

This study is a theoretical investigation of the initiation of detonation by nonideal blast waves. The study used the output of the CLOUD program as the source of flow data for blast waves generated by bursting spheres. Each cell that surrounds the bursti...

R. J. Cesarone

1977-01-01

24

Direct initiation of detonation by non-ideal blast waves

This study is a theoretical investigation of the initiation of detonation by nonideal blast waves. The study used the output of the CLOUD program as the source of flow data for blast waves generated by bursting spheres. Each cell that surrounds the bursting sphere is assumed to be reactive with an Arrhenius type kinetic rate law over a temperature range

R. J. Cesarone

1977-01-01

25

Tailored Blast Wave Production Pertaining to Supernova Remnants

NASA Astrophysics Data System (ADS)

We report on the first production of "tailored" blast waves in cluster media using a 1 ps laser pulse focused to 2 × 1016 W/cm2. This new technique allows cylindrical blast waves to be produced with a strong axial modulation of variable spatial frequency, as a seed for instability growth. Energy deposition is modified by changing the cluster density whilst keeping the atomic density of the target constant. Electron density maps show the production of strongly modulated blast waves and the development of a thin shell structure in H at late times, and the trajectories show blast waves forming in H, and Ar. In Xe, a blast wave does not form on the timescales studied. Analysis of astrophysical similarity parameters suggests that a hydrodynamically similar situation is created in H, and that further evolution would create a regime where radiative effects may be influential in Ar and Xe.

Moore, A. S.; Symes, D. R.; Smith, R. A.

26

Tailored Blast Wave Production Pertaining to Supernova Remnants

NASA Astrophysics Data System (ADS)

We report on the first production of “tailored” blast waves in cluster media using a 1 ps laser pulse focused to 2×1016 W/cm2. This new technique allows cylindrical blast waves to be produced with a strong axial modulation of variable spatial frequency, as a seed for instability growth. Energy deposition is modified by changing the cluster density whilst keeping the atomic density of the target constant. Electron density maps show the production of strongly modulated blast waves and the development of a thin shell structure in H at late times, and the trajectories show blast waves forming in H, and Ar. In Xe, a blast wave does not form on the timescales studied. Analysis of astrophysical similarity parameters suggests that a hydrodynamically similar situation is created in H, and that further evolution would create a regime where radiative effects may be influential in Ar and Xe.

Moore, A. S.; Symes, D. R.; Smith, R. A.

2005-07-01

27

Detonation waves in relativistic hydrodynamics

This paper is concerned with an algebraic study of the equations of detonation waves in relativistic hydrodynamics taking into account the pressure and the energy of thermal radiation. A new approach to shock and detonation wavefronts is outlined. The fluid under consideration is assumed to be perfect (nonviscous and nonconducting) and to obey the following equation of state: {ital p}=({gamma}{minus}1){rho} where {ital p}, {rho}, and {gamma} are the pressure, the total energy density, and the adiabatic index, respectively. The solutions of the equations of detonation waves are reduced to the problem of finding physically acceptable roots of a quadratic polynomial {Pi}({ital X}) where {ital X} is the ratio {tau}/{tau}{sub 0} of dynamical volumes behind and ahead of the detonation wave. The existence and the locations of zeros of this polynomial allow it to be shown that if the equation of state of the burnt fluid is known then the variables characterizing the unburnt fluid obey well-defined physical relations.

Cissoko, M. (Universite Pierre et Marie Curie, Paris VI, Laboratoire de Gravitation et de Cosmologie Relativistes, Institut Henri Poincare, 11 Rue Pierre et Marie Curie, 7500 Paris (France))

1992-02-15

28

Blast Waves From Non-ideal Explosives

NASA Astrophysics Data System (ADS)

The non-ideal behavior of explosives comes from different ways which retard the energy release from the explosive. These include a lack of oxygen balance which results in energy being released after the shock wave from the detonation has gone into the surrounding air and the detonation products react with this fresh source of oxygen as it is included within the shock wave. Also included are slow and/or multiple reactions which cause energy to be released late in the reaction zone of the detonation when the pressure of the detonations has dropped until the local sound speed has fallen below the detonation velocity. All energy released after this point cannot keep up with the detonation shock wave and must wait to catch up with the blast wave that propagates into the air. Both of these non-ideal characteristics of the explosive reduce the irreversible losses to the air close to the explosive charge by reducing the peak pressure, and therefore, the temperature compressive heating of the air. Less irreversible losses to the air means more energy propagates to greater distance. This presentation covers the research conducted into the influence of these non-ideal effects upon the propagation of peak pressures and the positive and negative impulses from non-ideal explosives.

Romero, Van D.; Williams, Pharis E.

1997-07-01

29

Blast waves from non-ideal explosives

NASA Astrophysics Data System (ADS)

The non-ideal behavior of explosives comes from different ways which retard the energy release from the explosive. These include a lack of oxygen balance which results in energy being released after the shock wave from the detonation has gone into the surrounding air and the detonation products react with this fresh source of oxygen as it is included within the shock wave. Also included are slow and/or multiple reactions which cause energy to be released late in the reaction zone of the detonation when the pressure of the detonations has dropped until the local sound speed has fallen below the detonation velocity. All energy released after this point cannot keep up with the detonation shock wave and must wait to catch up with the blast wave that propagates into the air. Both of these non-ideal characteristics of the explosive reduce the irreversible losses to the air close to the explosive charge by reducing the peak pressure, and therefore, the temperature compressive heating of the air. Less irreversible losses to the air means more energy propagates to greater distance. This presentation covers the research conducted into the influence of these non-ideal effects upon the propagation of peak pressures and the positive and negative impulses from non-ideal explosives.

Romero, Van; Williams, Pharis E.

1998-07-01

30

Evolution of blast wave profiles in simulated air blasts: experiment and computational modeling

NASA Astrophysics Data System (ADS)

Shock tubes have been extensively used in the study of blast traumatic brain injury due to increased incidence of blast-induced neurotrauma in Iraq and Afghanistan conflicts. One of the important aspects in these studies is how to best replicate the field conditions in the laboratory which relies on reproducing blast wave profiles. Evolution of the blast wave profiles along the length of the compression-driven air shock tube is studied using experiments and numerical simulations with emphasis on the shape and magnitude of pressure time profiles. In order to measure dynamic pressures of the blast, a series of sensors are mounted on a cylindrical specimen normal to the flow direction. Our results indicate that the blast wave loading is significantly different for locations inside and outside of the shock tube. Pressure profiles inside the shock tube follow the Friedlander waveform fairly well. Upon approaching exit of the shock tube, an expansion wave released from the shock tube edges significantly degrades the pressure profiles. For tests outside the shock tube, peak pressure and total impulse reduce drastically as we move away from the exit and majority of loading is in the form of subsonic jet wind. In addition, the planarity of the blast wave degrades as blast wave evolves three dimensionally. Numerical results visually and quantitatively confirm the presence of vortices, jet wind and three-dimensional expansion of the planar blast wave near the exit. Pressure profiles at 90° orientation show flow separation. When cylinder is placed inside, this flow separation is not sustained, but when placed outside the shock tube this flow separation is sustained which causes tensile loading on the sides of the cylinder. Friedlander waves formed due to field explosives in the intermediate-to far-field ranges are replicated in a narrow test region located deep inside the shock tube.

Chandra, N.; Ganpule, S.; Kleinschmit, N. N.; Feng, R.; Holmberg, A. D.; Sundaramurthy, A.; Selvan, V.; Alai, A.

2012-09-01

31

Radiative shell thinning in intense laser-driven blast waves

NASA Astrophysics Data System (ADS)

The structural evolution of blast waves launched by intense laser pulses in gases is investigated. These blast waves exhibit significant energy loss through radiation while propagating in xenon as evidenced by interferometric imaging revealing radiative precursors and deceleration parameters well below those of an energy-conserving wave. Thinning of the blast wave shell from radiative cooling is observed through comparison of shocks launched in gases of differing atomic number. Shell thinning is also measured when the gas density is altered, indicating the influence of conditions within the preshock medium. These results are compared with radiative-hydrodynamic simulations. British Crown Copyright 2009/MOD.

Osterhoff, J.; Symes, D. R.; Edens, A. D.; Moore, A. S.; Hellewell, E.; Ditmire, T.

2009-02-01

32

Spectral properties of blast-wave models of gamma-ray burst sources

We calculate the spectrum of blast-wave models of gamma-ray burst sources, for various assumptions about the magnetic field density and the relativistic particle acceleration efficiency. For a range of physically plausible models we find that the radiation efficiency is high and leads to nonthermal spectra with breaks at various energies comparable to those observed in the gamma-ray range. Radiation is

P. Meszaros; M. J. Rees; H. Papathanassiou

1994-01-01

33

Cosmic ray acceleration in supernova blast waves

NASA Astrophysics Data System (ADS)

Cosmic ray spectra produced over the lifetime of an evolving SNR blast wave are determined by solving the test particle approximation of diffusive shock acceleration in plane, steady shocks with homogeneous upstream and downstream media. The injection of 500-eV particles at the shock produces power laws up to at least 3 trillion eV. These power law spectra are at least as hard as the source spectra used in Leaky Box propagation calculations, as has been independently found by Bogdan and Voelk (1983). The correspondence of the present model to the reacceleration model of Blandford and Ostriker (1980) is shown, and it is demonstrated that the cooling effect in these models' expanding remnants may be sufficient to explain the overabundance of cosmic ray antiprotons in the 0.1-10 GeV kinetic energy range.

Moraal, H.; Axford, W. I.

1983-09-01

34

Blast wave investigated using a high enthalpy blast simulator

An experimental study to examine the behavior of blast propagation is described. Its decay characteristics are analyzed to establish an empirical relationship for peak pressure distribution. A scaled length parameter is used in the development of a peak pressure prediction scheme. An assessment is also made to improve the data correlation using the axial Mach disc distance in scaling the

K. C. Phan; C. V. Hurdle

1990-01-01

35

Blast wave investigation using a high enthalpy blast simulator

An experimental study to examine the behavior of blast propagation is described. Its decay characteristics are analyzed to establish an empirical relationship for peak pressure distribution which employs scaled length parameter. An assessment is also made to improve the data correlation using the axial Mach disk distance in scaling the radial distance from the tube exit.

K. C. Phan; C. V. Hurdle

1990-01-01

36

Relativistic Wave Equations in the Eikonal Approximation.

National Technical Information Service (NTIS)

The Bethe-Salpeter relativistic wave equation is eikonalized. From it, a finite target mass correction to the Dirac potential scattering approach is found. The limit of the heavy ion collision is discussed. The Glauber multiple scattering formalism is int...

A. Tekou

1985-01-01

37

Relativistic Bernstein waves in a degenerate plasma

Bernstein mode for a relativistic degenerate electron plasma is investigated. Using relativistic Vlasov-Maxwell equations, a general expression for the conductivity tensor is derived and then employing Fermi-Dirac distribution function a generalized dispersion relation for the Bernstein mode is obtained. Two limiting cases, i.e., non-relativistic and ultra-relativistic are discussed. The dispersion relations obtained are also graphically presented for some specific values of the parameters depicting how the propagation characteristics of Bernstein waves as well as the Upper Hybrid oscillations are modified with the increase in plasma number density.

Ali, Muddasir; Hussain, Azhar [Department of Physics, G.C. University, Lahore 54000 (Pakistan); Salam Chair in Physics, G.C. University, Lahore 54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, G.C. University, Lahore 54000 (Pakistan)

2011-09-15

38

Investigation of Ultrafast Laser-Driven Radiative Blast Waves

We have examined the evolution of cylindrically symmetric blast waves produced by the deposition of femtosecond laser pulses in gas jets. In high- Z gases radiative effects become important. We observe the production of an ionization precursor ahead of the shock front and deceleration parameters below the adiabatic value of 1\\/2 (for a cylinder), an effect expected when the blast

M. J. Edwards; A. J. MacKinnon; J. Zweiback; K. Shigemori; D. Ryutov; A. M. Rubenchik; K. A. Keilty; E. Liang; B. A. Remington; T. Ditmire

2001-01-01

39

A Thoracic Mechanism of Mild Traumatic Brain Injury Due to Blast Pressure Waves

The mechanisms by which blast pressure waves cause mild to moderate traumatic brain injury (mTBI) are an open question. Possibilities include acceleration of the head, direct passage of the blast wave via the cranium, and propagation of the blast wave to the brain via a thoracic mechanism. The hypothesis that the blast pressure wave reaches the brain via a thoracic

Amy Courtney; Michael Courtney

2008-01-01

40

Gamma-ray Burst Afterglow Model Fitting Based Directly on Blast Wave Simulations

NASA Astrophysics Data System (ADS)

Gamma-ray burst are the most luminous explosions in the universe, seen as sudden flashes in gamma-rays, often followed by a long-lasting afterglow signal detected from X-rays to radio. On the one hand, afterglow blast waves are complex two dimensional phenomena that require high-performance parallel computer hydrodynamical simulations to accurately model their evolution from ultra-relativistic collimated jets to quasi-spherical non-relativistic flow. These simulations require numerical techniques such as adaptive mesh refinement in a Lorentz boosted frame in order to fully resolve the physics of the outflow. On the other hand, the dynamics and resulting synchrotron emission ultimately depend on a limited number of parameters, leading to a number of useful scale invariances between different explosion parameters. This can be exploited to open a new avenue in afterglow data analysis, where we fit scale-invariant blast wave light curves and dynamics directly to (broadband) afterglow data. As a result, it is now possible to accurately model features such as the `jet break' of the light curve and the transition to non-relativistic flow, where simulation results differ markedly from earlier analytical prescriptions. I will present our latest results, where we use various methods to simulate blast waves from afterglows and other relativistic transients and from these simulations derive our novel approach to data analysis. Comparison with data from Swift presents a challenge for the jet break interpretation of many light curves and emphasizes the role of the observer angle even for observers still located within the opening angle of the relativistic jet.

Van Eerten, Hendrik; MacFadyen, A.

2013-01-01

41

The mechanisms by which blast waves are generated by a helical charge of detonating fuse in a 4.9 m diameter nuclear air blast simulator were studied in order to achieve control over the waveform produced. The problem of producing low pressure blast waves with long duration was overcome by immersing the charge in an aqueous foam in the firing chamber.

P. M. Clare

1980-01-01

42

Simulation of blast waves with shock tubes

It is shown that quasi-one-dimensional computational techniques can be successfully used to model the flow in large, geometrically complicated shock tubes. Such shock tubes, or blast simulators, can be used to simulate nuclear or conventional explosions by shaping the pressure history. Results from computations show favorable agreement when compared with data taken in a blast simulator facility in Gramat, France.

Andrew Mark

1990-01-01

43

Wave interaction in relativistic harmonic gyro-traveling-wave devices.

In gyro-traveling-wave devices, several waves can be excited at different cyclotron harmonics simultaneously. This paper analyzes the interaction between three waves synchronous with gyrating electrons at different cyclotron harmonics in two relativistic gyro-amplifier configurations; viz., gyro-traveling-wave tubes and gyrotwystrons. Two types of nonlinear interactions are considered: (a) excitation of two waves at cyclotron harmonics by a wave excited at the fundamental resonance, and (b) excitation of a wave at the fundamental resonance and another wave at the third harmonic by a wave excited at the second cyclotron harmonic. The effect of the overlapping of electron cyclotron resonances on the performance of relativistic gyrodevices is investigated as well. PMID:16803044

Ngogang, R; Nusinovich, G S; Antonsen, T M; Granatstein, V L

2006-05-03

44

Solitary Wave of a Relativistic Magnetosonic Wave Propagating Perpendicularly to a Magnetic Field.

National Technical Information Service (NTIS)

A relativistic theory for a nonlinear magnetosonic wave propagating perpendicularly to a magnetic field is developed. On the basis of a relativistic two-fluid cold plasma model, structure of a stationary magnetosonic wave is studied. Relativistic effects ...

Y. Ohsawa

1986-01-01

45

Tailored blast wave formation: Developing experiments pertinent to laboratory astrophysics

NASA Astrophysics Data System (ADS)

The first production of ``tailored'' blast waves in a cluster media using an intense, 2×1016 W cm-2, laser pulse is reported. This new technique produces cylindrical blast waves with a strong axial modulation of variable spatial frequency as a seed for instability growth. Spherical or cylindrical colliding blast waves can also be produced. Energy deposition in the cluster medium was modified using moderate-power (<1015 W cm-2) ``laser-machining,'' which destroyed clusters in selected regions while keeping the atomic density constant. Electron density profiles track the time evolution showing the production of strongly modulated blast waves and the development of a thin shell after ~6 ns in H2. Similarity parameters suggest that the hydrogen results are hydrodynamically scalable, but instabilities are precluded by the lack of radiation and low Reynolds number. Similar argon and xenon experiments do not form blast waves on the studied time scale, but indicate that radiation might become influential later in the evolution.

Moore, Alastair S.; Symes, Daniel R.; Smith, Roland A.

2005-05-01

46

Electromagnetic wave in a relativistic magnetized plasma

Results are presented from a theoretical investigation of the dispersion properties of a relativistic plasma in which an electromagnetic wave propagates along an external magnetic field. The dielectric tensor in integral form is simplified by separating its imaginary and real parts. A dispersion relation for an electromagnetic wave is obtained that makes it possible to analyze the dispersion and collisionless damping of electromagnetic perturbations over a broad parameter range for both nonrelativistic and ultrarelativistic plasmas.

Krasovitskiy, V. B. [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation)

2009-12-15

47

Blast wave diagnostic for the petawatt laser system

We report on a diagnostic to measure the trajectory of a blast wave propagating through a plastic target 400 {micro}m thick. This blast wave is generated by the irradiation of the front surface of the target with {approximately} 400 J of 1 {micro}m laser radiation in a 20 ps pulse focused to a {approximately} 50 {micro}m diameter spot, which produces an intensity in excess of 1O{sup 18} W/cm{sup 2}. These conditions approximate a point explosion and a blast wave is predicted to be generated with an initial pressure nearing 1 Gbar which decays as it travels approximately radially outward from the interaction region We have utilized streaked optical pyrometry of the blast front to determine its time of arrival at the rear surface of the target Applications of a self-similar Taylor-Sedov blast wave solution allows the amount of energy deposited to be estimated The experiment, LASNEX design simulations and initial results are discussed.

Budil, K. S., LLNL

1998-06-03

48

Testing the blast wave model with Swift GRBs

NASA Astrophysics Data System (ADS)

The complex structure of the light curves of Swift GRBs (e.g. superimposed flares and shallow decay) has made their interpretation and that of the blast wave caused by the burst, more difficult than in the pre-Swift era. We aim to constrain the blast wave parameters: electron energy distribution, p, density profile of the circumburst medium, k, and the continued energy injection index, q. We do so by comparing the observed multi-wavelength light curves and X-ray spectra of a Swift sample to the predictions of the blast wave model.We can successfully interpret all of the bursts in our multi-wavelength sample of 10, except two, within the framework of the blast wave model, and we can estimate with confidence the electron energy distribution index for 6 of the sample. Furthermore we identify jet breaks in almost half of the bursts. The values of k suggest that the circumburst density profiles are not drawn from only one of the constant density or wind-like media populations. A statistical analysis of the distribution of p reveals that, even in the most conservative case of least scatter, the values are not consistent with a single, universal value. This is in agreement with our results for a larger sample of X-ray only afterglows which we summarise here.

Curran, P. A.; Starling, R. L. C.; van der Horst, A. J.; Wijers, R. A. M. J.; de Pasquale, M.; Page, M.

2011-04-01

49

Blast Waves Generated by Constant Velocity Flames: A Simplified Approach.

National Technical Information Service (NTIS)

The self-similar solution to the blast waves generated by a constant velocity flame can be calculated easily if one assumes that the pressure and density between the flame and shock are constant, irrespective of geometry. The technique of calculation is d...

R. A. Strehlow

1974-01-01

50

Wave kinetics of relativistic quantum plasmas

A quantum kinetic equation, valid for relativistic unmagnetized plasmas, is derived here. This equation describes the evolution of a quantum quasi-distribution, which is the Wigner function for relativistic spinless charged particles in a plasma, and it is exactly equivalent to a Klein-Gordon equation. Our quantum kinetic equation reduces to the Vlasov equation in the classical limit, where the Wigner function is replaced by a classical distribution function. An approximate form of the quantum kinetic equation is also derived, which includes first order quantum corrections. This is applied to electron plasma waves, for which a new dispersion relation is obtained. It is shown that quantum recoil effects contribute to the electron Landau damping with a third order derivative term. The case of high frequency electromagnetic waves is also considered. Its dispersion relation is shown to be insensitive to quantum recoil effects for equilibrium plasma distributions.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2011-06-15

51

Towards a fast-running method for blast-wave mitigation by a prismatic blast wall

NASA Astrophysics Data System (ADS)

A procedure aimed at developing a fast-running method for blast-wave effects characterization behind a protection barrier is presented. Small-scale experiments of a hemispherical gaseous charge (stoichiometric propane-oxygen mixture) without and with a prismatic protective barrier are used to validate the use of an in-house CFD code for gaseous detonation. From numerical experiments, pressure loss of a blast wave at a corner is quantified. These fits, in conjunction with TM5-1300 reflection charts, are used to estimate the maximum overpressure around a protective barrier through geometrical and empirical laws. The results show good agreement with numerical and experimental data from the ANR-BARPPRO research project.

Éveillard, Sébastien; Lardjane, Nicolas; Vinçont, Jean-Yves; Sochet, Isabelle

52

Quick reproduction of blast-wave flow-field properties of nuclear, TNT, and ANFO explosions

In many instances, extensive blast-wave flow-field properties are required in gasdynamics research studies of blast-wave loading and structure response, and in evaluating the effects of explosions on their environment. This report provides a very useful computer code, which can be used in conjunction with the DNA Nuclear Blast Standard subroutines and code, to quickly reconstruct complete and fairly accurate blast-wave

C. P. T. Groth

1986-01-01

53

Navier-Stokes analysis of muzzle-blast-type waves

A Navier-Stokes solution is presented as a mathematical model to muzzle-blast-type waves. The study has two novel features. First, it is a combined internal/external analysis relating barrel flow parameters to muzzle environment parameters. Second, the dissipative and dispersive effects of viscosity on the propagation phenomenon are captured. The investigation also serves as a numerical analysis of axisymmetric, high-pressure waves in an unsteady, viscous flow. Conservation-form Navier-Stokes equations are integrated by a two-step, explicit finite-difference scheme. The shocks are captured and treated by the inclusion of artificial dissipative terms. Turbulence is accounted for by an algebraic eddy-viscosity model. The internal flow is solved by a predictor-corrector method of characteristics with the shock fitted in; its results compare very well with the experimental data available. The numerical results obtained simulate the muzzle blast waves and show the effects of viscosity. Comparison with the classical spherical blast wave theory shows the deviation in propagation patterns of the axisymmetric and spherical waves. 21 references.

Baysal, O.

1986-05-01

54

Navier-Stokes analysis of muzzle-blast-type waves

NASA Astrophysics Data System (ADS)

A Navier-Stokes solution is presented as a mathematical model to muzzle-blast-type waves. The study has two novel features. First, it is a combined internal/external analysis relating barrel flow parameters to muzzle environment parameters. Second, the dissipative and dispersive effects of viscosity on the propagation phenomenon are captured. The investigation also serves as a numerical analysis of axisymmetric, high-pressure waves in an unsteady, viscous flow. Conservation-form Navier-Stokes equations are integrated by a two-step, explicit finite-difference scheme. The shocks are captured and treated by the inclusion of artificial dissipative terms. Turbulence is accounted for by an algebraic eddy-viscosity model. The internal flow is solved by a predictor-corrector method of characteristics with the shock fitted in; its results compare very well with the experimental data available. The numerical results obtained simulate the muzzle blast waves and show the effects of viscosity. Comparison with the classical spherical blast wave theory shows the deviation in propagation patterns of the axisymmetric and spherical waves.

Baysal, O.

1986-05-01

55

High-speed photography of microscale blast wave phenomena

NASA Astrophysics Data System (ADS)

High-speed photography has been a primary tool for the study of blast wave phenomena, dating from the work of Toepler, even before the invention of the camera! High-speed photography was used extensively for the study of blast waves produced by nuclear explosions for which, because of the large scale, cameras running at a few hundred frames per second were adequate to obtain sharp images of the supersonic shock fronts. For the study of the blast waves produced by smaller explosive sources, ever-increasing framing rates were required. As a rough guide, for every three orders of magnitude decrease in charge size a ten-fold increase of framing rate was needed. This severely limited the use of photography for the study of blast waves from laboratory-scale charges. There are many techniques for taking single photographs of explosive phenomena, but the strongly time-dependent development of a blast wave, requires the ability to record a high-speed sequence of photographs of a single event. At ICHSPP25, Kondo et al of Shimadzu Corporation demonstrated a 1 M fps video camera that provides a sequence of up to 100 high-resolution frames. This was subsequently used at the Shock Wave Research Center of Tohoku University to record the blast waves generated by an extensive series of silver azide charges ranging in size from 10 to 0.5mg. The resulting images were measured to provide radius-time histories of the primary and secondary shocks. These were analyzed with techniques similar to those used for the study of explosions from charges with masses ranging from 500 kg to 5 kt. The analyses showed the cube-root scaling laws to be valid for the very small charges, and provided a detailed record of the peak hydrostatic pressure as a function of radius for a unit charge of silver azide, over a wide range of scaled distances. The pressure-radius variation was compared to that from a unit charge of TNT and this permitted a detailed determination of the TNT equivalence of silver azide as a function of peak pressure and radius. The availability of the Shimadzu high-speed framing camera has made it possible to perform experiments at the laboratory scale that previously could be done only on large-scale field trials. At the laboratory scale, many experiments can be performed on the same day, as compared to the months or even years required for the preparation of large-scale field experiments. The economic savings are even greater.

Dewey, John M.; Kleine, Harald

2005-03-01

56

Particle acceleration at relativistic shock waves

NASA Astrophysics Data System (ADS)

Relativistic sources, e.g. gamma-ray bursts, pulsar wind nebulae and powerful active galactic nuclei produce relativistic outflows that lead to the formation of collisionless shock waves, where particle acceleration is thought to take place. Our understanding of relativistic shock acceleration has improved in the past decade, thanks to the combination of analytical studies and high level numerical simulations. In ultra-relativistic shocks, particle acceleration is made difficult by the generically transverse magnetic field and large advection speed of the shocked plasma. Fast growing microturbulence is thus needed to make the Fermi process operative. It is thought, and numerical simulations support that view, that the penetration of supra-thermal particles in the shock precursor generates a magnetic turbulence which in turn produces the scattering process needed for particle acceleration through the Fermi mechanism. Through the comparison of the growth timescale of the microinstabilities in the shock precursor and the precursor crossing timescale, it is possible to delimit in terms of magnetization and shock Lorentz factor the region in which micro-turbulence may be excited, hence whether and how Fermi acceleration is triggered. These findings are summarized here and astrophysical consequences are drawn.

Lemoine, Martin; Pelletier, Guy

2012-04-01

57

Review of methods to attenuate shock/blast waves

NASA Astrophysics Data System (ADS)

Quick and reliable shock wave attenuation is the goal of every protection facility and therefore it is not surprising that achieving this has drawn much attention during the past hundred years. Different options have been suggested; their usefulness varying from a reasonable protection to the opposite, a shock enhancement. An example for a suggestion for shock mitigation that turned out to be an enhancement of the impinging shock wave was the idea to cover a protected object with a foam layer. While the pressure behind the reflected shock wave from the foam frontal surface was smaller than that recorded in a similar reflection from a rigid wall [25], the pressure on the “protected” surface, attached to the foam's rear-surface, was significantly higher than that recorded in a similar reflection from a bare, rigid wall [11]. In protecting humans and installations from destructive shock and/or blast waves the prime goal is to reduce the wave amplitude and the rate of pressure increase across the wave front. Both measures result in reducing the wave harmful effects. During the past six decades several approaches for achieving the desired protection have been offered in the open literature. We point out in this review that while some of the suggestions offered are practical, others are impractical. In our discussion we focus on recent schemes for shock/blast wave attenuation, characterized by the availability of reliable measurements (notably pressure and optical diagnostics) as well as high-resolution numerical simulations.

Igra, O.; Falcovitz, J.; Houas, L.; Jourdan, G.

2013-04-01

58

NASA Astrophysics Data System (ADS)

Radiative blast waves exhibiting instabilities are common and play an important role in astrophysics. Certain aspects of these astrophysical waves can be reproduced in suitably designed laboratory experiments. Previous laboratory experiments have shown that blast waves can be created from intense laser-cluster interactions and the evolution of these waves in high Z cluster gases is radiative, with trajectories that deviate from an adiabatic Sedov-Taylor expansion. With this approach, we have been studying the evolution of hydrodynamic perturbations on cylindrical blast waves in the radiative regime. In our experiment, cylindrical blast waves are generated by high intensity irradiation of an argon cluster jet. The blast waves' spatial profile is modified by initially destroying clusters in specific locations using another laser pulse. This modulation then becomes the seed to study the variation in the perturbations' amplitude. We observe some initial evidence for the oscillatory behavior predicted by the Vishniac model of perturbations on thin shell blast waves.

Quevedo, H. J.; Kim, I. T.; Bang, W.; Symes, D. R.; Osterhoff, J.; Faustlin, R.; Maurer, M.; Bernstein, A. C.; Moore, A. S.; Gumbrell, E. T.; Edens, A. D.; Smith, R. A.; Ditmire, T.

2008-04-01

59

Blast wave simulation with ground surface effect

Unsteady flowfield generated by the finite strength of a shock wave is computationally simulated with the discretization method. The results indicate that the overpressure depends on the ground surface geometry as well as the distance from the point of explosion. The present approach using the new computational-fluid-dynamic technology may improve the existing theory for estimating the unsteady motion and decay

Kozo Fujii; Fumio Shimizu; Yoshiaki Tamura; Fumio Higashino; Motoki Hinada; Ryojiro Akiba

1990-01-01

60

Cut cell strategy for 3-D blast waves numerical simulations

\\u000a \\u000a \\u000a Abstract. This paper presents the results obtained by a generalized cut cells strategy on 3-D blast waves problems. The mesh is cartesian\\u000a except when it is intersected by the surface of the solids inserted in the computational domain. The improvement, relatively\\u000a to a classical cut-cells method, is the treatment of the cut which preserves the real geometry of the

S. Cieslak; S. Ben Khelil; I. Choquet; A. Merlen

2001-01-01

61

Blast wave simulation using AUTODYN2D: A parametric study

This paper is concerned with use of the hydrocode AUTODYN2D for the simulation of blast wave interactions with structures. A comprehensive parametric study is presented including an investigation of the effect of grid size on program output. Comparisons are made with well-established simple-geometry experimental data and with an experiment of more complex geometry. In both cases, results indicate that AUTODYN2D

T. C. Chapman; T. A. Rose; P. D. Smith

1995-01-01

62

Radiative blast waves exhibiting instabilities are common and play an important role in astrophysics. Certain aspects of these astrophysical waves can be reproduced in suitably designed laboratory experiments. Previous laboratory experiments have shown that blast waves can be created from intense laser-cluster interactions and the evolution of these waves in high Z cluster gases is radiative, with trajectories that deviate

H. J. Quevedo; I. T. Kim; W. Bang; D. R. Symes; J. Osterhoff; R. Faustlin; M. Maurer; A. C. Bernstein; A. S. Moore; E. T. Gumbrell; A. D. Edens; R. A. Smith; T. Ditmire

2008-01-01

63

Testing the blast wave model with Swift GRBs

NASA Astrophysics Data System (ADS)

The complex structure of the light curves of Swift Gamma-Ray Bursts (GRBs) has made the identification of breaks, and the interpretation of the blast wave caused by the burst, more difficult than in the pre-Swift era. We aim to identify breaks, which are possibly hidden, and to constrain the blast wave parameters; electron energy distribution, p, density profile of the circumburst medium, k, and the continued energy injection index, q. We do so by comparing the observed multiwavelength light curves and X-ray spectra of our sample to the predictions of the blast wave model. We can successfully interpret all of the bursts in our sample of 10, except two, within this framework and we can estimate, with confidence, the electron energy distribution index for 6 of the sample. Furthermore, we identify jet breaks in a number of the bursts. A statistical analysis of the distribution of p reveals that, even in the most conservative case of least scatter, the values are not consistent with a single, universal value. The values of k suggest that the circumburst density profiles are not drawn from only one of the constant density or wind-like media populations.

Curran, P. A.; Starling, R. L. C.; van der Horst, A. J.; Wijers, R. A. M. J.

2009-05-01

64

Acceleration of electrons using relativistic plasma waves

NASA Astrophysics Data System (ADS)

The plasma beat-wave accelerator in the Neptune Laboratory at UCLA uses a ˜1 terawatt two-wavelength CO2 laser pulse to tunnel ionize hydrogen gas at conditions of resonance for driving a relativistic plasma wave. This plasma wave is used as an accelerating structure for an externally injected, ˜12 MeV, electron beam from the Neptune Photo-injector. The accelerated electron energy spectrum is measured using an electron spectrometer, consisting of a dipole magnet, and an array of surface barrier detectors and phosphors. Accelerated electrons have been detected out to ˜50 MeV using this setup. These experiments are also modeled in 2-D particle-in-cell simulations. These simulations show the self-channeling of the laser beam due to ion motion, which overcomes the defocusing caused by ionization induced refraction, effectively increasing the interaction length between the injected electrons and the plasma wave. Simulations are also performed to study the guiding of shorter (50--500 fs), but more intense, 0.8 mum laser pulses by preformed plasma channels. The three laser acceleration schemes, laser wake-field acceleration, plasma beat-wave acceleration, and self-modulated laser wake-field acceleration, are explored.

Narang, Ritesh

65

High-frequency measurements of blast wave propagation.

Blast wave propagation measurements were conducted to investigate nonlinear propagation effects on blast waveform evolution with distance. Measurements were made with a wide-bandwidth capacitor microphone for comparison with conventional 3.175-mm (1/8-in.) microphones with and without baffles. It was found that the 3.175-mm microphone did not have sufficient high-frequency response to capture the actual rise times in some regions. For a source of 0.57 kg (1.25 lb) of C-4 plastic explosive, the trend observed is that nonlinear effects steepened the waveform, thereby decreasing the shock rise time, up to a range of 50 m. At 100 m, the rise times had increased slightly. PMID:17004495

Loubeau, Alexandra; Sparrow, Victor W; Pater, Larry L; Wright, Wayne M

2006-09-01

66

Rankine-Hugoniot Relations in Relativistic Combustion Waves

NASA Astrophysics Data System (ADS)

As a foundational element describing relativistic reacting waves of relevance to astrophysical phenomena, the Rankine-Hugoniot relations classifying the various propagation modes of detonation and deflagration are analyzed in the relativistic regime, with the results properly degenerating to the non-relativistic and highly relativistic limits. The existence of negative-pressure downstream flows is noted for relativistic shocks, which could be of interest in the understanding of the nature of dark energy. Entropy analysis for relativistic shock waves is also performed for relativistic fluids with different equations of state (EoS), denoting the existence of rarefaction shocks in fluids with adiabatic index ? < 1 in their EoS. The analysis further shows that weak detonations and strong deflagrations, which are rare phenomena in terrestrial environments, are expected to exist more commonly in astrophysical systems because of the various endothermic reactions present therein. Additional topics of relevance to astrophysical phenomena are also discussed.

Gao, Yang; Law, Chung K.

2012-12-01

67

RANKINE-HUGONIOT RELATIONS IN RELATIVISTIC COMBUSTION WAVES

As a foundational element describing relativistic reacting waves of relevance to astrophysical phenomena, the Rankine-Hugoniot relations classifying the various propagation modes of detonation and deflagration are analyzed in the relativistic regime, with the results properly degenerating to the non-relativistic and highly relativistic limits. The existence of negative-pressure downstream flows is noted for relativistic shocks, which could be of interest in the understanding of the nature of dark energy. Entropy analysis for relativistic shock waves is also performed for relativistic fluids with different equations of state (EoS), denoting the existence of rarefaction shocks in fluids with adiabatic index {Gamma} < 1 in their EoS. The analysis further shows that weak detonations and strong deflagrations, which are rare phenomena in terrestrial environments, are expected to exist more commonly in astrophysical systems because of the various endothermic reactions present therein. Additional topics of relevance to astrophysical phenomena are also discussed.

Gao Yang; Law, Chung K., E-mail: cklaw@princeton.edu [Center for Combustion Energy and Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China)

2012-12-01

68

Simulation of a nuclear blast wave with a gaseous detonation tube. Technical report

There is an ongoing interest in simulating nonideal blast environments for nuclear effects research. In particular, one would like to be able to impose peaked blast waves on real ground surfaces and experimentally measure the ensuing dusty airblast environment. Proposed here is a gaseous detonation tube blast simulator. A disposable (or reusable) shock tube would be constructed on a in-situ

Kuhl

1983-01-01

69

Gamma-Ray Burst Afterglow Scaling Relations for the Full Blast Wave Evolution

NASA Astrophysics Data System (ADS)

We demonstrate that gamma-ray burst afterglow spectra and light curves can be calculated for arbitrary explosion and radiation parameters by scaling the peak flux and the critical frequencies connecting different spectral regimes. Only one baseline calculation needs to be done for each jet opening angle and observer angle. These calculations are done numerically using high-resolution relativistic hydrodynamical afterglow blast wave simulations which include the two-dimensional dynamical features of expanding and decelerating afterglow blast waves. Any light curve can then be generated by applying scaling relations to the baseline calculations. As a result, it is now possible to fully fit for the shape of the jet break, e.g., at early-time X-ray and optical frequencies. In addition, late-time radio calorimetry can be improved since the general shape of the transition into the Sedov-Taylor regime is now known for arbitrary explosion parameters so the exact moment when the Sedov-Taylor asymptote is reached in the light curve is no longer relevant. When calculating the baselines, we find that the synchrotron critical frequency ? m and the cooling break frequency ? c are strongly affected by the jet break. The ? m temporal slope quickly drops to the steep late-time Sedov-Taylor slope, while the cooling break ? c first steepens and then rises to meet the level of its shallow late-time asymptote.

van Eerten, Hendrik J.; MacFadyen, Andrew I.

2012-03-01

70

A relativistic wave equation for the Skyrmion

We propose a relativistically invariant wave equation for the Skyrme soliton. It is a differential equation on the space R{sup 1,3}xS{sup 3} which is invariant under the Lorentz group and isospin. The internal variable valued in SU(2){identical_to}S{sup 3} describes the orientation of the soliton. The mass of a particle of spin and isospin both equal to j=1/2 ,3/2 ... is predicted to be M=m{radical}((1+K{sub 2}j(j+1))/(1+K{sub 1}j(j+1)) ) which agrees with the known spectrum for low angular momentum. The iso-scalar magnetic moment is predicted to be -(K{sub 1})/(4m) {sigma}, where {sigma} is the spin.

Rajeev, S.G. [Department of Physics and Astronomy, Department of Mathematics, University of Rochester, Rochester, New York 14627 (United States)], E-mail: rajeev@pas.rochester.edu

2008-11-15

71

Surface waves on the relativistic quantum plasma half-space

NASA Astrophysics Data System (ADS)

We present a theoretical investigation on the propagation of surface waves on the relativistic quantum plasma half-space. The dispersion relations of surface plasmon polaritons (SPPs) and electrostatic surface waves containing relativistic quantum corrected terms are derived. Results show that the frequency of SPPs has a blue-shift, and surface Langmuir oscillations can propagate on the cold plasma half-space due to quantum effects. Numerical evaluation indicates that quantum effects to SPPs and electrostatic surface waves are significant and observable.

Zhu, Jun; Zhao, Hang; Qiu, Min

2013-10-01

72

Observations of Particle Acceleration in the Blast Waves of Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

The electron energy distribution index, p, is a fundamental parameter of the process by which electrons at shock fronts are accelerated to relativistic speeds and by which they radiate, via synchrotron emission. This acceleration process is applicable to a myriad of astronomical jet sources such as AGN, X-ray binaries and gamma-ray bursts (GRBs), as well as to particle acceleration in the solar wind and supernovae, and the acceleration of cosmic rays. The accurate measurement of the distribution of p is of fundamental importance to differentiate between the possible theories of electron acceleration at any relativistic shock front; there is division as to whether p has a universal value or whether it has a distribution, and if so, what that distribution is. Here one such source of synchrotron emission is examined: the blast waves of GRB afterglows observed by the Swift satellite. Within the framework of the GRB blast wave model, the constraints placed on the distribution of p by the observed X-ray spectral and temporal indices are examined and the distribution parametrized. The results show that the observed distribution of spectral indices is inconsistent with an underlying distribution of p composed of a single discrete value but consistent with a Gaussian distribution centred at p = 2.4 and having a width of 0.6. This finding disagrees with theoretical work that argues for a single, universal value of p, but also demonstrates that the width of the distribution is not as wide as has been suggested by some authors.

Curran, Peter A.

73

The design of a reflected wave eliminator (RWE) for the Large Blast\\/Thermal Simulator was investigated. Activities were divided into two categories, theoretical and computer modeled analysis, and conceptual design of RWE candidate configurations. The design effort was concentrated on active REWs where the open area changes over the time of the blast wave simulation. The computer analysis served to determine

J. Butz; M. Kuna; R. L. Guice; J. J. Gottlieb

1990-01-01

74

Solar-Flare-Initiated Shock Waves; Blast Waves Riding on the Solar Wind.

National Technical Information Service (NTIS)

Consider the speed of the solar flare initiated disturbance as having two separable components. These are: (1) the speed of the blast wave initiated by the impulsive release of energy by the solar flare and (2) the speed of the preexisting solar wind. In ...

D. F. Smart M. A. Shea

1983-01-01

75

Relativistic Theory on Wave Propagation in Inhomogeneous Magnetoplasmas.

National Technical Information Service (NTIS)

Several problems of wave propagation in inhomogeneous plasmas are discussed. All the topics stem from the physics of fusion plasmas, such as those studied in tokamaks. The mathematical modeling of such a plasma, including both relativistic effects as well...

M. J. Vanbruggen-kerkhof

1992-01-01

76

Study of Point Blast wave Instability in Numerical Experiment

NASA Astrophysics Data System (ADS)

The detection of cases demonstrating an unstable evolution of the point blast wave in perfect gas was the problem actually formulated since 1980s when it was found with the help of self-similar approach to stability problem that for cases of gas specific ratio ? being less than 1.20 bllast wave became unstable: the Rayleigh-Taylor type instability showed up at the shock front (Ref.1-3). Later these results were confirmed in computer experiments when 2D hydrodynamic code was used. This code selected shock wave front and used the 1-st order Godunov scheme. In this paper we set ourselves the task of doing that using 3D hydrodynamic code. So we carry out computer simulation of blast wave using 3D Eulerian code TREK (Ref.5,6). The other objective of computation is to determine if the regime of perturbation evolution depends on the second (angular) number of spherical harmonic. The computation geometry is as follows: At t=0, the initial pressure is set constant in the centre region, and the pressure is equal to zero beyond this region. The central region presents a slightly perturbed sphere: the value of sphere radius has a small perturbation proportional to spherical harmonic (Legendre polynomial). The entire material is ideal gas with density being equal of unit and ? = 1.1- 1.2. The perturbations considered are of reasonably high harmonic polar numbers n: n=16 and higher. Computation results are as follows: We prove the perturbation amplitude increase in case of n=16 and ? < 1.2 i.e. we get the direct proof of blast wave instability in these cases. We prove also that the perturbations evolution mode converts to the self-similar pattern in a short time (i.e. when the shock front radius increased by 3-4 times) independently from initial conditions and further proceeds according to the self-similar theory. We prove that oscillations period of non-axially symmetric harmonics is equal to that of axially symmetric ones with the same polar number n. We prove also that these periods are equal to that in self-similar theory (Ref.1-3). The non linear stage of evolution of blast wave axially symmetric perturbations is also studied. The computation of raising perturbations evolution is continued until the formation of singularities and jets on the axis of symmetry and their turbulizations. 1. V.Ktitorov, Voprosy Atomnoi Nauki i Tekhniki, Ser.TPF, No2, p.28, (1984); 2. D.Ryu and E.T.Vishniac, Astr.J, 313, p.820 (1987); 3. V.Ktitorov, Khimich. Fizika (Chem Phys Issues) V.14, No 2-3, p.169, (1995); 4. V.Ktitorov, V.Meltzas, Proceedings of the 6th IWPTM, p.251-258. 5. A.Stadnik, V.Tarasov, Yu. Yanilkin, Voprosy Atomnoi Nauki i Tekhniki, Ser.MMFP, No3, p.52, (1995); 6. Yu.Yanilkin et al., Proceedings of the 6th IWPTM,. p.520-526.

Ktitorov, Vladimir; Yanilkin, Yurii

1999-06-01

77

Reduction of optically observed artillery blast wave trajectories using low dimensionality models

NASA Astrophysics Data System (ADS)

Muzzle blast trajectories from firings of a 152 mm caliber gun howitzer were obtained with high-speed optical imagers and used to assess the fidelity with which low dimensionality models can be used for data reduction. Characteristic flow regions were defined for the blast waves. The near-field region was estimated to extend to 0.98 - 1.25 meters from the muzzle and the far-field region was estimated to begin at 2.61 - 3.31 meters. Blast wave geometries and radial trajectories were collected in the near through far-fields with visible imagers operating at 1,600 Hz. Beyond the near-field the blast waves exhibited a near-spherical geometry in which the major axis of the blast lay along the axis of the gun barrel and measured within 95% of the minor axis. Several blast wave propagation models were applied to the mid and far-field data to determine their ability to reduce the blast wave trajectories to fewer parameters while retaining the ability to distinguish amongst three munitions configurations. A total of 147 firings were observed and used to assess within-configuration variability relative to separation between configurations. Results show that all models perform well, and drag and point blast model parameters additionally provide insight into phenomenology of the blast.

Steward, Bryan J.; Gross, Kevin C.; Perram, Glen P.

2011-05-01

78

On the magnetization of gamma-ray burst blast waves

NASA Astrophysics Data System (ADS)

The origin of magnetic fields that permeate the blast waves of gamma-ray bursts (GRBs) is a long-standing problem. The present paper argues that in four GRBs revealing extended emission at >100 MeV, with follow-up in the radio, optical and X-ray domains at later times, this magnetization can be described as the partial decay of the micro-turbulence that is generated in the shock precursor. Assuming that the bulk of the extended emission >100 MeV can be interpreted as synchrotron emission of shock-accelerated electrons, we model the multi-wavelength light curves of GRB 090902B, GRB 090323, GRB 090328 and GRB 110731A, using a simplified then a full synchrotron calculation with power-law-decaying micro-turbulence ?B ? t?t (t denotes the time since injection through the shock, in the comoving blast frame). We find that these models point to a consistent value of the decay exponent -0.5 ? ?t ? -0.4.

Lemoine, Martin; Li, Zhuo; Wang, Xiang-Yu

2013-11-01

79

Observations Of Particle Acceleration In The Blast Waves Of Gamma-ray Bursts

NASA Astrophysics Data System (ADS)

The electron energy distribution index, p, is a fundamental parameter of the process by which electrons are accelerated to relativistic speeds and by which they radiate, via synchrotron emission. This acceleration process is applicable to a myriad of astronomical sources, from jet sources such as AGN, X-ray binaries and gamma-ray bursts, to particle acceleration in the solar wind and supernovae, and the acceleration of cosmic rays. The accurate measurement of the distribution of p is of fundamental importance to differentiate between the possible theories of electron acceleration at any relativistic shock front. There is division as to whether the electron energy distribution index has a universal value or whether it has a distribution, and if so, what that distribution is. In this presentation we examine one such source of synchrotron emission: the blast waves of gamma-ray bursts. Using our unique Monte Carlo method, we examine the constraints placed on the distribution of p by the observed spectral indices of gamma-ray bursts and parametrize the distribution. We find that the observed distribution of spectral indices is inconsistent with a discrete value of p, but consistent with a Gaussian distribution centred at p 2.4 and having a width of 0.6. This finding rules out the theoretical work that argues for a single, universal value of p, but also demonstrates that the width of the distribution is not as wide as has been suggested by some authors.

Curran, Peter A.; van der Horst, A. J.; Evans, P. A.

2010-02-01

80

Blast wave simulation with a discretization method towards the estimation of safety distance

NASA Astrophysics Data System (ADS)

Unsteady flow fields generated by a blast wave are computationally simulated with a discretization method. The result indicates that pressure rise due to the frontal shock wave strongly depends on the local ground surface geometry as well as the distance from the center of explosion. Overset zonal method with moving grid is developed to enhance the accuracy of the simulations for the quantitative estimation of the blast wave strength. The present approach using new computational fluid dynamic technology may improve the existing theory for the estimation of the unsteady motion and decay of the blast wave, leading to the better estimation of the safety distance for accidental explosions.

Shimizu, Fumio; Fujii, Kozo; Higashino, Fumio

81

Matter Density and Relativistic Models of Wave Function Collapse

NASA Astrophysics Data System (ADS)

Mathematical models for the stochastic evolution of wave functions that combine the unitary evolution according to the Schrödinger equation and the collapse postulate of quantum theory are well understood for non-relativistic quantum mechanics. Recently, there has been progress in making these models relativistic. But even with a fully relativistic law for the wave function evolution, a problem with relativity remains: Different Lorentz frames may yield conflicting values for the matter density at a space-time point. We propose here a relativistic law for the matter density function. According to our proposal, the matter density function at a space-time point x is obtained from the wave function ? on the past light cone of x by setting the i-th particle position in |?|2 equal to x, integrating over the other particle positions, and averaging over i. We show that the predictions that follow from this proposal agree with all known experimental facts.

Bedingham, Daniel; Dürr, Detlef; Ghirardi, GianCarlo; Goldstein, Sheldon; Tumulka, Roderich; Zanghì, Nino

2013-08-01

82

SPIKE PENETRATION IN BLAST-WAVE-DRIVEN INSTABILITIES

The problem of interest is the unstable growth of structure at density transitions affected by blast waves, which arise in natural environments such as core-collapse supernovae and in laboratory experiments. The resulting spikes of dense material, which penetrate the less dense material, develop broadened tips, but the degree of broadening varies substantially across both experiments and simulations. The variable broadening presumably produces variations in the drag experienced by the spike tips as they penetrate the less dense material. The present work has used semianalytic theory to address the question of how the variation in drag might affect the spike penetration, for cases in which the post-shock interface deceleration can be described by a power law in a normalized time variable. It did so by following the evolution of structure on the interface through the initial shock passage, the subsequent small-amplitude phase of Rayleigh-Taylor instability growth, and the later phase in which the spike growth involves the competition of buoyancy and drag. In all phases, the expansion of the system during its evolution was accounted for and was important. The calculated spike length is strongly affected by the drag attributed to spike tip broadening. One finds from such a calculation that it is not unreasonable for narrow spikes to keep up with the shock front of the blast wave. The implication is that the accuracy of prediction of spike penetration and consequent structure by simulations very likely depends on how accurately they treat the broadening of the spike tips and the associated drag. Experimental validation of spike morphology in simulations would be useful.

Drake, R. P., E-mail: rpdrake@umich.edu [Atmospheric, Oceanic, and Space Science, and Applied Physics, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States)

2012-01-10

83

Spike morphology in blast-wave-driven instability experiments

The laboratory experiments described in the present paper observe the blast-wave-driven Rayleigh-Taylor instability with three-dimensional (3D) initial conditions. About 5 kJ of energy from the Omega laser creates conditions similar to those of the He-H interface during the explosion phase of a supernova. The experimental target is a 150 {mu}m thick plastic disk followed by a low-density foam. The plastic piece has an embedded, 3D perturbation. The basic structure of the pattern is two orthogonal sine waves where each sine wave has an amplitude of 2.5 {mu}m and a wavelength of 71 {mu}m. In some experiments, an additional wavelength is added to explore the interaction of modes. In experiments with 3D initial conditions the spike morphology differs from what has been observed in other Rayleigh-Taylor experiments and simulations. Under certain conditions, experimental radiographs show some mass extending from the interface to the shock front. Current simulations show neither the spike morphology nor the spike penetration observed in the experiments. The amount of mass reaching the shock front is analyzed and potential causes for the spike morphology and the spikes reaching the shock are discussed. One such hypothesis is that these phenomena may be caused by magnetic pressure, generated by an azimuthal magnetic field produced by the plasma dynamics.

Kuranz, C. C.; Drake, R. P.; Grosskopf, M. J.; Fryxell, B.; Budde, A. [Department of Atmospheric, Oceanic and Space Science, Center for Radiative Shock Hydrodynamics, University of Michigan, 2455 Hayward Street, Ann Arbor, Michigan 48109 (United States); Hansen, J. F.; Miles, A. R. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Plewa, T. [Department of Scientific Computing, Florida State University, 400 Dirac Science Library, Tallahassee, Florida 32306 (United States); Hearn, N. [Center for Astrophysical Thermonuclear Flashes, University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637 (United States); Knauer, J. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States)

2010-05-15

84

Physiological changes in pigs exposed to a blast wave from a detonating high-explosive charge.

The aim of this project was to study respiration, circulation, and brain activity in pigs during and after a blast wave exposure. Ten anesthetized pigs were used. Seven were exposed to blast and three were controls. Physiological parameters of respiration and circulation as well as cortical activity were followed from 30 minutes before until 120 minutes after the real or simulated blast. There were no significant changes in heart rhythm, cardiac output, arterial oxygen or carbon dioxide tension, blood pH, or mixed venous saturation during the experiment. The blast exposure caused intestinal injuries but no lung damage. A transient flattening of the electroencephalogram was seen immediately after the blast in four experimental animals, in contrast to the unchanged baseline electroencephalogram of the control animals. This momentary depression of cortical activity accompanied by short-lasting apnea indicates a blast wave-induced effect on the brainstem or higher controlling center. PMID:10709373

Axelsson, H; Hjelmqvist, H; Medin, A; Persson, J K; Suneson, A

2000-02-01

85

Prospects for studying how high-intensity compression waves cause damage in human blast injuries

NASA Astrophysics Data System (ADS)

Blast injuries arising from improvised explosive devices are often complex leading to long-term disability in survivors. There is an urgent need to mitigate against the effects of blast that lead to these injuries, and to also improve post-traumatic therapeutic treatments related to problems associated with damage and healing processes and infections. We have initiated multidisciplinary studies to develop experimental facilities and strategies for analyzing the effects blast waves upon the human body, from cellular through to skeletal functions.

Brown, Katherine; Bo, Chiara; Ramaswamy, Arul; Masouros, Spiros; Newell, Nicolas; Hill, Adam; Clasper, Jon; Bull, Anthony; Proud, William

2011-06-01

86

Relativistic Theory of the Propagation of Plane Electromagnetic Waves

Based on the complete set of equations of thermodynamics of irreversible processes of a fluid in electromagnetic fields, a relativistic theory of the influence of electromagnetic waves on a simple fluid is developed. In particular, the oscillations of the fluid induced by a plane electromagnetic wave are evaluated, and the energy-momentum tensor is determined. It is further conjectured that Minkowski's

C. L. Tang; J. Meixner

1961-01-01

87

NASA Astrophysics Data System (ADS)

Interactions between a blast wave and an isolated density-inhomogeneity were investigated numerically. A blast wave that consisted of a leading-edge shock wave followed by rarefaction waves impinged on a spherical light-gas bubble that models the density-inhomogeneity. As a result, it was found that the baroclinically produced vorticity on the bubble/atmosphere interface was suppressed significantly by the presence of the rarefaction waves when the shock strength was weak. The rarefaction waves became less influential as the shock strength was increased.

Mori, Koichi

2012-05-01

88

Exact Damping for Relativistic Plasma Waves

The damping coefficient for a relativistic plasma may be reduced to a single integral with no approximations through use of the Newberger sum rules when k_z=0. Expanding the integral in a series, the leading term agrees with the leading term of the weak relativistic function F_7\\/2(z), but the remaining terms are not alike. The single expansion parameter is proportional to

D. G. Swanson

2000-01-01

89

Relativistic wave and particle mechanics formulated without classical mass

Highlights: > Formal derivation of the Klein-Gordon equation with an invariant frequency. > Formal derivation of the relativistic version of Newton's equation. > The classical mass is replaced by the invariant frequency. > The invariant frequencies for selected elementary particles are deduced. > The choice of natural units resulting from the developed theories is discussed. - Abstract: The fact that the concept of classical mass plays an important role in formulating relativistic theories of waves and particles is well-known. However, recent studies show that Galilean invariant theories of waves and particles can be formulated with the so-called 'wave mass', which replaces the classical mass and allows attaining higher accuracy of performing calculations [J.L. Fry and Z.E. Musielak, Ann. Phys. 325 (2010) 1194]. The main purpose of this paper is to generalize these results and formulate fundamental (Poincare invariant) relativistic theories of waves and particles without the classical mass. In the presented approach, the classical mass is replaced by an invariant frequency that only involves units of time. The invariant frequencies for various elementary particles are deduced from experiments and their relationship to the corresponding classical and wave mass for each particle is described. It is shown that relativistic wave mechanics with the invariant frequency is independent of the Planck constant, and that such theory can attain higher accuracy of performing calculations. The choice of natural units resulting from the developed theories of waves and particles is also discussed.

Fry, J.L. [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Musielak, Z.E., E-mail: zmusielak@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Chang, Trei-wen [Department of Physics, National Kaohsiung Normal University, Kaohsiung 802, Taiwan (China)

2011-08-15

90

Negative energy waves and quantum relativistic Buneman instabilities.

The quantum relativistic Buneman instability is investigated theoretically using a collective Klein-Gordon model for the electrons and a cold fluid model for the ions. The growth rate and unstable wave spectrum is investigated in different parameter regimes corresponding to various degrees of relativistic and quantum effects. The results may be important for streaming instabilities involving ion dynamics in very dense plasmas. PMID:23031033

Haas, F; Eliasson, B; Shukla, P K

2012-09-18

91

Large amplitude Langmuir and ion-acoustic waves in a relativistic two-fluid plasma

Large amplitude Langmuir and ion-acoustic waves in a weakly relativistic two-fluid plasma are analyzed by the pseudopotential method. The existence conditions for relativistic nonlinear Langmuir waves depend on the relativistic effect, the particular energy, and the ion mass to electron mass ratio. The allowable range of the normalized potential depends on the relativistic effect. It is shown that the Mach

Yasunori Nejoh; Heiji Sanuki

1994-01-01

92

Multidimensional effects on relativistic electrons in an oblique shock wave

Multidimensional effects on electron motion in a magnetosonic shock wave propagating obliquely to an external magnetic field are studied by means of a two-dimensional (two space coordinates and three velocities) relativistic, electromagnetic particle code. The simulations demonstrate that after trapping and energization in the main pulse of the shock wave, electrons can be detrapped from it keeping their ultrarelativistic energies. This detrapping is caused by magnetic fluctuations propagating along the wave front. Furthermore, some of the detrapped electrons can be accelerated to much higher energies by the shock wave because they can enter and exit the shock wave as a result of their gyromotions.

Shikii, Kenta; Toida, Mieko [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

2010-08-15

93

Jet and vortex flow induced by anisotropic blast wave: experimental and computational study

. This paper discusses gas-dynamic aspects of intense explosions in uniform environments. In experiments, the energy of a laser\\u000a is almost instantaneously released in a volume of air shaped as either a flattened or stretched cylinder generating a blast\\u000a wave. Its shape evolves in time and ultimately becomes spherical. But momentum transferred to the air when the blast wave\\u000a is

V. Svetsov; M. Popova; V. Rybakov; V. Artemiev; S. Medveduk

1997-01-01

94

Analytical Solution of the Blast Wave Problem in a Non-Ideal Gas

NASA Astrophysics Data System (ADS)

An analytical approach is used to construct the exact solution of the blast wave problem with generalized geometries in a non-ideal medium. It is assumed that the density ahead of the shock front varies according to a power of distance from the source of the blast wave. Also, an analytical expression for the total energy in a non-ideal medium is derived.

P. Singh, L.; D. Ram, S.; B. Singh, D.

2011-11-01

95

Study of Perturbations on High Mach Number Blast Waves in Various Gasses

NASA Astrophysics Data System (ADS)

We have performed a series of experiments examining the properties of high Mach number blast waves. Experiments were conducted on the Z-Beamlet^1 laser at Sandia National Laboratories. We created blast waves in the laboratory by using 10 J- 1000 J laser pulses to illuminate millimeter scale solid targets immersed in gas. Our experiments studied the validity of theories forwarded by Vishniac and Ryu^2-4 to explain the dynamics of perturbations on astrophysical blast waves. These experiments consisted of an examination of the evolution of perturbations of known primary mode number induced on the surface of blast waves by means of regularly spaced wire arrays. The temporal evolution of the amplitude of the induced perturbations relative to the mean radius of the blast wave was fit to a power law in time. Measurements were taken for a number of different mode numbers and background gasses and the results show qualitative agreement with previously published theories for the hydrodynamics of thin shell blast wave. The results for perturbations on nitrogen gas have been recently published^5. .^1 P. K. Rambo, I. C. Smith, J. L. Porter, et al., Applied Optics 44, 2421 (2005). ^2 D. Ryu and E. T. Vishniac, Astrophysical Journal 313, 820 (1987). ^3 D. Ryu and E. T. Vishniac, Astrophysical Journal 368, 411 (1991). ^4 E. T. Vishniac, Astrophysical Journal 274, 152 (1983). ^5 A. D. Edens, T. Ditmire, J. F. Hansen, et al., Physical Review Letters 95 (2005).

Edens, A.; Adams, R.; Rambo, P.; Shores, J.; Smith, I.; Atherton, B.; Ditmire, T.

2006-10-01

96

Imaging High Speed Particles in Explosive Driven Blast Waves

NASA Astrophysics Data System (ADS)

Researchers Mr. Charles Jenkins and Dr. Yasuyuki Horie at the High Explosive Research & Development (HERD) facility at Eglin AFB with sponsorship from DTRA has successfully imaged high speed explosively driven metallic particles. The process uses an adapted, commercially available Particle Image Velocimetry (PIV) instrument. Regional and particle flow vectors are determined from particle displacement between two images taken in rapid succession. The instrument consists of a 120 mJ, pulsed Nd:YAG laser, camera system, synchronizer, and proprietary imaging software. The new PIV capability provides the ability for scientists and engineers to map explosively driven metallic particles in a blast wave. Characteristics of particle motion, interaction and dispersion can be determined by this method, providing measurements of key parameters such as particle size, shape, velocity, and concentration. This new capability to image and track small (from a few microns to as large as several hundred microns) high-speed particles without direct intervention by physical means, ensures that the particles are unchanged in their environment and provides greater measurement accuracy of particle dynamics in very short time scales. The capability can also be used to map large areas (square feet) or to zoom down at higher magnifications to study particle features such as particle agglomeration.

Jenkins, Charles; Horie, Yasuyuki

2009-06-01

97

Oscillations in the wake of a flare blast wave

NASA Astrophysics Data System (ADS)

Context. Oscillations of coronal loops in the Sun have been reported in both imaging and spectral observations at the onset of flares. Images reveal transverse oscillations, whereas spectra detect line-of-sight velocity or Doppler-shift oscillations. The Doppler-shift oscillations are commonly interpreted as longitudinal modes. Aims: Our aim is to investigate the relationship between loop dynamics and flows seen in TRACE 195 Å images and Doppler shifts observed by SUMER in Si iii 1113.2 Å and FeXIX 1118.1 Å at the time of a C.8-class limb flare and an associated CME. Methods: We carefully co-aligned the sequence of TRACE 195 Å images to structures seen in the SUMER Si iii, CaX, and FeXIX emission lines. Additionally, H? observations of a lifting prominence associated with the flare and the coronal mass ejection (CME) are available in three bands around 6563.3 Å. They give constraints on the timing and geometry. Results: Large-scale Doppler-shift oscillations in FeXIX and transverse oscillations in intensity images were observed over a large region of the corona after the passage of a wide bright extreme-ultraviolet (EUV) disturbance, which suggests ionization, heating, and acceleration of hot plasma in the wake of a blast wave. The online movie associated to Fig. 2 is available at http://www.aanda.org and at http://www.mps.mpg.de/data/outgoing/tothova/movie.gif

Tothova, D.; Innes, D. E.; Stenborg, G.

2011-04-01

98

Tunneling dynamics in relativistic and nonrelativistic wave equations

We obtain the solution of a relativistic wave equation and compare it with the solution of the Schroedinger equation for a source with a sharp onset and excitation frequencies below cutoff. A scaling of position and time reduces to a single case all the (below cutoff) nonrelativistic solutions, but no such simplification holds for the relativistic equation, so that qualitatively different ''shallow'' and ''deep'' tunneling regimes may be identified relativistically. The nonrelativistic forerunner at a position beyond the penetration length of the asymptotic stationary wave does not tunnel; nevertheless, it arrives at the traversal (semiclassical or Buettiker-Landauer) time {tau}. The corresponding relativistic forerunner is more complex: it oscillates due to the interference between two saddle-point contributions and may be characterized by two times for the arrival of the maxima of lower and upper envelopes. There is in addition an earlier relativistic forerunner, right after the causal front, which does tunnel. Within the penetration length, tunneling is more robust for the precursors of the relativistic equation.

Delgado, F.; Muga, J. G.; Ruschhaupt, A. [Departamento de Quimica-Fisica, UPV-EHU, Apartado 644, 48080 Bilbao, (Spain); Garcia-Calderon, G. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 20 364, 01000 Mexico, D.F., (Mexico); Villavicencio, J. [Facultad de Ciencias, Universidad Autonoma de Baja California, Apartado Postal 1880, 22800 Ensenada, Baja California, (Mexico)

2003-09-01

99

Shock waves in relativistic nuclear matter. I

We develop the relativistic Rankine-Hugoniot relations for a three-dimensional plane shock and a three-dimensional oblique shock. Using these discontinuity relations together with various equations of state for nuclear matter, we calculate the temperatures and the compressibilities attainable by shock compression for a wide range of laboratory kinetic energy of the projectile.

Gleeson, A.M.; Raha, S.

1980-03-01

100

Relativistic wave and particle mechanics formulated without classical mass

NASA Astrophysics Data System (ADS)

The fact that the concept of classical mass plays an important role in formulating relativistic theories of waves and particles is well-known. However, recent studies show that Galilean invariant theories of waves and particles can be formulated with the so-called 'wave mass', which replaces the classical mass and allows attaining higher accuracy of performing calculations [J.L. Fry and Z.E. Musielak, Ann. Phys. 325 (2010) 1194]. The main purpose of this paper is to generalize these results and formulate fundamental (Poincaré invariant) relativistic theories of waves and particles without the classical mass. In the presented approach, the classical mass is replaced by an invariant frequency that only involves units of time. The invariant frequencies for various elementary particles are deduced from experiments and their relationship to the corresponding classical and wave mass for each particle is described. It is shown that relativistic wave mechanics with the invariant frequency is independent of the Planck constant, and that such theory can attain higher accuracy of performing calculations. The choice of natural units resulting from the developed theories of waves and particles is also discussed.

Fry, J. L.; Musielak, Z. E.; Chang, Trei-Wen

2011-08-01

101

Nonplanar Electrostatic Solitary Waves in a Relativistic Degenerate Dense Plasma

NASA Astrophysics Data System (ADS)

By employing the reductive perturbation technique, the propagation of cylindrical and spherical ion acoustic solitary waves is studied in an unmagnetized dense relativistic plasma, consisting of relativistically degenerate electrons and cold fluid ions. A modified Korteweg-de-Vries equation is derived and its numerical solutions have been analyzed to identify the basic features of electrostatic solitary structures that may form in such a degenerate Fermi plasma. Different degrees of relativistic electron degeneracy are discussed and compared. It is found that increasing number density leads to decrease the amplitude the width of the ion acoustic solitary wave in both the cylindrical and spherical geometries. The relevance of the work to the compact astrophysical objects, particularly white dwarfs is pointed out.

Ata-ur-Rahman; Mushtaq, A.; S., Ali; Qamar, A.

2013-04-01

102

Plane waves in a relativistic, homogeneous and isotropic elastic continuum

NASA Astrophysics Data System (ADS)

The propagation of gravitational and acoustic plane waves in a flat universe filled with a general relativistic, homogeneous and isotropic, spatially flat continuum is studied. The continuum is described by analogues of nonrelativistic characteristics, namely energy per particle, pressure and Lamé coefficients, and considered in the comoving proper-time gauge. For all modes with the given wave covector, differential equations governing the time dependence of the amplitudes are derived. In particular, longitudinal acoustic waves are described, in analogy with the nonrelativistic theory, by two coupled first-order equations. As an example, plane waves in a stiff ultrarigid continuum are considered.

Polák, Vratko; Balek, Vladimír

2008-02-01

103

Topology of relativistic refractive index surfaces for electron cyclotron waves

The dispersion of electron cyclotron waves in a weakly relativistic Maxwellian plasma is investigated. It is shown that the apparently very complicated picture of the coupling of the extraordinary (X) mode to Bernstein waves can be accounted for in a simple way by considering the refractive indices as Riemann-like surfaces in the Clemmow-Mullaly-Allis (CMA) parameter space, ( omega p2\\/ omega

J. Egedal; H. Bindslev

1994-01-01

104

A relativistic solitary wave in electron-positron ion plasma

The nonlinear propagation of circularly polarized electromagnetic (CPEM) waves with relativistically strong amplitude in an unmagnetized cold electron-positron ion plasma is investigated. The possibility of finding soliton solutions in such a plasma is explored. In one- and two-dimensions it is shown that the presence of a small fraction of massive ions in the plasma leads to stable localized solutions.

Berezhiani, V.I. [Georgian Academy of Sciences, Tbilisi (Georgia). Institute of Physics; Mahajan, S.M. [Univ. of Texas, Austin, TX (United States). Institute for Fusion Studies]|[International Centre for Theoretical Physics, Trieste (Italy)

1994-03-01

105

Blast shock wave mitigation using the hydraulic energy redirection and release technology.

A hydraulic energy redirection and release technology has been developed for mitigating the effects of blast shock waves on protected objects. The technology employs a liquid-filled plastic tubing as a blast overpressure transformer to transfer kinetic energy of blast shock waves into hydraulic energy in the plastic tubings. The hydraulic energy is redirected through the plastic tubings to the openings at the lower ends, and then is quickly released with the liquid flowing out through the openings. The samples of the specifically designed body armor in which the liquid-filled plastic tubings were installed vertically as the outer layer of the body armor were tested. The blast test results demonstrated that blast overpressure behind the body armor samples was remarkably reduced by 97% in 0.2 msec after the liquid flowed out of its appropriate volume through the openings. The results also suggested that a volumetric liquid surge might be created when kinetic energy of blast shock wave was transferred into hydraulic energy to cause a rapid physical movement or displacement of the liquid. The volumetric liquid surge has a strong destructive power, and can cause a noncontact, remote injury in humans (such as blast-induced traumatic brain injury and post-traumatic stress disorder) if it is created in cardiovascular system. The hydraulic energy redirection and release technology can successfully mitigate blast shock waves from the outer surface of the body armor. It should be further explored as an innovative approach to effectively protect against blast threats to civilian and military personnel. PMID:22745740

Chen, Yun; Huang, Wei; Constantini, Shlomi

2012-06-20

106

DYNAMICS AND AFTERGLOW LIGHT CURVES OF GAMMA-RAY BURST BLAST WAVES WITH A LONG-LIVED REVERSE SHOCK

We perform a detailed study on the dynamics of a relativistic blast wave with the presence of a long-lived reverse shock (RS). Although a short-lived RS has been widely considered, the RS is believed to be long-lived as a consequence of a stratification expected on the ejecta Lorentz factors. The existence of a long-lived RS causes the forward shock (FS) dynamics to deviate from a self-similar Blandford-McKee solution. Employing the ''mechanical model'' that correctly incorporates the energy conservation, we present an accurate solution for both the FS and RS dynamics. We conduct a sophisticated calculation of the afterglow emission. Adopting a Lagrangian description of the blast wave, we keep track of an adiabatic evolution of numerous shells between the FS and RS. An evolution of the electron spectrum is also followed individually for every shell. We then find the FS and RS light curves by integrating over the entire FS and RS shocked regions, respectively. Exploring a total of 20 different ejecta stratifications, we explain in detail how a stratified ejecta affects its blast wave dynamics and afterglow light curves. We show that, while the FS light curves are not sensitive to the ejecta stratifications, the RS light curves exhibit much richer features, including steep declines, plateaus, bumps, re-brightenings, and a variety of temporal decay indices. These distinctive RS features may be observable if the RS has higher values of the microphysics parameters than the FS. We discuss possible applications of our results in understanding the gamma-ray burst afterglow data.

Uhm, Z. Lucas; Zhang Bing [Department of Physics and Astronomy, University of Nevada-Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154 (United States); Hascoeet, Romain; Daigne, Frederic; Mochkovitch, Robert [Institut d'Astrophysique de Paris, UMR 7095 Universite Pierre et Marie Curie-CNRS, 98 bis Boulevard Arago, F-75014 Paris (France); Park, Il H., E-mail: uhm@physics.unlv.edu [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

2012-12-20

107

Relativistic collision operators for modeling noninductive current drive by waves

A weakly relativistic Fokker-Planck operator for electron-electron collision was first used by Karney and Fisch to calculate the efficiencies of current drive by waves with fast phase velocity [C. F. F. Karney and N. J. Fisch, Phys. Fluids 28, 116 (1985)]. The present work extends Karney and Fisch's work by expressing the weakly relativistic collision operator in potential form, and working out a general Legendre expansion of the potential functions. This general Legendre expansion reproduces the results in Karney and Fisch's paper and is useful in implementing the weakly relativistic operator in Fokker-Planck codes. To justify the use of the weakly relativistic collision operator for current drive applications under ITER conditions, a comparison is made of current drive efficiencies predicted by this operator and a fully relativistic collision operator. Good agreement between efficiencies predicted by these two models is found. This suggests that the weakly relativistic collision operator is sufficiently precise for modeling the current drive schemes under ITER conditions.

Hu, Y. J.; Hu, Y. M. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031, China and Center for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Lin-Liu, Y. R. [Department of Physics and Center for Mathematics and Theoretical Physics, National Central University, Taiwan (China)

2011-02-15

108

Simulation of a nuclear blast wave with a gaseous detonation tube. Technical report

There is an ongoing interest in simulating nonideal blast environments for nuclear effects research. In particular, one would like to be able to impose peaked blast waves on real ground surfaces and experimentally measure the ensuing dusty airblast environment. Proposed here is a gaseous detonation tube blast simulator. A disposable (or reusable) shock tube would be constructed on a in-situ ground surface of interest. The tube would be sealed and filled with a detonatable gas mixture. When a planar detonation wave is initiated at one end of the tube, it induces a peaked blast wave which expands self-similarly with time--the longer the detonation run distance, the longer the blast wave duration. Similarity analysis of such a wave (which consists of a constant-velocity Chapman-Jouguet detonation followed by an adiabatic rarefaction wave expressed in terms of a Riemann characteristic) results in a closed-form analytic solution for the flow field time history. It is shown that the static and dynamic pressure waveforms associated with this detonation give a high fidelity simulation of a nuclear surface burst.

Kuhl, A.L.

1983-03-01

109

NASA Astrophysics Data System (ADS)

Experimental investigations into the dynamics of cylindrical, laser-driven, high-Mach-number shocks are used to study the thermal cooling instability predicted to occur in astrophysical radiative blast waves. A streaked Schlieren technique measures the full blast-wave trajectory on a single-shot basis, which is key for observing shock velocity oscillations. Electron density profiles and deceleration parameters associated with radiative blast waves were recorded, enabling the calculation of important blast-wave parameters including the fraction of radiated energy, ?, as a function of time for comparison with radiation-hydrodynamics simulations.

Moore, A. S.; Gumbrell, E. T.; Lazarus, J.; Hohenberger, M.; Robinson, J. S.; Smith, R. A.; Plant, T. J. A.; Symes, D. R.; Dunne, M.

2008-02-01

110

Relativistic Landau damping of longitudinal waves in isotropic pair plasmas

Landau damping is described in relativistic electron-positron plasmas. Relativistic electron-positron plasma theory contains important new effects when compared with classical plasmas. For example, there are undamped superluminal wave modes arising from both a continuous and discrete mode structure, the former even in the classical limit. We present here a comprehensive analytical treatment of the general case resulting in a compact and useful form for the dispersion relation. The classical pair-plasma case is addressed, for completeness, in an appendix.

Laing, E. W.; Diver, D. A. [Department of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom)

2006-09-15

111

Channeling of relativistic laser pulses, surface waves, and electron acceleration.

The interaction of a high-energy relativistic laser pulse with an underdense plasma is studied by means of 3-dimensional particle in cell simulations and theoretical analysis. For powers above the threshold for channeling, the laser pulse propagates as a single mode in an electron-free channel during a time of the order of 1 picosecond. The steep laser front gives rise to the excitation of a surface wave along the sharp boundaries of the ion channel. The surface wave first traps electrons at the channel wall and preaccelerates them to relativistic energies. These particles then have enough energy to be further accelerated in a second stage through an interplay between the acceleration due to the betatron resonance and the acceleration caused by the longitudinal part of the surface wave electric field. It is necessary to introduce this two-stage process to explain the large number of high-energy electrons observed in the simulations. PMID:22463415

Naseri, N; Pesme, D; Rozmus, W; Popov, K

2012-03-05

112

Production of periodically modulated laser-driven blast waves in a clustering gas

NASA Astrophysics Data System (ADS)

To study hydrodynamic behavior on thin shell high Mach number blast waves, experiments have been performed in which spatially tailored shock waves have been launched in a gas of clusters using an intense 35 fs laser pulse. The target medium was first modified by destroying clusters in specific locations using a spatially modulated laser focus. Under subsequent intense laser irradiation, the efficient absorption properties of the remaining clustered regions compared to those regions with no clusters led to a pattern of hot and cold plasma resulting in a cylindrical blast wave with a periodic modulation imprinted on the shock front. This technique may provide a method for studying thin shell instabilities in strongly radiative blast waves.

Symes, D. R.; Osterhoff, J.; Fäustlin, R.; Maurer, M.; Bernstein, A. C.; Moore, A. S.; Gumbrell, E. T.; Edens, A. D.; Smith, R. A.; Ditmire, T.

2007-10-01

113

Blast wave simulation with a discretization method towards the estimation of safety distance

Unsteady flow fields generated by a blast wave are computationally simulated with a discretization method. The result indicates that pressure rise due to the frontal shock wave strongly depends on the local ground surface geometry as well as the distance from the center of explosion. Overset zonal method with moving grid is developed to enhance the accuracy of the simulations

Fumio Shimizu; Kozo Fujii; Fumio Higashino

1992-01-01

114

Images and Spectra from the Interior of a Relativistic Fireball

The power-law decay of gamma-ray burst (GRB) afterglow can be well described by synchrotron emission from a relativistic spherical blast wave, driven by an expanding fireball. We calculate the spectrum and the light curve expected from an adiabatic blast wave which is described by the Blandford-McKee self-similar solution. These calculations include emission from the whole blast wave and not just

Jonathan Granot; Tsvi Piran; Re'em Sari

1999-01-01

115

... blast over-pressurization wave travels at a high velocity and is affected by the environment; for example, ... injuries are similar to those observed following high-speed motor vehicle accidents. Quaternary blast injury can occur ...

116

POLYCYCLIC AROMATIC HYDROCARBON PROCESSING IN THE BLAST WAVE OF THE SUPERNOVA REMNANT N132D

We present Spitzer Infrared Spectrograph 14-36 {mu}m mapping observations of the supernova remnant N132D in the Large Magellanic Cloud. This study focuses on the processing of polycyclic aromatic hydrocarbons (PAHs) that we previously identified in the southern blast wave. The mid-infrared spectra show strong continuum emission from shock-heated dust and a unique, nearly featureless plateau in the 15-20 {mu}m region, which we attribute to PAH molecules. The typical PAH emission bands observed in the surrounding interstellar medium ahead of the blast wave disappear, which indicates shock processing of PAH molecules. The PAH plateau appears most strongly at the outer edge of the blast wave and coincides with diffuse X-ray emission that precedes the brightest X-ray and optical filaments. This suggests that PAH molecules in the surrounding medium are swept up and processed in the hot gas of the blast wave shock, where they survive the harsh conditions long enough to be detected. We also observe a broad emission feature at 20 {mu}m appearing with the PAH plateau. We speculate that this feature is either due to FeO dust grains or connected to the processing of PAHs in the supernova blast wave shock.

Tappe, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-72, Cambridge, MA 02138 (United States); Rho, J. [SOFIA Science Mission Operations/USRA, NASA Ames Research Center, MS 211-3, Moffett Field, CA 94035 (United States); Boersma, C. [NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035 (United States); Micelotta, E. R., E-mail: atappe@cfa.harvard.edu [Department of Physics and Astronomy, Western University, 1151 Richmond Street, London, Ontario N6A 3K7 (Canada)

2012-08-01

117

Polycyclic Aromatic Hydrocarbon Processing in the Blast Wave of the Supernova Remnant N132D

NASA Astrophysics Data System (ADS)

We present Spitzer Infrared Spectrograph 14-36 ?m mapping observations of the supernova remnant N132D in the Large Magellanic Cloud. This study focuses on the processing of polycyclic aromatic hydrocarbons (PAHs) that we previously identified in the southern blast wave. The mid-infrared spectra show strong continuum emission from shock-heated dust and a unique, nearly featureless plateau in the 15-20 ?m region, which we attribute to PAH molecules. The typical PAH emission bands observed in the surrounding interstellar medium ahead of the blast wave disappear, which indicates shock processing of PAH molecules. The PAH plateau appears most strongly at the outer edge of the blast wave and coincides with diffuse X-ray emission that precedes the brightest X-ray and optical filaments. This suggests that PAH molecules in the surrounding medium are swept up and processed in the hot gas of the blast wave shock, where they survive the harsh conditions long enough to be detected. We also observe a broad emission feature at 20 ?m appearing with the PAH plateau. We speculate that this feature is either due to FeO dust grains or connected to the processing of PAHs in the supernova blast wave shock.

Tappe, A.; Rho, J.; Boersma, C.; Micelotta, E. R.

2012-08-01

118

Relativistic wave-particle interaction in magnetospheric plasmas

NASA Astrophysics Data System (ADS)

The interaction between electromagnetic waves and high energy particles both in the magnetosphere of Earth and Jupiter has been investigated in a great detail. Different models for the electron distribution function has been used to determine the synchrotron radiation in the Jovian inner magnetosphere and the growth rate of R- mode waves in a relativistic plasma. Using a bi-loss-cone distribution function (composed of a high anisotropic component and a quasi-isotropic component), the whistler- mode wave growth has been calculated for the interchange events in the Io torus and for chorus emissions during a terrestrial substorm. We demonstrated that the path integrated gain can be dramatically enhanced over quiescent condition; exceed 20 e-foldings in the interchange event or approach 10 e-foldings during the terrestrial substorm. The wave excitation can cause strong pitch angle scattering leading to quasi-isotropic pitch angle distributions during Jovian interchange event and the terrestrial substorm. The relativistic wave- particle resonant diffusion curves for electron cyclotron resonance with both electromagnetic subluminous waves (electromagnetic R mode and L mode) and superluminous waves (R-X mode, L-O mode and L-X mode) have been constructed and their application are studied to electron acceleration in the Earth magnetosphere at the locations both inside and outside the plasmapause.

Xiao, Fuliang

2001-06-01

119

The modulational instability of the weakly nonlinear longitudinal Langmuir as well as the transverse electromagnetic waves, propagation in the relativistic plasma without the static fields is described. The nonlinear Schrödinger equation taking account of the nonlinear Landau damping for these waves has been derived by means of the relativistic Vlasov and Maxwell equations. The plasma with the weakly relativistic temperature

A. Pataraia; G. Melikidze

1980-01-01

120

Acceleration and heating of a relativistic electron beam due to nonlinear electron Landau and cyclotron damping of electrostatic waves in a magnetized plasma are investigated theoretically and numerically on the basis of the relativistic kinetic wave and transport equations derived from the relativistic Vlasov-Maxwell equations. Two electrostatic waves interact nonlinearly with the relativistic electron beam satisfying the resonance condition for nonlinear electron Landau and cyclotron damping of {omega}{sub k}-{omega}{sub k{sup '}}-(k{sub perpendicular}-k{sub perpendicula=} r{sup '})v{sub d}-(k{sub parallel}-k{sub parallel}{sup '})v{sub b}{approx_equal}m{omega}{sub ce} where v{sub b} and v{sub d} are the parallel and perpendicular velocities of the relativistic electron beam, respectively, and {omega}{sub ce} is the relativistic electron cyclotron frequency. The beat waves produced by two electrostatic waves resonate with the relativistic electron beam. The relativistic transport equations using the relativistic drifted Maxwellian momentum distribution function of the relativistic electron beam were derived and analyzed. They show obviously its acceleration and heating (deceleration or cooling). Nonlinear electron Landau damping of the two lower-hybrid waves has been studied by the numerical analysis of relativistic nonlinear wave-particle coupling coefficients and it was clarified that the highly relativistic electron beam can be accelerated efficiently via the Compton scattering due to nonlinear electron Landau damping of the lower-hybrid waves.

Sugaya, R. [Department of Physics, Faculty of Science, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)

2004-12-01

121

Effect of Interacting Rarefaction Waves on Relativistically Hot Jets

NASA Astrophysics Data System (ADS)

The effect of rarefaction acceleration on the propagation dynamics and structure of relativistically hot jets is studied through relativistic hydrodynamic simulations. We emphasize the nonlinear interaction of rarefaction waves excited at the interface between a cylindrical jet and the surrounding medium. From simplified one-dimensional (1D) models with radial jet structure, we find that a decrease in the relativistic pressure due to the interacting rarefaction waves in the central zone of the jet transiently yields a more powerful boost of the bulk jet than that expected from single rarefaction acceleration. This leads to a cyclic in situ energy conversion between thermal and bulk kinetic energies, which induces radial oscillating motion of the jet. The oscillation timescale is characterized by the initial pressure ratio of the jet to the ambient medium and follows a simple scaling relation, ?oscillationvprop(P jet, 0/P amb, 0)1/2. Extended two-dimensional simulations confirm that this radial oscillating motion in the 1D system manifests as modulation of the structure of the jet in a more realistic situation where a relativistically hot jet propagates through an ambient medium. We find that when the ambient medium has a power-law pressure distribution, the size of the reconfinement region along the propagation direction of the jet in the modulation structure ? evolves according to a self-similar relation ?vpropt ?/2, where ? is the power-law index of the pressure distribution.

Matsumoto, Jin; Masada, Youhei; Shibata, Kazunari

2012-06-01

122

Blast wave formation of the extended stellar shells surrounding elliptical galaxies

NASA Astrophysics Data System (ADS)

The existence of stellar shells at large distances from isolated elliptical galaxies is explained in terms of a blast wave associated with an active nucleus phase early in the history of the galaxy. The blast wave sweeps the initial interstellar medium out of the galaxy into an expanding shell which radiatively cools behind its leading shock front. Cooling of the shell following turnoff of the nucleus activity, which keeps the shell photoionized, leads to a brief epoch of star formation which is terminated by heating of the shell from supernovae and UV radiation from massive stars. The stars so formed follow similar, highly radial, bound orbits, moving in phase with each other and spending much of their time near apogalacteum, thus taking on the appearance of a shell. Multiple shells may be produced when conditions allow repeated episodes of shell cooling and supernovae heating to occur in the blast wave.

Williams, R. E.; Christiansen, W. A.

1985-04-01

123

On electromagnetic instabilities at ultra-relativistic shock waves

NASA Astrophysics Data System (ADS)

Recent work on Fermi acceleration at ultra-relativistic shock waves has demonstrated the need for strong amplification of the background magnetic field on very short scales. Amplification of the magnetic field by several orders of magnitude has also been suggested by observations of gamma-ray bursts afterglows, both in downstream and upstream plasmas. This paper addresses this issue of magnetic field generation in a relativistic shock precursor through micro-instabilities. In a generic superluminal configuration, the level of magnetization of the upstream plasma turns out to be a crucial parameter, notably because the length scale of the shock precursor is limited by the Larmor rotation of the accelerated particles in the background magnetic field and by the speed of the shock wave. We discuss in detail and calculate the growth rates of the following beam plasma instabilities seeded by the accelerated and reflected particle populations: for an unmagnetized shock, the Weibel and filamentation instabilities, as well as the ?erenkov resonant instabilities with electrostatic modes; for a magnetized shock, the Weibel instability and the resonant ?erenkov instabilities with the longitudinal electrostatic modes, as well as the Alfvén, Whisler and extraordinary modes. All these instabilities are generated upstream, then they are transmitted downstream. The modes excited by ?erenkov resonant instabilities take on particular importance with respect to the magnetization of the downstream medium since, being plasma eigenmodes, they have a longer lifetime than the Weibel modes. We discuss the main limitation of the wave growth associated with the length of precursor and the magnetization of the upstream medium for both oblique and parallel relativistic shock waves. We also characterize the proper conditions to obtain Fermi acceleration at ultra-relativistic shock waves: for superluminal shock waves, the Fermi process works for values of the magnetization parameter below some critical value, and there is an intrinsic limitation of the achievable cosmic ray energy depending on the ratio of the magnetization to its critical value. We recover results of most recent particle-in-cell simulations and conclude with some applications to astrophysical cases of interest. In particular, Fermi acceleration in pulsar winds is found to be unlikely whereas its development appears to hinge on the level of upstream magnetization in the case of ultra-relativistic gamma-ray burst external shock waves.

Lemoine, Martin; Pelletier, Guy

2010-02-01

124

Dispersion of waves in relativistic plasmas with isotropic particle distributions

The dispersion laws of Langmuir and transverse waves are calculated in the relativistic nonmagnetized formalism for several isotropic particle distributions: thermal, power law, relativistic Lorentzian {kappa}, and hybrid {beta}. For Langmuir waves the parameters of superluminal undamped, subluminal damped principal, and higher modes are determined for a range of distribution parameters. The undamped and principal damped modes are found to match smoothly. Principal damped and second damped modes are found not to match smoothly. The presence of maximum wavenumber is discovered above that no longitudinal modes formally exist. The higher damped modes are discovered to be qualitatively different for thermal and certain nonthermal distributions. Consistently with the known results, the Landau damping is calculated to be stronger for nonthermal power-law-like distributions. The dispersion law is obtained for the single undamped transverse mode. The analytic results for the simplest distributions are provided.

Shcherbakov, Roman V. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

2009-03-15

125

Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects

NASA Astrophysics Data System (ADS)

This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high-speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27-79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile.

Courtney, Amy C.; Andrusiv, Lubov P.; Courtney, Michael W.

2012-04-01

126

Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects.

This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high-speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27-79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile. PMID:22559580

Courtney, Amy C; Andrusiv, Lubov P; Courtney, Michael W

2012-04-01

127

Studying radiative shocks using laser driven blast waves in clustered gases

NASA Astrophysics Data System (ADS)

We report on the creation of radiative blast waves by irradiating gases of atomic clusters with intense short pulse laser light. The efficient absorption of the cluster medium leads to high energy deposition and development into a cylindrical shock. These non-equilibrium, optically thin shocks have great potential for hydrodynamic scaling with astrophysical relevance, particularly for supernova remnants. We discuss how cluster blast waves may become susceptible to spatial and temporal instabilities and the application of the RAPCAL atomic physics code to determine our plasma conditions.

Symes, D. R.; Hohenberger, M.; Doyle, H. W.; Smith, R. A.; Moore, A. S.; Gumbrell, E. T.; Rodriguez, R.; Gil, J. M.

2011-10-01

128

An intense ultrafast laser pulse can be very strongly absorbed in a moderate density gas composed of van der Waals bonded clusters. In this paper, the deposition of the energy of intense 30 fs light pulses in a gas of deuterium clusters has been diagnosed using a technique based on analysis of the trajectories of the resulting cylindrically symmetric blast waves. Using the well-known relation between blast wave velocity and energy deposition in gas, the laser energy deposited per unit length as a function of distance in gas jet plume was measured. These measurements were conducted in jets containing either deuterium clusters or simple deuterium molecules.

Zweiback, J.; Ditmire, T.

2001-10-01

129

Relativistic (covariant) kinetic theory of linear plasma waves and instabilities

The fundamental kinetic description is of vital importance in high-energy astrophysics and fusion plasmas where wave phenomena evolve on scales small comparing with binary collision scales. A rigorous relativistic analysis is required even for nonrelativistic plasma temperatures for which the classical theory yielded unphysical results: e.g. collisonless damping of superluminal waves (phase velocity exceeds the speed of light). The existing nonrelativistic approaches are now improved by covariantly correct dispersion theory. As an important application, the Weibel instability has been recently investigated and confirmed as the source of primordial magnetic field in the intergalactic medium.

Lazar, M. [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); 'Alexandru Ioan Cuza' University, Faculty of Physics, 6600 Iasi (Romania); Schlickeiser, R. [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Centre for Plasma Science and Astrophysics, Ruhr-University, D-44780 Bochum (Germany)

2006-06-19

130

Large amplitude Langmuir and ion-acoustic waves in a relativistic two-fluid plasma

Large amplitude Langmuir and ion-acoustic waves in a relativistic two-fluid plasma are analyzed by the pseudo-potential method. The existence conditions for relativistic nonlinear Langmuir waves depend on the relativistic effect, the particular energy, and the ion mass to electron mass ratio. The allowable range of the normalized potential depends on the relativistic effect. It is shown that the Mach number

Y. Nejoh; H. Sanuki

1994-01-01

131

Implementation of the exploding wire technique to study blast-wave-structure interaction

NASA Astrophysics Data System (ADS)

The effort invested in improving our understanding of the physics of high-energy explosion events has been steadily increasing since the latter part of the twentieth century. Moreover, the dramatic increase in computer power over the last two decades has made the numerical simulation approach the dominant tool for investigating blast phenomena and their effects. However, field tests, on both large and small scales, are still in use. In the current paper, we present an experimental tool to better resolve and study the blast-structure interaction phenomenon and to help validate the numerical simulations of the same. The experimental tool uses an exploding wire technique to generate small-scale cylindrical and spherical blast waves. This approach permits safe operation, high repeatability, and the use of advanced diagnostic systems. The system was calibrated using an analytical model, an empirical model, and numerical simulation. To insure that spherical blast geometry was achieved, a set of free air blast experiments was done in which high-speed photography was used to monitor the blast structure. A scenario in which an explosion occurred in the vicinity of a structure demonstrated the system's capabilities. Using this simple but not trivial configuration showed unequivocally the effectiveness of this tool. From this comparison, it was found that at early times of blast-structure interaction, the agreement between the two sets of results was very good, but at later times incongruences appeared. Effort has been made to interpret this observation. Furthermore, by using similitude analysis, the results obtained from the small-scale experiments can be applied to the full-scale problem. We have shown that an exploding wire system offers an inexpensive, safe, easy to operate, and effective tool for studying phenomena related to blast-wave-structure interactions.

Ram, O.; Sadot, O.

2012-11-01

132

Relativistic Electron Enhancement and Decay by Whistler Mode Chorus Waves

NASA Astrophysics Data System (ADS)

Relativistic electron flux in the outer radiation belt varies dramatically during magnetic storms. The flux intensity often exhibits a main-phase dropout, followed by a fast recovery and then gradual enhancement. Low-energy electrons from the plasma sheet are injected into the outer belt by the strong convection during the storm main phase. They reach ring-current energy in the course of earthward transport and become the seed population of wave-particle interactions. It is commonly believed that electron energy diffusion by the whistler mode chorus waves is the main process to account for the relativistic electron flux enhancement during the storm recovery. Using a global kinetic model we simulate ring current and radiation belt electron variations during super storms, large and moderate storms. We find in most cases that including diffusion with whistler mode chorus waves results in higher MeV-electron flux in the outer belt. However, in the case of a super storm, the electron flux is lower when chorus wave diffusion is considered. We will discuss why there is different response of energetic electrons to whistler mode chorus waves during super storms.

Fok, M. H.; Albert, J. M.; Zheng, Q.; Glocer, A.

2011-12-01

133

Determination of the upper crustal structure using seismic waves from quarry blasts

NASA Astrophysics Data System (ADS)

The territory of the Czech Republic is covered with a relatively dense network of quarries using blasting for rock disintegration. Blasts of large extent (more then 200 kg of explosive) take place mainly in coal open-pit mines, limestone quarries and basalt quarries. Seismic waves generated by industrial blasts are recorded by sensitive stations up to the distance of 200 km. Seismograms up to 120 km contain a clear Pg onset and in some cases Sg onset can also be recognized. A typical feature at these epicentral distances is the presence of very intensive surface waves, which frequently forms the dominant phase on the seismogram. In the recent years we started project, which aims to use seismograms generated by quarry blasts for developing of 3-D model of Bohemian Massif and for study of anisotropy in this region. An accurate determination of the origin time was one of the problems. This problem has been solved by developing of special seismograph BUMPRECORDER, for recording seismic waves very close to the blast (tens of meters).

Broz, M.; Brokesova, J.; Malek, J.; Novotny, O.; Strunc, J.; Zanda, L.

2003-04-01

134

A Comparison of Fully Relativistic and Non-relativistic Ray-tracing of Electron Bernstein Waves

NASA Astrophysics Data System (ADS)

Electron Bernstein waves (EBW) can be important for heating and driving current in high density, high temperature plasmas. Mode- converted EBWs are especially of interest in overdense (?pe>?ce) machines such as spherical tokamaks (ST), because few other types of plasma waves can propagate inside such a plasma. EBWs usually damp near cyclotron resonances, where full relativistic effects are important. This would be especially true in an ST reactor, such as the ARIES-ST study, where Te0˜16 keV. Recently, a fully-relativistic, high-frequency dispersion relation has been added to the ray-tracing code GENRAY [1]. This portion of the code was written by A.K. Ram and E. Nelson-Melby. Recent work shown at the 16th RF Topical Conference [2] have shown that there can be significant differences between the non- and fully-relativistic EBW dispersion relations. Ray- tracing of EBWs mode-converted through the O-X-B scenario at the edge of the ARIES-ST tokamak will be presented. [1] A.P. Smirnov and R.W. Harvey, Bull. APS 40, Ab. 8p35 (1995). [2] A.K. Ram, J. Decker, and Y. Peysson, J. Plasma Phys., accepted for publication (2005); E. Nelson-Melby et. al., Poster B-08. (2005).

Nelson-Melby, E.; Harvey, R. W.; Ram, A. K.

2005-10-01

135

Surfing and generation of cosmic rays in relativistic shock waves

NASA Astrophysics Data System (ADS)

We consider the problem of cosmic-ray generation through the surfing acceleration of charged particles in relativistic magnetosonic shock waves (the branch of fast magnetic sound) propagating in magnetized space plasmas. The dependence of the particle surfing acceleration efficiency on the angle ? Bn between the normal to the shock front plane and the magnetic field vector in the plasma upstream of the shock is analyzed in detail. We show that for angles satisfying the condition ? = ?? tan ? Bn ? 1, where ? = U/ c, ? = (1 - ?)2 -1/2, U is the shock velocity, and c is the speed of light, the particles can theoretically be accelerated through surfing for an unlimited time and can gain an unlimited energy. For angles satisfying the condition ? < 1, the kinetic energy ? of the particles is limited by ? = 2 mc 2?2/(1 - ?2) ( m is the particle rest mass). Our main conclusion is that the generation of cosmic rays through the surfing acceleration of particles in the front of a relativistic shock wave for ? ? 1 is also efficient when the angle ? Bn is very small, i.e., it differs significantly from a right angle. Estimates for the energies of particles accelerated through surfing in relativistic jets are provided.

Kichigin, G. N.

2009-09-01

136

Nonlinear propagation of high-frequency energy from blast waves as it pertains to bat hearing

NASA Astrophysics Data System (ADS)

Close exposure to blast noise from military weapons training can adversely affect the hearing of both humans and wildlife. One concern is the effect of high-frequency noise from Army weapons training on the hearing of endangered bats. Blast wave propagation measurements were conducted to investigate nonlinear effects on the development of blast waveforms as they propagate from the source. Measurements were made at ranges of 25, 50, and 100 m from the blast. Particular emphasis was placed on observation of rise time variation with distance. Resolving the fine shock structure of blast waves requires robust transducers with high-frequency capability beyond 100 kHz, hence the limitations of traditional microphones and the effect of microphone orientation were investigated. Measurements were made with a wide-bandwidth capacitor microphone for comparison with conventional 3.175-mm (?-in.) microphones with and without baffles. The 3.175-mm microphone oriented at 90° to the propagation direction did not have sufficient high-frequency response to capture the actual rise times at a range of 50 m. Microphone baffles eliminate diffraction artifacts on the rise portion of the measured waveform and therefore allow for a more accurate measurement of the blast rise time. The wide-band microphone has an extended high-frequency response and can resolve shorter rise times than conventional microphones. For a source of 0.57 kg (1.25 lb) of C-4 plastic explosive, it was observed that nonlinear effects steepened the waveform, thereby decreasing the shock rise time, from 25 to 50 m. At 100m, the rise times had increased slightly. For comparison to the measured blast waveforms, several models of nonlinear propagation are applied to the problem of finite-amplitude blast wave propagation. Shock front models, such as the Johnson and Hammerton model, and full-waveform marching algorithms, such as the Anderson model, are investigated and compared to experimental results. The models successfully predict blast wave rise times at medium distances in a homogeneous atmosphere, although rise time predictions are shorter than what was measured in an inhomogeneous atmosphere. Atmospheric turbulence, absent in the models, may be the primary cause of this difference in rise times at longer distances. Results from the measurements and models indicate that bats located within approximately 200 m of the detonation of 0.57kg of C-4 will be exposed to audible levels of high-frequency energy, but whether those levels could be damaging to bat hearing cannot be established at this time.

Loubeau, Alexandra

137

Study on dynamic response of masonry building to blasting and natural seismic waves

Seismic effect caused by blasting and natural seismic waves, which directly threatens safety of peripheral buildings, is the focus and difficulty to be solved in structural seismic field. A multi-layer masonry building was taken as analyzed object, proper resilience model and time-history method were adopted to develop a theoretical and numerical model. Based on numerical results, differences between structural dynamic

Haixia Wei; Ting Liu

2011-01-01

138

Quantifying Momentum Transfer Due to Blast Waves from Oxy-Acetylene Driven Shock Tubes.

National Technical Information Service (NTIS)

Shock tubes have been widely used since the 1950s to study physical phenomena such as shock waves, combustion chemistry, and the response of materiel to blast loading. Recently, laboratory-scale shock tubes driven by oxy- acetylene were described. It was ...

A. Courtney H. Her M. Courtney

2012-01-01

139

Relativistic solitary waves modulating long laser pulses in plasmas

NASA Astrophysics Data System (ADS)

This paper discusses the existence of solitary electromagnetic waves trapped in a self-generated Langmuir wave and embedded in an infinitely long circularly polarized electromagnetic wave propagating through a plasma. From a mathematical point of view they are exact solutions of the one-dimensional relativistic cold fluid plasma model with nonvanishing boundary conditions. Under the assumption of travelling wave solutions with velocity V and vector potential frequency ?, the fluid model is reduced to a Hamiltonian system. The solitary waves are homoclinic (grey solitons) or heteroclinic (dark solitons) orbits to fixed points. Using a dynamical systems description of the Hamiltonian system and a spectral method, we identify a large variety of solitary waves, including asymmetric ones, discuss their disappearance for certain parameter values and classify them according to (i) grey or dark character, (ii) the number of humps of the vector potential envelope and (iii) their symmetries. The solutions come in continuous families in the parametric V-? plane and extend up to velocities that approach the speed of light. The stability of certain types of grey solitary waves is investigated with the aid of particle-in-cell simulations that demonstrate their propagation for a few tens of the inverse of the plasma frequency.

Sánchez-Arriaga, G.; Siminos, E.; Lefebvre, E.

2011-04-01

140

Visualization of developing high temperature supersonic impulse jet induced by blast wave simulator

In order to investigate the developing characteristics of a high temperature supersonic impulse jet under an atmospheric ambient\\u000a condition, we generate jets induced by an incident shock wave at Mach number 2.89, emerging from the open end of a high enthalpy\\u000a blast wave simulator (HEBS). Developing high temperature supersonic impulse jets were visualized by the direction-indicating\\u000a color schlieren method and

T. Mizukaki

2007-01-01

141

Prospects for studying how high-intensity compression waves cause damage in human blast injuries

NASA Astrophysics Data System (ADS)

Since World War I, explosions have accounted for over 70% of all injuries in conflict. With the development of improved personnel protection of the torso, improved medical care and faster aeromedical evacuation, casualties are surviving with more severe injuries to the extremities. Understanding the processes involved in the transfer of blast-induced shock waves through biological tissues is essential for supporting efforts aimed at mitigating and treating blast injury. Given the inherent heterogeneities in the human body, we argue that studying these processes demands a highly integrated approach requiring expertise in shock physics, biomechanics and fundamental biological processes. This multidisciplinary systems approach enables one to develop the experimental framework for investigating the material properties of human tissues that are subjected to high compression waves in blast conditions and the fundamental cellular processes altered by this type of stimuli. Ultimately, we hope to use the information gained from these studies in translational research aimed at developing improved protection for those at risk and improved clinical outcomes for those who have been injured from a blast wave.

Brown, Katherine; Bo, Chiara; Masouros, Spyros; Ramasamy, Arul; Newell, Nicolas; Bonner, Timothy; Balzer, Jens; Hill, Adam; Clasper, Jon; Bull, Anthony; Proud, William

2012-03-01

142

Search for non-thermal radio emission from Eta Carina's outer blast wave with ATCA

NASA Astrophysics Data System (ADS)

Non-thermal hard X-ray and high-energy (HE; 1 MeV < E < 100 GeV) gamma-ray emission in the direction of Eta Carina has been recently detected using the INTEGRAL, AGILE and Fermi satellites. This emission can be either interpreted in the framework of particle acceleration in the colliding wind region between the two massive stars or in the very fast moving blast wave which originates in the historical 1843 "Great Eruption". The detection of a radio shell at the location of the shock would support the latter scenario and confirm Eta Carina as prime example of a new source type, namely, an LBV star whose massive ejecta accelerates electrons to non-thermal energies. While Fermi and INTEGRAL do not provide sufficient angular resolution to resolve the blast wave, high resolution radio observations using ATCA will be able to test non-thermal radio emission from this acceleration site. The current sensitivity of ATCA is such that a relatively modest observation time of 12 hours will be sufficient to image the synchrotron emission from the blast region down to magnetic field strengths well below typical ISM values and hence prove or reject our blast-wave hypothesis for the high energy emission.

Ohm, Stefan; Urquhart, James; Skilton, Joanna Lucy; Hinton, Jim; Domainko, Wilfried

2010-10-01

143

Dust acoustic solitary waves in a charge varying relativistic dusty plasma

The problem of nonlinear variable charge dust acoustic solitary waves in dusty plasma with relativistic electrons and ions is addressed. The appropriate relativistic charging currents, derived within the theoretical framework of the orbit-limited motion theory, are used. Our results show that in such a plasma, rarefactive spatially localized dust acoustic waves can exist. Their spatial patterns are significantly modified by the relativistic effects. In particular, it may be noted that relativistic effects make the solitary structure spikier. Our results should help to understand the salient features of coherent nonlinear structures that may occur in relativistic space plasmas.

Tribeche, Mouloud; Boukhalfa, Soufiane; Zerguini, Taha Houssine [Plasma Physics Group, Theoretical Physics Laboratory (TPL), Faculty of Sciences-Physics, University of Bab-Ezzouar, U.S.T.H.B, B.P. 32, El Alia, Algiers 16111 (Algeria)

2010-06-15

144

Dust acoustic solitary waves in a charge varying relativistic dusty plasma

NASA Astrophysics Data System (ADS)

The problem of nonlinear variable charge dust acoustic solitary waves in dusty plasma with relativistic electrons and ions is addressed. The appropriate relativistic charging currents, derived within the theoretical framework of the orbit-limited motion theory, are used. Our results show that in such a plasma, rarefactive spatially localized dust acoustic waves can exist. Their spatial patterns are significantly modified by the relativistic effects. In particular, it may be noted that relativistic effects make the solitary structure spikier. Our results should help to understand the salient features of coherent nonlinear structures that may occur in relativistic space plasmas.

Tribeche, Mouloud; Boukhalfa, Soufiane; Zerguini, Taha Houssine

2010-06-01

145

NASA Astrophysics Data System (ADS)

In this talk we discuss the nature of late-time, broad-banded instability development at an interface when a strong blast wave travels from a heavier to lighter fluid, as is the case in a supernova explosion. After a short period of Richtmyer-Meshkov growth, the interface is unstable via the Rayleigh-Taylor mechanism, which rapidly becomes the dominant energy source for growth. This situation is distinct from the classical case in two important ways, both of which can be understood in terms of a bubble merger model we have developed for blast-wave-driven systems. Rather than the constant acceleration feeding the instability to spawn ever larger scales and accelerate the growth, the decaying acceleration in the blast-wave case leads to a decay in the RT growth rate, and a freezing in of a preferred largest scale, which is dependent on the precise details of the system. In the language of bubble-merger models, this can be understood in terms of the time for the generation of the next largest scale being longer than the lifetime of the blast wave. Secondly, the continual expansion behind the blast front precludes the emergence of a self-similar regime, independent of the initial conditions, in the planar case. Self-similarity may be recovered in diverging systems but may be difficult to observe in reality because of rather restrictive conditions that must be met. These observations are borne out by hi-resolution numerical simulations using the higher order Godunov AMR hydrocode Raptor in 2 and 3D, and explain other simulations of instability growth in supernovae explosions; the initial "interfacial" structure is likely very important in determining the late-time growth. The model predictions are also consistent with numerous images of natural and manmade explosions.

Miles, Aaron

2004-11-01

146

Analysis of coaxial ridged disk-loaded slow-wave structures for relativistic traveling wave tubes

The coaxial ridged disk-loaded structure which is a new disk-loaded periodic system is presented and analyzed in this paper. As an all-metal slow-wave circuit, it has properties that can be used in high-power traveling wave tubes (TWT) and relativistic TWTs. The dispersion equation and coupling impedance of the structure are investigated in the first part of this paper. The results

Lingna Yue; Wenxiang Wang; Yubin Gong; Keqian Zhang

2004-01-01

147

Relativistic shock waves and the excitation of plerions

The shock termination of a relativistic magnetohydrodynamic wind from a pulsar is the most interesting and viable model for the excitation of the synchrotron sources observed in plerionic supernova remnants. We have studied the structure of relativistic magnetosonic shock waves in plasmas composed purely of electrons and positrons, as well as those whose composition includes heavy ions as a minority constituent by number. We find that relativistic shocks in symmetric pair plasmas create fully thermalized distributions of particles and fields downstream. Therefore, such shocks are not good candidates for the mechanism which converts rotational energy lost from a pulsar into the nonthermal synchrotron emission observed in plerions. However, when the upstream wind contains heavy ions which are minority constituent by number density, but carry the bulk of the energy density, much of the energy of the shock goes into a downstream, nonthermal power law distribution of positrons with energy distribution N(E)dE {proportional to}E{sup {minus}s}. In a specific model presented in some detail, s = 3. These characteristics are close to those assumed for the pairs in macroscopic MHD wind models of plerion excitation. The essential mechanism is collective synchrotron emission of left-handed extraordinary modes by the ions in the shock front at high harmonics of the ion cyclotron frequency, with the downstream positrons preferentially absorbing almost all of this radiation, mostly at their fundamental (relativistic) cyclotron frequencies. Possible applications to models of plerions and to constraints on theories of energy loss from pulsars are briefly outlines. 27 refs., 5 figs.

Arons, J. (California Univ., Berkeley, CA (USA)); Gallant, Y.A. (California Univ., Berkeley, CA (USA). Dept. of Physics); Hoshino, Masahiro; Max, C.E. (California Univ., Livermore, CA (USA). Inst. of Geophysics and Planetary Physics); Langdon, A.B. (Lawrence Livermore National Lab., CA (USA))

1991-01-07

148

We obtain renormalized sets of right and left eigenvectors of the flux vector Jacobians of the relativistic MHD equations, which are regular and span a complete basis in any physical state including degenerate ones. The renormalization procedure relies on the characterization of the degeneracy types in terms of the normal and tangential components of the magnetic field to the wave front in the fluid rest frame. Proper expressions of the renormalized eigenvectors in conserved variables are obtained through the corresponding matrix transformations. Our work completes previous analysis that present different sets of right eigenvectors for non-degenerate and degenerate states, and can be seen as a relativistic generalization of earlier work performed in classical MHD. Based on the full wave decomposition (FWD) provided by the renormalized set of eigenvectors in conserved variables, we have also developed a linearized (Roe-type) Riemann solver. Extensive testing against one- and two-dimensional standard numerical problems allows us to conclude that our solver is very robust. When compared with a family of simpler solvers that avoid the knowledge of the full characteristic structure of the equations in the computation of the numerical fluxes, our solver turns out to be less diffusive than HLL and HLLC, and comparable in accuracy to the HLLD solver. The amount of operations needed by the FWD solver makes it less efficient computationally than those of the HLL family in one-dimensional problems. However, its relative efficiency increases in multidimensional simulations.

Anton, Luis; MartI, Jose M; Ibanez, Jose M; Aloy, Miguel A.; Mimica, Petar [Departamento de AstronomIa y AstrofIsica, Universidad de Valencia, 46100 Burjassot, Valencia (Spain); Miralles, Juan A. [Departament de Fisica Aplicada, Universitat d'Alacant, Ap. Correus 99, 03080 Alacant (Spain)

2010-05-01

149

During magnetic storms, relativistic electrons execute nearly circular orbits about the Earth and traverse a spatially confined zone within the duskside plasmapause where electromagnetic ion cyclotron (EMIC) waves are preferentially excited. We examine the mechanism of electron pitch-angle diffusion by gyroresonant interaction with EMIC waves as a cause of relativistic electron precipitation loss from the outer radiation belt. Detailed calculations

Danny Summers; Richard M. Thorne

2003-01-01

150

The relativistic kinetic theory of parallel propagating electromagnetic waves in a magnetized equilibrium plasma is presented. On the basis of relativistic Vlasov-Maxwell equations, a general explicit dispersion relation is derived by a correct analytical continuation for all complex frequencies of electromagnetic waves.

M. Lazar; R. Schlickeiser

2003-01-01

151

High energy density radiative blast wave experiments in clustered gas targets

NASA Astrophysics Data System (ADS)

Using the efficient absorption of laser energy by clustered gases allows the study of high energy density systems at low average density with table-top scale lasers. Thus generation of radiative shocks at moderate drive energies in high Z materials can be achieved for the purpose of laboratory astrophysics. Using the Vulcan laser we have performed radiative shock experiments. We observe radiative shell thinning in Ar at high shock velocities, increasing the shocks susceptibility to instabilities. Utilising streaked Schlieren measurements, we measure shock velocity oscillations in Kr for the first time, indicative of the thermal cooling instability [1]. We also report on advanced diagnostics for characterisation of blast wave propagation. These include temporally resolved temperature measurement, proton radiography and the use of a second, perpendicular blast wave to probe the primary shock ambient medium. [4pt] [1] M. Hohenberger et al., submitted to Phys. Rev. Lett.

Doyle, Hugo; Olsson-Robbie, Stefan; Hohenberger, Matthias; Gumbrell, Edward; Moore, Alastair; Symes, Dan; Smith, Roland

2010-11-01

152

Electron Injection by Whistler Waves in Non-relativistic Shocks

NASA Astrophysics Data System (ADS)

Electron acceleration to non-thermal, ultra-relativistic energies (~10-100 TeV) is revealed by radio and X-ray observations of shocks in young supernova remnants (SNRs). The diffusive shock acceleration (DSA) mechanism is usually invoked to explain this acceleration, but the way in which electrons are initially energized or "injected" into this acceleration process starting from thermal energies is an unresolved problem. In this paper we study the initial acceleration of electrons in non-relativistic shocks from first principles, using two- and three-dimensional particle-in-cell (PIC) plasma simulations. We systematically explore the space of shock parameters (the Alfvénic Mach number, MA , the shock velocity, v sh, the angle between the upstream magnetic field and the shock normal, ? Bn , and the ion to electron mass ratio, mi /me ). We find that significant non-thermal acceleration occurs due to the growth of oblique whistler waves in the foot of quasi-perpendicular shocks. This acceleration strongly depends on using fairly large numerical mass ratios, mi /me , which may explain why it had not been observed in previous PIC simulations of this problem. The obtained electron energy distributions show power-law tails with spectral indices up to ? ~ 3-4. The maximum energies of the accelerated particles are consistent with the electron Larmor radii being comparable to that of the ions, indicating potential injection into the subsequent DSA process. This injection mechanism, however, requires the shock waves to have fairly low Alfénic Mach numbers, MA <~ 20, which is consistent with the theoretical conditions for the growth of whistler waves in the shock foot (MA <~ (mi /me )1/2). Thus, if the whistler mechanism is the only robust electron injection process at work in SNR shocks, then SNRs that display non-thermal emission must have significantly amplified upstream magnetic fields. Such field amplification is likely achieved by the escaping cosmic rays, so electron and proton acceleration in SNR shocks must be interconnected.

Riquelme, Mario A.; Spitkovsky, Anatoly

2011-05-01

153

Design of Jet-Driven, Radiative-Blast-Wave Experiments for Omega EP

We discuss the design of jet-driven, radiative-blast-wave experiments for the Omega EP (EP) laser facility. In experiments motivated by astrophysics, plasma jets have been produced by a number of research teams on a variety of laser and z-pinch facilities. Among those that have driven a bow shock into an ambient medium, none have yet been fast enough to create strong

R. Paul Drake; J. P. Knauer

2008-01-01

154

Biomechanical Assessment of Brain Dynamic Responses Due to Blast Pressure Waves

A mechanized and integrated computational scheme is introduced to determine the human brain responses in an environment where\\u000a the human head is exposed to explosions from trinitrotoluene (TNT), or other high-yield explosives, in military applications.\\u000a The procedure is based on a three-dimensional (3-D) non-linear finite element method (FEM) that implements a simultaneous\\u000a conduction of explosive detonation, shock wave propagation, blast–head

M. S. Chafi; G. Karami; M. Ziejewski

2010-01-01

155

The dynamics of energy loss through diagnostic and\\/or laser-entrance holes with or without shine shields is of interest to a class of inertial confinement fusion experiments envisioned for the National Ignition and ZR Facilities. We discuss the energy source in 2-D radiation-hydrodynamic simulations using Lasnex [G. Zimmermann et al.] for blast wave experiments recently fielded at the Z facility driven

Heidi Tierney; Robert Peterson; Darrell Peterson; Thomas Tierney

2006-01-01

156

Large blast-wave simulators (lbs) with cold-gas drivers: computational design studies. Final report

Computational, parametric design studies were carried out using the BRL-QID hydrocode to investigate the effects of variations in length of a US-LBS designed to simulate blast waves within a predefined test envelope. The simulation requirement was based on a 60m\\/kT 1\\/3 height-of-burst, scaled, tactical explosion for shock overpressures ranging from 14 to 240 kPa (2-35 psi) and weapon yields rangining

Opalka

1987-01-01

157

Gamma-ray burst phenomenology explained through the blast wave model

The essential physics of the blast wave model is contained in a formula recently proposed to describe the temporal evolution of the nonthermal synchrotron spectra from gamma-ray bursts (GRBs). This formula accounts for many of the well-established empirical trends in GRB physics, including the basic form of the fast-rise, gentle-decay FRED-type GRB light curves, the characteristic hard-to-soft spectral evolution and

C. D. Dermer

1999-01-01

158

Kepler's Supernova Remnant: an Imaging Study of the Blast Wave - Circumstellar Medium Interaction

NASA Astrophysics Data System (ADS)

Kepler's SNR {SN 1604 AD} is the prime example of a young Galactic SNR where the blast wave is running into the wind of the progenitor star. The interaction between the blast wave and the inhomogeneous circumstellar medium gives rise to knots, evolving on a time scale of years, that dominate the optical emission from the remnant. Also visible in the optical are fainter Balmer line filaments that exhibit a range of geometries - from normal sheet-like filaments to more diffuse clumps of emission, the latter unique to this remnant. We propose to image Kepler's SNR through several narrowband filters using ACS/WFC and WFPC2. The morphology and ionization structure of the knots will be obtained from H-alpha, [S II], and [O III] images. We will also obtain a [N II] image, which is known to be strong and spatially variable in the remnant. The proposed H-alpha images will be deep enough so that the physical scales and structure of the Balmer dominated non-radiative shocks can be investigated. Our data will be a critical part of multiwavelength studies of Kepler's SNR. They will complement Chandra and XMM X-ray data and VLA radio data, and provide a significant advance in understanding the processes of magnetic field amplification and cosmic ray acceleration in SNRs as well as the evolution and dynamics of the blast wave - circumstellar medium interaction.

Sankrit, Ravi

2003-07-01

159

Modeling of laser-generated radiative blast waves, with applications to late-term supernova remnants

NASA Astrophysics Data System (ADS)

The goal of laser astrophysics is to provide a means by which aspects of specific astrophysical phenomena can be reproduced in the laboratory. Although the hydrodynamic instabilities of early supernova remnants have already been studied using this method, the role of significant radiative losses in shock propagation (for example, in late-term remnants) has only been imperfectly modeled. This thesis introduces an improved self-similar analytic approach to radiative blast-wave evolution where the total amount of energy loss remains constant in proportion to the energy flux entering the shock front. The approximation is solved for the cases in which both energy loss from the shock front and heating of the shock (due to the presence of ionization precursors) are significant. Because this solution is independent of the exact method of cooling, it is appropriate for both the laboratory and astrophysical regimes. In addition, this thesis applies the analytic approximation to laboratory- produced radiative blast waves as well as to numerical models of these experimental blast waves. These results will allow for better design of laser-based experiments with further applications to astrophysical phenomena, as well as for an increase in the understanding of the challenges involved in scaling radiative phenomena between laboratory experiments and astrophysical theory.

Keilty, Katherine Anne

2003-11-01

160

On the Relativistic Damping of Transverse Waves Propagating in Magnetized Vlasov Plasmas

NASA Astrophysics Data System (ADS)

The general relativistic dispersion relations of transverse waves parallel propagating in magnetized Vlasov plasmas, are reconsidered. In a previous paper (Lazar and Schlickeiser 2003 Can. J. Phys. 81 1377) we have derived these equations by a rigorous relativistic kinetic theory and by a correct analytical continuation for all complex frequencies. Detailed expressions are more explicitly presented here for residues to completely describe the damped waves forward or backward moving waves, and left-handed or right-handed polarized waves. The cyclotron damping occurs when the circularly-polarized wave frequency nearly coincides with the gyrofrequency of plasma particle, modified by the relativistic Doppler effect in its own referential. The rigorous analysis of relativistically correct dispersion equations leads to an important correction of nonrelativistic theory: the superluminal EM waves undergo no cyclotron damping in magnetized equilibrium plasmas.

Lazar, M.; Schlickeiser, R.

2004-01-01

161

Anomalous skin effects in relativistic parallel propagating weakly magnetized electron plasma waves

Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized electron plasma is presented and general expressions for longitudinal and transverse permittivites are derived. It is found that the penetration depth for R- and L-waves increases as we move from non-relativistic to highly relativistic regime. The ambient magnetic field reduces/enhances the skin effects for R-wave/L-wave as the strength of the field is increased. In general, the weak magnetic field effects are pronounced for the weakly relativistic regime as compared with other relativistic cases. The results are also graphically illustrated. On switching off the magnetic field, previous results for field free case are retrieved [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Priniples of Plasma Electrodynamics (Springer-Verlag, Berlin, Heidelberg, 1984), Vol. 9, p. 106].

Abbas, Gohar; Bashir, M. F. [Salam Chair in Physics, G. C. University, Lahore 54000 (Pakistan); Department of Physics, G. C. University, Lahore 54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, G. C. University, Lahore 54000 (Pakistan)

2011-10-15

162

Initiation of reactive blast waves by external energy sources

NASA Astrophysics Data System (ADS)

This article is devoted to the analysis of the direct initiation, by concentrated centrally-symmetric external energy sources, of self-sustained detonation waves in gaseous reactive mixtures. The dynamics of the detonation front will be described in the fast reaction limit, when the thickness of the reaction layer that follows the shock front is very small compared with the shock radius. At early times, after starting the external thermal energy deposition, the detonation front, associated with a strongly expanding flow, is overdriven; thus it is reached by expansion waves that decrease its velocity towards the Chapman-Jouguet (CJ) value, for which the expansion waves can no longer reach the front. The decay occurs for detonation radii such that the energy released by the external source equals the heat released by the chemical reaction. For planar detonations the CJ velocity is only approached asymptotically for large times, while for cylindrical and spherical detonations the flow divergence provides an additional decay mechanism associated with the front curvature that causes the transition to the constant CJ velocity to occur at a finite value of the detonation radius. The time evolution of the flow field and the corresponding variation with deposition time of the transition radius is computed for energy sources of constant heating rate. The analysis includes a detailed quantitative description of the near-front flow structure for times close to the transition time, given here for the first time, along with the study of the evolution towards the Zel'dovich-Taylor cylindrical or spherical self-similar flow structure, which corresponds to a CJ detonation front ideally initiated at the center without any external energy source. The asymptotic decay to CJ is also described for planar detonations initiated with energy sources of constant heating rate and finite nonzero deposition time. A brief discussion will be given on how the reaction may be quenched by the flow divergence effects if the initiating energy is smaller than a critical value, thus failing to generate a self-propagating detonation wave.

Liñán, Amable; Kurdyumov, Vadim N.; Sánchez, Antonio L.

2012-11-01

163

Relativistic effects on large amplitude nonlinear langmuir waves in a two-fluid plasma

Large amplitude relativistic nonlinear Langmuir waves are analyzed by the pseudo-potential method. The existence conditions for nonlinear langmuir waves are confirmed by considering relativistic high-speed electrons in a two-fluid plasma. The significant feature of this investigation is that the propagation of nonlinear Langmuir waves depends on the ratio of the electron streaming velocity to the velocity of light, the normalized

Yasunori Nejoh

1994-01-01

164

Modelling the 2010 blast wave of the symbiotic-like nova V407 Cygni

NASA Astrophysics Data System (ADS)

The symbiotic-like binary Mira and nova V407 Cyg was observed in outburst in 2010 March and monitored in several wavelength bands. The outburst had, to some extent, characteristics similar to those observed during other nova eruptions, such as that occurred recently in RS Oph and U Sco, suggesting that the blast wave interacted with the giant companion and propagated through a dense circumstellar medium enveloping the binary system. Here we report on multidimensional hydrodynamic simulations describing the 2010 outburst of V407 Cyg, exploring the first 60 d of evolution. The model takes into account thermal conduction (including the effects of heat flux saturation) and radiative cooling; the pre-explosion system conditions included the companion star and a circumbinary density enhancement that are believed to influence the evolution and morphology of the blast wave. The simulations showed that the blast and the ejecta distribution are both aspherical due to the inhomogeneous circumstellar medium in which they expand; in particular, they are significantly collimated in polar directions (producing a bipolar shock morphology) if the circumstellar envelope is characterized by an equatorial density enhancement. The blast is partially shielded by the Mira companion, producing a wake with dense and hot post-shock plasma on the rear side of the companion star; most of the X-ray emission produced during the evolution of the blast arises from this plasma structure. The observed X-ray light curve can be reproduced, assuming values of outburst energy and ejected mass similar to those of RS Oph and U Sco, if a circumbinary gas density enhancement is included in the model. In particular, our 'best-fitting' model predicts that the 2010 blast propagated through a circumbinary gas density enhancement with radius of the order of 40 au and gas density ?106 cm-3 and that the mass of ejecta in the outburst was Mej? 2 × 10-7 M? with an explosion energy E0? 2 × 1044 erg. Alternatively, the model can produce a similar X-ray light curve without the need of a circumbinary gas density enhancement only if the outburst energy and ejected mass were similar to those at the upper end of ranges for classical novae, namely Mej? 5 × 10-5 M? and E0? 5 × 1046 erg.

Orlando, Salvatore; Drake, Jeremy J.

2012-01-01

165

A repetitive 0.14 THz relativistic surface wave oscillator

NASA Astrophysics Data System (ADS)

Preliminary experimental results of a repetitive 0.14 THz overmoded relativistic surface wave oscillator (RSWO) are presented in this paper. The repetitive RSWO is developed by using a rectangularly corrugated slow-wave structure with overmoded ratio of 3 and a foilless diode emitting annular electron beam with thickness of 0.5 mm. The high quality electron beams at the repetition rate of 10 are obtained over a wide range of diode voltage (180 kV < U < 240 kV) and current (700 A < I < 1.2 kA). The generation experiments of RSWO are conducted at an axial pulsed magnetic field whose maximum strength and duration can reach about 2.7 T and 1 s, respectively. The experimental results show that the RSWO successfully produces reasonable uniform terahertz pulses at repetition rate of 10, and the pulse duration, frequency, and power of a single pulse are about 1.5 ns, 0.154 THz, and 2.6 MW, respectively, whereas the dominated radiation mode of the RSWO is TM02.

Wang, Guangqiang; Wang, Jianguo; Tong, Changjiang; Li, Xiaoze; Wang, Xuefeng; Li, Shuang; Lu, Xicheng

2013-04-01

166

ELECTRON INJECTION BY WHISTLER WAVES IN NON-RELATIVISTIC SHOCKS

Electron acceleration to non-thermal, ultra-relativistic energies ({approx}10-100 TeV) is revealed by radio and X-ray observations of shocks in young supernova remnants (SNRs). The diffusive shock acceleration (DSA) mechanism is usually invoked to explain this acceleration, but the way in which electrons are initially energized or 'injected' into this acceleration process starting from thermal energies is an unresolved problem. In this paper we study the initial acceleration of electrons in non-relativistic shocks from first principles, using two- and three-dimensional particle-in-cell (PIC) plasma simulations. We systematically explore the space of shock parameters (the Alfvenic Mach number, M{sub A} , the shock velocity, v{sub sh}, the angle between the upstream magnetic field and the shock normal, {theta}{sub Bn}, and the ion to electron mass ratio, m{sub i} /m{sub e} ). We find that significant non-thermal acceleration occurs due to the growth of oblique whistler waves in the foot of quasi-perpendicular shocks. This acceleration strongly depends on using fairly large numerical mass ratios, m{sub i} /m{sub e} , which may explain why it had not been observed in previous PIC simulations of this problem. The obtained electron energy distributions show power-law tails with spectral indices up to {alpha} {approx} 3-4. The maximum energies of the accelerated particles are consistent with the electron Larmor radii being comparable to that of the ions, indicating potential injection into the subsequent DSA process. This injection mechanism, however, requires the shock waves to have fairly low Alfenic Mach numbers, M{sub A} {approx}< 20, which is consistent with the theoretical conditions for the growth of whistler waves in the shock foot (M{sub A} {approx}< (m{sub i} /m{sub e}){sup 1/2}). Thus, if the whistler mechanism is the only robust electron injection process at work in SNR shocks, then SNRs that display non-thermal emission must have significantly amplified upstream magnetic fields. Such field amplification is likely achieved by the escaping cosmic rays, so electron and proton acceleration in SNR shocks must be interconnected.

Riquelme, Mario A. [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Spitkovsky, Anatoly, E-mail: marh@astro.berkeley.edu, E-mail: anatoly@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2011-05-20

167

Resonant and non-resonant beat-wave excitation of relativistic plasma waves

NASA Astrophysics Data System (ADS)

The phase relationship between a beat-wave excited relativistic plasma wave and its laser pulse driver is important for the phase-locked acceleration of externally injected electrons. This relationship is studied using 2-D particle-in-cell simulations for both the resonant and non-resonant waves excited in a non-uniform plasma whose density is a time and space-varying quantity due to the slow ponderomotive expulsion of the plasma electrons by the laser pulse. It is found that the waves excited at the resonant density get dephased with respect to the beat pattern of the laser pulse. Therefore, externally injected electrons could interact with both accelerating and decelerating fields of the plasma wave, resulting in a decrease in the overall energy gain. Furthermore, the dynamics of this dephasing is highly sensitive of the initial plasma density and laser pulse parameters, as it is expected from an oscillator being driven just slightly off resonance. As opposed to the resonant case, the accelerating electric fields associated with the extremely non-resonant plasmons are always in phase with the beat-pattern of the laser pulse, regardless of the variations in the plasma density. Although the normalized amplitude of the oscillation is small, the longitudinal electric field of such a wave can still be substantial if the plasma density is much higher than the resonant density. The excitation of such non-resonant relativistic plasma waves by a TW CO2 laser pulse is shown to be possible for plasma densities as high as 12 times the resonant density. The density fluctuations and the fields associated with these waves are measured experimentally with a novel collinear Thomson scattering diagnostic system and by the energy change of the injected electrons, respectively.

Filip, Catalin Vasile

168

NASA Astrophysics Data System (ADS)

Multiphase flows, which involve compressible or incompressible fluids with linear or nonlinear dynamics, are found in all areas of technology at all length scales and flow regimes. In this contribution, we discuss application of aqueous-foam barriers against blast wave impact. The first experiments demonstrating this behaviour were conducted in the early 1980s in free-field tests. Based on structural requirements, various foams with different blast energy contents were tested with the aim of characterizing the time history of the blast pressure reduction. A number of consistent methodologies for calculating this pressure reduction in foam are based on the effective gas flow model. For estimating the uncertainties of these methodologies, we briefly demonstrate their comparison with existing experimental data. Thereafter, we present various modifications of modelling approaches and their comparison with new results of blast wave experiments.

Britan, A.; Shapiro, H.; Liverts, M.; Ben-Dor, G.; Chinnayya, A.; Hadjadj, A.

2013-02-01

169

NASA Astrophysics Data System (ADS)

Spatially and temporally resolved temperature measurements behind an expanding blast wave are made using picosecond (ps) N2 coherent anti-Stokes Raman scattering (CARS) following laser flash heating of mixtures containing aluminum nanoparticles embedded in ammonium-nitrate oxidant. Production-front ps-CARS temperatures as high as 3600 +/- 180 K--obtained for 50-nm-diameter commercially produced aluminum-nanoparticle samples--are observed. Time-resolved shadowgraph images of the evolving blast waves are also obtained to determine the shock-wave position and corresponding velocity. These results are compared with near-field blast-wave theory to extract relative rates of energy release for various particle diameters and passivating-layer compositions.

Roy, Sukesh; Jiang, Naibo; Stauffer, Hans U.; Schmidt, Jacob B.; Kulatilaka, Waruna D.; Meyer, Terrence R.; Bunker, Christopher E.; Gord, James R.

2013-05-01

170

The modulational instability of copropagating light waves was studied recently by McKinstrie and Bingham [Phys. Fluids B 1, 230 (1989)], who applied their general theory to the study of the relativistic modulational instability (RMI) of light waves in the beat-wave accelerator. However, in rarefied plasma, the RMI merges with stimulated Raman forward scattering. The longitudinal RMI is suppressed over most

C. J. McKinstrie; R. Bingham

1992-01-01

171

Variational wave equations for relativistic few-body systems in QFT

NASA Astrophysics Data System (ADS)

The variational method in a reformulated Hamiltonian formalism of quantum field theory is used to derive relativistic few-body wave equations for scalar and Fermion fields. Analytic and approximate solutions of some two-body bound states are presented.

Darewych, J. W.

2006-06-01

172

The Blast-Wave-Driven Instability as a Vehicle for Understanding Supernova Explosion Structure

Blast-wave-driven instabilities play a rich and varied role throughout the evolution of supernovae from explosion to remnant, but interpreting their role is difficult due to the enormous complexity of the stellar systems. We consider the simpler and fundamental hydrodynamic instability problem of a material interface between two constant-density fluids perturbed from spherical and driven by a divergent central Taylor-Sedov blast wave. The existence of unified solutions at high Mach number and small density ratio suggests that general conclusions can be drawn about the likely asymptotic structure of the mixing zone. To this end we apply buoyancy-drag and bubble merger models modified to include the effects of divergence and radial velocity gradients. In general, these effects preclude the true self-similar evolution of classical Raleigh-Taylor, but can be incorporated into a quasi-self-similar growth picture. Loss of memory of initial conditions can occur in the quasi-self-similar model, but requires initial mode numbers higher than those predicted for pre-explosion interfaces in Type II SNe, suggesting that their late-time structure is likely strongly influenced by details of the initial perturbations. Where low-modes are dominant, as in the Type Ia Tycho remnant, they result from initial perturbations rather than generation from smaller scales. Therefore, structure observed now contains direct information about the explosion process. When large-amplitude modes are present in the initial conditions, the contribution to the perturbation growth from the Richtmyer-Meshkov instability is significant or dominant compared to Rayleigh-Taylor. Such Richtmyer-Meshkov growth can yield proximity of the forward shock to the growing spikes and structure that strongly resembles that observed in the Tycho. Laser-driven high-energy-density laboratory experiments offer a promising avenue for testing model and simulation descriptions of blast-wave-driven instabilities and making connections to their astrophysical counterparts.

Miles, A R

2008-05-27

173

An X-ray-emitting blast wave from the recurrent nova RS Ophiuchi.

Stellar explosions such as novae and supernovae produce most of the heavy elements in the Universe. The onset of a nova is well understood as driven by runaway thermonuclear fusion reactions on the surface of a white dwarf in a binary star system; but the structure, dynamics and mass of the ejecta are not well known. In rare cases, the white dwarf is embedded in the wind nebula of a red-giant companion, and the explosion products plough through the nebula and produce X-ray emission. Here we report X-ray observations of such an event, from the eruption of the recurrent nova RS Ophiuchi. The hard X-ray emission from RS Ophiuchi early in the eruption emanates from behind a blast wave, or outward-moving shock wave, that expanded freely for less than 2 days and then decelerated owing to interaction with the nebula. The X-rays faded rapidly, suggesting that the blast wave deviates from the standard spherical shell structure. The early onset of deceleration indicates that the ejected shell had a low mass, the white dwarf has a high mass, and that RS Ophiuchi is therefore a progenitor of the type of supernova (type Ia) integral to studies of the expansion of the Universe. PMID:16855584

Sokoloski, J L; Luna, G J M; Mukai, K; Kenyon, Scott J

2006-07-20

174

Biomechanical assessment of brain dynamic responses due to blast pressure waves.

A mechanized and integrated computational scheme is introduced to determine the human brain responses in an environment where the human head is exposed to explosions from trinitrotoluene (TNT), or other high-yield explosives, in military applications. The procedure is based on a three-dimensional (3-D) non-linear finite element method (FEM) that implements a simultaneous conduction of explosive detonation, shock wave propagation, blast-head interactions, and the confronting human head. The processes of blast propagation in the air and blast interaction with the head are modeled by an Arbitrary Lagrangian-Eulerian (ALE) multi-material FEM formulation, together with a penalty-based fluid/structure interaction (FSI) algorithm. Such a model has already been successfully validated against experimental data regarding air-free blast and plate-blast interactions. The human head model is a 3-D geometrically realistic configuration that has been previously validated against the brain intracranial pressure (ICP), as well as shear and principal strains under different impact loadings of cadaveric experimental tests of Hardy et al. [Hardy W. N., C. Foster, M. Mason, S. Chirag, J. Bishop, M. Bey, W. Anderst, and S. Tashman. A study of the response of the human cadaver head to impact. Proc. 51 ( st ) Stapp. Car Crash J. 17-80, 2007]. Different scenarios have been assumed to capture an appropriate picture of the brain response at a constant stand-off distance of nearly 80 cm from the core of the explosion, but exposed to different amounts of a highly explosive (HE) material such as TNT. The over-pressures at the vicinity of the head are in the range of about 2.4-8.7 atmosphere (atm), considering the reflected pressure from the head. The methodology provides brain ICP, maximum shear stresses and maximum principal strain within the milli-scale time frame of this highly dynamic phenomenon. While focusing on the two mechanical parameters of pressure, and also on the maximum shear stress and maximum principal strain to predict the brain injury, the research provides an assessment of the brain responses to different amounts of over-pressure. The research also demonstrates the ability to predict the ICP, as well as the stress and strain within the brain, due to such an event. The research cannot identify, however, the specific levels of ICP, stress and strain that necessarily lead to traumatic brain injury (TBI) because there is no access to experimental data regarding head-blast interactions. PMID:19806456

Chafi, M S; Karami, G; Ziejewski, M

2009-10-06

175

Investigations of laser-driven radiative blast waves in clustered gases

NASA Astrophysics Data System (ADS)

Radiative blast waves can be created by focusing intense laser pulses into highly absorbing clustered gases. By considering the plasma conditions these shocks can be categorized as optically thin radiative shocks, a regime of particular interest for laboratory astrophysics experiments. A periodic spatial modulation is introduced to the shock front in order to investigate instability and shock collisions. Hydrodynamic simulations are presented which are in qualitative agreement with the experimental results. A technique to perform a single shot measurement of the entire shock trajectory and the possibility to detect oscillations in the shock velocity is discussed.

Symes, D. R.; Hohenberger, M.; Lazarus, J.; Osterhoff, J.; Moore, A. S.; Fäustlin, R. R.; Edens, A. D.; Doyle, H. W.; Carley, R. E.; Marocchino, A.; Chittenden, J. P.; Bernstein, A. C.; Gumbrell, E. T.; Dunne, Mike; Smith, R. A.; Ditmire, T.

2010-06-01

176

Interaction of supernova blast waves with wind-driven shells: formation of \\

Most of middle-aged supernova remnants (SNRs) have a distorted and\\u000acomplicated appearance which cannot be explained in the framework of the\\u000aSedov-Taylor model. We consider three typical examples of such SNRs (Vela SNR,\\u000aMSH 15-52, G 309.2-00.6) and show that their structure could be explained as a\\u000aresult of interaction of a supernova (SN) blast wave with the ambient medium

V. V. Gvaramadze; Abdus Salam

1999-01-01

177

Waves in general relativistic two-fluid plasma around a Schwarzschild black hole

NASA Astrophysics Data System (ADS)

Waves propagating in the relativistic electron-positron or ions plasma are investigated in a frame of two-fluid equations using the 3+1 formalism of general relativity developed by Thorne, Price and Macdonald (TPM). The plasma is assumed to be freefalling in the radial direction toward the event horizon due to the strong gravitational field of a Schwarzschild black hole. The local dispersion relations for transverse and longitudinal waves have been derived, in analogy with the special relativistic formulation as explained in an earlier paper, to take account of relativistic effects due to the event horizon using WKB approximation.

Rahman, M. Atiqur

2012-10-01

178

Electrostatic solitary waves in a quantum plasma with relativistically degenerate electrons

A model for nonlinear ion waves in an unmagnetized plasma with relativistically degenerate electrons and cold fluid ions is presented here. The inertia is given here by the ion mass while the restoring force is provided by the relativistic electron degeneracy pressure, and the dispersion is due to the deviation from charge neutrality. A nonlinear Korteweg-de Vries equation is derived for small but finite amplitude waves and is used to study the properties of localized ion acoustic solitons for parameters relevant for dense astrophysical objects such as white dwarf stars. Different degrees of relativistic electron degeneracy are discussed and compared.

Masood, W. [TPPD, PINSTECH, P. O. Nilore, Islamabad (Pakistan) and National Center for Physics (NCP), Islamabad (Pakistan); Eliasson, B. [Institut fuer Theoretische Physik IV, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany) and Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2011-03-15

179

Laboratory observation of secondary shock formation ahead of a strongly radiative blast wave

High Mach number blast waves were created by focusing a laser pulse on a solid pin, surrounded by nitrogen or xenon gas. In xenon, the initial shock is strongly radiative, sending out a supersonic radiative heat wave far ahead of itself. The shock propagates into the heated gas, diminishing in strength as it goes. The radiative heat wave also slows, and when its Mach number drops to two with respect to the downstream plasma, the heat wave drives a second shock ahead of itself to satisfy mass and momentum conservation in the heat wave reference frame; the heat wave becomes subsonic behind the second shock. For some time both shocks are observed simultaneously. Eventually the initial shock diminishes in strength so much that it can longer be observed, but the second shock continues to propagate long after this time. This sequence of events is a new phenomenon that has not previously been discussed in the literature. Numerical simulation clarifies the origin of the second shock, and its position is consistent with an analytical estimate.

Hansen, J.F.; Edwards, M.J.; Froula, D.H.; Gregori, G.; Edens, A.D.; Ditmire, T. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); LRC-Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom); Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); University of Texas at Austin, Austin, Texas 78712 (United States)

2006-02-15

180

Laboratory observation of secondary shock formation ahead of a strongly radiative blast wave

High Mach number blast waves were created by focusing a laser pulse on a solid pin, surrounded by nitrogen or xenon gas. In xenon, the initial shock is strongly radiative, sending out a supersonic radiative heat wave far ahead of itself. The shock propagates into the heated gas, diminishing in strength as it goes. The radiative heat wave also slows, and when its Mach number drops to 2 with respect to the downstream plasma, the heat wave drives a second shock ahead of itself to satisfy mass and momentum conservation in the heat wave reference frame; the heat wave becomes subsonic behind the second shock. For some time both shocks are observed simultaneously. Eventually the initial shock dimimishes in strength so much that it can longer be observed, but the second shock continues to propagate long after this time. This sequence of events is a new phenomenon that has not previously been discussed in literature. Numerical simulation clarifies the origin of the second shock, and its position is consistent with an analytical estimate.

Hansen, J F; Edwards, M J; Froula, D H; Gregori, G; Edens, A; Ditmire, T

2005-11-16

181

In this article, the dispersion characteristics of the paraxial (near axis) electromagnetic (EM) waves in a relativistic electron beam guided by the ion channel are investigated. Equilibrium fields such as ion-channel electrostatic field and self-fields of relativistic electron beam are included in this formalism. In accordance with the equilibrium field structure, radial and azimuthal waves are selected as base vectors for EM waves. It is shown that the dispersion of the radially polarized EM and space charge waves are influenced by the equilibrium fields, but azimuthally polarized wave remain unaffected. In some wave number domains, the radially polarized EM and fast space charge waves are coupled. In these regions, instability is analyzed as a function of equilibrium structure. It is shown that the total equilibrium radial force due to the ion channel and electron beam and also relativistic effect play a key role in the coupling of the radially polarized EM wave and space charge wave. Furthermore, some asymptotic behaviors such as weak and strong ion channel, nonrelativistic case and cutoff frequencies are discussed. This instability could be used as an amplification mechanism for radially polarized EM waves in a beam-plasma system where a relativistic electron beam is guided by the ion channel.

Mirzanejhad, Saeed; Sohbatzadeh, Farshad; Ghasemi, Maede; Sedaghat, Zeinab; Mahdian, Zeinab [Department of Physics, Faculty of Science, Mazandaran University, 47416-95447 Babolsar (Iran, Islamic Republic of)

2010-05-15

182

The objective of this modeling and simulation study was to establish the role of stress wave interactions in the genesis of traumatic brain injury (TBI) from exposure to explosive blast. A high resolution (1 mm{sup 3} voxels), 5 material model of the human head was created by segmentation of color cryosections from the Visible Human Female dataset. Tissue material properties were assigned from literature values. The model was inserted into the shock physics wave code, CTH, and subjected to a simulated blast wave of 1.3 MPa (13 bars) peak pressure from anterior, posterior and lateral directions. Three dimensional plots of maximum pressure, volumetric tension, and deviatoric (shear) stress demonstrated significant differences related to the incident blast geometry. In particular, the calculations revealed focal brain regions of elevated pressure and deviatoric (shear) stress within the first 2 milliseconds of blast exposure. Calculated maximum levels of 15 KPa deviatoric, 3.3 MPa pressure, and 0.8 MPa volumetric tension were observed before the onset of significant head accelerations. Over a 2 msec time course, the head model moved only 1 mm in response to the blast loading. Doubling the blast strength changed the resulting intracranial stress magnitudes but not their distribution. We conclude that stress localization, due to early time wave interactions, may contribute to the development of multifocal axonal injury underlying TBI. We propose that a contribution to traumatic brain injury from blast exposure, and most likely blunt impact, can occur on a time scale shorter than previous model predictions and before the onset of linear or rotational accelerations traditionally associated with the development of TBI.

Ford, Corey C. (University of New Mexico, Albuquerque, NM); Taylor, Paul Allen

2008-02-01

183

Experiments To Assess Preheat In Blast-wave-driven Instability Experiments

NASA Astrophysics Data System (ADS)

The use of high-energy lasers has become an established means of driving laboratory astrophysical experiments. Such lasers can produce energy densities in sub-millimeter scales that allow one to explore the dynamics that occur in astrophysical systems containing strong shocks, such as supernovae. An experiment by the University of Michigan and collaborators has focused on hydrodynamic instabilities occurring at the H-He interface during a supernovae, by following the development of a scaled target interface. In the initial laser ablation of these targets, however, the laser pulse can interact with the plasma to create some unwanted energetic electrons and photons. This `extra’ energy can in turn heat the material interface ahead of the shock and causes an uncertainty in the initial conditions encountered by the blast wave. Additional experiments have been preformed in order to characterize this `preheat’ in similar target geometries under identical laser conditions. These experiment measured the optical emission and target surface motion ahead of the blast wave. An accurate assessment of preheating is essential to specify a target's pre-shock initial conditions to a high degree of accuracy, in order to better interpret the hydrodynamics experiment. This research was sponsored by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Research Grants DE-FG52-07NA28058, DE-FG52-04NA00064, and other grants and contracts.

Krauland, Christine; Kuranz, C.; Drake, R.; Grosskopf, M.; Campbell, D.; Boehly, T.

2008-05-01

184

Two-Dimensional Blast-Wave-Driven Rayleigh-Taylor Instability: Experiment and Simulation

NASA Astrophysics Data System (ADS)

This paper shows results from experiments diagnosing the development of the Rayleigh-Taylor instability with two-dimensional initial conditions at an embedded, decelerating interface. Experiments are performed at the Omega Laser and use ~5 kJ of energy to create a planar blast wave in a dense, plastic layer that is followed by a lower density foam layer. The single-mode interface has a wavelength of 50 ?m and amplitude of 2.5 ?m. Some targets are supplemented with additional modes. The interface is shocked then decelerated by the foam layer. This initially produces the Richtmyer-Meshkov instability followed and then dominated by Rayleigh-Taylor growth that quickly evolves into the nonlinear regime. The experimental conditions are scaled to be hydrodynamically similar to SN1987A in order to study the instabilities that are believed to occur at the He/H interface during the blast-wave-driven explosion phase of the star. Simulations of the experiment were performed using the FLASH hydrodynamics code.

Kuranz, C. C.; Drake, R. P.; Harding, E. C.; Grosskopf, M. J.; Robey, H. F.; Remington, B. A.; Edwards, M. J.; Miles, A. R.; Perry, T. S.; Blue, B. E.; Plewa, T.; Hearn, N. C.; Knauer, J. P.; Arnett, D.; Leibrandt, D. R.

2009-05-01

185

Computational Study of Thrust Generation from Laser-Driven Blast Wave

We have performed axisymmetric simulations in order to investigate the thrust generation resulting from the interference between the projectile and the blast wave produced by a pulsed laser. The results obtained by our numerical code well agree for the pressure history and the momentum coupling coefficient with the experimental data. In such analysis, it is found that the approximate impulse estimated only by the pressure history at the projectile base is difficult to predict the actual one. Since the shock wave rapidly attenuates in low fill pressure, and the interaction with the projectile almost finishes in the shroud, a high momentum coupling coefficient can be achieved unlike the case of high fill pressure in which the projectile experiences the subsequent negative thrust.

Ohnishi, Naofumi [Center for Research Strategy and Support, Tohoku University, Sendai 980-8579 (Japan); Department of Aerospace Engineering, Tohoku University, Sendai 980-8579 (Japan); Ogino, Yousuke [Department of Aerospace Engineering, Tohoku University, Sendai 980-8579 (Japan)

2008-04-28

186

Propagation and absorption of electromagnetic waves in fully relativistic plasmas

Electron cyclotron heating calculations were made for plasmas with electron temperatures above 10 keV. It was assumed that n/sub parallel/ = 0 so that Doppler broadening is not present and relativistic effects are maximum. The plasma distribution function is assumed to be an isotropic relativistic Maxwellian. (MOW)

Batchelor, D.B.; Goldfinger, R.C.; Weitzner, H.

1983-01-01

187

Numerical analysis of blast-induced wave propagation using FSI and ALEmulti-material formulations

As explosive blasts continue to cause casualties in both civil and military environments, there is a need to identify the dynamic interaction of blast loading with structures, to know the shock mitigating mechanisms and, most importantly, to identify the mechanisms of blast trauma. This paper examines the air-blast simulation using Arbitrary Lagrangian Eulerian (ALE) multi-material formulation. It will explain how

Mehdi Sotudeh Chafi; Ghodrat Karami; Mariusz Ziejewski

2009-01-01

188

NASA Astrophysics Data System (ADS)

In this paper, small but finite amplitude electrostatic solitary waves in a relativistic degenerate magnetoplasma, consisting of relativistically degenerate electrons and non-degenerate cold ions, are investigated. The Zakharov-Kuznetsov equation is derived employing the reductive perturbation technique and its solitary wave solution is analyzed. It is shown that only compressive electrostatic solitary structures can propagate in such a degenerate plasma system. The effects of plasma number density, ion cyclotron frequency, and direction cosines on the profiles of ion acoustic solitary waves are investigated and discussed at length. The relevance of the present investigation vis-a-vis pulsating white dwarfs is also pointed out.

Ata-ur-Rahman; Masood, W.; Eliasson, B.; Qamar, A.

2013-09-01

189

Numerical simulation of laser--target interaction and blast wave formation

A numerical hydrodynamics chemistry model to simulate the laser--targetinteraction experiment at the Naval Research Laboratory's PHAROS(/ital Laser//nteraction/ /ital and//elated/ /ital Plasma//henomena/ (Plenum, New York, 1986), Vol. 7,p. 857) is presented. Both laser--target and debris--background interactionsare modeled, solving mass continuity, total momentum, and separate ion andelectron internal energy equations. The model is appropriate for backgrounddensitiesgreater than or equal to1 Torr. To accurately treat both the early-time planar ablation andthe later spherical expansion of the blast wave, as well as the rear-side shockfront, an oblate spheroidal coordinate system was adopted. The aluminum targetablates into and interacts with an ambient nitrogen gas, filling the facilitychamber. The simulation models the target continuously from the solid state tothe state of a highly ionized nonequilibrium plasma, including all charge statesof aluminum and all charge states of the nitrogen background. The laser beam hasa wavelength of 1 ..mu.., a /similar to/5 nsec full width at half-maximum (FWHM), anintensity at the target surface /similar to/10/sup 13/ W/cm/sup 2/, and total energy varyingfrom 20--100 J. The model accurately reproduces the measured time-of-flightprofile and the mass of ablated aluminum. Expansion of the blast wave in themodel follows the ideal Sedov relation until radiation losses force a deviationdue to a failure in the constant energy assumption. In the shock wave region thesimulations show electron density of a few times 10/sup 18/ cm/sup /minus/3/, temperaturesranging from 10--20 eV, and dominant nitrogen species of N/sup +3/ and N/sup +4/,all in agreement with experimental measurement.

Giuliani, J. L., Jr.; Mulbrandon, M.; Hyman, E.

1989-07-01

190

National Technical Information Service (NTIS)

The blast-wave flows both outside and inside a power house of a nuclear-power generating station, from an accidental explosion of an explosive like TNT or its equivalent during transportation past the power house by a train, are studied numerically and as...

J. J. Gottlieb T. Saito K. Y. Zhang

1985-01-01

191

National Technical Information Service (NTIS)

A new protocol was developed for laboratory study of the interaction of hazardous bioaerosols with shock/blast waves. The method determined the viability of endospores as a function of shock strength (post-shock temperature) and used laser-based diagnosti...

J. B. Jeffries K. E. Mortelmans R. K. Hanson

2011-01-01

192

In the present paper, we have made an attempt to study the effects of the presence of a magnetic field on the cavity formation inside a blast wave propagating into a perfectly conducting gas with density varying as some power of distance from the plane or line of explosion. In order to obtain the closed form solutions for the flow

J. P. Vishwakarma; A. K. Yadav

2003-01-01

193

Discrete phase space - I: Variational formalism for classical relativistic wave fields

NASA Astrophysics Data System (ADS)

The classical relativistic wave equations are presented as partial difference equations in the arena of covariant discrete phase space. These equations are also expressed as difference-differential equations in discrete phase space and continuous time. The relativistic invariance and covariance of the equations in both versions are established. The partial difference and difference-differential equations are derived as the Euler-Lagrange equations from the variational principle. The difference and difference-differential conservation equations are derived. Finally, the total momentum, energy, and charge of the relativistic classical fields satisfying difference-differential equations are computed.

Das, A.

194

NASA Astrophysics Data System (ADS)

To combat the problem of traumatic brain injury (TBI), a signature injury of the current military conflicts, there is an urgent need to design head protection systems with superior blast/ballistic impact mitigation capabilities. Toward that end, the blast impact mitigation performance of an advanced combat helmet (ACH) head protection system equipped with polyurea suspension pads and subjected to two different blast peak pressure loadings has been investigated computationally. A fairly detailed (Lagrangian) finite-element model of a helmet/skull/brain assembly is first constructed and placed into an Eulerian air domain through which a single planar blast wave propagates. A combined Eulerian/Lagrangian transient nonlinear dynamics computational fluid/solid interaction analysis is next conducted in order to assess the extent of reduction in intra-cranial shock-wave ingress (responsible for TBI). This was done by comparing temporal evolutions of intra-cranial normal and shear stresses for the cases of an unprotected head and the helmet-protected head and by correlating these quantities with the three most common types of mild traumatic brain injury (mTBI), i.e., axonal damage, contusion, and subdural hemorrhage. The results obtained show that the ACH provides some level of protection against all investigated types of mTBI and that the level of protection increases somewhat with an increase in blast peak pressure. In order to rationalize the aforementioned findings, a shockwave propagation/reflection analysis is carried out for the unprotected head and helmet-protected head cases. The analysis qualitatively corroborated the results pertaining to the blast-mitigation efficacy of an ACH, but also suggested that there are additional shockwave energy dissipation phenomena which play an important role in the mechanical response of the unprotected/protected head to blast impact.

Grujicic, M.; Bell, W. C.; Pandurangan, B.; Glomski, P. S.

2011-08-01

195

Modulational behavior of electromagnetic waves in ultra-relativistic electron-positron plasmas

NASA Astrophysics Data System (ADS)

The dynamical properties of electromagnetic (EM) waves in ultra-relativistic electron-positron (EP) plasmas are analytically investigated on the basis of the nonlinear governing equations obtained from a kinetic way. It is shown that the EM wave envelope will collapse and be trapped into a localized region for the modulation interaction with low frequency density variation induced by ponderomotive force. The correlation between the localized strong wave field and the pulsar radio emission is discussed.

Liu, Y.; Liu, S. Q.; Dai, B.

2013-07-01

196

Simulations of Magnetic Field Generation in Laser-Produced Blast Waves

NASA Astrophysics Data System (ADS)

Magnetic fields are ubiquitous in the Universe. The origin of these fields and process by which they are amplified are not fully understood, although amplification is thought to involve turbulence. Experiments being conducted at medium-scale laser facilities (such as the LULI laser the Janus laser) can investigate the self-generation of magnetic fields under conditions that resemble astrophysical shocks. In these experiments, two 527 nm, 1.5 ns long laser beams are focused onto a 500 ?m diameter graphite rod producing an explosion and asymmetric blast wave into a Helium filled chamber. A variety of diagnostics measure the velocity, electron density, and show that a large scale magnetic field is produced. We report preliminary hydrodynamic and MHD simulations using FLASH of a simplified version of the experiment. The results provide insights into the origin and generation of the magnetic field.

Lamb, D.; Fatenejad, M.; Gregori, G.; Miniati, F.; Park, H.-S.; Remington, B.; Ravasio, A.; Koenig, M.; Murphy, C. D.

2011-11-01

197

The effect of blast wave re-focusing on a laser-induced plasma

NASA Astrophysics Data System (ADS)

The effect of laser-induced plasma confinement on lifetime and temperature is reported using cylindrical reflectors. This is determined experimentally in a gas cell, with hydrogen as test gas, and cylindrical shock reflectors of different diameters. The temperature evolution of confined and unconfined laser-induced plasma has been measured using plasma emission spectroscopy. Temperatures were determined through the plasma line-to-continuum thermometry technique in the hydrogen Balmer series using the H? and H? transitions at ? = 656 nm and ? = 486 nm, respectively. The experiments found that re-focusing the blast wave can significantly increase temperatures during the exponential decay of the plasma. The experimental results also show that confinement increases peak plasma temperatures, and that plasma lifetimes are only marginally affected by the confinement.

Brieschenk, Stefan; Kleine, Harald; O'Byrne, Sean

2013-03-01

198

Effects of Turbulence on Taylor-Sedov Blast Waves in Radially-Symmetric Geometries

NASA Astrophysics Data System (ADS)

Progress in extending studies of the classical Taylor--Sedov blast wave problem by incorporating effects due to turbulence is reported. Investigations consist of the analytical development and initial numerical findings describing the evolution of large and instantaneous energy releases from point explosions (in radially-symmetric systems) while coupling turbulent instabilities. The closure of the Reynolds-Favre averaged mean flow equations is accomplished using a K-- ? model in the gradient diffusion approximation. To reduce the complexity of the problem, self-similar analysis is used to reduce the space-time dependent system of partial differential equations to coupled, nonlinear ordinary differential equations in the self-similarity variable. Preliminary approximations considered in the problem are also discussed.

Moran-Lopez, Tiberius; Zaide, Daniel; Holloway, James; Schilling, Oleg

2009-11-01

199

NASA Astrophysics Data System (ADS)

We study the self-modulation of a circularly polarized Alfvén wave in a strongly magnetized relativistic electron-positron plasma with finite temperature. This nonlinear wave corresponds to an exact solution of the equations, with a dispersion relation that has two branches. For a large magnetic field, the Alfvén branch has two different zones, which we call the normal dispersion zone (where d?/dk>0) and the anomalous dispersion zone (where d?/dk<0). A nonlinear Schrödinger equation is derived in the normal dispersion zone of the Alfvén wave, where the wave envelope can evolve as a periodic wave train or as a solitary wave, depending on the initial condition. The maximum growth rate of the modulational instability decreases as the temperature is increased. We also study the Alfvén wave propagation in the anomalous dispersion zone, where a nonlinear wave equation is obtained. However, in this zone the wave envelope can evolve only as a periodic wave train.

López, Rodrigo A.; Asenjo, Felipe A.; Muñoz, Víctor; Chian, Abraham C.-L.; Valdivia, J. A.

2013-08-01

200

We study the self-modulation of a circularly polarized Alfvén wave in a strongly magnetized relativistic electron-positron plasma with finite temperature. This nonlinear wave corresponds to an exact solution of the equations, with a dispersion relation that has two branches. For a large magnetic field, the Alfvén branch has two different zones, which we call the normal dispersion zone (where d?/dk>0) and the anomalous dispersion zone (where d?/dk<0). A nonlinear Schrödinger equation is derived in the normal dispersion zone of the Alfvén wave, where the wave envelope can evolve as a periodic wave train or as a solitary wave, depending on the initial condition. The maximum growth rate of the modulational instability decreases as the temperature is increased. We also study the Alfvén wave propagation in the anomalous dispersion zone, where a nonlinear wave equation is obtained. However, in this zone the wave envelope can evolve only as a periodic wave train. PMID:24032950

López, Rodrigo A; Asenjo, Felipe A; Muñoz, Víctor; Chian, Abraham C-L; Valdivia, J A

2013-08-19

201

ON THE AMPLIFICATION OF MAGNETIC FIELD BY A SUPERNOVA BLAST SHOCK WAVE IN A TURBULENT MEDIUM

We have performed extensive two-dimensional magnetohydrodynamic simulations to study the amplification of magnetic fields when a supernova blast wave propagates into a turbulent interstellar plasma. The blast wave is driven by injecting high pressure in the simulation domain. The interstellar magnetic field can be amplified by two different processes, occurring in different regions. One is facilitated by the fluid vorticity generated by the 'rippled' shock front interacting with the background turbulence. The resulting turbulent flow keeps amplifying the magnetic field, consistent with earlier work. The other process is facilitated by the growth of the Rayleigh-Taylor instability at the contact discontinuity between the ejecta and the shocked medium. This can efficiently amplify the magnetic field and tends to produce the highest magnetic field. We investigate the dependence of the amplification on numerical parameters such as grid-cell size and on various physical parameters. We show that the magnetic field has a characteristic radial profile such that the downstream magnetic field gets progressively stronger away from the shock. This is because the downstream magnetic field needs a finite time to reach the efficient amplification, and will get further amplified in the Rayleigh-Taylor region. In our simulation, we do not observe a systematic strong magnetic field within a small distance to the shock. This indicates that if the magnetic-field amplification in supernova remnants indeed occurs near the shock front, other processes such as three-dimensional instabilities, plasma kinetics, and/or cosmic ray effect may need to be considered to explain the strong magnetic field in supernova remnants.

Guo Fan; Li Shengtai; Li Hui; Li, David [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Giacalone, Joe; Jokipii, J. R. [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721 (United States)

2012-03-10

202

NASA Astrophysics Data System (ADS)

We investigate the propagation of electromagnetic waves in resistive e± pair plasmas using a one-fluid theory derived from the relativistic two-fluid equations. When the resistivity normalized by the electron/positron inertia variable exceeds a critical value, the dispersion relation for electromagnetic waves shows that the group velocity is larger than the light speed in vacuum. However, in such a case, it also is found that the plasma parameter is less than unity: that is, the electron-positron pair medium no longer can be treated as plasma. Thus, the simple two-fluid approximation is invalid. This confirms that superluminal propagation of electromagnetic wave is forbidden in a plasma—a conclusion consistent with the relativistic principle of causality. As an alternative, we propose a new set of equations for “causal relativistic magnetohydrodynamics,” which both have nonzero resistivity and yet are consistent with the causality principle.

Koide, Shinji

2008-12-01

203

Classification and stability of plasma motion in periodic linearly polarized relativistic waves

Based on a relativistic fluid-Maxwell model, laser-induced plasma dynamics is investigated for relativistic periodic waves. Within a one-dimensional (1D) description, the Akhiezer-Polovin model is applied to the existence of periodic, nonlinearly coupled electromagnetic and electrostatic waves, and the corresponding particle motion. Known existence criteria for periodic solutions are generalized. The corresponding stability behaviors are investigated by 1D integrators of the relativistic fluid-Maxwell model. It is shown that in contrast to the vacuum solution, linearly polarized coupled electromagnetic-electrostatic waves are unstable in plasmas. The magnitudes of the growth rates are investigated in terms of the maximum amplitudes and normalized phase velocities.

Lehmann, G.; Spatschek, K. H. [Institut fuer Theoretische Physik, Heinrich-Heine-Universitaet Duesseldorf, D-40225 Duesseldorf (Germany)

2010-07-15

204

Dual precipitation of relativistic electrons and ring current ions by EMIC waves

NASA Astrophysics Data System (ADS)

We show evidence that EMIC (electro-magnetic ion cyclotron) waves cause coincident scattering of both ring current ions and radiation belt electrons at subaurora latitude using comprehensive data sets of ground search coil magnetometer, all sky camera, precipitating particles and ther-mal plasma structure measured by low-altitude satellites. The isolated proton aurora caused by precipitated ions was appeared concurrently with the intense EMIC (Pc1) waves. At this time, the isolated precipitation of relativistic electrons was identified. Theoretical estimation based on the observed wave-parameters supports that the observed EMIC waves actually cause coincident ions and electrons. We statistically confirm that the coincident precipitation of ring current ions and relativistic electrons occurs associated with EMIC waves in the half of isolated proton precipitation events.

Miyoshi, Yoshizumi; Sakaguchi, Kaori; Shiokawa, Kazuo; Albert, Jay; Evans, David; Connors, Martin; Jordanova, Vania

205

Relativistic backward-wave tube with mechanically tunable generation frequency over a 14% range

NASA Astrophysics Data System (ADS)

A tunable-frequency low-magnetic-field relativistic microwave oscillator is realized experimentally based on a relativistic backward-wave tube with a modulating resonance reflector. The generated frequency is tuned mechanically by moving the oscillator slow-wave structure relative to the reflector. At fixed parameters of the corrugations and of the electron bunch, a frequency tuning range of about 14% measured between -3-dB (relative to the maximum peak generated microwave power) points is realized. The maximum pulse power of 3.4 ± 0.7 GW was obtained at a carrier frequency of 3.65 GHz in a magnetic field of 0.44 T.

Tot'meninov, E. M.; Vykhodtsev, P. V.; Kitsanov, S. A.; Klimov, A. I.; Rostov, V. V.

2011-07-01

206

Two dimensional electrostatic shock waves in relativistic electron positron ion plasmas

Ion-acoustic shock waves (IASWs) are studied in an unmagnetized plasma consisting of electrons, positrons and hot ions. In this regard, Kadomtsev-Petviashvili-Burgers (KPB) equation is derived using the small amplitude perturbation expansion method. The dependence of the IASWs on various plasma parameters is numerically investigated. It is observed that ratio of ion to electron temperature, kinematic viscosity, positron concentration, and the relativistic ion streaming velocity affect the structure of the IASW. Limiting case of the KPB equation is also discussed. Stability of KPB equation is also presented. The present investigation may have relevance in the study of electrostatic shock waves in relativistic electron-positron-ion plasmas.

Masood, W.; Rizvi, H. [Theoretical Plasma Physics Division, PINSTECH, P.O. Nilore, Islamabad 54000 (Pakistan)

2010-05-15

207

NASA Astrophysics Data System (ADS)

In this work I studied the nature and important effects of massive galaxy cluster merger phenomena. Due to inherent complexity of such events analytical solution is impossible, so, numerical simulations are performed using ENZO-2.1 hydrodynamic code. It is noticed that the formation of Mega parsec scale merger shocks in such events substantially change the energy distribution of Inter Cluster Medium. A striking similarity is noticed between expanding intra cluster medium during mergers with the blast wave formation in supernovae explosion. The blast wave meets the void/ accretion shocks when propagated out to the virial radius. Particle acceleration at the meeting point produce a significant amount of synchrotron radio emission through which curved shocks are made visible in radio waves. This study thus also sheds some light on the formation of curved and nearly symmetric radio emission found in Abell 3376, Abell 3667, CIZA J2242.8+5301, plck g287.0+32.9 etc. clusters.

Paul, Surajit

2012-12-01

208

NASA Astrophysics Data System (ADS)

To understand the resonant acceleration of magnetospheric relativitic electrons by ULF waves, we need to combine the observations and simulations together. Recent work by Tan et al. [2004] showed that an interval of enhanced relativistic-electron fluxes (by up to an order-of-magnitude) was observed simultaneously with strong Pc-5 ULF oscillations, whose electric field is mainly in the radial direction. The acceleration continues for more than 2 hours. Elkington et al. [2003] suggested that the interaction of magnetospheric relativistic electrons and the global toroidal mode ULF wave (with radial electric field component) in a a simple compressed dipole model can result in resonant acceleration. In this paper, we use particle tracing simulation to investigate the acceleration of relativistic electrons by ULF waves locally concentrated on dawn-dusk flanks in a more realistic magnetosphere. The relation between the spectrum of the ULF wave and the drift period of acclerated electrons will be discussed. The simulation model was then applied to understand the interval reported in Tan et al. [2004] by incorporating the electric field observed by CRRES satellite. Tan L. C., Shing F. Fung, and X. Shao, Space Observation of Magnetospheric Relativistic Electrons Accelerated by Pc-5 ULF Waves, this AGU meeting, Spring, 2004. Elkington, S. R., et al., Resonant acceleration and diffusion of outer zone electrons in an asymmetric geomagnetic field, J. Geophys. Res., 108 (A3), 2003.

Shao, X.; Fung, S.; Tan, L.

2004-05-01

209

Relativistic surface-wave generators based on two-dimensional periodic structures

NASA Astrophysics Data System (ADS)

In order to increase the integral output radiation power of relativistic surface-wave generators, it is suggested to use two-dimensional (2D) periodic slow-wave systems. Numerical simulations of dynamics of a new variant of these generators showed that additional wave beams, which appear in the 2D structure and propagate in the transverse direction, are capable of synchronizing radiation from a wide sheet electron beam. This circumstance makes it possible to implement surface-wave generators operating in the millimeter wavelength range at a gigawatt power level—e.g., based on the ELMI high-current accelerator at the Institute of Nuclear Physics (Novosibirsk).

Ginzburg, N. S.; Zaslavskii, V. Yu.; Malkin, A. M.; Sergeev, A. S.

2012-02-01

210

Invited review: Relativistic wave-function based electron correlation methods

NASA Astrophysics Data System (ADS)

Recent developments in molecular relativistic electronic-structure theory are reviewed, with a particular emphasis on post-Hartree-Fock electron correlation methodology. The approaches discussed encompass methods devised for the treatment of small molecules, such as four-component coupled cluster of general excitation rank, ranging to two-component methods based on perturbation theory which are applicable to larger molecules. A critique of the merits and shortcomings of the available methodology is put forward, including a comparison where appropriate.

Fleig, Timo

2012-02-01

211

Relativistic three-centimeter backward-wave tube with 3 GW pulse power

NASA Astrophysics Data System (ADS)

In this paper, we present the results of investigations of a uniform three-centimeter relativistic backward-wave tube (BWT) with circular waveguide operating mode E01 with pulse power 3 GW and efficiency about 20%. We have obtained a dependence of the radiation pulse duration on the generated power. We discuss the problems involved in shortening the duration of the microwave pulses in oscillators with high microwave field intensity on the surface of the slow-wave structure.

Gunin, A. V.; Kitsanov, S. A.; Klimov, A. I.; Korovin, S. D.; Pegel', I. V.; Polevin, S. D.; Roitman, A. M.; Rostov, V. V.; Stepchenko, A. S.; Sukhov, M. Yu.

1996-12-01

212

A detailed study of entropy jump across shock waves in relativistic fluid dynamics

Summary A detailed study of the function ? which characterizes entropy jump across shock waves is carried out for relativistic hydrodynamics\\u000a at thermal equilibrium. It is shown that the function ? is defined only if the normal velocity of the shock waves does not\\u000a exceed the speed of light in vacuo, consistently with the claims of relativity; moreover, the entropy jump

A. Strumia

1986-01-01

213

Notes on possible S-wave resonances in relativistic two-particle systems.

National Technical Information Service (NTIS)

Some models of relativistic two-particle systems are examined for possible irregularities in the S-wave continuous spectrum. None are found, though we show that with singular effective interaction potentials it is quite easy to run into artificial resonan...

D. V. Shapoval I. V. Simenog O. G. Sitenko

1993-01-01

214

Identifying invariance properties helps in simplifying calculations and consolidating concepts. Presently the Special Relativistic invariance of dispersion relations and their associated scalar wave operators is investigated for general dispersive homogeneous linear media. Invariance properties of the four-dimensional Fourier- transform integrals is demonstrated, from which the invariance of the scalar Green- function is inferred. Dispersion relations and the associated group velocities

Dan Censor

2009-01-01

215

On Electron-Cyclotron Waves in Relativistic Non-Thermal Tokamak Plasmas

Waves propagating at an arbitrary angle to the steady magnetic field in fully relativistic plasmas with a small population of superthermal particles are investigated. It is found that for arbitrary N|| -values, a noticeable increase of the plasma cut-off density occurs with the increase of the weight and temperature of the superthermal tail. Its presence does not change the features

Lj. Nikoli?; M. M. Škori?

216

Two-fluid relativistic waves and free electron lasers in pulsar plasmas

A relativistic two-fluid approach for a streaming magnetized pair plasma is developed. Such a scenario corresponds to secondary plasmas created at the polar caps of pulsar magnetospheres. Recent studies show that the temperature of such plasmas is very close to the rest mass energy of the particles. It is therefore critical to determine the exact properties of waves at such

A. Rualdo Soto-Chavez; Swadesh M. Mahajan; Richard D. Hazeltine

2010-01-01

217

A compact P-band coaxial relativistic backward wave oscillator with three periods slow wave structure was investigated experimentally. The experimental results show that the frequency of the P-band coaxial relativistic backward wave oscillator is 897 MHz and the microwave power is 1.47 GW with an efficiency of about 32% in the case in which the diode voltage is 572 kV, the beam current is 8.0 kA, and the guide magnetic field is about 0.86 T. In addition, the device can generate a 3.14 GW microwave radiation as the guide magnetic field increases to 1.2 T at the diode voltage of 997 kV and the beam current of 15.3 kA. The experimental results are in good agreement with those obtained earlier by numerical simulations.

Gao Liang; Qian Baoliang; Ge Xingjun; Zhang Xiaoping; Jin Zhenxing [College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2012-08-15

218

NASA Astrophysics Data System (ADS)

A comprehensive methodology to accurately predict the dynamic response of composite panels under blast wave pressure loading has been successfully developed for the first time. It includes the modeling of geometrically nonlinear dynamic effect, progressive failure and strain-rate effect on constitutive equation and strength. For dynamic analysis, a nonlinear solid shell element formulation is combined with the trapezoidal rule for numerical integration in time. The progressive damage incorporates the effect of the material failure, such as fiber failure, matrix cracking and fiber-matrix shearing failure on the stiffness and strength. Material degradation models based on the rule of mixtures are proposed for each failure mode. To implement the strain-rate effect on the constitutive equation of the material, a viscoplastic model is adopted. In this model, three material parameters are determined by conducting uniaxial tension tests on off-axis specimen. The effect of strain rates on material strength is implemented via the linear least square fit of the test data. A key ingredient of the analysis is a geometrically nonlinear solid shell element based on the assumed strain formulation to alleviate element locking. In this approach, the composite shell is treated as a three-dimensional solid. Accordingly, the change of shell thickness is allowed and the kinematics of deformation is described by six vector components at a point on the shell midsurface. The mass matrix always remains constant during the analysis. Example problems under static and dynamic loadings are solved to investigate the behavior of composite panels undergoing large deformation while experiencing material damage. The analysis results are compared with the test data available. Results of the numerical analysis show that the effect of the progressive failure and strain-rates on structural responses are considerable. For a composite plate under static pressure loadings, maximum displacement and structural collapse load match well with the experimental data when the progressive failure effect is included. For a composite panel under blast wave loadings, the maximum displacements obtained by numerical analysis are in good agreement with the test data.

Park, Hun

219

We present a fully relativistic model for polarized inclusive quasielastic proton-nucleus scattering that includes relativistic distorted waves for the projectile and ejectile (RDWIA), as well as the relativistic random-phase approximation (RPA) applied to the target nucleus. Using a standard relativistic impulse approximation treatment of quasielastic scattering and a two-body Scalar, Pseudoscalar, Vector, Axial vector, Tensor (SPVAT) form of the current operator, it is shown how the behavior of the projectile/ejectile and target can be decoupled. Distortion effects are included via a full partial-wave expansion of the relativistic wave functions. Target correlations are included via the relativistic RPA applied to mean-field theory in quantum hadrodynamics. A number of novel analytical and numerical techniques are employed to aid in this highly nontrivial calculation. A baseline plane-wave calculation is performed for the reaction {sup 40}Ca(p-vector,p-vector{sup '}) at an energy of 500 MeV and an angle {theta}{sub c.m.}=40 deg. Here it is found that the effect of isoscalar correlations is a quenching of the cross section that is expected to become more pronounced at lower energies or for higher-density targets. A RDWIA calculation shows additional reduction and if isoscalar target correlations are included this effect is enhanced.

Niekerk, D. D. van; Ventel, B. I. S. van der; Titus, N. P.; Hillhouse, G. C. [Department of Physics, Stellenbosch University, Private Bag X1, Matieland 7602 (South Africa); University for Information Science and Technology, Building at ARM, Partizanska Street, Ohrid 6000 (Macedonia, The Former Yugoslav Republic of)

2011-04-15

220

We present analysis and modeling of X-ray spectra from the blast wave shock of DEM L71 in the Large Magellanic Cloud. This remnant exhibits widespread Balmer-dominated emission characteristic of nonradiative shocks in partially neutral gas. We have used Chandra ACIS-S data and optical Fabry-Pérot spectra of the blast wave to measure the electron and proton temperatures, respectively. In principle, when

Cara E. Rakowski; Parviz Ghavamian; John P. Hughes

2003-01-01

221

NASA Astrophysics Data System (ADS)

In this work several relevant parameters and properties for krypton and xenon plasmas are analyzed, such as, for example, the average ionization, the plasma thermodynamic regimes, the radiative power losses and the mean opacities. This analysis is performed in a range of density and temperature typically found in laboratory experiments to generate radiative blast waves in laser-heated clustered plasmas. A polynomial fit of those parameters is also presented. Finally an analysis of the thermal cooling instability is performed.

Rodriguez, R.; Gil, J. M.; Espinosa, G.; Florido, R.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Symes, D. R.; Hohenberger, M.; Smith, R. A.

2012-04-01

222

Design of jet-driven, radiative-blast-wave experiments for 10 kJ class lasers

We discuss the design of jet-driven, radiative-blast-wave experiments for a 10 kJ class pulsed laser facility. The astrophysical\\u000a motivation is the fact that jets from Young Stellar Objects are typically radiative and that the resulting radiative bow shocks\\u000a produce complex structure that is difficult to predict. To drive a radiative bow shock, the jet velocity must exceed the threshold\\u000a for strong

R. P. Drake; J. P. Knauer

2009-01-01

223

Design of jet-driven, radiative-blast-wave experiments for 10 kJ class lasers

We discuss the design of jet-driven, radiative-blast-wave experiments for a 10 kJ class pulsed laser facility. The astrophysical motivation is the fact that jets from Young Stellar Objects are typically radiative and that the resulting radiative bow shocks produce complex structure that is difficult to predict. To drive a radiative bow shock, the jet velocity must exceed the threshold for

R. P. Drake; J. P. Knauer

2009-01-01

224

Laser driven high energy density radiative blast waves launched in clustered gases

NASA Astrophysics Data System (ADS)

Intense lasers deposit energy efficiently in clustered gases creating hot plasma with low density, conditions ideal for launching radiative blast waves (BWs) of interest for laboratory astrophysics (LA). We report measurements in a range of gases irradiated by the Astra-Gemini laser with energies >10J. Optical imaging, self emission and temporally resolved x-ray spectra are used to characterise BW evolution. The high repetition rate of the laser allows us to explore the influence of atomic number and density on the BW dynamics. Altering the emitted radiation and opacity of the medium has a strong effect on the BW profile and energy loss. Strongly radiative BWs exhibit shell thinning, increasing their susceptibility to instabilities. We have demonstrated the onset of a velocity instability, driven by the exchange of energy between the shock and precursor in krypton BWs. We discuss the threshold conditions for this behaviour and the potential to study spatial shock front instabilities. Our results will be compared to simulations and analytical calculations with a view to designing scalable LA experiments.

Olsson-Robbie, Stefan; Doyle, Hugo; Lowe, Hazel; Price, Chris; Bigourd, Damien; Patankar, Siddharth; Mecseki, Katalin; Booth, Nicola; Scott, Robbie; Moore, Alastair; Hohenberger, Matthias; Rodriguez, Rafael; Gumbrell, Edward; Symes, Daniel; Smith, Roland

2012-10-01

225

New similarity solutions are presented for the structure of supernova blast waves driven by clumped supernova ejecta. The solutions are obtained using a spherically symmetric two-fluid hydrodynamic model in which clumps of ejecta stream through diffuse background gas. The clumps couple to the diffuse gas through mass ablation and the associated momentum and energy transfer. The most striking difference between these solutions and previous solutions is that clumps may move ahead of the shock front in the ambient medium, leading a precursor which heats the medium in advance of the main shock. The results appear to provide a natural explanation for the X-ray halo seen in Cas A and for various other aspects of the morphology of this supernova remnant. The difference between Cas A and remnants such as Tycho, in which clumps of ejecta are only observed within the confines of an interstellar shock front, may be explained by differences in evolutionary epoch, or differences in the structure of the ambient medium, or intrinsic differences in the clumps.

Hamilton, A.J.S.

1985-04-15

226

The dispersion relation for circularly polarized electromagnetic waves propagating in the direction of an external magnetic field in a relativistic electron-positron plasma with arbitrary constant drift velocities is obtained for constant temperature in the homentropic regime. This result is an exact solution of the nonlinear magnetofluid unification field formalism introduced by S. Mahajan [Phys. Rev. Lett. 90, 035001 (2003)], where the electromagnetic and fluid fields are coupled through the relativistic enthalpy density. The behavior of electromagnetic and Alfven branches of the dispersion relation are discussed for different temperatures.

Asenjo, Felipe A.; Munoz, Victor; Valdivia, Juan Alejandro [Departamento de Fisica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Hada, Tohru [Department of Earth System Science and Technology, Kyushu University, Fukuoka 816-8580 (Japan)

2009-12-15

227

Frequency multiplication of light back-reflected from a relativistic wake wave

A method of coherent high-frequency electromagnetic radiation generation, proposed by Bulanov, Esirkepov, and Tajima [Phys. Rev. Lett. 91, 085001 (2003)], is experimentally demonstrated. This method is based on the radiation frequency multiplication during reflection at a mirror flying with relativistic velocity. The relativistic mirror is formed by the electron density modulations in a strongly nonlinear wake wave, excited in an underdense plasma in the wake behind an ultrashort laser pulse. In our experiments, the reflection of a countercrossing laser pulse from the wake wave is observed. The detected frequency multiplication factor is in the range from 55 to 114, corresponding to a reflected radiation wavelength from 7 to 15 nm. This may open a way towards tunable high-intensity sources of ultrashort coherent electromagnetic pulses in the extreme ultraviolet and x-ray spectral regions. Parameters of the reflecting wake wave can be determined using the reflected radiation as a probe.

Pirozhkov, A. S.; Ma, J.; Kando, M.; Esirkepov, T. Zh.; Fukuda, Y.; Chen, L.-M.; Daito, I.; Ogura, K.; Homma, T.; Hayashi, Y.; Kotaki, H.; Sagisaka, A.; Mori, M.; Koga, J. K.; Kawachi, T.; Daido, H.; Bulanov, S. V.; Kimura, T.; Kato, Y.; Tajima, T. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemidai, Kizugawa, Kyoto 619-0215 (Japan)

2007-12-15

228

Relativistic effects on cyclotron wave absorption by an energetic electron tail in the PLT tokamak

Electron cyclotron wave absorption by mildly relativistic electrons in the low density regime of the PLT tokamak is investigated. Appreciable wave damping is found for vertical propagation at frequencies of 50, 60, and 70 GHz when the spatially constant cyclotron frequency is 89 GHz. The perpendicular temperature T/sub perpendicular/(v/sub parallel/) of the fast tail is also measured from emission of radiation in the same direction. The results obtained are in satisfactory agreement with the theory of wave emission and absorption.

Mazzucato, E.; Efthimion, P.; Fidone, I.

1984-07-01

229

We present the effective range expansions for the 1S0 and 3S1 scattering phase shifts, and the relativistic deuteron wave functions that accompany our recent high precision fits (with \\chi^2/N{data} \\simeq 1) to the 2007 world np data below 350 MeV. The wave functions are expanded in a series of analytical functions (with the correct asymptotic behavior at both large and small arguments) that can be Fourier-transformed from momentum to coordinate space and are convenient to use in any application. A fortran subroutine to compute these wave functions can be obtained from the authors.

Franz Gross, Alfred Stadler

2010-09-01

230

A dual-resonant reflector in powerful relativistic backward wave oscillator

A dual-resonant reflector is proposed to suppress the radio frequency breakdown and enhance the reflection in a high power relativistic backward wave oscillator. The backward wave is reflected by two reflector cavities step by step, therefore, a high reflectivity is obtained. A preliminary high power microwave generation experiment of backward wave oscillator (BWO) with a general resonant reflector and a dual-resonant reflector was carried out. A microwave with power over 3 GW, frequency 9.6 GHz, efficiency 30%, and pulse width 22 ns was generated. The experiment results show that the efficiency of BWO with a dual-RR is enhanced about 2%-6%.

Song Wei; Chen Changhua; Zhang Ligang; Hu Yongmei; Yang Meng; Zhang Xiaowei; Zhang Lijun [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an, Shanxi 710024 (China)

2011-06-15

231

In the present work large amplitude electromagnetic waves in cold plasmas at relativistic intensities are studied analytically in a plane wave geometry. Special attention is drawn to the nonlinear coupling of electromagnetic and electrostatic modes. In the framework of the Akhiezer-Polovin model, periodic and more general quasiperiodic waves are taken into account. For small densities a two-time-scale method is used to calculate an analytical solution up to the fourth order in the plasma density. Nonlinear dispersion relations are calculated for coupled waves, taking into account the full plasma response for linear as well as for circular polarization. In the presence of a large amplitude electrostatic wave, the results show a major difference from the commonly considered dispersion relation for electromagnetic waves. Finally, the solutions of the Akhiezer-Polovin model are compared with particle-in-cell simulations.

Pesch, T. C.; Kull, H.-J. [Institute of Theoretical Physics A, RWTH Aachen University, Templergraben 55, 52056 Aachen (Germany)

2010-01-15

232

Compression-related EMIC waves and associated precipitation of relativistic electrons

NASA Astrophysics Data System (ADS)

In this paper, we have presented observations of solar wind compression-related dayside electromagnetic ion cyclotron (EMIC) waves and associated precipitation of relativistic electrons on Jan 1, 2007. Dayside structured EMIC waves were observed by the Finish network of search coil magnetometers for several hours during the period of enhanced solar wind compression. Simultaneously, NOAA 15 and NOAA 16 satellites passing through the region of EMIC wave activity and registered a localized enhancements of precipitating electrons flux with energies >3MeV .While in this region, precipitations of protons with energies >30 keV enhanced. The footprints of NOAA 15 and NOAA 16 during this precipitation event fit well with the Finish network of search coil magnetometers observing Pc1 waves simultaneously. Since such a Pc1 wave can be considered as a signature of an EMIC wave propagating off the equatorial plane to low altitudes. Our observations suggest that compression-related EMIC waves can interact with relativistic electrons and cause them to precipitate into the atmosphere.

Wang, Dedong; Yuan, Zhigang; Deng, Xiaohua; Zhou, Meng; Huang, Shiyong

2013-04-01

233

Relativistic warm plasma theory of nonlinear laser-driven electron plasma waves.

A relativistic, warm fluid model of a nonequilibrium, collisionless plasma is developed and applied to examine nonlinear Langmuir waves excited by relativistically intense, short-pulse lasers. Closure of the covariant fluid theory is obtained via an asymptotic expansion assuming a nonrelativistic plasma temperature. The momentum spread is calculated in the presence of an intense laser field and shown to be intrinsically anisotropic. Coupling between the transverse and longitudinal momentum variances is enabled by the laser field. A generalized dispersion relation is derived for Langmuir waves in a thermal plasma in the presence of an intense laser field. Including thermal fluctuations in three-velocity-space dimensions, the properties of the nonlinear electron plasma wave, such as the plasma temperature evolution and nonlinear wavelength, are examined and the maximum amplitude of the nonlinear oscillation is derived. The presence of a relativistically intense laser pulse is shown to strongly influence the maximum plasma wave amplitude for nonrelativistic phase velocities owing to the coupling between the longitudinal and transverse momentum variances. PMID:20866340

Schroeder, C B; Esarey, E

2010-05-13

234

NASA Astrophysics Data System (ADS)

The variational method in a reformulated Hamiltonian formalism of quantum electrodynamics (QED) is used to derive relativistic wave equations for systems consisting of n fermions and antifermions of various masses. The derived interaction kernels of these equations include one-photon exchange interactions. The equations have the expected Schrödinger non-relativistic limit. Application to some exotic few lepton systems is discussed briefly.

Emami-Razavi, Mohsen; Bergeron, Nantel; Darewych, Jurij W.

2012-11-01

235

Smooth Light Curves from a Bumpy Ride: Relativistic Blast Wave Encounters a Density Jump

Some gamma-ray burst (GRB) afterglow light curves show significant variability, which often includes episodes of rebrightening. Such temporal variability had been attributed in several cases to large fluctuations in the external density, or density ''bumps''. Here we carefully examine the effect of a sharp increase in the external density on the afterglow light curve by considering, for the first time, a full treatment of both the hydrodynamic evolution and the radiation in this scenario. To this end we develop a semi-analytic model for the light curve and carry out several elaborate numerical simulations using a one dimensional hydrodynamic code together with a synchrotron radiation code. Two spherically symmetric cases are explored in detail--a density jump in a uniform external medium, and a wind termination shock. The effect of density clumps is also constrained. Contrary to previous works, we find that even a very sharp (modeled as a step function) and large (by a factor of a >> 1) increase in the external density does not produce sharp features in the light curve, and cannot account for significant temporal variability in GRB afterglows. For a wind termination shock, the light curve smoothly transitions between the asymptotic power laws over about one decade in time, and there is no rebrightening in the optical or X-rays that could serve as a clear observational signature. For a sharp jump in a uniform density profile we find that the maximal deviation {Delta}{alpha}{sub max} of the temporal decay index {alpha} from its asymptotic value (at early and late times), is bounded (e.g, {Delta}{alpha}{sub max} < 0.4 for {alpha} = 10); {Delta}{alpha}{sub max} slowly increases with {alpha}, converging to {Delta}{alpha}{sub max} {approx} 1 at very large {alpha} values. Therefore, no optical rebrightening is expected in this case as well. In the X-rays, while the asymptotic flux is unaffected by the density jump, the fluctuations in {alpha} are found to be comparable to those in the optical. Finally, we discuss the implications of our results for the origin of the observed fluctuations in several GRB afterglows.

Nakar, Ehud; /Caltech; Granot, Jonathan; /KIPAC, Menlo Park

2006-06-06

236

Relativistic solitary waves with phase modulation embedded in long laser pulses in plasmas

We investigate the existence of nonlinear phase-modulated relativistic solitary waves embedded in an infinitely long circularly polarized electromagnetic wave propagating through a plasma. These states are exact nonlinear solutions of the 1-dimensional Maxwell-fluid model for a cold plasma composed of electrons and ions. The solitary wave, which consists of an electromagnetic wave trapped in a self-generated Langmuir wave, presents a phase modulation when the group velocity V and the phase velocity V{sub ph} of the long circularly polarized electromagnetic wave do not match the condition VV{sub ph} = c{sup 2}. The main properties of the waves as a function of their group velocities, wavevectors, and frequencies are studied, as well as bifurcations of the dynamical system that describes the waves when the parameter controlling the phase modulation changes from zero to a finite value. Such a transition is illustrated in the limit of small amplitude waves where an analytical solution for a grey solitary wave exists. The solutions are interpreted as the stationary state after the collision of a long laser pulse with an isolated solitary wave.

Sanchez-Arriaga, G.; Siminos, E.; Lefebvre, E. [CEA, DAM, DIF, 91297 Arpajon (France)

2011-08-15

237

NASA Astrophysics Data System (ADS)

A possible mechanism for relativistic electron acceleration in the magnetosphere is drift-resonance interaction with ULF waves. Effective acceleration is expected if there exists a resonant condition between the electron drift periods and wave periods, so that azimuthally drifting electrons will periodically experience the same electric perturbation fields and be accelerated. In order to confirm the acceleration mechanism, it is important to identify the wave mode responsible for the acceleration. We have made a detailed analysis of the perturbation electric and magnetic field data taken during a relativistic electron acceleration event [Tan et al., 2004]. We found that both toroidal and poloidal wave components are present in the ULF wave data and that both components have discrete frequency spectra that are consistent with the discrete Alfven wave spectra typically measured on the ground. By interpreting the relative phases of the observed perturbation field quantities in the context of global MHD wave structure in the magnetosphere, we have determined the CRRES and GOES spacecraft positions relative to the nodes of the magnetospheric MHD waves, and therefore determined the wave modes of the observed Pc5 waves. In this paper, we will describe our wave analysis and discuss the implications of our results on relativistic-electron acceleration in the magnetosphere. Tan, L. C., S. F. Fung, and X. Shao (2004), Observation of magnetospheric relativistic electrons accelerated by Pc-5 ULF waves, Geophys. Res. Lett., 31, L14802, doi:10.1029/2004GL019459.

Tan, L.; Fung, S.; Shao, X.

2005-05-01

238

NASA Astrophysics Data System (ADS)

Recent paper by Tan, Fung and Shao [2004] shows evidences of resonant interaction and acceleration of energectic electrons with PC5 ULF waves (1-10 mHz) by analyzing CRRES and GOES satellites observations for Aug. 27, 1991 event. The event shows energetic electron flux being modulated and enhanced in 2 hours. In this presentation, we present a model of characteristic distributions of toroidal and poloidal waves in the equatorial plane during the event. By tracing particles in the electric field mapped out with CRRES observations using this model, we compared details of energetic electron flux variation to those observed by CRRES. We will also compare efficiencies of acceleration by toroidal wave to those by poloidal wave. Discussions will be given on furtehr implications of the model. Tan, L. C., S. F. Fung, and X. Shao (2004), Observation of magnetospheric relativistic electrons accelerated by Pc-5 ULF waves, Geophys. Rev. Lett., L14802, doi:10.1029/2004GL019459.

Shao, X.; Fung, S.; Tan, L.

2004-12-01

239

Evolution of Relativistic Plasma-Wave front in LWFA

NASA Astrophysics Data System (ADS)

In a laser wake field accelerator experiment where the length of the pump laser pulse is several plasma period long, the leading edge of the laser pulse undergoes frequency downshifting as the laser energy is transferred to the wake. Therefore, after some propagation distance, the group velocity of the leading edge of the pump pulse, and therefore of the driven electron plasma wave, will slow down. This can have implications for the dephasing length of the accelerated electrons and therefore needs to be understood experimentally. We have carried out an experimental investigation where we have measured the velocity vf of the `wave-front' of the plasma wave driven by a nominally 50fs (FWHM), intense (a0 ˜ 1), 0.8?m laser pulse. To determine the speed of the wave front, time- and space-resolved reflectometry, interferometry, and Thomson scattering were used. Although low density data (ne˜ 1.3 * 10^19cm-3) showed no significant changes in vf over 1.5mm (and no accelerated electrons), high-density data (ne˜ 5*10^19cm-3) shows accelerated electrons and an approximately 5% drop in vf after a propagation distance of about 800?m.

Fang, Fang; Clayton, Christopher; Marsh, Kenneth; Ralph, Joseph; Pak, Arthur; Lopes, Nelson; Joshi, Chandrashekhar

2007-11-01

240

Guided Waves in Moving Dispersive Media Part II: Relativistic Velocities

The detailed modal field structure has been determined for electromagnetic waves propagating in a uniform cylindrical lossIess waveguide of arbitrary cross section filled with a moving medium. The medium is assumed to be homogeneous, isotropic, and nondissipative, but may be dispersive. It moves uniformly, with a constant speed v, parllel to the axis of the waveguide. The solutions obtained are

H. Berger; J. W. E. Griemsmann

1968-01-01

241

Exact relativistic expressions for wave refraction in a generally moving fluid

NASA Astrophysics Data System (ADS)

The law for the refraction of a wave when the two fluids and the interface are moving with relativistic velocities is given in an exact form, at the same time correcting a first order error in a previous paper [Cavalleri and Tonni, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.57.3478 57, 3478 (1998)]. The treatment is then extended to a generally moving fluid with variable refractive index, ready to be applied to the refraction of acoustic, electromagnetic, or magnetohydrodynamic waves in the atmosphere of rapidly rotating stars. In the particular case of a gas cloud receding because of the universe expansion, our result can be applied to predict observable micro- and mesolensings. The first order approximation of our exact result for the deviation due to refraction of the light coming from a further quasar has a relativistic dependence equal to the one obtained by Einsteins’ linearized theory of gravitation.

Cavalleri, G.; Tonni, E.; Barbero, F.

2013-04-01

242

Relativistic plane-wave Born theory and its application to electron-impact excitation

An exact treatment of the relativistic plane-wave Born (RPWB) cross section for electron-impact excitation is provided for an arbitrary atom or ion. This result represents an improvement over the cross section obtained from the widely used Bethe high-energy theory developed in the 1930s. The results obtained from this RPWB approach can be applied to a broad class of problems in fundamental electron-impact scattering theory. As an illustration, the approach is used to approximate the high-l, partial-wave contribution in more accurate calculations of the excitation cross section, a problem which has been lacking a fully relativistic treatment for more than 20 years.

Fontes, Christopher J.; Zhang Honglin [Applied Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2007-10-15

243

Weak discontinuity waves in a relativistic mixture of two stiffened gas components

NASA Astrophysics Data System (ADS)

A simple interface-capturing approach is developed in order to deduce the relativistic fluid equations for a two-component mixture, using a stiffened gas equation of state. The two species are assumed to be at thermal equilibrium and the total pressure of the mixture is expressed in terms of the pressures of the two components by Dalton's law. Moreover, weak discontinuity waves compatible with such a fluid are examined.

Conforto, F.; Giambò, S.

2010-11-01

244

Resonant diffusion curves for electron cyclotron resonance with field-aligned electromagnetic R mode and L mode electromagnetic ion cyclotron (EMIC) waves are constructed using a fully relativistic treatment. Analytical solutions are derived for the case of a single-ion plasma, and a numerical scheme is developed for the more realistic case of a multi-ion plasma. Diffusion curves are presented for plasma parameters

Danny Summers; Richard M. Thorne; Fuliang Xiao

1998-01-01

245

In this study we report on ground-based observations of short bursts of relativistic electron precipitation (REP), detected by a subionospheric propagation sensor in Sodankylä, Finland during 2005. In two ~4 hour case study periods from L = 5.2, around local midnight, several hundred short-lived radio wave perturbations were observed, covering a wide range of arrival azimuths. The vast majority (~99%)

Craig J. Rodger; Mark A. Clilverd; David Nunn; Pekka T. Verronen; Jacob Bortnik; Esa Turunen

2007-01-01

246

Computational studies of wave-shaping in a blast simulator by perforated plates in the driver

Computational simulation of shock tubes with baffles on their driver sections were performed using the (BRL) Quasi-One-Dimensional (Q1D) computer code. The credibility of the code was established through comparisons with experimental data. A numerical parametric study was performed in which baffle positions and area openings in a computational model of a candidate Large Blast\\/Thermal Simulator (LB\\/TS) were manipulated until blast

D. M. Hisley

1987-01-01

247

Management of primary blast injury

Blast waves are produced following the detonation of munitions, the firing of large caliber guns, or from any type of explosion. These blast waves can be powerful enough to injure the individuals exposed to them. This type of injury is called primary blast injury (PBI) and the organs most vulnerable to PBI are the gas-filled organs, namely the ear, the

Gregory J. Argyros

1997-01-01

248

Method of accelerating photons by a relativistic plasma wave

Photons of a laser pulse have their group velocity accelerated in a plasma as they are placed on a downward density gradient of a plasma wave of which the phase velocity nearly matches the group velocity of the photons. This acceleration results in a frequency upshift. If the unperturbed plasma has a slight density gradient in the direction of propagation, the photon frequencies can be continuously upshifted to significantly greater values.

Dawson, John M. (Pacific Palisades, CA); Wilks, Scott C. (Santa Monica, CA)

1990-01-01

249

NASA Astrophysics Data System (ADS)

The klystron-like relativistic backward wave oscillator (RBWO) combines the transition radiation with Cerenkov radiation and has demonstrated microwave output of high power and high efficiency. The coaxial slow wave structure device can produce microwave with a lower frequency in a smaller cross section. For the purpose of high efficiency, low frequency, and miniaturization, a coaxial klystron-like RBWO with a premodulation cavity is presented. Particle-in-cell simulations show that a microwave with power of 1.15 GW and frequency of 2.1 GHz is generated with conversion efficiency of 48%, whereas for the device with a reflector, the efficiency is 38%.

Xiao, Renzhen; Teng, Yan; Chen, Changhua; Sun, Jun

2011-11-01

250

The klystron-like relativistic backward wave oscillator (RBWO) combines the transition radiation with Cerenkov radiation and has demonstrated microwave output of high power and high efficiency. The coaxial slow wave structure device can produce microwave with a lower frequency in a smaller cross section. For the purpose of high efficiency, low frequency, and miniaturization, a coaxial klystron-like RBWO with a premodulation cavity is presented. Particle-in-cell simulations show that a microwave with power of 1.15 GW and frequency of 2.1 GHz is generated with conversion efficiency of 48%, whereas for the device with a reflector, the efficiency is 38%.

Xiao Renzhen; Teng Yan; Chen Changhua; Sun Jun [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024 (China)

2011-11-15

251

Rapid startup in relativistic backward wave oscillator by injecting external backward signal

Investigation on accelerating the building up of oscillation and achieving a rapid startup in powerful relativistic backward wave oscillator by injecting a weak external backward signal is carried out in this paper. Synchronizing the signal with the backward wave excited by intense electron beam extracting with slow wave structure, the initial noise is greatly reduced and mode competition is restrained. The analysis is demonstrated by high power X-band backward wave oscillator experiment, in which a plasma switch is designed to realize the backward signal injection. The results show that the significant reduction of microwave output delay is attained and the start time of oscillation is ahead of 10 ns with the energy conversion efficiency increases about 62%.

Song, W.; Teng, Y.; Zhang, Z. Q.; Li, J. W.; Sun, J.; Chen, C. H.; Zhang, L. J. [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an, Shanxi 710024 (China)

2012-08-15

252

The shock wave generated by an explosion ("blast wave") may cause injury in any or all of the following: (1) direct impact on the tissues of variations in environmental pressure; (2) flying glass and other debris set in motion by it; (3) propulsion of the body. Injuries in the first category affect gas-containing organs (ears, lungs and intestines), and acute death is attributed to air forced into the coronary vessels via damaged pulmonary alveoli. It is estimated that overpressure sufficient to cause lung injury may occur up to five miles from a 20-megaton nuclear explosion. The greatest single hazard from blast is, however, flying glass, and serious wounding from this cause is possible up to 12 miles from an explosion of this magnitude. PMID:6015742

de Candole, C A

1967-01-28

253

The shock wave generated by an explosion (“blast wave”) may cause injury in any or all of the following: (1) direct impact on the tissues of variations in environmental pressure; (2) flying glass and other debris set in motion by it; (3) propulsion of the body. Injuries in the first category affect gas-containing organs (ears, lungs and intestines), and acute death is attributed to air forced into the coronary vessels via damaged pulmonary alveoli. It is estimated that overpressure sufficient to cause lung injury may occur up to five miles from a 20-megaton nuclear explosion. The greatest single hazard from blast is, however, flying glass, and serious wounding from this cause is possible up to 12 miles from an explosion of this magnitude.

de Candole, C. A.

1967-01-01

254

Including the relativistic kinetic energy in a spline-augmented plane-wave band calculation

The first-order relativistic correction to the kinetic energy of an electron, the mass-velocity term, is not bounded from below. It can, therefore, not be used within a variational framework. To overcome this deficiency we developed a method to include the entire relativistic kinetic energy {radical}(p{sup 2}c{sup 2}+m{sub 0}{sup 2}c{sup 4}){minus}m{sub 0}c{sup 2} in a spline-augmented plane-wave band calculation. The first results for silver are quite promising, especially for d and p states: The analysis of the energies of the core states as well as of the valence band structure suggests that the energies of d bands are reproduced within 1 mRy. However, the combination of the relativistic kinetic energy with the Darwin term leads to energies which are too low for s-like valence states by 10 mRy. Therefore, the s and d valence band complex is spread out and the Fermi level is lowered by the same amount as the s states. We expect to overcome these deficiencies in future investigations by using a alternative form of the relativistic potential correction along the lines proposed by Douglas and Kroll. {copyright} {ital 1997} {ital The American Physical Society}

Fehrenbach, G.M.; Schmidt, G. [Sektion Physik der Ludwig Maximilians Universitaet Muenchen, Theresienstrae 37, 80333 Munich (Federal Republic of Germany)

1997-03-01

255

Skull flexure from blast waves: a mechanism for brain injury with implications for helmet design

Traumatic brain injury [TBI] has become a signature injury of current military conflicts. The debilitating effects of TBI are long-lasting and costly. Although the mechanisms by which impacts cause TBI have been well researched, the mechanisms by which blasts cause TBI are not understood. Various possibilities have been investigated, but blast-induced deformation of the skull has been neglected. From numerical hydrodynamic simulations, we have discovered that nonlethal blasts can induce sufficient flexure of the skull to generate potentially damaging loads in the brain, even if no impact occurs. The possibility that this mechanism may contribute to TBI has implications for the diagnosis of soldiers and the design of protective equipment such as helmets.

Moss, W C; King, M J; Blackman, E G

2009-04-14

256

Accidental head explosion: an unusual blast wave injury as a result of self-made fireworks.

A 33-year old hobby pyrotechnician sustained a lethal craniofacial trauma secondary to a salute fireworks blast. He was examining a misfire of a self-constructed salute gun, when it detonated, causing an explosively rupture of his forehead, which led to his immediate death. An autopsy was performed to achieve knowledge of the injury and to be able to reconstruct the events that lead to it. The pressure effect of the explosion caused a shredded rupture of the forehead with a regional spread of brain tissue and small polygonal skull fragments up to 30m from the detonation site. Furthermore multiple cinderlike fragments of black powder were embedded in the skin of the face and the anterior aspect of the neck (s.c. blast tattoo). The complete destruction of the forehead in combination with the multiple blast tattooing suggested that the explosion detonated while he was leaning over the device. PMID:21570222

Kunz, S N; Zinka, B; Peschel, O; Fieseler, S

2011-05-12

257

The generalized equations of motion for the gyroresonance interaction between energetic electrons and coherent VLF waves in the magnetosphere are employed to study quasi-relativistic electron precipitation. It is suggested that these exact equations be used for particle energies higher than 50 keV (corresponding to a 10% correction in average pitch angle scattering with respect to a nonrelativistic formulation). Based on these equations and the relativistic cyclotron resonance condition, a previous test particle simulation method (Inan, 1977; Inan et al., 1978, 1982) is extended to higher energies and is used to study the wave-particle interactions involving the near-loss-cone quasi-relativistic particles. The root mean square (rms) pitch angle scattering of the near-loss-cone particles and the corresponding precipitated energy spectrum are then calculated and compared. It is argued that the full width at half maximum (FWHM) of the rms scattering pattern would give an upper bound to that of the energy spectrum of the precipitated flux. Furthermore the peak widths are demonstrated to be within the upper limit values measured by recent satellite experiments. This agreement between the computed and measured spectral width lends credence to the suggestions that the observed narrow peaks in precipitated energy spectra may indeed be caused by monochromatic signals injected into the magnetosphere by VLF transmitters.

Chang, H.C.; Inan, U.S.

1983-01-01

258

Skull Flexure from Blast Waves: A Mechanism for Brain Injury with Implications for Helmet Design

NASA Astrophysics Data System (ADS)

Traumatic brain injury (TBI) has become a signature injury of current military conflicts, with debilitating, costly, and long-lasting effects. Although mechanisms by which head impacts cause TBI have been well researched, the mechanisms by which blasts cause TBI are not understood. From numerical hydrodynamic simulations, we have discovered that nonlethal blasts can induce sufficient skull flexure to generate potentially damaging loads in the brain, even without a head impact. The possibility that this mechanism may contribute to TBI has implications for injury diagnosis and armor design.

Moss, William C.; King, Michael J.; Blackman, Eric G.

2009-09-01

259

Skull Flexure from Blast Waves: A Mechanism for Brain Injury with Implications for Helmet Design

Traumatic brain injury [TBI] has become a signature injury of current military conflicts, with debilitating, costly, and long-lasting effects. Although mechanisms by which head impacts cause TBI have been well-researched, the mechanisms by which blasts cause TBI are not understood. From numerical hydrodynamic simulations, we have discovered that non-lethal blasts can induce sufficient skull flexure to generate potentially damaging loads in the brain, even without a head impact. The possibility that this mechanism may contribute to TBI has implications for injury diagnosis and armor design.

Moss, W C; King, M J; Blackman, E G

2009-04-30

260

Relativistic Jet Dynamics and Calorimetry of Gamma-ray Bursts

NASA Astrophysics Data System (ADS)

We present numerical solutions of the two-dimensional relativistic hydrodynamics equations describing the deceleration and expansion of highly relativistic conical jets, of opening angles 0.05 <= ?0 <= 0.2, propagating into a medium of uniform density. Jet evolution is followed from a collimated relativistic outflow to the quasi-spherical non-relativistic phase. We show that relativistic sideways expansion becomes significant beyond the radius r ? at which the expansion Lorentz factor drops to ?-1 0. This is consistent with simple analytic estimates, which predict faster sideways expansion than has been claimed based on earlier numerical modeling. For t > ts = r ?/c the emission of radiation from the jet blast wave is similar to that of a spherical blast wave carrying the same energy (significant deviations at t ~ ts occur only for well off-axis observers, ?obs ~ 1 Gt ?0). Thus, the total (calorimetric) energy of gamma-ray burst blast waves may be estimated with only a small fractional error based on t > ts observations.

Wygoda, N.; Waxman, E.; Frail, D. A.

2011-09-01

261

On the basis of perturbative QCD and the relativistic quark model we calculate relativistic and bound state corrections in the pair production of S-wave and P-wave charmonium states. Relativistic factors in the production amplitude connected with the relative motion of heavy quarks and the transformation law of the bound state wave function to the reference frame of the moving S- and P-wave mesons are taken into account. For the gluon and quark propagators entering the production vertex function we use a truncated expansion in the ratio of the relative quark momenta to the center-of-mass energy {radical}(s) up to the second order. The relativistic treatment of the wave functions makes all such second order terms convergent, thus allowing the reliable calculation of their contributions to the production cross section. Relativistic corrections to the quark bound state wave functions in the rest frame are considered by means of the QCD generalization of the standard Breit potential. It turns out that the examined effects change essentially the nonrelativistic results of the cross section for the reaction e{sup +}+e{sup -{yields}}J/{Psi}({eta}{sub c})+{chi}{sub cJ}(h{sub c}) at the center-of-mass energy {radical}(s)=10.6 GeV.

Elekina, E. N.; Martynenko, A. P. [Samara State University, Pavlov Street 1, Samara 443011 (Russian Federation)

2010-03-01

262

Relativistic modulational instability of electron-acoustic waves in an electron-pair ion plasma

The modulational instability of finite amplitude electron-acoustic waves (EAWs) along the external magnetic field is studied in an electron-pair ion plasma. Accounting for the relativistic electron mass variation nonlinearity and the Boltzmann distribution of both positive and negative ions, new regimes for the relativistic modulational instability (MI) for the low frequency (below the electron gyrofrequency) short-wavelength (in comparison with the ion gyroradius) modes are obtained numerically. It is found that the presence of a significant fraction of negative ions suppresses the MI growth/decay rate for the modulated EAW packets. The results could be of important for understanding the origin of amplitude modulated EAW packets in space (e.g., Earth's magnetotail) as well as in laboratory plasmas.

Misra, A. P. [Department of Mathematics, Siksha Bhavana, Visva-Bharati University, Santiniketan-731 235 (India); Shukla, P. K. [Institut fuer Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultaet fuer Physik and Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany and School of Physics, University of KwaZulu-Natal, 4000 Durban (South Africa)

2008-12-15

263

Ion-acoustic solitary waves in ultra-relativistic degenerate pair-ion plasmas

The arbitrary and the small amplitude ion-acoustic solitary waves (IASWs) have been studied. The former is studied by using the Sagdeev pseudo-potential approach in a plasma consisting of the degenerate ultrarelativistic electrons, positrons, and the non-relativistic classical ions. It is seen that only compressive solitary waves can propagate through such plasmas. The numerical calculations show that the region of existence of the ion-acoustic solitary waves depends upon the positron (ion) number density and the plasma thermal temperature. This study is appropriate for applications in inertial confinement fusion laboratory research as well as the study of astrophysical dense objects such as white dwarf and dense neutron stars.

Rasheed, A.; Tsintsadze, N. L. [Department of Physics, G.C. University, Lahore 54000 (Pakistan); Salam Chair in Physics, G.C. University, Lahore 54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, G.C. University, Lahore 54000 (Pakistan)

2011-11-15

264

We present the effective range expansions for the {sup 1}S{sub 0} and {sup 3}S{sub 1} scattering phase shifts, and the relativistic deuteron wave functions that accompany our recent high precision fits (with {chi}{sup 2}/N{sub data{approx_equal}}1) to the 2007 world np data below 350 MeV. The wave functions are expanded in a series of analytical functions (with the correct asymptotic behavior at both large and small arguments) that can be Fourier-transformed from momentum to coordinate space and are convenient to use in any application. A fortran subroutine to compute these wave functions can be obtained from the authors.

Gross, Franz; Stadler, Alfred [College of William and Mary, Williamsburg, Virginia 23185 (United States) and Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Centro de Fisica Nuclear da Universidade de Lisboa, P-1649-003 Lisboa (Portugal) and Departamento de Fisica da Universidade de Evora, P-7000-671 Evora (Portugal)

2010-09-15

265

NASA Astrophysics Data System (ADS)

We have studied the propagation of ion acoustic shock waves involving planar and non-planar geometries in an unmagnetized plasma, whose constituents are non-degenerate ultra-cold ions, relativistically degenerate electrons, and positrons. By using the reductive perturbation technique, Korteweg-deVries Burger and modified Korteweg-deVries Burger equations are derived. It is shown that only compressive shock waves can propagate in such a plasma system. The effects of geometry, the ion kinematic viscosity, and the positron concentration are examined on the ion acoustic shock potential and electric field profiles. It is found that the properties of ion acoustic shock waves in a non-planar geometry significantly differ from those in planar geometry. The present study has relevance to the dense plasmas, produced in laboratory (e.g., super-intense laser-dense matter experiments) and in dense astrophysical objects.

Ata-ur-Rahman; Ali, S.; Mirza, Arshad M.; Qamar, A.

2013-04-01

266

Versatile gas gun target assembly for studying blast wave mitigation in materials

NASA Astrophysics Data System (ADS)

Traumatic brain injury (TBI) has become a serious problem for military personnel returning from recent conflicts. This has increased interest in investigating blast mitigating materials for use in helmets. In this paper we describe a new versatile target assembly that is used with an existing gas gun for studying these materials.

Bartyczak, S.; Mock, W., Jr.

2012-03-01

267

We develop a nonlinear theory for self-modulation of a circularly polarized electromagnetic wave in a relativistic hot weakly magnetized electron-positron plasma. The case of parallel propagation along an ambient magnetic field is considered. A nonlinear Schrödinger equation is derived for the complex wave amplitude of a self-modulated wave packet. We show that the maximum growth rate of the modulational instability decreases as the temperature of the pair plasma increases. Depending on the initial conditions, the unstable wave envelope can evolve nonlinearly to either periodic wave trains or solitary waves. This theory has application to high-energy astrophysics and high-power laser physics. PMID:22680585

Asenjo, Felipe A; Borotto, Felix A; Chian, Abraham C-L; Muñoz, Víctor; Valdivia, J Alejandro; Rempel, Erico L

2012-04-05

268

Relativistic distorted-wave analysis of quasielastic proton-nucleus scattering

A relativistic distorted-wave impulse approximation formalism is presented for the calculation of quasielastic proton-nucleus scattering. It is shown that the double differential cross section may be written as a contraction between the hadronic tensor (describing the projectile and ejectile) and the polarization tensor (describing the nuclear target) and that this mathematical structure also holds for the case where distortions are included. The eikonal approximation is used to introduce distortions in the wave functions, and the nuclear response is described using a Fermi gas model. The highly oscillatory nine-dimensional integrand contained in the expression for the double differential cross section is computed using a novel technique based on combining traditional Gaussian integration methods with the powerful fitting functions in the matlab programming language. This work has successfully calculated the distorted-wave quasielastic differential cross section for proton-nucleus scattering within a fully relativistic framework. It is found that the distortions lead to a reduction in the double differential cross section and have a negligible effect on the computed spin observables.

Titus, N. P.; Ventel, B. I. S. van der; Niekerk, D. D. van; Hillhouse, G. C. [Department of Physics, University of Stellenbosch, Private Bag X1, Matieland 7602 (South Africa); University for Information Science and Technology, Partizanska Street, Ohrid 6000 (Macedonia, The Former Yugoslav Republic of)

2011-04-15

269

NASA Astrophysics Data System (ADS)

In a statistical study O'Brien et al. [2001] showed that magnetospheric relativistic electrons (MRE) can be accelerated significantly during the recovery phase of a magnetic storm when there exists sustained solar wind speeds of > 450 km s-1 and long duration of Pc5 ULF activity. While this statistical result supports the general tendency for MRE's to depend on solar wind speeds and ULF activity, individual events can behave quite differently. For example, during the storm recovery phases on September 25, 2001 and November 25, 2001, when the solar wind speeds were > 600 kms-1, the MRE data measured by LANL and GOES spacecraft indicate a 4-fold and negligible increases of 1.1-1.5 MeV electrons during ~3-hour strong ULF wave activity periods as observed by Cluster spacecraft at noon and dusk, respectively. In this paper, we present detailed comparisons between these two events. Our results show that the main difference between the two events is a strong day-night asymmetry of ULF wave distributions in the September event in contrast with the uniform ULF wave distribution in the November event. O'Brien, T. P., et al., 2001, Which magnetic storms produce relativistic electrons at geosynchronous orbit? J. Geophys. Res., 106, 15,533.

Tan, L. C.; Shao, X.; Sharma, A. S.; Fung, S. F.

2009-05-01

270

NASA Astrophysics Data System (ADS)

A theory for dressed quantum ion acoustic waves (QIAWs), which includes higher-order corrections when QIAWs are investigated by the reductive perturbation method, is presented for unmagnetized plasmas containing positive and negative ions and weakly relativistic electron beams. The properties of the QIAWs are investigated using a quantum hydrodynamic model, from which a Korteweg-de Vries equation is derived using the reductive perturbation method. An equation including higher-order dispersion and nonlinearity corrections is also derived, and the physical parameter space is discussed for the importance of these corrections.

Wang, Yunliang; Dong, Yushan; Eliasson, B.

2013-11-01

271

A compact P-band coaxial relativistic backward wave oscillator (BWO) with only three periods slow wave structure (SWS) is investigated both theoretically and numerically. The characteristics of the coaxial SWS are analyzed when the SWS is changed from the structure with only outer conductor ripple to the structure with both inner and outer conductor ripples. It is found that the existence of the inner conductor ripple can reduce the period length of coaxial SWS to maintain the same operating frequency of the BWO and can largely increase the temporal growth rate and the spatial growth rate of the device. Then, the effects of SWS period numbers on the generation of the microwave in the P-band relativistic BWO are studied by PIC simulations. The results show that three periods SWS cannot only make the device more compact but also has a wide region of single-frequency operation and relatively large efficiency and output power in a wide range of the diode voltage. Typical simulation results show that, with a 585 kV and 7.85 kA electron beam guided by a 0.8 T solenoidal field, the microwave of 1.65 GW is generated at the frequency of 900 MHz, and the interaction efficiency is about 36%. Compared with the conventional P-band coaxial relativistic BWO with five periods SWS, the axial length of the SWS is reduced by about one half, which is only 38.4 cm, and the saturation time of the microwave signal is reduced by about 10 ns.

Gao Liang; Qian Baoliang; Ge Xingjun [College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2011-10-15

272

The rapid relativistic distorted wave method of Zhang et al for excitation, which uses the atomic structure data of Sampson et al, has been extended to ionization. In this approach the same Dirac-Fock-Slater potential evaluated using a single mean configuration is used in calculating the orbitals of all electrons bound and free. Values for the cross sections Q for ionization of various ions have been calculated and generally good agreement is obtained with other recent relativistic calculations. When results are expressed in terms of the reduced ionization cross section Q{sub R}, which is proportional to I{sup 2}Q, they are close to the non-relativistic Coulomb-Born-Exchange values of Moores et al for hydrogenic ions except for high Z and/or high energies. This suggests that fits of the Q{sub R} to simple functions of the impact electron energy in threshold units with coefficients that are quite slowly varying functions of an effective Z can probably be made. This would be convenient for plasma modeling applications. 24 refs., 2 tabs.

Zhang, Hong Lin; Sampson, D.H. (Pennsylvania State Univ., University Park, PA (USA). Dept. of Astronomy)

1990-10-22

273

Extremely high-power microwave emission is generated when a pulsed relativistic electron beam propagates down the axis of a corrugated-wall wave guide. The radiation occurs at a frequency such that the phase velocities of the negative-energy space charge wave on the beam and a low-order TM mode in the wave guide are equal. Power levels of 500 MW are generated. The

Y. Carmel; J. Ivers; R. E. Kribel; J. Nation

1974-01-01

274

NASA Astrophysics Data System (ADS)

By analyzing CRRES and GOES observations on Aug. 27 1991, Tan et al. [2004] reported evidence of magnetospheric relativistic electron acceleration by resonant interactions with PC5 ULF waves. The event showed strong ULF wave activities after a storm sudden commencement (SSC) and energetic electron fluxes were enhanced in 2 hours. The electron flux peak observed in energy channels (0.6 - 1.1 MeV) were modulated by local electric field observed by CRRES. In this study, we set up a drift-resonant interaction model between ULF wave and magnetospheric relativistic electrons to model the observed electron flux in the event. In this model, the poloidal mode wave is concentrated in the dayside and the toroidal mode wave is concentrated in two flanks. The toroidal mode waves in the dawn and dusk flanks are in anti-phase. We found that electron can be accelerated jointly by the poloidal wave in the dayside and toroidal wave in flanks. The dayside poloidal wave serves as the dominant source of electron acceleration. The simulated electron flux variations agree well with observations both in fine details and long period behavior. These agreements in electron behavior indicate that the ULF wave plays an important role in accelerating MeV relativistic electrons around the geosynchronous orbit. General applications of the model during SSC events are also discussed. Tan, L. C., S. F. Fung, and X. Shao, Observation of magnetospheric relativistic electrons accelerated by Pc-5 ULF waves, Geophys. Rev. Lett., L14802, doi: 10.1029/2004GL019459, 2004.

Shao, X.; Fung, S.; Tan, L.; Papadopoulos, K.

2007-12-01

275

Excitation of a surface plasma wave over a plasma cylinder by a relativistic electron beam

A relativistic electron beam propagating in a plasma cylinder excites a surface plasma wave (SPW) via the Cerenkov interaction. The wave frequency decreases with beam velocity. The growth rate, however, initially increases with frequency {omega}, attains a maximum, and then falls off due to the localization of the SPW near the surface. For typical parameters, maximum growth occurs at {omega}/{omega}{sub P}{approx_equal}0.36, where {omega}{sub P} is the plasma frequency. With the increase in the radius of the thin plasma cylinder, the optimum growth rate increases in magnitude. The annular beam propagating outside the plasma cylinder excites the SPW with larger growth rate for the same beam current and the beam radius r{sub b}=1.02a, where a is the radius of the thin plasma cylinder.

Kumar, Gagan; Tripathi, V. K. [Physics Department, Indian Institute of Technology Delhi, New Delhi-110016 (India)

2008-07-15

276

Relativistic backward-wave tube with nonuniform phase velocity of the synchronous harmonic

NASA Astrophysics Data System (ADS)

We have investigated the possibility of increasing the efficiency of a moderately relativistic backward-wave tube (BWT) by longitudinal modification of the phase velocity profile of the synchronous (-1) spatial harmonic. We have shown theoretically that the efficiency of oscillators with a nonuniform electrodynamic system may reach 60% in the approximation of a near zero space-charge field. We have found that the use of nonuniform periodic structures leads to reduction of the critical value of the space-charge field, and also impairment of the adaptive properties of the device. In our experiments, we have realized backward-wave oscillators (BWO) with 40% efficiency and microwave radiation power of 500 MW.

Korovin, S. D.; Polevin, S. D.; Roitman, A. M.; Rostov, V. V.

1996-12-01

277

The classical general-relativistic cross sections for the scattering of either an electromagnetic wave or a gravitational wave by a scalar particle are calculated and found to agree with the results of the quantized linearized field theory.

Peter J. Westervelt

1971-01-01

278

Theory and Simulations on Beat Wave Excitation of Relativistic Plasma Waves

The generation of excitation of large amplitude plasma waves by the beating of two collinear laser beams is studied analytically and via computer experiments. When the difference (beat) frequency of the two lasers is near the natural frequency of the plasma, a large amplitude wave appropriate for accelerating particles to ultrahigh energies can be excited. The subject is divided into

Warren Bicknell Mori

1987-01-01

279

Blast-wave diagnosis of self-focusing of an intense laser pulse in a cluster medium

Self-focusing of intense laser pulses in a gas of atomic clusters is diagnosed in both long (>700 fs) and short (<100 fs) pulse regimes. This investigation uses blast-wave analysis techniques, which are sensitive to deposited energy, as a tool to identify locations of self-focusing. The detection of highly energetic x rays from the interaction of the short pulse with the clusters suggests the activation of electron acceleration in the self-focused high-intensity channels produced. The self-focusing is attributed to the optical properties of the clusters since it occurs at moderate laser powers and the cluster parameters are critical to the extent of the channel that forms.

Symes, Daniel R.; Moore, Alastair S.; Comley, Andrew J.; Lazarus, James; Hohenberger, Matthias; Tisch, John W. G.; Smith, Roland A. [Blackett Laboratory, Imperial College of Science, Technology and Medicine, Prince Consort Road, London SW7 2BZ (United Kingdom)

2007-06-15

280

Blast-wave diagnosis of self-focusing of an intense laser pulse in a cluster medium

NASA Astrophysics Data System (ADS)

Self-focusing of intense laser pulses in a gas of atomic clusters is diagnosed in both long (>700 fs) and short (<100 fs) pulse regimes. This investigation uses blast-wave analysis techniques, which are sensitive to deposited energy, as a tool to identify locations of self-focusing. The detection of highly energetic x rays from the interaction of the short pulse with the clusters suggests the activation of electron acceleration in the self-focused high-intensity channels produced. The self-focusing is attributed to the optical properties of the clusters since it occurs at moderate laser powers and the cluster parameters are critical to the extent of the channel that forms.

Symes, Daniel R.; Moore, Alastair S.; Comley, Andrew J.; Lazarus, James; Hohenberger, Matthias; Tisch, John W. G.; Smith, Roland A.

2007-06-01

281

Design of jet-driven, radiative-blast-wave experiments for 10 kJ class lasers

NASA Astrophysics Data System (ADS)

We discuss the design of jet-driven, radiative-blast-wave experiments for a 10 kJ class pulsed laser facility. The astrophysical motivation is the fact that jets from Young Stellar Objects are typically radiative and that the resulting radiative bow shocks produce complex structure that is difficult to predict. To drive a radiative bow shock, the jet velocity must exceed the threshold for strong radiative effects. Using a 10 kJ class laser, it is possible to produce such a jet that can drive a radiative bow shock in gas that is dense enough to permit diagnosis by x-ray radiography. We describe the design and simulations of such experiments. The basic approach is to shock the jet material and then accelerate it through a collimating hole and into a Xe ambient medium. We identify issues that must be addressed through experimentation or further simulations in order to field successful experiments.

Drake, R. P.; Knauer, J. P.

2009-08-01

282

A 1D-3D mixed method for the numerical simulation of blast waves in confined geometries

NASA Astrophysics Data System (ADS)

Blast wave generated by a high detonating spherical charge and propagating in confined domains is modeled using the Euler equations. The problem is split into two parts. The first calculation part relies on spherical isotropy to solve the problem in the radial component. Overpressure distribution is presented and shows a very good agreement with experimental and numerical data. The one-dimensional data need to be made three-dimensional mesh-compatible thanks to an appropriate remapping technique. To this end, a remapping technique is presented and its effectiveness, accuracy and efficiency are demonstrated. The second calculation part consists of a three-dimensional computation fed with the remapped data. The effectiveness of this mixed approach is demonstrated through three-dimensional applications in confined domains.

Benselama, Adel M.; William-Louis, Mame J.-P.; Monnoyer, François

2009-10-01

283

Infrared and X-Ray Evidence for Circumstellar Grain Destruction by the Blast Wave of Supernova 1987A

NASA Astrophysics Data System (ADS)

Multiwavelength observations of supernova remnant 1987A show that its morphology and luminosity are rapidly changing at X-ray, optical, infrared (IR), and radio wavelengths as the blast wave from the explosion expands into the circumstellar equatorial ring, produced by mass loss from the progenitor star. The observed IR radiation arises from the interaction of dust grains that formed in mass outflow with the soft X-ray-emitting plasma component of the shocked gas. Spitzer Infrared Spectrograph spectra at 5-30 ?m taken on day 6190 since the explosion show that the emission arises from ~1.1×10-6 Msolar of silicate grains radiating at a temperature of ~180+20-15 K. Subsequent observations on day 7137 show that the IR flux had increased by a factor of 2 while maintaining an almost identical spectral shape. The observed IR-to-X-ray flux ratio (IRX) is consistent with that of a dusty plasma with standard Large Magellanic Cloud dust abundances. IRX has decreased by a factor of ~2 between days 6190 and 7137, providing the first direct observation of the ongoing destruction of dust in an expanding supernova blast wave on dynamic timescales. Detailed models consistent with the observed dust temperature, the ionization timescale of the soft X-ray emission component, and the evolution of IRX suggest that the radiating silicate grains are immersed in a 3.5×106 K plasma with a density of (0.3-1)×104 cm-3 and have a size distribution that is confined to a narrow range of radii between 0.023 and 0.22 ?m. Smaller grains may have been evaporated by the initial UV flash from the supernova.

Dwek, Eli; Arendt, Richard G.; Bouchet, Patrice; Burrows, David N.; Challis, Peter; Danziger, I. John; De Buizer, James M.; Gehrz, Robert D.; Kirshner, Robert P.; McCray, Richard; Park, Sangwook; Polomski, Elisha F.; Woodward, Charles E.

2008-04-01

284

NASA Astrophysics Data System (ADS)

The MINIS balloon campaign was conducted in January of this year to obtain the first multi-point measurements of relativistic electron precipitation (REP). Two balloons were launched in the northern hemisphere at Churchill, Manitoba, carrying an X-ray scintillator and H? photometer, and four balloons were launched in the southern hemisphere at SANAE, Antarctica, carrying the same scintillator and additional field instruments. Observations from previous balloon campaigns suggest wave-particle interaction with EMIC waves as the precipitation mechanism for REP due to the location of the events in the dusk sector, near the edge of the plasmapause. [Millan et al., 2002]. REP events were detected on Jan. 21st and 25th by the MINIS campaign during the SSC, main phase, and recovery phase of the geomagnetic storm produced by the Jan. 20, 2005 CME. We investigate the precipitation mechanism for these events; specifically, whether EMIC waves play a role in REP. Ground based search coil magnetometer data are used to determine the presence of EMIC waves. We also use IMAGE Satellite data to determine the location of the REP events with respect to the plasmapause and correlated proton precipitation.

Woodger, L. A.; Millan, R. M.; Sample, J. G.; McCarthy, M. P.; Bale, S.; Bering, E. A.; Blake, J. B.; Collier, A. B.; Holzworth, R. H.; Hughes, A. R.; Kokorowski, M.; Lay, E.; Lin, R. P.; Moraal, H.; O'Brien, T. P.; Parks, G. K.; Pulupa, M.; Reddell, B. D.; Smith, D. M.; Stoker, P.

2005-12-01

285

Global primary blast injury: a rat model.

Blast wave injury from bombs cause a unique but poorly understood spectrum of injuries. Previous blast wave models involved high energy explosives detonated in an open field without the sophisticated monitoring of laboratory equipment. We characterized a rodent model that produces a global blast injury in a safe laboratory environment. Male rats, prospectively randomized to four groups of ten, were anesthetized and subjected to a blast at 2.0 cm, 2.5 cm, or 3.5 cm from the blast nozzle. The control group received no blast. Intensity of the blast (80-120 psi peak pressure, 1-2 msec duration) was controlled by varying the distance of the blast wave generator to the rat. The rats were monitored for three hours following the blast and then euthanized. Bradycardia was an immediate but transient response to blast injury. Mean arterial pressure was bimodal with severe hypotension occurring immediately after the blast and, again, two to three hours later. The characteristic injuries from a blast wave, such as pulmonary hemorrhage with increased lung weight, intestinal serosal hemorrhage, and hemoperitoneum, were found in the rats subjected to the blast pressure wave. In conclusion, our rodent model accurately reproduces the clinical spectrum of injuries seen in blast victims and will provide a powerful tool for studying the pathophysiology and potential treatments of bomb blast victims. PMID:9793276

Irwin, R J; Lerner, M R; Bealer, J F; Lightfoot, S A; Brackett, D J; Tuggle, D W

1998-10-01

286

NASA Astrophysics Data System (ADS)

A weakly nonlinear analysis is carried out to derive a Korteweg-de Vries-Burgers-like equation for small, but finite amplitude, ion-acoustic waves in a dissipative plasma consisting of weakly relativistic ions, thermal positrons and nonextensive electrons. The travelling wave solution has been acquired by employing the tangent hyperbolic method. Our results show that in a such plasma, ion-acoustic shock waves, the strength and steepness of which are significantly modified by relativistic, nonextensive and dissipative effects, may exist. Interestingly, we found that because of ion kinematic viscosity, an initial solitonic profile develops into a shock wave. This later evolves towards a monotonic profile (dissipation-dominant case) as the electrons deviate from their Maxwellian equilibrium. Our investigation may help to understand the dissipative structures that may occur in high-energy astrophysical plasmas.

Tribeche, Mouloud; Pakzad, Hamid Reza

2012-06-01

287

This paper discusses the existence of ion-acoustic solitary waves and their interaction in a weakly relativistic two-dimensional thermal plasma. Two Korteweg-de Vries equations for small but finite amplitude solitary waves in both {xi} and {eta} directions are derived. The phase shifts and trajectories of two solitary waves after the collision with an arbitrary angle {alpha} are also obtained. The effects of parameters of the normalized ion temperature {sigma}, the ratio of heat capacity {delta}, the relativistic factor F{sub {gamma}}, and the colliding angle {alpha} on the amplitudes, the widths and the phase shifts of both the colliding solitary waves are studied. The effects of these parameters on the new nonlinear wave created by the collision between two solitary waves are examined as well. The results suggest that these parameters can significantly influence the amplitude, the width of the newly formed nonlinear wave and the colliding solitary waves. The phase shifts of the colliding solitary waves strongly depend on the colliding angle {alpha}. Moreover, there are compressive solitary waves in such a system.

Han Jiuning; Duan Wenshan [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Du Shenglin [Baiyin Experimental High School, Baiyin 730900 (China)

2008-11-15

288

National Technical Information Service (NTIS)

This paper summarizes a new formalism which makes the analysis and understanding of both the relativistic klystron (RK) and the standing-wave free-electron laser (SWFEL) two-beam accelerator (TBA) available to a wide audience of accelerator physicists. A ...

J. S. Wurtele D. H. Whittum A. M. Sessler

1992-01-01

289

Electron acceleration to relativistic energies at a strong quasi-parallel shock wave

NASA Astrophysics Data System (ADS)

Electrons can be accelerated to ultrarelativistic energies at strong (high Mach number) collisionless shock waves that form when stellar debris rapidly expands after a supernova. Collisionless shock waves also form in the flow of particles from the Sun (the solar wind), and extensive spacecraft observations have established that electron acceleration at these shocks is effectively absent whenever the upstream magnetic field is roughly parallel to the shock-surface normal (quasi-parallel conditions). However, it is unclear whether this magnetic dependence of electron acceleration also applies to the far stronger shocks around young supernova remnants, where local magnetic conditions are poorly understood. Here we present Cassini spacecraft observations of an unusually strong solar system shock wave (Saturn's bow shock) where significant local electron acceleration has been confirmed under quasi-parallel magnetic conditions for the first time, contradicting the established magnetic dependence of electron acceleration at solar system shocks. Furthermore, the acceleration led to electrons at relativistic energies (about megaelectronvolt), comparable to the highest energies ever attributed to shock acceleration in the solar wind. These observations suggest that at high Mach numbers, such as those of young supernova remnant shocks, quasi-parallel shocks become considerably more effective electron accelerators.

Masters, A.; Stawarz, L.; Fujimoto, M.; Schwartz, S. J.; Sergis, N.; Thomsen, M. F.; Retinò, A.; Hasegawa, H.; Zieger, B.; Lewis, G. R.; Coates, A. J.; Canu, P.; Dougherty, M. K.

2013-03-01

290

Electron acceleration to relativistic energies at a strong quasi-parallel shock wave

NASA Astrophysics Data System (ADS)

Electrons can be accelerated to ultrarelativistic energies at strong (high-Mach number) collisionless shock waves that form when stellar debris rapidly expands after a supernova. Collisionless shock waves also form in the flow of particles from the Sun (the solar wind), and extensive spacecraft observations have established that electron acceleration at these shocks is effectively absent whenever the upstream magnetic field is roughly parallel to the shock surface normal (quasi-parallel conditions). However, it is unclear whether this magnetic dependence of electron acceleration also applies to the far stronger shocks around young supernova remnants, where local magnetic conditions are poorly understood. Here we present Cassini spacecraft observations of an unusually strong solar system shock wave (Saturn's bow shock) where significant local electron acceleration has been confirmed under quasi-parallel magnetic conditions for the first time, contradicting the established magnetic dependence of electron acceleration at solar system shocks. Furthermore, the acceleration led to electrons at relativistic energies (~MeV), comparable to the highest energies ever attributed to shock-acceleration in the solar wind. These observations suggest that at high-Mach numbers, like those of young supernova remnant shocks, quasi-parallel shocks become considerably more effective electron accelerators.

Masters, Adam; Stawarz, Lukasz; Fujimoto, Masaki; Schwartz, Steve; Sergis, Nick; Thomsen, Michelle; Retino, Alessandro; Hasegawa, Hiroshi; Zieger, Bertalan; Lewis, Gethyn; Coates, Andrew; Canu, Patrick; Dougherty, Michele

2013-04-01

291

Investigation of an improved relativistic backward wave oscillator in efficiency and power capacity

Investigation of relativistic backward wave oscillator with high efficiency and power capacity is presented in this paper. To obtain high power and high efficiency, a TM{sub 021} mode resonant reflector is used to reduce the pulse shortening and increase power capacity to about 1.7 times. Meanwhile, an extraction cavity at the end of slow wave structure is employed to improve the efficiency from less than 30% to over 40%, through the beam-wave interaction intensification and better energy conversion from modulated electron beam to the electromagnetic field. Consistent with the numerical results, microwave with a power of 3.2 GW, a frequency of 9.75 GHz, and a pulse width of 27 ns was obtained in the high power microwave generation experiment, where the electron beam energy was configured to be {approx}910 kV and its current to be {approx}8.6 kA. The efficiency of the RBWO exceeds 40% at a voltage range of 870 kV-1000 kV.

Song, W.; Chen, C. H.; Sun, J.; Zhang, X. W.; Shao, H.; Song, Z. M.; Huo, S. F.; Shi, Y. C.; Li, X. Z. [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024 (China)

2012-10-15

292

Need for relativistic corrections in the analysis of spatial adiabatic passage of matter waves

NASA Astrophysics Data System (ADS)

We investigate the coherent transport of a single particle and a Bose-Einstein condensate between the two extreme traps of a triple-well potential by means of the spatial adiabatic passage technique. This matter wave transport technique consists of adiabatically following an energy eigenstate of the system that only populates the vibrational ground states of the two extreme wells and presents at all times a node in the central region. Unraveling the (nonlinear) time-dependent Schrödinger equation in terms of Bohmian quantum trajectories, we show that by slowing down the total time duration of the transport process, Bohmian velocities in the central region are orders of magnitude larger than the mean atomic velocities. This leads to a very counterintuitive effect: in the regime of almost perfect adiabaticity, these velocities require relativistic corrections to properly address the transfer process and avoid superluminal propagation.

Benseny, A.; Bagudà, J.; Oriols, X.; Mompart, J.

2012-05-01

293

NASA Astrophysics Data System (ADS)

Recent work of Tan et al. [2011] found evidence of relativistic electron acceleration by the compressional-mode ULF waves during a storm sudden commencement event on September 25, 2001 from the observations by four Cluster spacecraft measuring ULF waves and low-energy electron flux, and five LANL spacecraft measuring energetic electron fluxes over a wide energy range. We perform global MHD simulation through NASA/CCMC to investigate the excitation and distribution of compressional ULF waves during the event. Comparison with satellite and ground observations are given. In this event, the energetic electron flux measured by LANL shows modulation of low-energy electrons and acceleration of high-energy electrons by the compressional poloidal-mode electric field oscillations within 2-3 hours. Implication of simulated ULF wave distribution for relativistic electron acceleration will be discussed. Tan, L. C., X. Shao, A. S. Sharma, and S. F. Fung (2011), Relativistic electron acceleration by compressional-mode ULF waves: Evidence from correlated Cluster, Los Alamos National Laboratory spacecraft, and ground-based magnetometer measurements, J. Geophys. Res., 116, A07226, doi:10.1029/2010JA016226.

Shao, X.; Tan, L. C.; Fung, S. F.; Vassiliadis, D.; Sharma, A. S.

2011-12-01

294

NASA Astrophysics Data System (ADS)

The stationary state with magnetically trapped particles is investigated at the saturation of the relativistic Weibel instability, within the ``multiring'' model in a Hamiltonian framework. The multistream model and its multiring extension have been developed in Paper I, under the assumption that the generalized canonical momentum is conserved in the perpendicular direction. One dimensional relativistic Bernstein-Greene-Kruskal waves with deeply trapped particles are addressed using similar mathematical formalism developed by Lontano et al. [Phys. Plasmas 9, 2562 (2002); Phys. Plasmas 10, 639 (2003)] using several streams and in the presence of both electrostatic and magnetic trapping mechanisms.

Ghizzo, A.

2013-08-01

295

NASA Astrophysics Data System (ADS)

In the presence of an applied uniform magnetic field B0, the properties of 2-dimensional (2D) magnetosonic solitary waves of relativistic amplitude in the plasma containing electron, light ions He+, and heavy ions O+ are presented. In the weakly relativistic limit, a Kadomtsev-Petviashvili (KP) equation is derived by reductive perturbation method. We give the N-soliton solution of the KP equation and find dromion solutions of a potential of the physical field. The interaction law of the dromions is obtained, which shows there is no exchange of energy, momentum, and angular momentum before and after interaction of the dromions except for phase shifts.

Wang, Yun-Liang; Zhou, Zhong-Xiang; Lu, Yan-Zhen; Ni, Xiao-Dong; Shen, Jiang; Zhang, Yu

2009-06-01

296

NASA Astrophysics Data System (ADS)

A klystron-like relativistic backward wave oscillator with a ratio of transverse dimension to free-space wavelength being about four is presented. In the beam-wave interaction region, the electron beam interacts with surface wave and volume wave simultaneously. The cathode holder plays an important role in the reflection of backward waves. A guard electrode, an electron collector ring, and a reflection ring are used to optimize the beam-wave interaction. The particle in cell simulation results reveal that microwaves with a power of 2 GW and a frequency of 12.3 GHz are generated with an efficiency of 42% when the diode voltage is 400 kV, the beam current 12 kA, and the magnetic field 0.48 T.

Xiao, Renzhen; Tan, Weibing; Li, Xiaoze; Song, Zhimin; Sun, Jun; Chen, Changhua

2012-09-01

297

A klystron-like relativistic backward wave oscillator with a ratio of transverse dimension to free-space wavelength being about four is presented. In the beam-wave interaction region, the electron beam interacts with surface wave and volume wave simultaneously. The cathode holder plays an important role in the reflection of backward waves. A guard electrode, an electron collector ring, and a reflection ring are used to optimize the beam-wave interaction. The particle in cell simulation results reveal that microwaves with a power of 2 GW and a frequency of 12.3 GHz are generated with an efficiency of 42% when the diode voltage is 400 kV, the beam current 12 kA, and the magnetic field 0.48 T.

Xiao Renzhen; Tan Weibing; Li Xiaoze; Song Zhimin; Sun Jun; Chen Changhua [National Key Laboratory of Science and Technology on High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an 710024 (China)

2012-09-15

298

In this paper, we analyze the factors that affect the microwave pulse duration in a klystron-like relativistic backward wave oscillator (RBWO), including the diode voltage, the guiding magnetic field, the electron beam collector, the extraction cavity, and the gap between the electron beam and the slow wave structure (SWS). The results show that the microwave pulse duration increases with the diode voltage until breakdown occurs on the surface of the extraction cavity. The pulse duration at low guiding magnetic field is generally 5-10 ns smaller than that at high magnetic field due to the asymmetric electron emission and the larger energy spread of the electron beam. The electron beam collector can affect the microwave pulse duration significantly because of the anode plasma generated by bombardment of the electron beam on the collector surface. The introduction of the extraction cavity only slightly changes the pulse duration. The decrease of the gap between the electron beam and the SWS can increase the microwave pulse duration greatly.

Xiao Renzhen; Zhang Xiaowei; Zhang Ligang; Li Xiaoze; Zhang Lijun [National Key Laboratory of Science and Technology on High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an 710024 (China)

2012-07-15

299

Advances in Applying Iterative Learning Control to a Relativistic Backward Wave Oscillator

NASA Astrophysics Data System (ADS)

Previous results pertaining to the control of various parameters of a relativistic backward wave oscillator (BWO) include maintaining a specified or desired power over several frequencies, and maintaining a desired frequency over a range of output power. A problem of much greater complexity is the simultaneous control of both, involving the independent mapping of both power and frequency dependence on the two input variables, cathode voltage and slow wave structure (SWS) displacement. As stated in our earlier works,(C. T. Abdallah, V. S. Soualian and E. Schamiloglu, IEEE Trans. Plasma Sci. 26), 905 (1998).^,(C. T. Abdallah, W. Yang, E. Schamiloglu, and L. D. Moreland, IEEE Trans. Plasma Sci. 24), 879 (1996). both power and frequency have a sinusoidal dependence on the displacement of the SWS with respect to the cutoff neck, and a near linear dependence on the cathode voltage. Presently, we are studying the ability to control both output variables, power and frequency, utilizing an iterative learning control law. This law minimizes the L_1-norm of both output variables by updating the input variables.

Park, Todd; Soualian, Vatche; Abdallah, Chaouki; Schamiloglu, Edl

1998-11-01

300

Initial decay of flow properties of planar, cylindrical and spherical blast waves

Analytical expressions are presented for the initial decay of all major flow properties just behind planar, cylindrical, and spherical shock wave fronts whose trajectories are known as a function of either distance versus time or shock overpressure versus distance. These expressions give the time and\\/or distance derivatives of the flow properties not only along constant time and distance lines but

H. S. I. Sadek; J. J. Gottlieb

1983-01-01

301

We constrain blast wave parameters and the circumburst media of a subsample of 10 BeppoSAX gamma-ray bursts (GRBs). For this sample we derive the values of the injected electron energy distribution index, p, and the density structure index of the circumburst medium, k, from simultaneous spectral fits to their X-ray, optical, and NIR afterglow data. The spectral fits have been

R. L. C. Starling; A. J. van der Horst; E. Rol; R. A. M. J. Wijers; C. Kouveliotou; K. Wiersema; P. A. Curran; P. Weltevrede

2008-01-01

302

NASA Astrophysics Data System (ADS)

On 2010 October 16th SDO/AIA observed its first flare using automatic exposure control. Coincidentally, this flare also exhibited a large number of interesting features. Firstly, a large ribbon significantly to the solar west of the flare kernel was ignited and was visible in all AIA wavelengths, posing the question as to how this energy was deposited and how it relates to the main flare site. A faint blast wave also emanates from the flare kernel, visible in AIA and observed traveling to the solar west at an estimated speed of 1000 km/s. This blast wave is associated with a weak white-light CME observed with STEREO B and a Type II radio burst observed from Green Bank Observatory (GBSRBS). One possibility is that this blast wave is responsible for the heating of the ribbon. However, closer scrutiny reveals that the flare site and the ribbon are in fact connected magnetically via coronal loops which are heated during the main energy release. These loops are distinct from the expected hot, post-flare loops present within the main flare kernel. RHESSI spectra indicate that these loops are heated to approximately 10 MK in the immediate flare aftermath. Using the multi-temperature capabilities of AIA in combination with RHESSI, and by employing the cross-correlation mapping technique, we are able to measure the loop temperatures as a function of time over several post-flare hours and hence measure the loop cooling rate. We find that the time delay between the appearance of loops in the hottest channel, 131 A, and the cool 171 A channel, is 70 minutes. Yet the causality of this event remains unclear. Is the ribbon heated via these interconnected loops or via a blast wave?

Christe, Steven; Inglis, A.; Aschwanden, M.; Dennis, B.

2011-05-01

303

Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, results from three-dimensional numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams, 9(2), 209 (1991)] are presented. Using the multi-physics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J.A. Greenough, J. Comp. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pre-transition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernova are discussed.

Miles, A R; Edwards, M J; Greenough, J A

2004-11-08

304

Study of the freeze-out process in heavy ion collisions at relativistic energies

NASA Astrophysics Data System (ADS)

In this work, we investigate the freeze-out process in heavy ion collisions at different relativistic energies. We present a study of standard blast-wave fits and Tsallis blast-wave fits performed to the transverse momentum spectra obtained in Au+Au collisions at RHIC energies. In addition, comparisons with simulated heavy ion collisions data using the UrQMD code will be presented to provide more detailed insight into the properties of the space-time evolution such as collective dynamics of the dense matter.

Ristea, O.; Jipa, A.; Ristea, C.; Esanu, T.; Calin, M.; Barzu, A.; Scurtu, A.; Abu-Quoad, I.

2013-03-01

305

Relativistic corrections to the exclusive decays of C-even bottomonia into S-wave charmonium pairs

Within the nonrelativistic quantum chromodynamics (NRQCD) factorization formalism, we compute the relativistic corrections to the exclusive decays of bottomonia with even charge conjugation parity into S-wave charmonium pairs at leading order in the strong coupling constant. Relativistic corrections are resummed for a class of color-singlet contributions to all orders in the charm-quark velocity v{sub c} in the charmonium rest frame. Almost every process that we consider in this work has negative relativistic corrections ranging from -20 to -35%. Among the various processes, the relativistic corrections of the next-to-leading order in v{sub c} to the decay rate for {chi}{sub b2}{yields}{eta}{sub c}(mS)+{eta}{sub c}(nS) with m, n=1 or 2 are very large. In every case, the resummation of the relativistic corrections enhances the rate in comparison with the next-to-leading-order results. We compare our results with available predictions based on the NRQCD factorization formalism. The NRQCD predictions are significantly smaller than those based on the light-cone formalism by 1 or 2 orders of magnitude.

Sang Wenlong; Kim, U-Rae [Department of Physics, Korea University, Seoul 136-701 (Korea, Republic of); Rashidin, Reyima [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); School of Physics Science and Technology, Xinjiang University, Urumqi 830046 (China); Lee, Jungil [Department of Physics, Korea University, Seoul 136-701 (Korea, Republic of); KISTI, Daejeon 305-806 (Korea, Republic of)

2011-10-01

306

Laboratory observation of secondary shock formation ahead of a strongly radiative blast wave

We have previously reported the experimental discovery of a second shock forming ahead of a radiative shock propagating in Xe. The initial shock is spherical, radiative, with a high Mach number, and it sends a supersonic radiative heat far ahead of itself. The heat wave rapidly slows to a transonic regime and when its Mach number drops to two with respect to the downstream plasma, the heat wave drives a second shock ahead of itself to satisfy mass and momentum conservation in the heat wave reference frame. We now show experimental data from a range of mixtures of Xe and N{sub 2}, gradually changing the properties of the initial shock and the environment into which the shock moves and radiates (the radiative conductivity and the heat capacity). We have successfully observed second shock formation over the entire range from 100% Xe mass fraction to 100% N{sub 2}. The formation radius of the second shock as a function of Xe mass fraction is consistent with an analytical estimate.

Hansen, J F; Edwards, M J; Froula, D H; Edens, A D; Gregori, G; Ditmire, T R

2006-04-20

307

Shock wave synthesis of ?-Si3[O,N]4 in the new Freiberg blasting facility under different conditions

NASA Astrophysics Data System (ADS)

The new subterranean blasting facility at the TU Bergakademie Freiberg allows experiments at elevated capacities of 20 kg C4-equivalent. The new installation permits the investigation of phase transitions of ? Si3N4 under dynamic loading. We studied the influence of plate thickness (shock duration) and different precursor-pressure powder (Cu, NaCl) mixtures at charge masses between 2000 and 20.000 g C4. Systematic studies showed that the Mach-reflection (so called "upstreaming jetting phenomena") is of vital importance for the synthesis success, due to the fact that the T-p ratio will increase dramatically [Milyavskii et al., 2006]. We synthesized pure ?-Si3[O,N]4 from H-bearing precursors at pressures > 25 GPa [Schlothauer et al., 2011]. The phase transition Si2N2NH into ?-Si3[O,N]4 is completely reconstructive and requires a high temperature-pressure-ratio of 176 K/GPa at pressures up to 35 GPa. Despite the high energy density during the shock wave synthesis process it will be inevitable to prepare the samples under an inert nitrogen atmosphere. References Milyavskii, V. V., V. E. Fortov, A. A. Frolova, K. V. Khishchenko, A. A. Charakhch'yan, and L. V. Shurshalov (2006), Calculation of shock compression of porous media in conical solid-state targets with an outlet hole, Computational Mathematics and Mathematical Physics, 46(5), 873 890. Schlothauer, T., M. R. Schwarz, M. Ovidiu, E. Brendler, R. Moeckel, E. Kroke, and G. Heide (2011), Shock wave synthesis of oxygen-bearing spinel-type silicon nitride (g-Si3(O,N)4 in the pressurerange from 30 to 72 GPa with high purity, in Minerals as Advanced Materials II, edited by S. V. Krivovichev, pp. 389 401, Springer. Berlin Heidelberg.

Renno, A. D.; Schlothauer, T.; Schwarz, M. R.; Heide, G.; Kroke, E.

2011-12-01

308

Gravitational waves and the deformation of compact objects: Topics in relativistic astrophysics

NASA Astrophysics Data System (ADS)

In this dissertation, we present various theoretical investigations of sources of gravitational waves, relevant to interpreting the data from current and planned gravitational wave detectors; an idee fixe is the deformation of compact objects. We begin in the strong field, vacuum regime, with a construction of initial data for the numerical simulation of black hole binaries (specializing to the case of nonspinning holes in a quasicircular orbit). The data we construct contain more of the binary's expected physics than any other current data set. In particular, they contain both the binary's outgoing radiation and the expected tidal deformations of the holes. Such improved initial data will likely be necessary for simulations to achieve the accuracy required to supply advanced gravitational wave detectors with templates for parameter estimation. We end in the weak field, hydrodynamic regime with a calculation of the expected accuracy with which one can combine standard electromagnetic and gravitational wave observations of white dwarf binaries to measure the masses of the binary's components. In particular, we show that this measurement will not be contaminated by finite size effects for realistic sources observed by LISA, though such effects could be important for exceptional sources and/or advanced mHz gravitational wave detectors. In the middle, we make a detour into the messy and poorly constrained realm of the physics of neutron star interiors, calculating the shear modulus of hadron--quark mixed phase in hybrid stars. Here we include a rough treatment of charge screening, dimensional continuation of the lattice, and the contributions from changing the cell volume when shearing lowerdimensional lattices. We find that the last of these contributions is necessary to stabilize the lattice for those dimensions, where it makes a considerable contribution to the shear modulus. We then move back to sounder theoretical footing in making a general relativistic calculation of the maximum elastic quadrupole deformation that could be sustained by a star with a known shear modulus and breaking strain (provided by, e.g., the hadron--quark mixed phase in the core, or the more standard lattice of nuclei in the crust). We find that the standard Newtonian calculation considerably overestimates the quadrupole, particularly for massive, compact stars. We also present the dimensionally continued Poisson summation formula we discovered while performing the shear modulus calculation, and thought interesting enough to prove rigorously. Our method of proof also provides a new way of proving other (Voronoi) summation formulae obtained from functions satisfying modular transformations, and allows one to relax certain of the standard hypotheses.

Johnson-McDaniel, Nathan Kieran

309

NASA Astrophysics Data System (ADS)

The effects of ion mobility and positron fraction on the solitary waves of the laser field envelope and the potential of the electrostatic field in weak relativistic electron-positron-ion plasma are investigated. The parameter region for the existence of solitary waves is obtained analytically, and a reasonable choice of parameters is clarified. Both cases of mobile and immobile ions are considered. It is found that the amplitudes of solitary waves in the former case are larger compared to the latter case. For small plasma density, the localized solitary wave solutions in terms of the approximate perturbation analytical method are very consistent with those by exact numerical calculations. However, as the plasma density increases the analytical method loses its validity more and more. The influence of the positron fraction on the amplitudes of solitary waves shows a monotonous increasing relation. The implications of our results to particle acceleration are also discussed briefly.

Lu, Ding; Li, Zi-Liang; Xie, Bai-Song

2013-09-01

310

NASA Astrophysics Data System (ADS)

The propagation of circularly polarized electromagnetic waves along a constant background magnetic field in an electron-positron plasma is calculated by means of both a fluid and a kinetic theory treatment. In the fluid theory, relativistic effects are included in the particle motion, the wave field, and in the thermal motion by means of a function f, which depends only on the plasma temperature. In this work we analyze the consistency of the fluid results with those obtained from a kinetic treatment, based on the relativistic Vlasov equation. The corresponding kinetic dispersion relation is numerically studied for various temperatures, and results are compared with the fluid treatment. Analytic expressions for the Alfvén velocity are obtained for the fluid and kinetic models, and it is shown that, in the kinetic treatment, the Alfvén branch is suppressed for large temperatures.

Domínguez, Macarena; Muñoz, Víctor; Valdivia, Juan Alejandro

2012-05-01

311

We developed an exact analytical treatment for space-charge waves within a relativistic electron beam in terms of (self-reproducing) propagating eigenmodes. This result is of obvious theoretical relevance as it constitutes one of the few exact solution for the evolution of charged particles under the action of self-interactions. It also has clear numerical applications in particle accelerator physics where it can

Gianluca Geloni; Evgeni Saldin; Evgeni Schneidmiller; Mikhail Yurkov

2005-01-01

312

Stability, Causality, and Shock Waves in the Israel - Theory of Relativistic Dissipative Fluids.

NASA Astrophysics Data System (ADS)

The stability, causality, and hyperbolicity properties were analyzed for the Israel-Stewart theory of relativistic dissipative fluids formulated in the energy frame. The equilibria of the theory which are stable for small perturbations were found by constructing a Liapunov functional. The conditions which guarantee that small perturbations about equilibrium will propagate with velocities less than the speed of light and will obey a system of hyperbolic differential equations were determined by calculating the characteristic velocities. It was shown that the stability conditions are equivalent to the causality and hyperbolicity conditions. The behavior of the theory far from equilibrium was studied by considering the plane symmetric motions of an inviscid ultrarelativistic Boltzmann gas. The theory was shown to be hyperbolic for large deviations from equilibrium, and acausality implies instability in this example. The plane steady shock wave solutions were also studied for the Israel-Stewart theory formulated in the Eckart frame. The theory was shown to fail to adequately describe the structure of strong shock waves. Physically acceptable solutions do not exist above a maximum upstream Mach number in any thermally nonconducting and viscous fluid described by the theory because the solutions become multiple-valued when the characteristic velocity is exceeded. It was also proven that physically acceptable solutions do not exist for thermally conducting and viscous fluids above either a maximum upstream Mach number, or else below a minimum downstream Mach number (or both). These limiting Mach numbers again correspond to the characteristic velocities of the fluid. Only extremely weak plane steady shock solutions can be single-valued in the Israel-Stewart theory for the ultrarelativistic Boltzmann gas or for the degenerate free Fermi gas.

Olson, Timothy Scott

1990-08-01

313

Experiments to assess preheat in blast-wave-drive instability experiments

NASA Astrophysics Data System (ADS)

The use of multi-kilojoule, ns lasers to launch shock waves has become a standard method for initiating hydrodynamic experiments in Laboratory Astrophysics. However, the intense laser ablation that creates moving plasma also leads to the production of unwanted energetic x-rays and suprathermal electrons, both of which can be sources of material preheating. In principle, this preheat can alter the conditions of the experimental setup prior to the occurrence of the intended dynamics. At the University of Michigan, ongoing Rayleigh-Taylor instability experiments are defined by precise initial conditions, and potential deformation due to preheat could greatly affect their accuracy. An experiment devised and executed in an attempt to assess the preheat in this specific case will be presented, along with the quantitative analysis of the data obtained and comparison with 2D simulations.

Krauland, Christine; Drake, Paul; Kuranz, Carolyn; Grosskopf, Michael; Boehly, Tom

2009-11-01

314

A dual-band relativistic backward wave oscillator with dual electron beams generating C-band and X-band microwaves is investigated experimentally. The frequencies, powers, and radiation patterns of the dual-band microwaves are measured. With the diode voltage of 657 kV and the total beam current of 14 kA guided by a magnetic field of about 1.7 T, the dual-band microwaves are generated with dominant frequencies of 4.58 and 8.30 GHz close to the results from the particle-in-cell simulation. The powers of the C-band and X-band microwaves are 520 and 113 MW, respectively. The effects of variations in the guiding magnetic field and diode voltage on the powers of the dual-band microwaves are presented and discussed. The radiation patterns of the dual-band microwaves from the radiating antenna are tested both corresponding to a TM{sub 01} mode and the independency of the operation processes of them is discussed.

Wang Ting; Qian Baoliang; Zhang Jiande; Zhang Xiaoping; Cao Yibing; Zhang Qiang [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2011-01-15

315

NASA Astrophysics Data System (ADS)

A dual-band relativistic backward wave oscillator with dual electron beams generating C-band and X-band microwaves is investigated experimentally. The frequencies, powers, and radiation patterns of the dual-band microwaves are measured. With the diode voltage of 657 kV and the total beam current of 14 kA guided by a magnetic field of about 1.7 T, the dual-band microwaves are generated with dominant frequencies of 4.58 and 8.30 GHz close to the results from the particle-in-cell simulation. The powers of the C-band and X-band microwaves are 520 and 113 MW, respectively. The effects of variations in the guiding magnetic field and diode voltage on the powers of the dual-band microwaves are presented and discussed. The radiation patterns of the dual-band microwaves from the radiating antenna are tested both corresponding to a TM01 mode and the independency of the operation processes of them is discussed.

Ting, Wang; Bao-Liang, Qian; Jian-de, Zhang; Xiao-Ping, Zhang; Yi-Bing, Cao; Qiang, Zhang

2011-01-01

316

It is shown that the interaction of the superstrong laser radiation with an isotropic plasma leads to the generation of low frequency electromagnetic (EM) waves and in particular a quasistationary magnetic field. When the relativistic circularly polarized transverse EM wave propagates along z-axis, it creates a ponderomotive force, which affects the motion of particles along the direction of its propagation. On the other hand, motion of the particles across the direction of propagation is defined by the ponderomotive potential. The dispersion relation for the transverse EM wave using a special distribution function, which has an anisotropic form, is derived. The dispersion relation is subsequently investigated for a number of special cases. In general, it is shown that the growth rate of the EM wave strongly depends upon its intensity.

Gillani, S. S. A.; Shah, H. A. [Department of Physics, Government College University, Lahore 54000 (Pakistan); Tsintsadze, N. L. [Department of Physics, Government College University, Lahore 54000 (Pakistan); Salam Chair in Physics, Government College University, Lahore 54000 (Pakistan); Institute of Physics, Tbilisi 380077 (Georgia); Razzaq, M. [Department of Physics, Government College University, Lahore 54000 (Pakistan); Salam Chair in Physics, Government College University, Lahore 54000 (Pakistan)

2010-08-15

317

NASA Astrophysics Data System (ADS)

We present results from mid-IR spectroscopic observations of two young supernova remnants (SNRs) in the Large Magellanic Cloud made with the Spitzer Space Telescope. We imaged SNRs B0509-67.5 and B0519-69.0 with Spitzer in 2005, and follow-up spectroscopy presented here confirms the presence of warm, shock-heated dust, with no lines present in the spectrum. We use model fits to Spitzer Infrared Spectrograph (IRS) data to estimate the density of the post-shock gas. Both remnants show asymmetries in the infrared images, and we interpret bright spots as places where the forward shock is running into material that is several times denser than elsewhere. The densities we infer for these objects depend on the grain composition assumed, and we explore the effects of differing grain porosity on the model fits. We also analyze archival XMM-Newton RGS spectroscopic data, where both SNRs show strong lines of both Fe and Si, coming from ejecta, as well as strong O lines, which may come from ejecta or shocked ambient medium. We use model fits to IRS spectra to predict X-ray O line strengths for various grain models and values of the shock compression ratio. For 0509-67.5, we find that compact (solid) grain models require nearly all O lines in X-ray spectra to originate in reverse-shocked ejecta. Porous dust grains would lower the strength of ejecta lines relative to those arising in the shocked ambient medium. In 0519-69.0, we find significant evidence for a higher than standard compression ratio of 12, implying efficient cosmic-ray acceleration by the blast wave. A compact grain model is favored over porous grain models. We find that the dust-to-gas mass ratio of the ambient medium is significantly lower than what is expected in the interstellar medium.

Williams, Brian J.; Borkowski, Kazimierz J.; Reynolds, Stephen P.; Ghavamian, Parviz; Raymond, John C.; Long, Knox S.; Blair, William P.; Sankrit, Ravi; Smith, R. Chris; Points, Sean; Winkler, P. Frank; Hendrick, Sean P.

2011-03-01

318

To combat the problem of traumatic brain injury (TBI), a signature injury of the current military conflicts, there is an urgent\\u000a need to design head protection systems with superior blast\\/ballistic impact mitigation capabilities. Toward that end, the\\u000a blast impact mitigation performance of an advanced combat helmet (ACH) head protection system equipped with polyurea suspension\\u000a pads and subjected to two different

M. Grujicic; W. C. Bell; B. Pandurangan; P. S. Glomski

319

A Test of the Blandford & McKee solution using Adaptive Mesh and Fixed Mesh Relativistic Hydro Codes

NASA Astrophysics Data System (ADS)

We present preliminary results of a detailed comparison of the evolution of a relativistically expanding, spherical blast wave, using both a spatially fixed, uniformly high resolution relativistic hydrodynamics code, and also the FLASH adaptive mesh relativistic hydro solver.We examine the goodness of fit of the Blandford & McKee solutions for the two cases, both in the vicinity of the shock and far away from it. This work was carried out in the Exploration of the Universe Division at Goddard Space Flight Center under the auspices of the JCA at UMBC.

Cannizzo, J. K.

2006-06-01

320

A nonlinear quantum theory of stimulated Cherenkov radiation of transverse electromagnetic waves from a low-density relativistic electron beam in an isotropic dielectric medium is presented. A quantum model based on the Klein-Gordon equation is used. The growth rates of beam instabilities caused by the effect of stimulated Cherenkov radiation have been determined in the linear approximation. Mechanisms of the nonlinear saturation of relativistic quantum Cherenkov beam instabilities have been analyzed and the corresponding analytical solutions have been obtained.

Bobylev, Yu. B.; Kuzelev, M. V. [Moscow State University, Faculty of Physics (Russian Federation)

2012-06-15

321

Near-term development of the existing PHERMEX standing-wave linac would provide a 40 to 60 MeV electron beam with a current of 3 kA capable of answering a number of fundamental issues concerning endoatmospheric, ultra-relativistic electron beam propagation. Inherent high-repetition rate and multiple-pulse capability would allow alternative propagation scenarios to be investigated. Much of the theoretical expertise required to support the technology development and time-resolved beam propagation experiments presently resides within the Theoretical Applications Division.

Moir, D.C.; Faehl, R.J.; Newberger, B.S.; Thode, L.E.

1981-01-01

322

NASA Astrophysics Data System (ADS)

We present results from a new set of three-dimensional general-relativistic hydrodynamic simulations of rotating iron core collapse. We assume octant symmetry and focus on axisymmetric collapse, bounce, the early postbounce evolution, and the associated gravitational wave (GW) and neutrino signals. We employ a finite-temperature nuclear equation of state, parametrized electron capture in the collapse phase, and a multispecies neutrino leakage scheme after bounce. The latter captures the important effects of deleptonization, neutrino cooling and heating and enables approximate predictions for the neutrino luminosities in the early evolution after core bounce. We consider 12-M? and 40-M? presupernova models and systematically study the effects of (i) rotation, (ii) progenitor structure, and (iii) postbounce neutrino leakage on dynamics, GW, and neutrino signals. We demonstrate that the GW signal of rapidly rotating core collapse is practically independent of progenitor mass and precollapse structure. Moreover, we show that the effects of neutrino leakage on the GW signal are strong only in nonrotating or slowly rotating models in which GW emission is not dominated by inner core dynamics. In rapidly rotating cores, core bounce of the centrifugally deformed inner core excites the fundamental quadrupole pulsation mode of the nascent protoneutron star. The ensuing global oscillations (f˜700-800Hz) lead to pronounced oscillations in the GW signal and correlated strong variations in the rising luminosities of antineutrino and heavy-lepton neutrinos. We find these features in cores that collapse to protoneutron stars with spin periods ?2.5ms and rotational energies sufficient to drive hyperenergetic core-collapse supernova explosions. Hence, GW or neutrino observations of a core-collapse event could deliver strong evidence for or against rapid core rotation. Joint GW+neutrino observations would allow one to make statements with high confidence. Our estimates suggest that the GW signal should be detectable throughout the Milky Way by advanced laser-interferometer GW observatories, but a water-Cherenkov neutrino detector would have to be of near-megaton size to observe the variations in the early neutrino luminosities from a core collapse event at 1 kpc.

Ott, C. D.; Abdikamalov, E.; O'Connor, E.; Reisswig, C.; Haas, R.; Kalmus, P.; Drasco, S.; Burrows, A.; Schnetter, E.

2012-07-01

323

NASA Astrophysics Data System (ADS)

Radiative shock waves play a pivotal role in the transport energy into the stellar medium. This fact has led to many efforts to scale the astrophysical phenomena to accessible laboratory conditions and their study has been highlighted as an area requiring further experimental investigations. Low density material with high atomic mass is suitable to achieve radiative regime, and, therefore, low density xenon gas is commonly used for the medium in which the radiative shock propagates. In this work the average ionization and the thermodynamic regimes of xenon plasmas are determined as functions of the matter density and temperature in a wide range of plasma conditions. The results obtained will be applied to characterize blast waves launched in xenon clusters.

Rodriguez, R.; Gil, J. M.; Florido, R.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Symes, D. R.; Hohenberger, M.; Smith, R. A.

2011-06-01

324

Long range correlations and the soft ridge in relativistic nuclear collisions

Relativistic Heavy Ion Collider experiments exhibit correlations peaked in relative azimuthal angle and extended in rapidity. Called the ridge, this peak occurs both with and without a jet trigger. We argue that the untriggered ridge arises when particles formed by flux tubes in an early Glasma stage later manifest transverse flow. Combining a blast wave model of flow fixed by single-particle spectra with a simple description of the Glasma, we find excellent agreement with current data.

Gavin, Sean; Moschelli, George [Department of Physics and Astronomy, Wayne State University, 666 W. Hancock, Detroit, Michigan 48202 (United States); McLerran, Larry [Physics Department and RIKEN Brookhaven Research Center, Building 510A, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2009-05-15

325

Long range correlations and the soft ridge in relativistic nuclear collisions

NASA Astrophysics Data System (ADS)

Relativistic Heavy Ion Collider experiments exhibit correlations peaked in relative azimuthal angle and extended in rapidity. Called the ridge, this peak occurs both with and without a jet trigger. We argue that the untriggered ridge arises when particles formed by flux tubes in an early Glasma stage later manifest transverse flow. Combining a blast wave model of flow fixed by single-particle spectra with a simple description of the Glasma, we find excellent agreement with current data.

Gavin, Sean; McLerran, Larry; Moschelli, George

2009-05-01

326

Long range correlations and the soft ridge in relativistic nuclear collisions

Relativistic Heavy Ion Collider experiments exhibit correlations peaked in relative azimuthal angle and extended in rapidity. Called the ridge, this peak occurs both with and without a jet trigger. We argue that the untriggered ridge arises when particles formed by flux tubes in an early Glasma stage later manifest transverse flow. Combining a blast wave model of flow fixed by single-particle spectra with a simple description of the Glasma, we find excellent agreement with current data.

McLerran, L.; Gavin, S., Moschelli, G.

2009-05-19

327

NASA Astrophysics Data System (ADS)

The symmetry properties of the S matrix in a fully relativistic distorted-wave treatment of electron-impact ionization are investigated. It is shown that the square modulus of the scattering matrix element in which the spin states of all four electrons are determined is not invariant under the reversal of the direction of alignment of all spins. The largest of two contributions to this noninvariance originates from the relativistic modifications of the continuum wave functions induced by the distorting potential of the target atom. A second smaller contribution is manifested on reducing the eight-dimensional matrix elements of the QED covariant propagator to purely spatial two-electron integrals. The triple differential cross section (TDCS) exhibits a spin asymmetry unless the entire scattering process occurs in a single plane. There will be a difference in the TDCS between an (e,2e) event in which the initial beam is polarized parallel or antiparallel with respect to the beam direction even if the target is unpolarized and the final spin states are not determined. The TDCS will remain unchanged if, in addition to reversal of the direction of spin alignment, one appropriate momentum component of one of the two outgoing electrons is reversed.

Pyper, N. C.; Kampp, Marco; Whelan, Colm T.

2005-05-01

328

Relativistic Plasma Dispersion Relation.

National Technical Information Service (NTIS)

The relativistic plasma dispersion relation for waves propagating perpendicular to a constant magnetic field is transformed into a rapidly converging series of integrals. Landau damping of the electrostatic waves is recovered in the limit of zero magnetic...

B. N. A. Lamborn

1969-01-01

329

Relativistic plasma dispersion relation

The relativistic plasma dispersion relation for waves propagating perpendicular to a constant magnetic field is transformed into a rapidly converging series of integrals. Landau damping of the electrostatic waves is recovered in the limit of zero magnetic field.

B N A Lamborn; B. N. A

1969-01-01

330

Shock waves in relativistic nuclear matter, I. [Rankine-Hugoniot relations

The relativistic Rankine-Hugoniot relations are developed for a 3-dimensional plane shock and a 3-dimensional oblique shock. Using these discontinuity relations together with various equations of state for nuclear matter, the temperatures and the compressibilities attainable by shock compression for a wide range of laboratory kinetic energy of the projectile are calculated. 12 references.

A. M. Gleeson; S. Raha

1979-01-01

331

Stability, Causality, and Shock Waves in the Israel - Theory of Relativistic Dissipative Fluids

The stability, causality, and hyperbolicity properties were analyzed for the Israel-Stewart theory of relativistic dissipative fluids formulated in the energy frame. The equilibria of the theory which are stable for small perturbations were found by constructing a Liapunov functional. The conditions which guarantee that small perturbations about equilibrium will propagate with velocities less than the speed of light and will

Timothy Scott Olson

1990-01-01

332

Two-fluid temperature-dependent relativistic waves in magnetized streaming pair plasmas

A relativistic two-fluid temperature-dependent approach for a streaming magnetized pair plasma is considered. Such a scenario corresponds to secondary plasmas created at the polar caps of pulsar magnetospheres. In the model the generalized vorticity rather than the magnetic field is frozen into the fluid. For parallel propagation four transverse modes are found. Two are electromagnetic plasma modes which at high

A. R. Soto-Chavez; S. M. Mahajan; R. D. Hazeltine

2010-01-01

333

Scalar-relativistic, all-electron density functional theory (DFT) calculations were done for free, neutral atoms of all elements of the periodic table using the universal Gaussian basis set. Each core, closed-subshell contribution to a total atomic electron density distribution was separately fitted to a spherical electron density function: a linear combination of s-type Gaussian functions. The resulting core subshell electron densities are useful for systematically and compactly approximating total core electron densities of atoms in molecules, for any atomic core defined in terms of closed subshells. When used to augment the electron density from a wave function based on a calculation using effective core potentials (ECPs) in the Hamiltonian, the atomic core electron densities are sufficient to restore the otherwise-absent electron density maxima at the nuclear positions and eliminate spurious critical points in the neighborhood of the atom, thus enabling quantum theory of atoms in molecules (QTAIM) analyses to be done in the neighborhoods of atoms for which ECPs were used. Comparison of results from QTAIM analyses with all-electron, relativistic and nonrelativistic molecular wave functions validates the use of the atomic core electron densities for augmenting electron densities from ECP-based wave functions. For an atom in a molecule for which a small-core or medium-core ECPs is used, simply representing the core using a simplistic, tightly localized electron density function is actually sufficient to obtain a correct electron density topology and perform QTAIM analyses to obtain at least semiquantitatively meaningful results, but this is often not true when a large-core ECP is used. Comparison of QTAIM results from augmenting ECP-based molecular wave functions with the realistic atomic core electron densities presented here versus augmenting with the limiting case of tight core densities may be useful for diagnosing the reliability of large-core ECP models in particular cases. For molecules containing atoms of any elements of the periodic table, the production of extended wave function files that include the appropriate atomic core densities for ECP-based calculations, and the use of these wave functions for QTAIM analyses, has been automated. PMID:21780749

Keith, Todd A; Frisch, Michael J

2011-07-22

334

Rock damage control in bedrock blasting excavation for a nuclear power plant

Drill and blast is a major method for bedrock excavation in nuclear power plant engineering. Under blasting excavation, blast-induced vibration propagates in rock mass and induces damage to surrounding rock. Studying the characteristics of wave propagation and blast-induced damage to rock mass is most important to restrict the damage extension. In the present paper, in support of the bedrock blasting

Li Haibo; Xia Xiang; Li Jianchun; Zhao Jian; Liu Bo; Liu Yaqun

2011-01-01

335

NASA Astrophysics Data System (ADS)

Only a handful of supernovae (SNe) have been studied in multiwavelengths from the radio to X-rays, starting a few days after the explosion. The early detection and classification of the nearby Type IIb SN 2011dh/PTF 11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at one of the youngest phase ever of a core-collapse SN (days 3-12 after the explosion) in the radio, millimetre and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding SN shock wave does not exhibit equipartition (?e/?B ˜ 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R-2. Within modelling uncertainties we find an average velocity of the fast parts of the ejecta of 15 000 ± 1800 km s-1, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast wave regime between the previously defined compact and extended SN Type IIb subtypes. Our results highlight the importance of early (˜1 d) high-frequency observations of future events. Moreover, we show the importance of combined radio/X-ray observations for determining the microphysics ratio ?e/?B.

Horesh, Assaf; Stockdale, Christopher; Fox, Derek B.; Frail, Dale A.; Carpenter, John; Kulkarni, S. R.; Ofek, Eran O.; Gal-Yam, Avishay; Kasliwal, Mansi M.; Arcavi, Iair; Quimby, Robert; Cenko, S. Bradley; Nugent, Peter E.; Bloom, Joshua S.; Law, Nicholas M.; Poznanski, Dovi; Gorbikov, Evgeny; Polishook, David; Yaron, Ofer; Ryder, Stuart; Weiler, Kurt W.; Bauer, Franz; Van Dyk, Schuyler D.; Immler, Stefan; Panagia, Nino; Pooley, Dave; Kassim, Namir

2013-09-01

336

30 CFR 57.6306 - Loading, blasting, and security.

Code of Federal Regulations, 2010 CFR

...device, all persons shall leave the blast area except persons in a blasting shelter or other location that protects them from concussion (shock wave), flying material, and gases. (f) Before firing a blastâ (1) Ample warning shall be given to...

2009-07-01

337

30 CFR 56.6306 - Loading, blasting, and security.

Code of Federal Regulations, 2010 CFR

...device, all persons shall leave the blast area except persons in a blasting shelter or other location that protects them from concussion (shock wave), flying material, and gases. (f) Before firing a blastâ (1) Ample warning shall be given to...

2009-07-01

338

30 CFR 57.6306 - Loading, blasting, and security.

Code of Federal Regulations, 2013 CFR

...device, all persons shall leave the blast area except persons in a blasting shelter or other location that protects them from concussion (shock wave), flying material, and gases. (f) Before firing a blastâ (1) Ample warning shall be given to...

2013-07-01

339

30 CFR 56.6306 - Loading, blasting, and security.

Code of Federal Regulations, 2013 CFR

2013-07-01

340

Analytic Representation of Relativistic Wave Equations II: The Square-Root Operator Case

In this paper, using the theory of fractional powers for operators, we construct the most general (analytic) representation for the square-root operator of relativistic quantum theory. We allow for arbitrary, but time-independent, vector potential and mass terms. Our representation is uniquely determined by the Green's function for the corresponding Schrödinger equation. We find that the square-root operator is represented by

Tepper L. Gill; W. W. Zachary

341

NASA Astrophysics Data System (ADS)

Measurement of azimuthal anisotropy is one of the most important study because of its relation to the initial stage. Especially, the elliptical anisotropy which is measured as the second coefficient of Fourier expansion of particle azimuthal distribution is believed to carry the information about the initial geometrical anisotropy. It seems the identified hadron v 2 depends on the number of quark contents of the hadron. The experimental result of quark number scaling of v 2 suggests quark level collectivity in the hot dense matter and quark coalescence mechanism to form hadron from quark matter via quark-gluon phase transition. The measured v 2 and p T spectra are analyzed with various assumptions based on the blast wave model in order to understand the freeze-out temperature and collective flow after the system expansion.

Ikeda, Yoshimasa

2012-12-01

342

We present a theoretical model and its numerical realization, which describes a submicron cavity formation in a transparent dielectric under a tight focusing of a ultrashort laser pulse. The model contains two parts. The first one provides the laser energy deposition in the sample along with the energy balance--the reflection and transmission of the laser pulse. It resolves the full set of Maxwell's equations in the two-dimensional geometry coupled to the material equations describing the atomic ionization by the laser electric field and the secondary electron collisions and the recombination processes. The second part describes the launch of the blast wave and the cavity formation under the deposited laser energy. The results of numerical simulations are compared with a qualitative theoretical model and experimental results.

Hallo, Ludovic; Tikhonchuk, Vladimir T.; Mezel, Candice; Breil, Jerome [Universite Bordeaux 1, CNRS, CEA, UMR 5107, 33405 Talence Cedex (France); Bourgeade, Antoine [CEA-CESTA, BP 1, 33114 Le Barp (France)

2007-07-01

343

Relativistic distorted-wave collision strengths have been calculated for the three transitions among the three levels with a hole in the n = 2 shell and for the 327 transitions from these levels to the excited levels with two holes in the n = 2 shell and one electron in the n = 3 shell in all the 71 F-like ions with nuclear charge number Z in the range 22 {le} Z {le} 92. The results are given here for a sample of 18 values of Z. The calculations were made for the six final, or scattered, electron energies E{prime} = 0.008, 0.04, 0.10, 0.21, 0.41, and 0.75, where E{prime} is in units of Z{sub eff}{sup 2} rydbergs with Z{sub eff} = Z {minus}6.667. In addition, the transition energies and electric dipole oscillator strengths are given. To the authors knowledge the present work is the first comprehensive publication of the results of fully relativistic calculations of the collision strengths for excitation of F-like ions.

Sampson, D.H.; Zhang, Hong Lin; Fontes, C.J. (Pennsylvania State Univ., University Park (United States))

1991-05-01

344

NASA Astrophysics Data System (ADS)

We developed an exact analytical treatment for space-charge waves within a relativistic electron beam in terms of (self-reproducing) propagating eigenmodes. This result is of obvious theoretical relevance as it constitutes one of the few exact solution for the evolution of charged particles under the action of self-interactions. It also has clear numerical applications in particle accelerator physics where it can be used as the first self-consistent benchmark for space-charge simulation programs. Today our work is of practical relevance in FEL technology in relation with all those schemes where an optically modulated electron beam is needed and with the study of longitudinal space-charge instabilities in magnetic bunch compressors.

Geloni, Gianluca; Saldin, Evgeni; Schneidmiller, Evgeni; Yurkov, Mikhail

2005-12-01

345

RF phase control in a high-power high-efficiency klystron-like relativistic backward wave oscillator

NASA Astrophysics Data System (ADS)

The klystron-like relativistic backward wave oscillator (RBWO) with a dual-cavity extractor has demonstrated 10 GW output power with 48% efficiency in recent simulations. To realize radio-frequency (RF) phase control for the purpose of coherent power combining, a high-power high-efficiency klystron-like RBWO with an input signal is presented. In the device, an independent input cavity is introduced before the resonant reflector to reduce the leakage power from the input port, and the applied RF signal is injected into the input cavity through a mode convertor and a coaxial waveguide along the magnet, which avoids separating the magnet by the injection waveguide, and suppresses the asymmetric modes excited in the input cavity. For a frequency difference of 15 MHz between the input signal and free-running klystron-like RBWO, an input power of 10 MW is sufficient to control the phase of 10 GW output microwave.

Xiao, Renzhen; Chen, Changhua; Song, Wei; Zhang, Xiaowei; Sun, Jun; Song, Zhimin; Zhang, Lijun; Zhang, Ligang

2011-07-01

346

The Relativistic Transformation for an Electromagnetic Plane Wave with General Time Dependence

ERIC Educational Resources Information Center

|In special relativity, the transformation between inertial frames for an electromagnetic plane wave is usually derived for the time-harmonic case (the field is a sinusoid of infinite duration), even though all practical waves are of finite duration and may not even contain a dominant sinusoid. This paper presents an alternative derivation in…

Smith, Glenn S.

2012-01-01

347

The Relativistic Transformation for an Electromagnetic Plane Wave with General Time Dependence

ERIC Educational Resources Information Center

In special relativity, the transformation between inertial frames for an electromagnetic plane wave is usually derived for the time-harmonic case (the field is a sinusoid of infinite duration), even though all practical waves are of finite duration and may not even contain a dominant sinusoid. This paper presents an alternative derivation in which…

Smith, Glenn S.

2012-01-01

348

NASA Astrophysics Data System (ADS)

Relativistic electron flux in the outer radiation belt tends to increase during the high-speed solar wind stream (HSS) events. However, HSS events do not always cause large flux enhancement. To determine the HSS events that cause such enhancement and the mechanisms that are responsible for accelerating the electrons, we analyzed long-term plasma data sets, for periods longer than one solar cycle. We demonstrate that during HSS events with the southward interplanetary magnetic field (IMF)-dominant HSS (SBz-HSS), relativistic electrons are accelerated by whistler mode waves; however, during HSS events with the northward IMF-dominant HSS, this acceleration mechanism is not effective. The differences in the responses of the outer radiation belt flux variations are caused by the differences in the whistler mode wave-electron interactions associated with a series of substorms. During SBz-HSS events, hot electron injections occur and the thermal plasma density decreases due to the shrinkage of the plasmapause, causing large flux enhancement of relativistic electrons through whistler mode wave excitation. These results explain why large flux enhancement of relativistic electrons tends to occur during SBz-HSS events.

Miyoshi, Y.; Kataoka, R.; Kasahara, Y.; Kumamoto, A.; Nagai, T.; Thomsen, M. F.

2013-09-01

349

NASA Astrophysics Data System (ADS)

A weakly nonlinear analysis is carried out to derive the appropriate Korteweg-de Vries-Burgers-like equation for small, but finite amplitude, ion-acoustic waves in a dissipative plasma consisting of relativistic ions, Maxwell-Boltzmann distributed positrons and superthermal electrons. Our results show that in a such plasma, ion-acoustic shock waves, the spatial patterns of which are significantly modified by the relativistic and dissipative effects, may exist. Interestingly, we found that because of ion kinematic viscosity, an initial solitonic profile develops into a shock wave. This later evolves towards a monotonic profile (dissipation-dominant case) as the electrons deviate from their thermodynamic equilibrium. As the relativistic character of the plasma becomes important, the shock wave amplitude decreases. Our investigation may be taken as a prerequisite for the understanding of the shock-waves observed in the ionosphere and the auroral acceleration regions. We recall that when a high energy cosmic ray interacts with the earth's atmosphere, it may produce an electron-positron pair with enormous velocities. The data obtained during the Alpha Magnetic Spectrometer (AMS) flight permitting to probe the radiation belts in the Earth's innermost magnetosphere provided an evidence of the presence of positrons.

Pakzad, Hamid Reza; Tribeche, Mouloud

2013-04-01

350

The surface plasma waves in a magnetized dusty plasma elliptical cylinder driven by elliptic relativistic electron beam propagating inside the elliptical cylinder are studied. The dispersion relation of surface plasma waves has been retrieved from the derived dispersion relation by considering that the beam is absent and there is no dust in the plasma cylinder. Mathematically, it is shown that the beam can interact with the surface plasma waves via Cerenkov interaction and fast cyclotron interaction. The growth rate and phase velocity in every cases are obtained. Finally, the numerical results and graphs are presented.

Abdoli-Arani, A.; Jazi, B. [Department of Physics, University of Kashan, Kashan (Iran, Islamic Republic of)

2012-05-15

351

Precipitation of trapped relativistic electrons by amplified whistler waves in the magnetosphere

Numerical study of a loss-cone negative mass instability to amplify whistler waves by energetic electrons in the radiation belts is presented. The results show that a very low intensity whistler wave can be amplified by 50 keV electrons more than 25 dB, consistent with the Siple experimental result [Helliwell et al., J. Geophys. Res. 85, 3360 (1980)]. The dependencies of the amplification factor on the energetic electron density and on the initial wave intensity are evaluated. It is shown that the amplification factor decreases as the initial wave intensity increases. However, this gain can still exceed 15 dB for a 30 dB increase of the initial wave intensity, which is needed for the purpose of precipitating MeV electrons in the radiation belts. We then show that there exists a double resonance situation, by which, as an example, a wave is simultaneously in cyclotron resonance with 50 keV electrons as well as with 1.5 MeV electrons; the wave is first amplified by 50 keV electrons and then precipitates 1.5 MeV electrons. With the aid of the cyclotron resonance, the threshold field for the commencement of chaos in the electron trajectories is reduced considerably from that for a general case. Pitch angle scattering of 1.5 MeV electrons is demonstrated. The results show that a whistler wave with magnetic field amplitude of 0.08% of the background magnetic field can scatter electrons from an initial pitch angle of 86.5 deg. to a pitch angle <50 deg.

Kuo, S. P.; Kuo, Steven S.; Huynh, James T.; Kossey, Paul [Department of Electrical and Computer Engineering, Polytechnic University, Six MetroTech Center, New York, New York 11201 (United States); Northrop Grumman Space Technology, One Space Park, Redondo Beach, California 90278 (United States); Raytheon Space and Airborne Systems, El Segundo, California 90245 (United States); Air Force Research Laboratory/Space Vehicle Branch, Hanscom Air Force Base, Massachusetts 01731 (United States)

2007-06-15

352

Klystronlike relativistic backward wave oscillator (RBWO) can produce microwave power exceeding 5 GW with a high efficiency larger than 40%. In the experiment of klystronlike RBWO, for about 1 MV peak diode voltages, increasing magnetic field from 1.43 to 1.89 T slowed the impedance collapse until it was suppressed completely. The introduction of a stainless steel obstructing ring aggravated the impedance collapse, whereas replacing the stainless steel obstructing ring with a flat stainless steel provided a more stable impedance variation during the pulse duration. These impedance collapses did not affect microwave generation seriously and may be attributed to the radial expansion of cathode plasma initialing from the cathode shank so that part of reverse currents were collected at the anode wall, contributing to the measured diode current. On the other hand, it was found that microwave generation shot-to-shot reproducibility was closely related to the diode impedance variation. When there was no or very low microwave measured, diode impedance collapse appeared at the latter of the pulse. The microwave generation shot-to-shot reproducibility was improved greatly after the electron collector was enlarged on radius with 1 mm. A possible explanation is that the anode plasma produced from electron collector expands axially and enters the diode region at a very high velocity of several mm/ns. The movement of the anode plasma in the beam-wave interaction region affects the microwave generation, which reduces the microwave power during the whole pulse duration significantly.

Xiao Renzhen; Sun Jun; Huo Shaofei; Li Xiaoze; Zhang Ligang; Zhang Xiaowei; Zhang Lijun [Northwest Institute of Nuclear Technology, Xi'an 710024 (China)

2010-12-15

353

Two-dimensional s-polarized solitary waves in relativistic plasmas. I. The fluid plasma model.

The properties of two-dimensional linearly s-polarized solitary waves are investigated by fluid-Maxwell equations and particle-in-cell (PIC) simulations. These self-trapped electromagnetic waves appear during laser-plasma interactions, and they have a dominant electric field component E(z), normal to the plane of the wave, that oscillates at a frequency below the electron plasma frequency ?(pe). A set of equations that describe the waves are derived from the plasma fluid model in the case of cold or warm plasma and then solved numerically. The main features, including the maximum value of the vector potential amplitude, the total energy, the width, and the cavitation radius are presented as a function of the frequency. The amplitude of the vector potential increases monotonically as the frequency of the wave decreases, whereas the width reaches a minimum value at a frequency of the order of 0.82 ?(pe). The results are compared with a set of PIC simulations where the solitary waves are excited by a high-intensity laser pulse. PMID:22060509

Sánchez-Arriaga, G; Lefebvre, E

2011-09-09

354

Two-dimensional s-polarized solitary waves in relativistic plasmas. I. The fluid plasma model

The properties of two-dimensional linearly s-polarized solitary waves are investigated by fluid-Maxwell equations and particle-in-cell (PIC) simulations. These self-trapped electromagnetic waves appear during laser-plasma interactions, and they have a dominant electric field component E{sub z}, normal to the plane of the wave, that oscillates at a frequency below the electron plasma frequency {omega}{sub pe}. A set of equations that describe the waves are derived from the plasma fluid model in the case of cold or warm plasma and then solved numerically. The main features, including the maximum value of the vector potential amplitude, the total energy, the width, and the cavitation radius are presented as a function of the frequency. The amplitude of the vector potential increases monotonically as the frequency of the wave decreases, whereas the width reaches a minimum value at a frequency of the order of 0.82 {omega}{sub pe}. The results are compared with a set of PIC simulations where the solitary waves are excited by a high-intensity laser pulse.

Sanchez-Arriaga, G.; Lefebvre, E. [CEA, DAM, DIF, F-91297 Arpajon (France)

2011-09-15

355

A number of experimental models of blast brain injury have been implemented in rodents and larger animals. However, the variety of blast sources and the complexity of blast wave biophysics have made data on injury mechanisms and biomarkers difficult to analyze and compare. Recently, we showed the importance of rat position toward blast generated by an external shock tube. In this study, we further characterized blast producing moderate traumatic brain injury and defined "composite" blast and primary blast exposure set-ups. Schlieren optics visualized interaction between the head and a shock wave generated by external shock tube, revealing strong head acceleration upon positioning the rat on-axis with the shock tube (composite blast), but negligible skull movement upon peak overpressure exposure off-axis (primary blast). Brain injury signatures of a primary blast hitting the frontal head were assessed and compared to damage produced by composite blast. Low to negligible levels of neurodegeneration were found following primary blast compared to composite blast by silver staining. However, persistent gliosis in hippocampus and accumulation of GFAP/CNPase in circulation was detected after both primary and composite blast. Also, markers of vascular/endothelial inflammation integrin alpha/beta, soluble intercellular adhesion molecule-1, and L-selectin along with neurotrophic factor nerve growth factor-beta were increased in serum within 6?h post-blasts and persisted for 7?days thereafter. In contrast, systemic IL-1, IL-10, fractalkine, neuroendocrine peptide Orexin A, and VEGF receptor Neuropilin-2 (NRP-2) were raised predominantly after primary blast exposure. In conclusion, biomarkers of major pathological pathways were elevated at all blast set-ups. The most significant and persistent changes in neuro-glial markers were found after composite blast, while primary blast instigated prominent systemic cytokine/chemokine, Orexin A, and Neuropilin-2 release, particularly when primary blast impacted rats with unprotected body. PMID:22403567

Svetlov, Stanislav I; Prima, Victor; Glushakova, Olena; Svetlov, Artem; Kirk, Daniel R; Gutierrez, Hector; Serebruany, Victor L; Curley, Kenneth C; Wang, Kevin K W; Hayes, Ronald L

2012-02-09

356

Explosive overpressure brain injury (OBI) impacts the lives of both military and civilian population. We hypothesize that a single exposure to OBI results in increased hypothalamic expression of oxidative stress and activation of the sympatho-adrenal medullary axis. Since a key component of blast-induced organ injury is the primary overpressure wave, we assessed selective biochemical markers of autonomic function and oxidative stress in male Sprague Dawley rats subjected to head-directed overpressure insult. Rats were subjected to single head-directed OBI with a 358kPa peak overpressure at the target. Control rats were exposed to just noise signal being placed at ~2m distance from the shock tube nozzle. Sympathetic nervous system activation of the adrenal medullae (AM) was evaluated at 6h following blast injury by assessing the expression of catecholamine biosynthesizing enzymes, tyrosine hydroxylase (TH), dopamine-? hydroxylase (D?H), neuropeptide Y (NPY) along with plasma norepinephrine (NE). TH, D?H and NPY expression increased 20%, 25%, and 91% respectively, following OBI (P<0.05). Plasma NE was also significantly elevated by 23% (P<0.05) following OBI. OBI significantly elevated TH (49%, P<0.05) in the nucleus tractus solitarius (NTS) of the brain stem while AT1 receptor expression and NADPH oxidase activity, a marker of oxidative stress, was elevated in the hypothalamus following OBI. Collectively, the increased levels of TH, D?H and NPY expression in the rat AM, elevated TH in NTS along with increased plasma NE suggest that single OBI exposure results in increased sympathoexcitation. The mechanism may involve the elevated AT1 receptor expression and NADPH oxidase levels in the hypothalamus. Taken together, such effects may be important factors contributing to pathology of brain injury and autonomic dysfunction associated with the clinical profile of patients following OBI. PMID:23570732

Tümer, Nihal; Svetlov, Stanislav; Whidden, Melissa; Kirichenko, Nataliya; Prima, Victor; Erdos, Benedek; Sherman, Alexandra; Kobeissy, Firas; Yezierski, Robert; Scarpace, Philip J; Vierck, Charles; Wang, Kevin K W

2013-04-06

357

The recently developed structure model that uses the generator coordinate method to perform configuration mixing of angular-momentum projected wave functions, generated by constrained self-consistent relativistic mean-field calculations for triaxial shapes (3DAMP+GCM), is applied in a systematic study of ground states and low-energy collective states in the even-even magnesium isotopes {sup 20-40}Mg. Results obtained using a relativistic point-coupling nucleon-nucleon effective interaction in the particle-hole channel and a density-independent {delta} interaction in the pairing channel are compared to data and with previous axial 1DAMP+GCM calculations, both with a relativistic density functional and the nonrelativistic Gogny force. The effects of the inclusion of triaxial degrees of freedom on the low-energy spectra and E2 transitions of magnesium isotopes are examined.

Yao, J. M.; Mei, H.; Chen, H. [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Meng, J. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Department of Physics, University of Stellenbosch, Stellenbosch (South Africa); Ring, P. [Physik-Department der Technischen Universitaet Muenchen, D-85748 Garching (Germany); Vretenar, D. [Physics Department, Faculty of Science, University of Zagreb, HR-10000 Zagreb (Croatia)

2011-01-15

358

The nonlinear propagation of ion acoustic waves in electron-positron-ion plasma comprising of Boltzmannian electrons, positrons, and relativistic thermal ions has been examined. The Korteweg-de Vries-Burger equation has been derived by reductive perturbation technique, and its shock like solution is determined analytically through tangent hyperbolic method. The effect of various plasma parameters on strength and structure of shock wave is investigated. The pert graphical view of the results has been presented for illustration. It is observed that strength and steepness of the shock wave enervate with an increase in the ion temperature, relativistic streaming factor, positron concentrations, electron temperature and they accrue with an increase in coefficient of kinematic viscosity. The convective, dispersive, and dissipative properties of the plasma are also discussed. It is determined that the electron temperature has remarkable influence on the propagation and structure of nonlinear wave in such relativistic plasmas. The numerical analysis has been done based on the typical numerical data from a pulsar magnetosphere.

Saeed, R.; Shah, Asif [Theoretical Plasma Physics Division, PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan)

2010-03-15

359

We develop a Markov process theory of charged particle scattering from stationary, transverse, magnetic waves. We examine approximations that lead to quasilinear theory, in particular the resonant diffusion approximation. We find that, when appropriate, the resonant diffusion approximation simplifies the result of the weak turbulence approximation without significant further restricting the regime of applicability. We also explore a theory generated by expanding drift and diffusion rates in terms of a presumed small correlation time. This small correlation time expansion leads to results valid for relatively small pitch angle and large wave energy density - a regime that may govern pitch angle scattering of high-energy electrons into the geomagnetic loss cone.

Lemons, Don S. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-01-15

360

Spectrum of abdominal organ injury in a primary blast type

INTRODUCTION: Abdominal organ injury in a primary blast type is always challenging for diagnosis. Air containing abdominal viscera is most vulnerable to effects of primary blast injury. In any patient exposed to a primary blast wave who presents with an acute abdomen, an abdominal organ injury is to be kept in a clinical suspicion. AIM: Study various abdominal organ injuries

Imtiaz Wani; Fazal Q Parray; Tariq Sheikh; Rauf A Wani; Abid Amin; Imran Gul; Mir Nazir

2009-01-01

361

Relativistic Wave Equations for Particles with Internal Structure and Mass Spectrum

We consider a class of wave equations which couple an infinite number of tensors or spinors of all ranks. Such a system of equations naturally possesses an infinite number of mass levels, and each eigenfunction implicitly contains a built-in form factor. Two simple examples of first order differential equations are examined. One is based on the set of all finite

Yoichiro Nambu

1966-01-01

362

General relativistic shock waves in fluids for which pressure equals energy density

A shock wave in a self-gravitating fluid obeying the equation of state: pressure equal to energy density is shown to travel with the velocity of light in a space-time determined by the Einstein field equations. The jump conditions that must be satisfied by the hydrodynamic variables are derived and discussed as are those that must be satisfied by the metric

A. H. Taub

1973-01-01

363

Primary and secondary skeletal blast trauma.

This study examines primary (resulting from blast wave) and secondary (resulting from disintegrated, penetrating fragments) blast trauma to the skeleton. Eleven pigs were exposed to semi-controlled blast events of varying explosive type, charge size, and distance, including some cases with shrapnel. Skeletal trauma was found to be extensive, presenting as complex, comminuted fractures with numerous small, displaced bone splinters and fragments. Traumatic amputation of the limbs and cranium was also observed. Fractures were concentrated in areas nearer the blast, but there was generally no identifiable point of impact. Fractures were more random in appearance and widespread than those typically associated with gunshot or blunt force injury events. These patterns appear to be uniquely associated with blast trauma and may therefore assist forensic anthropologists and other forensic examiners in the interpretation of skeletal trauma by enabling them to differentiate between blast trauma and trauma resulting from some other cause. PMID:21981586

Christensen, Angi M; Smith, Victoria A; Ramos, Vanessa; Shegogue, Candie; Whitworth, Mark

2011-10-07

364

We investigate the tunneling conductance on the surface of topological insulator ferromagnet (F)\\/insulator (I)\\/superconductor (S) junction where superconducting type is either s- or d-wave paring. Topological insulators (TI) are insulating in bulk but conducting on the surface with the Dirac-fermion-like carriers. In contrast to the Dirac fermions in graphene, relativistic mass of the Dirac fermions in TI can be easily

Assanai Suwanvarangkoon; I-Ming Tang; Rassmidara Hoonsawat; Bumned Soodchomshom

2011-01-01

365

Rodent model of direct cranial blast injury.

Traumatic brain injury resulting from an explosive blast is one of the most serious wounds suffered by warfighters, yet the effects of explosive blast overpressure directly impacting the head are poorly understood. We developed a rodent model of direct cranial blast injury (dcBI), in which a blast overpressure could be delivered exclusively to the head, precluding indirect brain injury via thoracic transmission of the blast wave. We constructed and validated a Cranium Only Blast Injury Apparatus (COBIA) to deliver blast overpressures generated by detonating .22 caliber cartridges of smokeless powder. Blast waveforms generated by COBIA replicated those recorded within armored vehicles penetrated by munitions. Lethal dcBI (LD(50) ? 515?kPa) was associated with: (1) apparent brainstem failure, characterized by immediate opisthotonus and apnea leading to cardiac arrest that could not be overcome by cardiopulmonary resuscitation; (2) widespread subarachnoid hemorrhages without cortical contusions or intracerebral or intraventricular hemorrhages; and (3) no pulmonary abnormalities. Sub-lethal dcBI was associated with: (1) apnea lasting up to 15?sec, with transient abnormalities in oxygen saturation; (2) very few delayed deaths; (3) subarachnoid hemorrhages, especially in the path of the blast wave; (4) abnormal immunolabeling for IgG, cleaved caspase-3, and ?-amyloid precursor protein (?-APP), and staining for Fluoro-Jade C, all in deep brain regions away from the subarachnoid hemorrhages, but in the path of the blast wave; and (5) abnormalities on the accelerating Rotarod that persisted for the 1 week period of observation. We conclude that exposure of the head alone to severe explosive blast predisposes to significant neurological dysfunction. PMID:21639724

Kuehn, Reed; Simard, Philippe F; Driscoll, Ian; Keledjian, Kaspar; Ivanova, Svetlana; Tosun, Cigdem; Williams, Alicia; Bochicchio, Grant; Gerzanich, Volodymyr; Simard, J Marc

2011-08-08

366

Stability of relativistic stars

NASA Astrophysics Data System (ADS)

Stable relativistic stars form a two-parameter family, parametrized by mass and angular velocity. Limits on each of these quantities are associated with relativistic instabilities discovered by Chandrasekhar: A radial instability, to gravitational collapse or explosion, marks the upper and lower limits on their mass; and an instability driven by gravitational waves may set an upper limit on their spin. Our summary of relativistic stability theory given here is based on and includes excerpts from the book Rotating Relativistic Stars, by the present authors (Friedman & Sterigioulas 2011).

Friedman, John L.; Stergioulas, Nikolaos

2011-03-01

367

A computational model of blast loading on the human eye.

Ocular injuries from blast have increased in recent wars, but the injury mechanism associated with the primary blast wave is unknown. We employ a three-dimensional fluid-structure interaction computational model to understand the stresses and deformations incurred by the globe due to blast overpressure. Our numerical results demonstrate that the blast wave reflections off the facial features around the eye increase the pressure loading on and around the eye. The blast wave produces asymmetric loading on the eye, which causes globe distortion. The deformation response of the globe under blast loading was evaluated, and regions of high stresses and strains inside the globe were identified. Our numerical results show that the blast loading results in globe distortion and large deviatoric stresses in the sclera. These large deviatoric stresses may be indicator for the risk of interfacial failure between the tissues of the sclera and the orbit. PMID:23591604

Bhardwaj, Rajneesh; Ziegler, Kimberly; Seo, Jung Hee; Ramesh, K T; Nguyen, Thao D

2013-04-17

368

Experimental work is underway by a SLAC-LLNL-LBL collaboration to investigate the feasibility of using relativistic klystrons as a power source for future high gradient accelerators. Two different relativistic klystron configurations have been built and tested to date: a high grain multicavity klystron at 11.4 GHz and a low gain two cavity subharmonic buncher driven at 5.7 GHz. In both configurations power is extracted at 11.4 GHz. In order to understand the basic physics issues involved in extracting RF from a high power beam, we have used both a single resonant cavity and a multi-cell traveling wave structure for energy extraction. We have learned how to overcome our previously reported problem of high power RF pulse shortening, and have achieved peak RF power levels of 170 MW with the RF pulse of the same duration as the beam current pulse. 6 refs., 3 figs., 3 tabs.

Allen, M.A.; Azuma, O.; Callin, R.S.; Deruyter, H.; Eppley, K.R.; Fant, K.S.; Fowkes, W.R.; Herrmannsfeldt, W.B.; Hoag, H.A.; Koontz, R.F.

1989-03-01

369

NASA Astrophysics Data System (ADS)

The reductive perturbation method is used to derive a generic form of nonlinear Schrödinger equation (NLSE) that describes the nonlinear evolution of electrostatic (ES)/electromagnetic (EM) waves in fully relativistic two-fluid plasmas. The matrix eigenvector analysis shows that there are two mutually exclusive modes of waves, each mode involving only either one of two electric potentials, A and ?. The general result is applied to the electromagnetic mode in electron-ion plasmas with relativistically high electron temperature (Te>>mec2). In the limit of high frequency (ck>>?e), the NLSE predicts bump type electromagnetic soliton structures having width scaling as ~kTe5/2. It is shown that, in electron-positron pair plasmas with high temperature, dip type electromagnetic solitons can exist. The NLSE is also applied to electrostatic (Langmuir) wave and it is shown that dip type solitons can exist if k?D<<1, where ?D is the electron's Debye length. For the k?D>>1, however, the solution is of bump type soliton with width scaling as ~1/(k5Te). It is also shown that dip type solitons can exist in cold plasmas having relativistically high streaming speed.

Lee, Nam C.

2012-08-01

370

The reductive perturbation method is used to derive a generic form of nonlinear Schroedinger equation (NLSE) that describes the nonlinear evolution of electrostatic (ES)/electromagnetic (EM) waves in fully relativistic two-fluid plasmas. The matrix eigenvector analysis shows that there are two mutually exclusive modes of waves, each mode involving only either one of two electric potentials, A and {phi}. The general result is applied to the electromagnetic mode in electron-ion plasmas with relativistically high electron temperature (T{sub e} Much-Greater-Than m{sub e}c{sup 2}). In the limit of high frequency (ck Much-Greater-Than {omega}{sub e}), the NLSE predicts bump type electromagnetic soliton structures having width scaling as {approx}kT{sub e}{sup 5/2}. It is shown that, in electron-positron pair plasmas with high temperature, dip type electromagnetic solitons can exist. The NLSE is also applied to electrostatic (Langmuir) wave and it is shown that dip type solitons can exist if k{lambda}{sub D} Much-Less-Than 1, where {lambda}{sub D} is the electron's Debye length. For the k{lambda}{sub D} Much-Greater-Than 1, however, the solution is of bump type soliton with width scaling as {approx}1/(k{sup 5}T{sub e}). It is also shown that dip type solitons can exist in cold plasmas having relativistically high streaming speed.

Lee, Nam C. [Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of)

2012-08-15

371

NASA Astrophysics Data System (ADS)

Relativistic distorted-wave collision strengths have been calculated for the 16 ?n=0 optically allowed transitions with n=2 in the 67 Be-like ions with nuclear charge number Z in the range 26?Z?92. The calculations were made for the four final, or scattered, electron energies E'=0.20, 0.42, 0.80, and 1.40, where E' is in units of Zeff2 Ry with Z=Z-2.5. In the present calculation, an improved "top-up" method, which employs relativistic plane waves, was used to obtain the high partial-wave contribution for each transition, in contrast to the partial-relativistic Coulomb-Bethe approximation used in previous work by Zhang and Sampson [H.L. Zhang and D.H. Sampson, At. Data Nucl. Data Tables 52 (1992) 143]. In that earlier work, collision strengths were also provided for Be-like ions, but for a more comprehensive data set consisting of all 45 ?n=0 transitions, six scattered energies, and the 85 ions with Z in the range 8?Z?92. The collision strengths covered in the present work should be more accurate than the corresponding data given by Zhang and Sampson [H.L. Zhang and D.H. Sampson, At. Data Nucl. Data Tables 52 (1992) 143] and are presented here to replace those earlier results.

Zhang, Hong Lin; Fontes, Christopher J.

2013-07-01

372

NASA Astrophysics Data System (ADS)

We demonstrate the use of a fast InGaAs array and spectrometer to measure properties related to near-infrared absorption and emission (750 nm -1500 nm) following a high explosive detonation. Using a broadband light source and a rigid absorption gauge, gas temperatures are measured at a rate of 20 kHz for a period of several milliseconds behind the blast wave from a PETN, PBXN-5, and PBXN-113 detonations. The temperature and concentration of water vapor is determined by fitting experimental transmission spectra to a simulated database. Strong emission signatures obtained during the PETN breakout event (integrated over approximately the first 20 microseconds) indicate the presence of high energy nitrogen and oxygen atoms. Measurements from water absorption at a distance of 23 cm from the PETN charge indicate temperatures decaying from 1600 K to 600 K during the first few milliseconds, and measurements of non-ideal explosives with optically thick postdetonation environments are also demonstrated. These measurements are intended to aid the development of detonation and explosive simulations.

Koch, Jon D.; Carney, Joel; Lightstone, James; Piecuch, Scott

2012-03-01

373

Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, we present the first results from a computational study of such a system under drive conditions to be attainable on the National Ignition Facility. Using the multiphysics, AMR, higher order Godunov Eulerian hydrocode, Raptor, we consider the late nonlinear instability evolution for multiple amplitude and phase realizations of a variety of multimode spectral types. We show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions by allowing for memory of the initial conditions to be retained in the mix width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. Certain aspects of the initial conditions, including the rms amplitude, are shown to have a strong effect on the time to transition to the quasi-self-similar regime.

Miles, A R; Edwards, M J; Greenough, J A

2004-03-26

374

Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, results from three-dimensional (3D) numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams 9, 209 (1991)] are presented. Using the multiphysics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J. A. Greenough, J. Comput. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pretransition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernovae are discussed.

Miles, A.R.; Blue, B.; Edwards, M.J.; Greenough, J.A.; Hansen, J.F.; Robey, H.F.; Drake, R.P.; Kuranz, C.; Leibrandt, D.R. [Lawrence Livermore National Laboratory, L-021, 7000 East Avenue, P.O. Box 808, Livermore, California 94551 (United States); University of Michigan, 2455 Hayward Street, Ann Arbor, Michigan 48109 (United States)

2005-05-15

375

NASA Astrophysics Data System (ADS)

The detailed mechanism of blast-induced traumatic brain injury (bTBI) has not been revealed yet. Thus, reliable laboratory animal models for bTBI are needed to investigate the possible diagnosis and treatment for bTBI. In this study, we used laser-induced shock wave (LISW) to induce TBI in rats and investigated the histopathological similarities to actual bTBI. After craniotomy, the rat brain was exposed to a single shot of LISW with a diameter of 3 mm at various laser fluences. At 24 h after LISW exposure, perfusion fixation was performed and the extracted brain was sectioned; the sections were stained with hematoxylin-eosin. Evans blue (EB) staining was also used to evaluate disruption of the blood brain barrier. At certain laser fluence levels, neural cell injury and hemorrhagic lesions were observed in the cortex and subcortical region. However, injury was limited in the tissue region that interacted with the LISW. The severity of injury increased with increasing laser fluence and hence peak pressure of the LISW. Fluorescence originating from EB was diffusively observed in the injuries at high fluence levels. Due to the grade and spatial controllability of injuries and the histological observations similar to those in actual bTBI, brain injuries caused by LISWs would be useful models to study bTBI.

Hatano, Ben; Matsumoto, Yoshihisa; Otani, Naoki; Saitoh, Daizoh; Tokuno, Shinichi; Satoh, Yasushi; Nawashiro, Hiroshi; Matsushita, Yoshitaro; Sato, Shunichi

2011-02-01

376

We solve the relativistic Riemann problem in viscous matter using the relativistic Boltzmann equation and the relativistic causal dissipative fluid-dynamical approach of Israel and Stewart. Comparisons between these two approaches clarify and point out the regime of validity of second-order fluid dynamics in relativistic shock phenomena. The transition from ideal to viscous shocks is demonstrated by varying the shear viscosity to entropy density ratio {eta}/s. We also find that a good agreement between these two approaches requires a Knudsen number Kn<1/2.

Bouras, I.; El, A.; Fochler, O.; Greiner, C. [Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main (Germany); Molnar, E. [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt am Main (Germany); KFKI, Research Institute of Particle and Nuclear Physics, H-1525 Budapest, P.O. Box 49 (Hungary); Niemi, H. [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt am Main (Germany); Xu, Z.; Rischke, D. H. [Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main (Germany); Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt am Main (Germany)

2010-08-15

377

Nonlinear model and simulation technique of the interaction and energy transfer between a fast wave and a large-orbit relativistic electron beam in a coaxial electrostatic wiggler are presented. Unlike the situations in a magnetostatic-wiggler free-electron laser (MWFEL) and in an electron cyclotron maser (ECM), the electrostatic potential of the electrons plays an important role and participates in the energy exchange between the wave and the electron beam. Compared to MWFEL and ECM, the coaxial electrostatic-wiggler configuration has a distinguishing peculiarity that besides the electron-beam's kinetic energy, its electrostatic potential energy can be effectively transferred to the fast wave. Simulation shows that wave could be amplified with ultrahigh gain by extracting both the kinetic energy and electrostatic potential energy of the electron beam.

Zhang Shichang [Institute of Photoelectronics, Campus Mail Box 50, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)

2010-05-15

378

Proceedings of the eleventh annual symposium on explosives and blasting research

These proceedings contain 26 papers presented at the conference. Topics relate to performance of explosives, blast wave propagation, charge malfunctions, building response to ground vibrations, tunnel excavations, detonator design, reduction of ground vibration, blast design, blast fragmentation measurement, and blast analysis. Most of the papers have been processed separately for inclusion on the data base.

NONE

1995-12-31

379

NASA Astrophysics Data System (ADS)

A repository of fundamental experimental and analytical data concerning the complex phenomena associated with gun-muzzle blast and flash effects is presented, proceeding from gun muzzle signatures to modern gun-propulsion concepts, interior and transitional ballistics, and characterizations of blast-wave research and muzzle flash. Data are presented in support of a novel hypothesis which explains the ignition of secondary flash and elucidates the means for its suppression. Both chemical and mechanical (often competing) methods of flash suppression are treated. The historical work of Kesslau and Ladenburg is noted, together with French, British, Japanese and American research efforts and current techniques of experimental characterization for gun muzzle phenomena.

Klingenberg, Guenter; Heimerl, Joseph M.

380

NASA Astrophysics Data System (ADS)

Transport properties of massive Dirac particles are investigated through an oscillating barrier. The Floquet quasienergies related to the time-dependent potential appear both in transmission and reflection as sidebands around the incoming electron's energy. We take all relevant sidebands into account and present time averaged transmission and reflection probabilities in a wide energy range. Most qualitative features of scattering on a static barrier—like Klein paradox—are still visible, but the transmission probability in the evanescent regime observably increases due to the oscillation of the potential. The strongly inelastic scattering process is shown to lead to multiple Fano-type resonances and temporal trapping of the particles inside the oscillating potential. We also present a detailed study of the time evolution of the wave packets generated in the scattering process. Our results can be relevant for graphene with an induced energy gap.

Szabó, Lóránt Zs.; Benedict, Mihály G.; Czirják, Attila; Földi, Péter

2013-08-01

381

Animation of electromagnetic waves propagating in open resonators of relativistic Cerenkov devices

NASA Astrophysics Data System (ADS)

The paper is devoted to the high power overmoded microwave devices' design problem. Reasonable estimation of electron beam limit power level is given. The problems connected with degeneration of electromagnetic modes with different azimuthal indexes near the p-cutoff of the operating E01 mode are considered and illustrated on instance of an experimental device. Dispersive curves for the case of electromagnetic waves' cyclotron absorption process are studied. The results of investigation of limit power level transported in open resonators of one-mode and overmoded devices by operating and parasitic modes are displayed by series of animation frames. All estimations and calculations are fulfilled by help the 3D linear mode computer code 'MULTIWAVES-2000'.

Pikunov, Viktor M.; Chernyavskiy, Igor A.

2001-08-01

382

NASA Astrophysics Data System (ADS)

Preface; Prologue: Conference overview Bernard Carr; Part I. The Universe At Large and Very Large Redshifts: 2. The size and age of the Universe Gustav A. Tammann; 3. Active galaxies at large redshifts Malcolm S. Longair; 4. Observational cosmology with the cosmic microwave background George F. Smoot; 5. Future prospects in measuring the CMB power spectrum Philip M. Lubin; 6. Inflationary cosmology Michael S. Turner; 7. The signature of the Universe Bernard J. T. Jones; 8. Theory of large-scale structure Sergei F. Shandarin; 9. The origin of matter in the universe Lev A. Kofman; 10. New guises for cold-dark matter suspects Edward W. Kolb; Part II. Physics and Astrophysics Of Relativistic Compact Objects: 11. On the unification of gravitational and inertial forces Donald Lynden-Bell; 12. Internal structure of astrophysical black holes Werner Israel; 13. Black hole entropy: external facade and internal reality Valery Frolov; 14. Accretion disks around black holes Marek A. Abramowicz; 15. Black hole X-ray transients J. Craig Wheeler; 16. X-rays and gamma rays from active galactic nuclei Roland Svensson; 17. Gamma-ray bursts: a challenge to relativistic astrophysics Martin Rees; 18. Probing black holes and other exotic objects with gravitational waves Kip Thorne; Epilogue: the past and future of relativistic astrophysics Igor D. Novikov; I. D. Novikov's scientific papers and books.

Jones, Bernard J. T.; Markovic, Dragoljub

1997-06-01

383

Gravitational-Wave Memory from the Relativistic Jet of Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

The gravitational-wave (GW) memory from a radiating and decelerating point mass is studied in detail. It is found that for isotropic photon emission the memory generated from the photons is essentially the same as the memory from the point mass that radiated the photons, so that it is anti-beamed. On the other hand, for anisotropic emission the memory from the photons may have a non-vanishing amplitude, even if it is seen at small viewing angles. In the decelerating phases of gamma-ray burst (GRB) jets the kinetic energy of the jet is converted into the energy of gamma-ray photons. It would then be possible to observe a variation in the GW memory associated with GRB jets on the timescale of the gamma-ray emission if the emission is partially anisotropic. Such anisotropy in gamma-ray emission has been suggested by polarizations detected in recent observations of GRBs. The GW memory from GRB jets would provide clues for clarifying the geometry of the jets and the emission mechanism in GRBs. Thus, it will be an interesting target for the next-generation detectors of GWs.

Akiba, Shota; Nakada, Megumi; Yamaguchi, Chiyo; Iwamoto, Koichi

2013-06-01

384

Quasi-optical theory of coaxial and cylindrical relativistic surface-wave oscillators

NASA Astrophysics Data System (ADS)

In terms of a quasi-optical approach, a nonlinear nonstationary theory of surface-wave oscillators, coaxial and cylindrical multiwave Cherenkov oscillators (MCOs) fed by large-diameter tubular electron beams, is constructed. The small curvature of the waveguide walls allows one to appreciably simplify the MCO dynamics analysis by considering a quasi-plane model. In this model, local surface fields near the corrugated cylindrical wall are close to fields of a plane corrugated with the same depth and period and the cylindrical geometry is taken into account by introducing azimuthal periodicity conditions. The results obtained in terms of the averaged approach are compared with those of direct numerical particle-in-cell (PIC) simulation and experimental data. Remarkably, PIC simulation demonstrates the existence of a single-frequency oscillation regime at long perimeters in which the self-synchronization of different azimuthal modes takes place. As a result, an azimuthally asymmetric stationary field distribution sets in, which can be assigned to dissipative structures well known in the theory of self-sustained oscillation systems.

Ginzburg, N. S.; Zaslavskii, V. Yu.; Malkin, A. M.; Sergeev, A. S.

2013-02-01

385

Relativistic distorted-wave collision strengths are given for the 248 possible transitions from the ground level to the excited levels with n = 4 and 5 in the 33 Ni-like ions with nuclear charge number Z in the range 60 {much lt} Z {much lt} 92. The calculations were made for the six final, or scattered, electron energies E{prime} = 0.002, 0.01, 0.03, 0.07, 0.15, and 0.28, where E{prime} is in units of Z{sub eff}{sup 2} rydbergs with Z{sub eff} = Z {minus} 22.5. In addition, the transition energies and electric dipole oscillator strengths are given. To the authors knowledge the present work is the first comprehensive publication of the results of fully relativistic calculations of the collision strengths for excitation of highly charged Ni-like ions.

Zhang, Hong Lin; Sampson, D.H.; Fontes, C.J. (Pennsylvania State Univ., University Park (United States))

1991-05-01

386

NASA Astrophysics Data System (ADS)

Attention is given to the influence of the depth of the absoption zone of relativistic electron beams (REB) on the characteristics of pressure waves generated in metallic targets. A comparison is made between experimental data on the fixation of the velocity of the free target surface after a shock-wave encounter and the results of a computer-based numerical simulation. It is found that, for targets with thicknesses comparable to the classical depth of the energy liberation zone, the computed pressure wave parameters are sensitive to the magnitude of the energy for the given parameters of the REB. It is concluded that, in thick copper and aluminum targets, the absorption of the REB is determined by the classical mechanism.

Akkerman, A. F.; Bushman, A. V.; Demidov, B. A.; Zavgorodnii, S. F.; Ivkin, M. V.

1986-11-01

387

Monte Carlo Simulations of Nonlinear Particle Acceleration in Parallel Trans-relativistic Shocks

NASA Astrophysics Data System (ADS)

We present results from a Monte Carlo simulation of a parallel collisionless shock undergoing particle acceleration. Our simulation, which contains parameterized scattering and a particular thermal leakage injection model, calculates the feedback between accelerated particles ahead of the shock, which influence the shock precursor and "smooth" the shock, and thermal particle injection. We show that there is a transition between nonrelativistic shocks, where the acceleration efficiency can be extremely high and the nonlinear compression ratio can be substantially greater than the Rankine-Hugoniot value, and fully relativistic shocks, where diffusive shock acceleration is less efficient and the compression ratio remains at the Rankine-Hugoniot value. This transition occurs in the trans-relativistic regime and, for the particular parameters we use, occurs around a shock Lorentz factor ?0 = 1.5. We also find that nonlinear shock smoothing dramatically reduces the acceleration efficiency presumed to occur with large-angle scattering in ultra-relativistic shocks. Our ability to seamlessly treat the transition from ultra-relativistic to trans-relativistic to nonrelativistic shocks may be important for evolving relativistic systems, such as gamma-ray bursts and Type Ibc supernovae. We expect a substantial evolution of shock accelerated spectra during this transition from soft early on to much harder when the blast-wave shock becomes nonrelativistic.

Ellison, Donald C.; Warren, Donald C.; Bykov, Andrei M.

2013-10-01

388

In the UCLA plasma beat wave accelerator, a high intensity two frequency CO{sub 2} laser ({lambda}{sub 1}=10.6 {mu}m, {lambda}{sub 2}=10.3 {mu}m) is used to drive a large amplitude relativistic plasma wave. The plasma wave acts as a moving phase grating and scatters the incident pump waves into Stokes and anti-Stokes sidebands ({omega}{sub 1}{minus}{omega}{sub p}, {omega}{sub 2}+{omega}{sub p}). The observation of these sidebands in the forward direction confirms the presence of the relativistic plasmon, and also gives an estimate of the amplitude{endash}length product (n{sub 1}/n{sub 0}{times}L) of the wave. Since the Stokes and anti-Stokes signals are picosecond pulses at 10.9 and 10.0 {mu}m, respectively, this light cannot be time resolved directly on a conventional detector or streak camera. The forward scattered light can be analyzed, however, by mixing the 10 {mu}m light with visible light from a laser diode (670 nm) in a nonlinear crystal (AgGaS{sub 2}) to produce frequency shifted light at 630 nm. The intensity of the 630 nm light is proportional to the product of the intensities of the two incident laser pulses, and can be time resolved on a streak camera. Experimental results for the plasma wave amplitude, spatial length, and temporal length are shown. {copyright} {ital 1997 American Institute of Physics.}

Lal, A.; Gordon, D.; Marsh, K.; Wharton, K.; Clayton, C.; Joshi, C. [Department of Electrical Engineering, UCLA, Los Angeles, California 90024 (United States)

1997-01-01

389

Blast exposure is associated with traumatic brain injury (TBI), neuropsychiatric symptoms, and long-term cognitive disability. We examined a case series of postmortem brains from U.S. military veterans exposed to blast and/or concussive injury. We found evidence of chronic traumatic encephalopathy (CTE), a tau protein-linked neurodegenerative disease, that was similar to the CTE neuropathology observed in young amateur American football players and a professional wrestler with histories of concussive injuries. We developed a blast neurotrauma mouse model that recapitulated CTE-linked neuropathology in wild-type C57BL/6 mice 2 weeks after exposure to a single blast. Blast-exposed mice demonstrated phosphorylated tauopathy, myelinated axonopathy, microvasculopathy, chronic neuroinflammation, and neurodegeneration in the absence of macroscopic tissue damage or hemorrhage. Blast exposure induced persistent hippocampal-dependent learning and memory deficits that persisted for at least 1 month and correlated with impaired axonal conduction and defective activity-dependent long-term potentiation of synaptic transmission. Intracerebral pressure recordings demonstrated that shock waves traversed the mouse brain with minimal change and without thoracic contributions. Kinematic analysis revealed blast-induced head oscillation at accelerations sufficient to cause brain injury. Head immobilization during blast exposure prevented blast-induced learning and memory deficits. The contribution of blast wind to injurious head acceleration may be a primary injury mechanism leading to blast-related TBI and CTE. These results identify common pathogenic determinants leading to CTE in blast-exposed military veterans and head-injured athletes and additionally provide mechanistic evidence linking blast exposure to persistent impairments in neurophysiological function, learning, and memory. PMID:22593173

Goldstein, Lee E; Fisher, Andrew M; Tagge, Chad A; Zhang, Xiao-Lei; Velisek, Libor; Sullivan, John A; Upreti, Chirag; Kracht, Jonathan M; Ericsson, Maria; Wojnarowicz, Mark W; Goletiani, Cezar J; Maglakelidze, Giorgi M; Casey, Noel; Moncaster, Juliet A; Minaeva, Olga; Moir, Robert D; Nowinski, Christopher J; Stern, Robert A; Cantu, Robert C; Geiling, James; Blusztajn, Jan K; Wolozin, Benjamin L; Ikezu, Tsuneya; Stein, Thor D; Budson, Andrew E; Kowall, Neil W; Chargin, David; Sharon, Andre; Saman, Sudad; Hall, Garth F; Moss, William C; Cleveland, Robin O; Tanzi, Rudolph E; Stanton, Patric K; McKee, Ann C

2012-05-16

390

Relativistic astrophysical phenomena such as gamma-ray bursts (GRBs) and active galactic nuclei often require long-lived strong magnetic fields that cannot be achieved by shock compression alone. Here, we report on three-dimensional special-relativistic magnetohydrodynamic (MHD) simulations that we performed using a second-order Godunov-type conservative code to explore the amplification and decay of macroscopic turbulence dynamo excited by the so-called Richtmyer-Meshkov instability

Tsuyoshi Inoue; Katsuaki Asano; Kunihito Ioka

2011-01-01

391

A quantum theory of instabilities of a relativistic electron beam due to the stimulated Cherenkov effect in a dielectric and the stimulated Compton effect in vacuum is presented. The instability growth rates are found in a linear approximation and are shown to go over to the familiar growth rates in the classical approximation. A nonlinear theory of instabilities in the quantum case is developed. Analytic solutions are obtained that describe the nonlinear saturation of the amplitudes of the electromagnetic waves emitted by the beam.

Kuzelev, M. V. [Moscow State University (Russian Federation)

2010-07-15

392

The phenomenon of passive compression of frequency-modulated (FM) pulses in a dispersive media (DM) was used to increase the peak microwave power up to the multigigawatt level. A helically corrugated waveguide was used as the DM, while a relativistic X-band backward-wave oscillator (RBWO) with a descending-during-the-pulse accelerating voltage served as a source of FM pulses. Compression of pulses down to a halfwidth of 2.2 ns accompanied by a 4.5-fold power increase up to a value of about 3.2 GW has been demonstrated.

Bratman, V. L.; Denisov, G. G.; Kolganov, N. G.; Mishakin, S. V.; Samsonov, S. V. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); Cross, A. W.; He, W.; Zhang, L.; McStravick, M.; Whyte, C. G.; Young, A. R.; Ronald, K.; Robertson, C. W.; Phelps, A. D. R. [Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow, Scotland G4 0NG (United Kingdom)

2010-11-15

393

Blast-induced mild traumatic brain injury.

Traumatic brain injury (TBI) has been a major cause of mortality and morbidity in the wars in Iraq and Afghanistan. Blast exposure has been the most common cause of TBI, occurring through multiple mechanisms. What is less clear is whether the primary blast wave causes brain damage through mechanisms that are distinct from those common in civilian TBI and whether multiple exposures to low-level blast can lead to long-term sequelae. Complicating TBI in soldiers is the high prevalence of posttraumatic stress disorder. At present, the relationship is unclear. Resolution of these issues will affect both treatment strategies and strategies for the protection of troops in the field. PMID:21093677

Elder, Gregory A; Mitsis, Effie M; Ahlers, Stephen T; Cristian, Adrian

2010-10-15

394

The concentrations of wave functions about classical periodic orbits, or quantum scars, are a fundamental phenomenon in physics. An open question is whether scarring can occur in relativistic quantum systems. To address this question, we investigate confinements made of graphene whose classical dynamics are chaotic and find unequivocal evidence of relativistic quantum scars. The scarred states can lead to strong conductance fluctuations in the corresponding open quantum dots via the mechanism of resonant transmission.

Huang, Liang [Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Lai Yingcheng [Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Ferry, David K.; Goodnick, Stephen M. [Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Center for Solid State Electronics Research, Arizona State University, Tempe, Arizona 85287 (United States); Akis, Richard [Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Center for Solid State Electronics Research, Arizona State University, Tempe, Arizona 85287 (United States)

2009-07-31

395

Relativistic quantum revivals.

Quantum revivals are now a well-known phenomena within nonrelativistic quantum theory. In this Letter we display the effects of relativity on revivals and quantum carpets. It is generally believed that revivals do not occur within a relativistic regime. Here we show that while this is generally true, it is possible, in principle, to set up wave packets with specific mathematical properties that do exhibit exact revivals within a fully relativistic theory. PMID:20366519

Strange, P

2010-03-26

396

Traumatic brain injury (TBI) from blast produces a number of conundrums. This review focuses on five fundamental questions including: (1) What are the physical correlates for blast TBI in humans? (2) Why is there limited evidence of traditional pulmonary injury from blast in current military field epidemiology? (3) What are the primary blast brain injury mechanisms in humans? (4) If TBI can present with clinical symptoms similar to those of Post-Traumatic Stress Disorder (PTSD), how do we clinically differentiate blast TBI from PTSD and other psychiatric conditions? (5) How do we scale experimental animal models to human response? The preponderance of the evidence from a combination of clinical practice and experimental models suggests that blast TBI from direct blast exposure occurs on the modern battlefield. Progress has been made in establishing injury risk functions in terms of blast overpressure time histories, and there is strong experimental evidence in animal models that mild brain injuries occur at blast intensities that are similar to the pulmonary injury threshold. Enhanced thoracic protection from ballistic protective body armor likely plays a role in the occurrence of blast TBI by preventing lung injuries at blast intensities that could cause TBI. Principal areas of uncertainty include the need for a more comprehensive injury assessment for mild blast injuries in humans, an improved understanding of blast TBI pathophysiology of blast TBI in animal models and humans, the relationship between clinical manifestations of PTSD and mild TBI from blunt or blast trauma including possible synergistic effects, and scaling between animals models and human exposure to blasts in wartime and terrorist attacks. Experimental methodologies, including location of the animal model relative to the shock or blast source, should be carefully designed to provide a realistic blast experiment with conditions comparable to blasts on humans. If traditional blast scaling is appropriate between species, many reported rodent blast TBI experiments using air shock tubes have blast overpressure conditions that are similar to human long-duration nuclear blasts, not high explosive blasts. PMID:22012085

Bass, Cameron R; Panzer, Matthew B; Rafaels, Karen A; Wood, Garrett; Shridharani, Jay; Capehart, Bruce

2011-10-20

397

Note: A table-top blast driven shock tube

NASA Astrophysics Data System (ADS)

The prevalence of blast-induced traumatic brain injury in conflicts in Iraq and Afghanistan has motivated laboratory scale experiments on biomedical effects of blast waves and studies of blast wave transmission properties of various materials in hopes of improving armor design to mitigate these injuries. This paper describes the design and performance of a table-top shock tube that is more convenient and widely accessible than traditional compression driven and blast driven shock tubes. The design is simple: it is an explosive driven shock tube employing a rifle primer that explodes when impacted by the firing pin. The firearm barrel acts as the shock tube, and the shock wave emerges from the muzzle. The small size of this shock tube can facilitate localized application of a blast wave to a subject, tissue, or material under test.

Courtney, Michael W.; Courtney, Amy C.

2010-12-01

398

NASA Astrophysics Data System (ADS)

Simultaneous observations by Cluster and Los Alamos National Laboratory (LANL) spacecraft and Canadian Array for Real-Time Investigations of Magnetic Activity and International Monitor for Auroral Geomagnetic Effects magnetometer arrays during a sudden storm commencement on 25 September 2001 show evidence of relativistic electron acceleration by compressional-mode ULF waves. The waves are driven by the quasiperiodic solar wind dynamical pressure fluctuations that continuously buffet the magnetosphere for ˜3 h. The compressional-mode ULF waves are identified by comparing the power of magnetic field magnitude fluctuations with the total magnetic field power. The radial distribution and azimuthal propagation of both toroidal and poloidal-mode ULF waves are derived from ground-based magnetometer data. The energetic electron fluxes measured by LANL show modulation of low-energy electrons and acceleration of high-energy electrons by the compressional poloidal-mode electric field oscillations. The energy threshold of accelerated electrons at the geosynchronous orbit is ˜0.4 MeV, which is roughly consistent with drift-resonant interaction of magnetospheric electrons with compressional-mode ULF waves.

Tan, Lun C.; Shao, X.; Sharma, A. S.; Fung, Shing F.

2011-07-01

399

NASA Astrophysics Data System (ADS)

Our recently developed collisional-radiative model which included fine-structure cross sections calculated with a fully relativistic distorted-wave method [R.K. Gangwar, L. Sharma, R. Srivastava, A.D. Stauffer, J. Appl. Phys. 111, 053307 (2012)] has been extended to study non-Maxwellian inductively coupled argon plasmas. We have added more processes to our earlier collisional-radiative model by further incorporating relativistic distorted-wave electron impact cross sections from the 3p54sJ = 0, 2 metastable states, (1s3, 1s5 in Paschen's notation) to the 3p55p (3pi) excited states. The population of various excited levels at different pressures in the range of 1-25 mTorr for an inductively coupled argon plasma have been calculated and compared with the recent optical absorption spectroscopy measurements as well as emission model results of Boffard et al. [Plasma Sources Sci. Technol. 19, 065001 (2010)]. We have also calculated the intensities of two emission lines, 420.1 nm (3p9 ? 1s5) and 419.8 nm (3p5 ? 1s4) and compared with measured intensities reported by Boffard et al. [J. Phys. D 45, 045201 (2012)]. Our results are in good agreement with the measurements.

Dipti, HASH(0x100f5750); Gangwar, Reetesh Kumar; Srivastava, Rajesh; Stauffer, Allan Daniel

2013-10-01

400

NASA Astrophysics Data System (ADS)

After five years of operation, the 17 GHz MKII relativistic klystron in service at the MIT Plasma Science and Fusion Center was upgraded with a new output structure to provide a common source of high peak power for continuing operation of the 17 GHz linac, for RF gun testing and for energizing a recently developed circularly polarized beam deflection RF system to evaluate the ultra short electron bunch performance of the linac. The salient features of the impedance and phase velocity tapered new traveling wave output structure designed for high gain and stability are described; and initial high power test results of the 17 GHz relativistic klystron are presented. The output structure was designed as a beam driven bunching and phase shifting 2?/3 mode circuit using codes that were developed over a 40 year period designing, fabricating and testing high current traveling wave linac bunchers. The electrical length of the new (MKIII) output circuit was extended to 1200 degrees using a group to phase velocity harmonic mean ratio of 0.124 to provide total skin losses of less than 5 percent and a phase/frequency sensitivity of only 0.6 degree/MHz. A dual feed racetrack shaped output cavity having a decelerating gradient of 150 kV/cm and beam apertures substantially larger than ?0/2, to allow reduction of space charge debunching forces, are added advantages of this 25 MW, 71 dB gain RF amplifier.

Haimson, J.; Mecklenburg, B.

2003-12-01

401

Mixing Effect in Internal Blast

NASA Astrophysics Data System (ADS)

Detonation product gases are usually assumed to be completely mixed with an existing atmosphere by the time a peak quasi-static pressure (Pqs) is reached within an enclosed internal blast environment. With incomplete mixing, however, comes a loss in pressure from unburned fuel as well as a previously unrecognized source of error: heat capacity of the gas increases substantially with temperature, providing an energy sink in regions of unmixed hot gas. Our objective was to look at the extent of mixing by measuring gas temperature at several locations within a blast chamber at the time of peak Pqs. We recorded ranges of up to 400° C depending on charge location within the chamber, which is presumed to affect turbulence and mixing. Losses in peak Pqs of up to 13% may be attributed to this mixing effect for 1-kg Pentolite charges in a 62-m3 chamber in the simple geometries tested. A reasonably accurate Pqs may be extracted from blast wave reverberations in a chamber, allowing a closer look at effects such as gas mixing and consistency among multiple gages. These results point to an explanation for missing energy and a better understanding of heat flow in internal blast.

Granholm, R. H.; Sandusky, H. W.

2009-12-01

402

Blast traumatic brain injury in the rat using a blast overpressure model.

Traumatic brain injury (TBI) is a serious health concern for civilians and military populations, and blast-induced TBI (bTBI) has become an increasing problem for military personnel over the past 10 years. To understand the biological and psychological effects of blast-induced injuries and to examine potential interventions that may help to prevent, attenuate, and treat effects of bTBI, it is valuable to conduct controlled animal experiments. This unit discusses available paradigms to model traumatic brain injury in animals, with an emphasis on the relevance of these various models to study blast-induced traumatic brain injury (bTBI). This paper describes the detailed methods of a blast overpressure (BOP) paradigm that has been used to conduct experiments with rats to model blast exposure. This particular paradigm models the pressure wave created by explosions, including improvised explosive devices (IEDs). PMID:23315947

Yarnell, Angela M; Shaughness, Michael C; Barry, Erin S; Ahlers, Stephen T; McCarron, Richard M; Grunberg, Neil E

2013-01-01

403

Fully relativistic plasma dispersion function

Properties of a relativistic plasma dispersion function (PDF) that is required for the description of waves propagating perpendicular to a magnetic field in a fully relativistic, magnetized, Maxwellian plasma, are presented. Series, asymptotic series, recurrence relations, integral representations, derivatives, generating functions, approximations, differential equations, and connections with standard transcendental functions are discussed, as are the PDF’s analytic properties.

Le´on P. J. Kamp

1994-01-01

404

Relativistic Effects on Chemical Properties.

ERIC Educational Resources Information Center

|Discusses how anomalous chemical properties may be explained by considering relativistic effects. Traces development of the relativistic wave equation (Dirac equation) starting with the Borh treatment of the hydrogen atom and discusses major consequences of the Dirac equation. Suggests that these topics receive greater attention in the…

McKelvey, Donald R.

1983-01-01

405

Chaotic dynamics of the relativistic kicked rotor

NASA Astrophysics Data System (ADS)

The relativistic periodically driven classical and quantum rotor problems are studied. Kinetical properties of the relativistic standard map is discussed. Quantum rotor is treated by solving the Dirac equation in the presence of the periodic ?-function potential. The relativistic quantum mapping which describes the evolution of the wave function is derived. The time-dependence of the energy are calculated.

Milibaeva, G. M.; Matrasulov, D. U.; Salomov, U. R.; Sundaram, Bala

406

We consider the relativistic deformation of quantum waves and mechanical bodies carrying intrinsic angular momentum (AM). When observed in a moving reference frame, the centroid of the object undergoes an AM-dependent transverse shift. This is the relativistic analogue of the spin-Hall effect, which occurs in free space without any external fields. Remarkably, the shifts of the geometric and energy centroids differ by a factor of 2, and both centroids are crucial for the Lorentz transformations of the AM tensor. We examine manifestations of the relativistic Hall effect in quantum vortices and mechanical flywheels and also discuss various fundamental aspects of this phenomenon. The perfect agreement of quantum and relativistic approaches allows applications at strikingly different scales, from elementary spinning particles, through classical light, to rotating black holes. PMID:22540559

Bliokh, Konstantin Y; Nori, Franco

2012-03-21

407

Relativistic Effects in Resonance Absorption.

National Technical Information Service (NTIS)

The role of the relativistic-electron-mass variation in the generation of plasma waves by the linear mode-conversion of intense electromagnetic waves is investigated. The increase in the electron mass in high intensity regions of the mode-converted wave r...

J. F. Drake Y. C. Lee

1976-01-01

408

Blast Loading Experiments of Surrogate Models for Tbi Scenarios

NASA Astrophysics Data System (ADS)

This study aims to characterize the interaction of explosive blast waves through simulated anatomical models. We have developed physical models and a systematic approach for testing traumatic brain injury (TBI) mechanisms and occurrences. A simplified series of models consisting of spherical PMMA shells housing synthetic gelatins as brain simulants have been utilized. A series of experiments was conducted to compare the sensitivity of the system response to mechanical properties of the simulants under high strain-rate explosive blasts. Small explosive charges were directed at the models to produce a realistic blast wave in a scaled laboratory test cell setting. Blast profiles were measured and analyzed to compare system response severity. High-speed shadowgraph imaging captured blast wave interaction with the head model while particle tracking captured internal response for displacement and strain correlation. The results suggest amplification of shock waves inside the head near material interfaces due to impedance mismatches. In addition, significant relative displacement was observed between the interacting materials suggesting large strain values of nearly 5%. Further quantitative results were obtained through shadowgraph imaging of the blasts confirming a separation of time scales between blast interaction and bulk movement. These results lead to the conclusion that primary blast effects could cause TBI occurrences.

Alley, M. D.; Son, S. F.

2009-12-01

409

Radio and X-ray Observations of the Type Ic SN 2007gr Reveal an Ordinary, Non-relativistic Explosion

NASA Astrophysics Data System (ADS)

We present extensive radio and X-ray observations of the nearby Type Ic SN 2007gr in NGC 1058 obtained with the Very Large Array (VLA) and the Chandra X-ray Observatory and spanning 5 to 150 days after explosion. Through our detailed modeling of these data, we estimate the properties of the blast wave and the circumstellar environment. We find evidence for a freely expanding and non-relativistic explosion with an average blast wave velocity, \\overline{v}? 0.2c, and a total internal energy for the radio emitting material of E ? 2 × 1046 erg assuming equipartition of energy between electrons and magnetic fields (epsilon e = epsilon B = 0.1). The temporal and spectral evolution of the radio emission points to a stellar wind-blown environment shaped by a steady progenitor mass loss rate of \\dot{M}? 6× 10^{-7} M_{?} yr^{-1} (wind velocity, vw = 103 km s-1). These parameters are fully consistent with those inferred for other SNe Ibc and are in line with the expectations for an ordinary, homologous SN explosion. Our results are at odds with those of Paragi et al. who recently reported evidence for a relativistic blast wave in SN 2007gr based on their claim that the radio emission was resolved away in a low signal-to-noise Very Long Baseline Interferometry (VLBI) observation. Here we show that the exotic physical scenarios required to explain the claimed relativistic velocity—extreme departures from equipartition and/or a highly collimated outflow—are excluded by our detailed VLA radio observations. Moreover, we present an independent analysis of the VLBI data and propose that a modest loss of phase coherence provides a more natural explanation for the apparent flux density loss which is evident on both short and long baselines. We conclude that SN 2007gr is an ordinary Type Ibc supernova.

Soderberg, A. M.; Brunthaler, A.; Nakar, E.; Chevalier, R. A.; Bietenholz, M. F.

2010-12-01

410

Relativistic astrophysical phenomena such as gamma-ray bursts (GRBs) and active galactic nuclei often require long-lived strong magnetic fields that cannot be achieved by shock compression alone. Here, we report on three-dimensional special-relativistic magnetohydrodynamic (MHD) simulations that we performed using a second-order Godunov-type conservative code to explore the amplification and decay of macroscopic turbulence dynamo excited by the so-called Richtmyer-Meshkov instability (RMI; a Rayleigh-Taylor-type instability). This instability is an inevitable outcome of interactions between shock and ambient density fluctuations. We find that the magnetic energy grows exponentially in a few eddy-turnover times because of field-line stretching and then, following the decay of kinetic turbulence, decays with a temporal power-law exponent of -0.7. The magnetic energy fraction can reach {epsilon}{sub B} {approx} 0.1 but depends on the initial magnetic field strength, which can diversify the observed phenomena. We find that the magnetic energy grows by at least two orders of magnitude compared to the magnetic energy immediately behind the shock, provided the kinetic energy of turbulence injected by the RMI is greater than the magnetic energy. This minimum degree of amplification does not depend on the amplitude of the initial density fluctuations, while the growth timescale and the maximum magnetic energy depend on the degree of inhomogeneity in the density. The transition from Kolmogorov cascade to MHD critical balance cascade occurs at {approx}1/10th the initial inhomogeneity scale, which limits the maximum synchrotron polarization to less than {approx}2%. We derive analytical formulas for these numerical results and apply them to GRBs. New results include the avoidance of electron cooling with RMI turbulence, the turbulent photosphere model via RMI, and the shallow decay of the early afterglow from RMI. We also perform a simulation of freely decaying turbulence with relativistic velocity dispersion. We find that relativistic turbulence begins to decay much more quickly than one eddy-turnover time because of rapid shock dissipation, which does not support the relativistic turbulence model by Narayan and Kumar.

Inoue, Tsuyoshi [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Chuou-ku, Sagamihara 252-5258 (Japan); Asano, Katsuaki [Interactive Research Center of Science, Graduate School of Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Ioka, Kunihito, E-mail: inouety@phys.aoyama.ac.jp [KEK Theory Center and the Graduate University for Advanced Studies, Oho, Tsukuba 305-0801 (Japan)

2011-06-20

411

NASA Astrophysics Data System (ADS)

Relativistic astrophysical phenomena such as gamma-ray bursts (GRBs) and active galactic nuclei often require long-lived strong magnetic fields that cannot be achieved by shock compression alone. Here, we report on three-dimensional special-relativistic magnetohydrodynamic (MHD) simulations that we performed using a second-order Godunov-type conservative code to explore the amplification and decay of macroscopic turbulence dynamo excited by the so-called Richtmyer-Meshkov instability (RMI; a Rayleigh-Taylor-type instability). This instability is an inevitable outcome of interactions between shock and ambient density fluctuations. We find that the magnetic energy grows exponentially in a few eddy-turnover times because of field-line stretching and then, following the decay of kinetic turbulence, decays with a temporal power-law exponent of -0.7. The magnetic energy fraction can reach epsilon B ~ 0.1 but depends on the initial magnetic field strength, which can diversify the observed phenomena. We find that the magnetic energy grows by at least two orders of magnitude compared to the magnetic energy immediately behind the shock, provided the kinetic energy of turbulence injected by the RMI is greater than the magnetic energy. This minimum degree of amplification does not depend on the amplitude of the initial density fluctuations, while the growth timescale and the maximum magnetic energy depend on the degree of inhomogeneity in the density. The transition from Kolmogorov cascade to MHD critical balance cascade occurs at ~1/10th the initial inhomogeneity scale, which limits the maximum synchrotron polarization to less than ~2%. We derive analytical formulas for these numerical results and apply them to GRBs. New results include the avoidance of electron cooling with RMI turbulence, the turbulent photosphere model via RMI, and the shallow decay of the early afterglow from RMI. We also perform a simulation of freely decaying turbulence with relativistic velocity dispersion. We find that relativistic turbulence begins to decay much more quickly than one eddy-turnover time because of rapid shock dissipation, which does not support the relativistic turbulence model by Narayan & Kumar.

Inoue, Tsuyoshi; Asano, Katsuaki; Ioka, Kunihito

2011-06-01

412

Power extraction in relativistic klystron amplifier

NASA Astrophysics Data System (ADS)

The several types of the relativistic klystron amplifier output circuits are discussed. The composition and properties of the electromagnetic fields in the klystron electrodynamics structures filled by a relativistic electron beam are described. The calculation results of the electron wave propagation in the relativistic klystron TW output circuits are presented. The linear theory numerical data are compared with the 'cold' experimental results. 2D investigations results of the KMT-3 relativistic klystron with the single and double gaps are analyzed.

Pikunov, Victor M.; Sandalov, Aleksandr N.; Rodyakin, Vladimir E.

1995-09-01

413

Deuteron production and elliptic flow in relativistic heavy ion collisions

The hadronic transport model ART is extended to include the production and annihilation of deuterons via the reactions BB{r_reversible}dM, where B and M stand for baryons and mesons, respectively, as well as their elastic scattering with mesons and baryons in the hadronic matter. This new hadronic transport model is used to study the transverse momentum spectrum and elliptic flow of deuterons in relativistic heavy ion collisions, with the initial hadron distributions after hadronization of the produced quark-gluon plasma taken from a blast wave model. The results are compared with those measured by the PHENIX and STAR Collaborations for Au+Au collisions at {radical}(s{sub NN})=200 GeV and also with those obtained from the coalescence model based on freeze-out nucleons in the transport model.

Oh, Yongseok [Cyclotron Institute and Physics Department, Texas A and M University, College Station, Texas 77843 (United States); Korea Institute of Science and Technology Information, Daejeon 305-806 (Korea, Republic of); Lin Ziwei [Department of Physics, East Carolina University, Greenville, North Carolina 27858 (United States); Ko, Che Ming [Cyclotron Institute and Physics Department, Texas A and M University, College Station, Texas 77843 (United States)

2009-12-15

414

NASA Astrophysics Data System (ADS)

The nonlinear propagation of finite amplitude ion acoustic solitary waves in a plasma consisting of adiabatic warm ions, nonisothermal electrons, and a weakly relativistic electron beam is studied via a two-fluid model. A multiple scales technique is employed to investigate the nonlinear regime. The existence of the electron beam gives rise to four linear ion acoustic modes, which propagate at different phase speeds. The numerical analysis shows that the propagation speed of two of these modes may become complex-valued (i.e., waves cannot occur) under conditions which depend on values of the beam-to-background-electron density ratio ?, the ion-to-free-electron temperature ratio ?, and the electron beam velocity v0; the remaining two modes remain real in all cases. The basic set of fluid equations are reduced to a Schamel-type equation and a linear inhomogeneous equation for the first and second-order potential perturbations, respectively. Stationary solutions of the coupled equations are derived using a renormalization method. Higher-order nonlinearity is thus shown to modify the solitary wave amplitude and may also deform its shape, even possibly transforming a simple pulse into a W-type curve for one of the modes. The dependence of the excitation amplitude and of the higher-order nonlinearity potential correction on the parameters ?, ?, and v0 is numerically investigated.

Esfandyari-Kalejahi, A.; Kourakis, I.; Shukla, P. K.

2008-02-01

415

NASA Astrophysics Data System (ADS)

The critical electric field of quantum electrodynamics, called also the Schwinger field, is so strong that it produces electron-positron pairs from vacuum, converting the energy of light into matter. Since the dawn of quantum electrodynamics, there has been a dream on how to reach it on Earth. With the rise of laser technology this field has become feasible through the construction of extremely high power lasers or/and with the sophisticated use of nonlinear processes in relativistic plasmas. This is one of the most attractive motivations for extremely high power laser development, i.e. producing matter from vacuum by pure light in fundamental process of quantum electrodynamics in the nonperturbative regime. Recently it has been realized that a laser with intensity well below the Schwinger limit can create an avalanche of electron-positron pairs similar to a discharge before attaining the Schwinger field. It has also been realized that the Schwinger limit can be reached using an appropriate configuration of laser beams. In experiments on the collision of laser light and high intensity electromagnetic pulses generated by relativistic flying mirrors, with electron bunches produced by a conventional accelerator and with laser wake field accelerated electrons the studying of extreme field limits in the nonlinear interaction of electromagnetic waves is proposed. The regimes of dominant radiation reaction, which completely changes the electromagnetic wave-matter interaction, will be revealed. This will result in a new powerful source of high brightness gamma-rays. A possibility of the demonstration of the electronpositron pair creation in vacuum via multi-photon processes can be realized. This will allow modeling under terrestrial laboratory conditions neutron star magnetospheres, cosmological gamma ray bursts and the Leptonic Era of the Universe.

Bulanov, Sergei V.; Esirkepov, Timur Z.; Hayashi, Yukio; Kando, Masaki; Kiriyama, Hiromitsu; Koga, James K.; Kondo, Kiminori; Kotaki, Hideyuki; Pirozhkov, Alexander S.; Bulanov, Stepan S.; Zhidkov, Alexei G.; Chen, Pisin; Neely, David; Kato, Yoshiaki; Narozhny, Nikolay B.; Korn, Georg

2011-05-01

416

This paper outlines the process model and model-based control techniques implemented on the hot blast stoves for the No. 7 Blast Furnace at the Inland Steel facility in East Chicago, Indiana. A detailed heat transfer model of the stoves is developed. It is then used as part of a predictive control scheme to determine the minimum amount of fuel necessary to achieve the blast air requirements. The controller also considers maximum and minimum temperature constraints within the stove.

Muske, K.R. [Villanova Univ., PA (United States). Dept. of Chemical Engineering; Hansen, G.A.; Howse, J.W.; Cagliostro, D.J. [Los Alamos National Lab., NM (United States); Chaubal, P.C. [Inland Steel Industries Inc., East Chicago, IN (United States). Research Labs.

1998-12-31

417

Acute blast injury reduces brain abeta in two rodent species.

Blast-induced traumatic brain injury (TBI) has been a major cause of morbidity and mortality in the conflicts in Iraq and Afghanistan. How the primary blast wave affects the brain is not well understood. In particular, it is unclear whether blast injures the brain through mechanisms similar to those found in non-blast closed impact injuries (nbTBI). The ?-amyloid (A?) peptide associated with the development of Alzheimer's disease is elevated acutely following TBI in humans as well as in experimental animal models of nbTBI. We examined levels of brain A? following experimental blast injury using enzyme-linked immunosorbent assays for A? 40 and 42. In both rat and mouse models of blast injury, rather than being increased, endogenous rodent brain A? levels were decreased acutely following injury. Levels of the amyloid precursor protein (APP) were increased following blast exposure although there was no evidence of axonal pathology based on APP immunohistochemical staining. Unlike the findings in nbTBI animal models, levels of the ?-secretase, ?-site APP cleaving enzyme 1, and the ?-secretase component presenilin-1 were unchanged following blast exposure. These studies have implications for understanding the nature of blast injury to the brain. They also suggest that strategies aimed at lowering A? production may not be effective for treating acute blast injury to the brain. PMID:23267342

De Gasperi, Rita; Gama Sosa, Miguel A; Kim, Soong Ho; Steele, John W; Shaughness, Michael C; Maudlin-Jeronimo, Eric; Hall, Aaron A; Dekosky, Steven T; McCarron, Richard M; Nambiar, Madhusoodana P; Gandy, Sam; Ahlers, Stephen T; Elder, Gregory A

2012-12-21

418

Blast injuries are an increasing problem in both military and civilian practice. Primary blast injury to the lungs (blast lung) is found in a clinically significant proportion of casualties from explosions even in an open environment, and in a high proportion of severely injured casualties following explosions in confined spaces. Blast casualties also commonly suffer secondary and tertiary blast injuries resulting in significant blood loss. The presence of hypoxaemia owing to blast lung complicates the process of fluid resuscitation. Consequently, prolonged hypotensive resuscitation was found to be incompatible with survival after combined blast lung and haemorrhage. This article describes studies addressing new forward resuscitation strategies involving a hybrid blood pressure profile (initially hypotensive followed later by normotensive resuscitation) and the use of supplemental oxygen to increase survival and reduce physiological deterioration during prolonged resuscitation. Surprisingly, hypertonic saline dextran was found to be inferior to normal saline after combined blast injury and haemorrhage. New strategies have therefore been developed to address the needs of blast-injured casualties and are likely to be particularly useful under circumstances of enforced delayed evacuation to surgical care.

Kirkman, E.; Watts, S.; Cooper, G.

2011-01-01

419

Neuropathology of explosive blast traumatic brain injury.

During the conflicts of the Global War on Terror, which are Operation Enduring Freedom (OEF) in Afghanistan and Operation Iraqi Freedom (OIF), there have been over a quarter of a million diagnosed cases of traumatic brain injury (TBI). The vast majority are due to explosive blast. Although explosive blast TBI (bTBI) shares many clinical features with closed head TBI (cTBI) and penetrating TBI (pTBI), it has unique features, such as early cerebral edema and prolonged cerebral vasospasm. Evolving work suggests that diffuse axonal injury (DAI) seen following explosive blast exposure is different than DAI from focal impact injury. These unique features support the notion that bTBI is a separate and distinct form of TBI. This review summarizes the current state of knowledge pertaining to bTBI. Areas of discussion are: the physics of explosive blast generation, blast wave interaction with the bony calvarium and brain tissue, gross tissue pathophysiology, regional brain injury, and cellular and molecular mechanisms of explosive blast neurotrauma. PMID:22836523

Magnuson, John; Leonessa, Fabio; Ling, Geoffrey S F

2012-10-01

420

Relativistic viscoelastic fluid mechanics

A detailed study is carried out for the relativistic theory of viscoelasticity which was recently constructed on the basis of Onsager's linear nonequilibrium thermodynamics. After rederiving the theory using a local argument with the entropy current, we show that this theory universally reduces to the standard relativistic Navier-Stokes fluid mechanics in the long time limit. Since effects of elasticity are taken into account, the dynamics at short time scales is modified from that given by the Navier-Stokes equations, so that acausal problems intrinsic to relativistic Navier-Stokes fluids are significantly remedied. We in particular show that the wave equations for the propagation of disturbance around a hydrostatic equilibrium in Minkowski space-time become symmetric hyperbolic for some range of parameters, so that the model is free of acausality problems. This observation suggests that the relativistic viscoelastic model with such parameters can be regarded as a causal completion of relativistic Navier-Stokes fluid mechanics. By adjusting parameters to various values, this theory can treat a wide variety of materials including elastic materials, Maxwell materials, Kelvin-Voigt materials, and (a nonlinearly generalized version of) simplified Israel-Stewart fluids, and thus we expect the theory to be the most universal description of single-component relativistic continuum materials. We also show that the presence of strains and the corresponding change in temperature are naturally unified through the Tolman law in a generally covariant description of continuum mechanics.

Fukuma, Masafumi; Sakatani, Yuho [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)

2011-08-15