Relevant bibliographies by topics / OPTICALLY THICK PLASMA / Journal articles
To see the other types of publications on this topic, follow the link: OPTICALLY THICK PLASMA.

Journal articles on the topic 'OPTICALLY THICK PLASMA'

Author: Grafiati
Published: 4 June 2021
Last updated: 15 February 2022

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'OPTICALLY THICK PLASMA.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Mahdavi, M., T. Koohrokhi, and Z. Barfami. "The Effect of Energy Leakage Probability on Burn Propagation in an Optically Thick Fusion Plasma." ISRN High Energy Physics 2012 (2012): 1–10. http://dx.doi.org/10.5402/2012/838394.

Full text
Abstract:
In an optically thick plasma, the mean free path of bremsstrahlung photons is smaller than the plasma radius, and radiation can be treated as a photon gas in thermal equilibrium. In these conditions, the black body radiation spectrum exceeds the number of hot photons, and reabsorption processes such as inverse bremsstrahlung radiation and inverse Compton scattering become important. It has been shown that a dense fusion plasma like the one being used in ICF method is initially optically thick. When the fuel pellet is burning, the temperature of its electrons rises (approximately greater than 90 KeV), and the pellet becomes rapidly optically thin. In this paper, we have shown that the energy leakage probability makes electron temperature remain low (approximately smaller than 55 KeV), and as a result the fuel pellet remains optically thick during burning.
APA, Harvard, Vancouver, ISO, and other styles
2

Rodger, A. S., and N. Labrosse. "Spectral gradient of the thermal millimetre continuum as a diagnostic for optical thickness in the solar atmosphere." Astronomy & Astrophysics 617 (September 2018): L6. http://dx.doi.org/10.1051/0004-6361/201833848.

Full text
Abstract:
Aims. In this Letter we aim to show how the gradient of the thermal millimetre continuum spectrum, as emitted from the quiet solar atmosphere, may be used as a diagnostic for the optical thickness regime at the centre of the observing frequency band. Methods. We show the theoretical derivation of the gradient of the millimetre continuum for both logarithmic- and linear-scale spectra. We compare this expression with the empirical relationship between the slope of the millimetre continuum spectrum and the plasma optical thickness computed from both isothermal and multi-thermal two-dimensional cylindrical radiative transfer models. Results. It is found that the logarithmic-scale spectral gradient provides a clear diagnostic for the optical thickness regime for both isothermal and multi-thermal plasmas, provided that a suitable correction is made for a non-constant gaunt factor over the frequency band. For the use of observers we present values for this correction at all ALMA bands and at a wide range of electron temperatures. Conclusions. We find that the spectral gradient can be used to find (a) whether the source is fully optically thin, (b) the optical thickness of the source if it lies within the transitional regime between optically thin and thick plasma (τ ≈ 10−1−101), or (c) whether the source is fully optically thick for an isothermal plasma. A multi-thermal plasma will act the same as an isothermal plasma for case (a), however, the transitional regime will only extend from τ ≈ 10−1 to τ ≈ 100. Above τ = 1 the slope of the continuum will depend increasingly on the temperature gradient, as well as the optical thickness, reducing the reliability of the diagnostic.
APA, Harvard, Vancouver, ISO, and other styles
3

Bakshi, V., and W. C. Nunnally. "Measurement of temperatures in optically thick railgun plasma armatures." IEEE Transactions on Magnetics 31, no. 1 (January 1995): 673–77. http://dx.doi.org/10.1109/20.364613.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Shikhovtseva, E. S. "Equilibrium x-ray emission of an optically thick plasma." Astrophysics 28, no. 3 (1988): 392–99. http://dx.doi.org/10.1007/bf01112979.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Zhen, Zhiqiang, and Jian He. "Opacity of Krypton X-ray lines in high-temperature plasma implosion." Modern Physics Letters B 33, no. 33 (November 30, 2019): 1950418. http://dx.doi.org/10.1142/s0217984919504189.

Full text
Abstract:
For accurate electron temperature and density diagnostics in laser high-temperature plasma implosion, opacity of Krypton (Kr) helium-[Formula: see text] and Balmer-[Formula: see text] lines are discussed, and ratio of escape factor of the two X-rays are calculated, both for Gaussian and Holtzmarkian profiles. Finally, the line ratios of the two X-ray lines are analyzed for optically thin and thick plasmas. Results indicate that for the Gaussian profile, the line ratio varies greatly with the opacity of the Kr helium-[Formula: see text] line, which provides excellent source for temperature and electron density diagnostics; while for the Holtzmarkian profile, the line ratio varies less with the opacity of the Kr helium-[Formula: see text] line, which can be used for escape factor diagnostics. This method is significant in accurate plasma diagnostics using X-rays under the condition of optically thick.
APA, Harvard, Vancouver, ISO, and other styles
6

Pawelec, E., V. Caubet-Hilloutou, and S. Mazouffre. "Fabry–Pérot lineshape analysis in an optically thick expanding plasma." Plasma Sources Science and Technology 16, no. 3 (August 1, 2007): 635–42. http://dx.doi.org/10.1088/0963-0252/16/3/024.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Orlov, N. Yu, S. Yu Gus'kov, S. A. Pikuz, V. B. Rozanov, T. A. Shelkovenko, N. V. Zmitrenko, and D. A. Hammer. "Theoretical and experimental studies of the radiative properties of hot dense matter for optimizing soft X-ray sources." Laser and Particle Beams 25, no. 3 (July 20, 2007): 415–23. http://dx.doi.org/10.1017/s0263034607000535.

Full text
Abstract:
Theoretical and experimental studies of radiative properties of hot dense plasmas that are used as soft X-ray sources have been carried out depending on the plasma composition. Important features of the theoretical model, which can be used for complex materials, are discussed. An optimizing procedure that can determine an effective complex material to produce optically thick plasma by laser interaction with a thick solid target is applied. The efficiency of the resulting material is compared with the efficiency of other composite materials that have previously been evaluated theoretically. It is shown that the optimizing procedure does, in practice, find higher radiation efficiency materials than have been found by previous authors. Similar theoretical research is performed for the optically thin plasma produced from exploding wires. Theoretical estimations of radiative efficiency are compared with experimental data that are obtained from measurements of X-pinch radiation energy yield using two exploding wire materials, NiCr and Alloy 188. It is shown that theoretical calculations agree well with the experimental data.
APA, Harvard, Vancouver, ISO, and other styles
8

SAWADA, Keiji, Yusuke YAMADA, Takamasa MIYACHIKA, Naomichi EZUMI, Atsushi IWAMAE, and Motoshi GOTO. "Collisional-Radiative Model for Spectroscopic Diagnostic of Optically Thick Helium Plasma." Plasma and Fusion Research 5 (2010): 001. http://dx.doi.org/10.1585/pfr.5.001.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Karabourniotis, D., E. Drakakis, and B. Zacharopoulos. "Electron and population temperatures in a non-LTE optically thick plasma." Journal of Physics D: Applied Physics 25, no. 2 (February 14, 1992): 188–94. http://dx.doi.org/10.1088/0022-3727/25/2/009.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Liao, Lamei, and Jian He. "Discussion on laser-induced plasma diagnostics under condition of optically thick." Optik 127, no. 11 (June 2016): 4878–80. http://dx.doi.org/10.1016/j.ijleo.2016.02.037.

Full text
APA, Harvard, Vancouver, ISO, and other styles
11

MÍNGUEZ, E., R. RODRÍGUEZ, J. M. GIL, P. SAUVAN, R. FLORIDO, J. G. RUBIANO, P. MARTEL, and R. MANCINI. "Opacities and line transfer in high density plasma." Laser and Particle Beams 23, no. 2 (June 2005): 199–203. http://dx.doi.org/10.1017/s0263034605050354.

Full text
Abstract:
In this work, we first presents a review of the work that research teams have developed in collaboration in order to determine the optical properties of plasmas during the recent years, and showing the achievements reached. The second part of this paper is devoted to one of these improvements, which is to include reabsorption of the radiation in the calculations of dense optically thick plasmas in non-LTE conditions. Two models recently developed for this purpose are presented. The quantitative study was focused on aluminum plasmas, which was obtained recently at LULI experiments.
APA, Harvard, Vancouver, ISO, and other styles
12

Crusius, A. "The influence of a thermal plasma on synchrotron radiation." Laser and Particle Beams 6, no. 3 (August 1988): 421–36. http://dx.doi.org/10.1017/s026303460000536x.

Full text
Abstract:
The synchrotron emission from relativistic electrons in a thermal plasma with large-scale random magnetic fields is considered. In this case, the spectral synchrotron power of a single electron can be given in closed form allowing exact analytical expressions for the synchrotron emissivity, absorption coefficient, intensity and total energy loss of particles to be derived. The influence of various physical parameters such as gas density, magnetic field strength, particle's Lorentz factor on the resulting emissivities, intensities and energy loss is discussed in detail. Below the Razin– Tsytovich frequency vR = 20 Hz (ne/l cm−3) (B/l Gauss)−1, the spectral appearance of synchrotron radiation both in the optically thin and thick case is quite different than the vacuum behaviour. Since in the quasar broad line regions, vR is of the order 1011 Hz the suppression of synchrotron radiation may explain why most quasars are radio quiet. Likewise, the necessary physical conditions for the occurrence of synchrotron masering in the optically thick case are given. We obtain optical depth |τ|>1 for compact nonthermal sources. The total energy loss of a single particle is shown to be exponentially reduced at Lorentz factors less than γR = 2·1. 10−3 (ne/1 cm−3)½ (B/1 Gauss)−1.
APA, Harvard, Vancouver, ISO, and other styles
13

Caditz, D. M., and S. Tsuruta. "Relativistic Adiabatic Shocks in Accretion Flows." Symposium - International Astronomical Union 195 (2000): 381–84. http://dx.doi.org/10.1017/s0074180900163193.

Full text
Abstract:
Accretion flows onto compact astronomical sources are likely to be supersonic, and shock waves may therefore be common in such flows. Plasma passing through a shock front will be compressed and heated according to the jump conditions across the shock discontinuity. Shocks in accretion flows may therefore have important consequences for the flow structure and emission characteristics. The equations governing adiabatic (nonradiative) shocks in relativistic plasmas are presented including the effects of radiation pressure and energy density, and pair equilibria in the postshock flow. We find that postshock states for accretion flows within cool, optically thick, accretion-driven sources such as AGN become radiation- or pair-dominated, and the postshock plasma will likely become optically thin before returning to steady-state conditions.
APA, Harvard, Vancouver, ISO, and other styles
14

Gornushkin, I. B., C. L. Stevenson, B. W. Smith, N. Omenetto, and J. D. Winefordner. "Modeling an inhomogeneous optically thick laser induced plasma: a simplified theoretical approach." Spectrochimica Acta Part B: Atomic Spectroscopy 56, no. 9 (September 2001): 1769–85. http://dx.doi.org/10.1016/s0584-8547(01)00254-3.

Full text
APA, Harvard, Vancouver, ISO, and other styles
15

Likhachev, A. V., and V. V. Pikalov. "Three-dimensional emission tomography of optically thick plasma for the known absorption." Optics and Spectroscopy 88, no. 5 (May 2000): 667–75. http://dx.doi.org/10.1134/1.626858.

Full text
APA, Harvard, Vancouver, ISO, and other styles
16

Karabourniotis, D., and C. Karras. "Line broadening in optically thick gas discharges: Influence on plasma temperature determination." Journal of Applied Physics 57, no. 11 (June 1985): 4861–69. http://dx.doi.org/10.1063/1.335306.

Full text
APA, Harvard, Vancouver, ISO, and other styles
17

Rezaei, Fatemeh. "Two-lines method for estimation of plasma temperature and characterization of plasma parameters in optically thick plasma conditions." Applied Optics 59, no. 10 (March 25, 2020): 3002. http://dx.doi.org/10.1364/ao.384949.

Full text
APA, Harvard, Vancouver, ISO, and other styles
18

Petrucci, P. O., D. Gronkiewicz, A. Rozanska, R. Belmont, S. Bianchi, B. Czerny, G. Matt, et al. "Radiation spectra of warm and optically thick coronae in AGNs." Astronomy & Astrophysics 634 (February 2020): A85. http://dx.doi.org/10.1051/0004-6361/201937011.

Full text
Abstract:
A soft X-ray excess above the 2–10 keV power-law extrapolation is generally observed in the X-ray spectra of active galactic nuclei. The origin of this excess is still not well understood. Presently there are two competitive models: blurred ionized reflection and warm Comptonization. In the case of warm Comptonization, observations suggest a corona temperature in the range 0.1–2 keV and a corona optical depth of about 10–20. Moreover, radiative constraints from spectral fits with Comptonization models suggest that most of the accretion power should be released in the warm corona and the disk below is basically non-dissipative, radiating only the reprocessed emission from the corona. However, the true radiative properties of such a warm and optically thick plasma are not well known. For instance, the importance of the Comptonization process, the potential presence of strong absorption and/or emission features, and the spectral shape of the output spectrum have been studied only very recently. Here, we present simulations of warm and optically thick coronae using the TITAN radiative transfer code coupled with the NOAR Monte-Carlo code, the latter fully accounting for Compton scattering of continuum and lines. Illumination from above by hard X-ray emission and from below by an optically thick accretion disk are taken into account, as well as (uniform) internal heating. Our simulations show that for a large part of the parameter space, the warm corona with sufficient internal mechanical heating is dominated by Compton cooling and neither strong absorption nor emission lines are present in the outgoing spectra. In a smaller part of the parameter space, the calculated emission agrees with the spectral shape of the observed soft X-ray excess. Remarkably, this also corresponds to the conditions of radiative equilibrium of an extended warm corona covering a non-dissipative accretion disk almost entirely. These results confirm that warm Comptonization is a valuable model that can explain the origin of the soft X-ray excess.
APA, Harvard, Vancouver, ISO, and other styles
19

Kondo, Y., G. E. ,. Jr McCluskey, and S. B. Parsons. "Variable, optically thick plasma in the interacting binaries R Arae and HD 207739." Astrophysical Journal 295 (August 1985): 580. http://dx.doi.org/10.1086/163401.

Full text
APA, Harvard, Vancouver, ISO, and other styles
20

Abada-Simon, Meil. "AE Aquarii continuum emissions from Radio low frequencies to Infra-Red." International Astronomical Union Colloquium 190 (2004): 314–20. http://dx.doi.org/10.1017/s0252921100002268.

Full text
Abstract:
AbstractAE Aquarii radio flares are attributed to synchrotron optically thick emission from expanding plasma clouds, and the turnover frequency and the optically thin part of the synchrotron spectrum seem to be between the sub-millimetre and infra-red wavelengths. We present the various processes which may affect the synchrotron radiation at both very low (radio) frequencies and at higher energies, and what they infer on the properties of the radio flare source and its surroundings. We also envisage that both thermal and non-thermal emission processes may explain the puzzling spectrum of AE Aqr.
APA, Harvard, Vancouver, ISO, and other styles
21

Pavlov, G. G., Iu A. Shibanov, N. A. Silantev, and W. Nagel. "The anisotropic radiative transfer problem in optically thick, strongly magnetized plasma - A comparison of results." Astrophysical Journal 291 (April 1985): 170. http://dx.doi.org/10.1086/163053.

Full text
APA, Harvard, Vancouver, ISO, and other styles
22

Akatsuka, H., and M. Suzuki. "Numerical Study on Population Inversion and Lasing Conditions in an Optically Thick Recombining Helium Plasma." Contributions to Plasma Physics 34, no. 4 (1994): 539–61. http://dx.doi.org/10.1002/ctpp.2150340403.

Full text
APA, Harvard, Vancouver, ISO, and other styles
23

Schlickeiser, R., and A. Crusius-Wătzel. "Magnetic Fields in Radio-Quiet Quasars." Symposium - International Astronomical Union 140 (1990): 400. http://dx.doi.org/10.1017/s0074180900190643.

Full text
Abstract:
As an hypothesis the sharp far–infrared turnovers in the spectra of several radio–quiet galactic nuclei [1–3] are attributed to the modifications of synchrotron emission arising from the presence of a thermal background plasma. We calculate the synchrotron emission from a power-law distribution of relativistic electrons N(γ) = Noγ–s in a large–scale random magnetic field of strength B embedded in a thermal plasma of density ne. Two major modifications of the classical vacuum theory of synchrotron emission are established [4]:A) synchrotron sources can be optically thick only in a small frequency range around the Razin -Tsytovich frequency, whereas at smaller and higher frequencies the sources are optically thin;B) at frequencies above VR the synchrotron intensity in a plasma behaves exactly the same way as in the vacuum case, whereas at frequencies below VR the intensity is exponentially reduced,
APA, Harvard, Vancouver, ISO, and other styles
24

Sander, C., J. E. Schmutz, and M. Kurrat. "Analysis of Radiation Discretization for Modelling a Spark Gap for Surge Currents." PLASMA PHYSICS AND TECHNOLOGY 4, no. 1 (2017): 56–60. http://dx.doi.org/10.14311/ppt.2017.1.56.

Full text
Abstract:
In this paper we address a method for spectrally resolved radiation modelling in thermal plasmas encountered in surge protective devices based on spark gaps. Compared to most switching applications, power input and plasma pressure are much higher which leads to an optically thick plasma with line broadening and enhanced wall ablation. In this situation it is possible to capture the full effect of spectrally resolved radiation on plasma dynamics by performing line-by-line calculations with downsampled absorption spectra. We show that it is possible to achieve radiation convergence with 1000 lines. Approaches for a further reduction of calculation times using band-averaged models and $\kappa$-group models are discussed. The κ-group model is based upon a grouping of the absorption coefficients into subgroups with different ranges of κ before averaging. The spectral calculation results are compared to the approximative methods and significant differences for Rosseland means are observed.
APA, Harvard, Vancouver, ISO, and other styles
25

Lutovinov, Alexander A., Sergei S. Tsygankov, Vadim A. Arefiev, and Mikhail G. Revnivtsev. "Spectral evolution of the galactic microquasars XTE J1550-564 and GRO J1655-40 during outbursts." Proceedings of the International Astronomical Union 6, S275 (September 2010): 321–22. http://dx.doi.org/10.1017/s1743921310016303.

Full text
Abstract:
AbstractWe present results of a broadband spectroscopy of the galactic microquasars and black hole candidates XTE J1550-564 and GRO J1655-40, performed with the INTEGRAL and RXTE observatories during strong outbursts in 2003 and 2005, respectively. The spectral parameters evolution was traced during brightening and fading phases of each outburst to search a possible hysteresis and transitions from state to state. We estimated a size and optical depth of different regions around XTE J1550-564, like a hot plasma zone and optically thick accretion disk. Upper limits to the annihilation 511 keV line emission were obtained for both sources using data of the SPI spectrometer onboard the INTEGRAL observatory.
APA, Harvard, Vancouver, ISO, and other styles
26

Paygin, Vladimir, Edgar Dvilis, Sergey Stepanov, Oleg Khasanov, Damir Valiev, Timofei Alishin, Maurizio Ferrari, Alessandro Chiasera, Vyacheslav Mali, and Alexander Anisimov. "Manufacturing Optically Transparent Thick Zirconia Ceramics by Spark Plasma Sintering with the Use of Collector Pressing." Applied Sciences 11, no. 3 (February 1, 2021): 1304. http://dx.doi.org/10.3390/app11031304.

Full text
Abstract:
The efficiency of using the collector pressing scheme in the Spark Plasma Sintering (SPS) process has been confirmed in improving the optical, physical, and mechanical properties of yttria-stabilized zirconia (YSZ) ceramics with an increased shape factor. An approach for developing a seal surface and determining the optimal method of increasing pressure and temperature during SPS on this surface was used to optimize the consolidation modes of the materials. It has been shown that transparent/translucent YSZ ceramics with an increased shape factor (14 mm in diameter and up to 5 mm in height, h/d = 0.36) can be successfully fabricated by the SPS technique combined with the collector pressing scheme. The optical properties and microhardness of ceramics obtained using the collector scheme are better to the optical properties of ceramics obtained using the conventional uniaxial pressing scheme.
APA, Harvard, Vancouver, ISO, and other styles
27

Nomura, S., T. Kaneko, G. Ito, K. Komurasaki, and Y. Arakawa. "Diode-Laser Induced Fluorescence Spectroscopy of an Optically Thick Plasma in Combination with Laser Absorption Spectroscopy." Journal of Spectroscopy 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/198420.

Full text
Abstract:
Distortion of laser-induced fluorescence profiles attributable to optical absorption and saturation broadening was corrected in combination with laser absorption spectroscopy in argon plasma flow. At high probe-laser intensity, saturated absorption profiles were measured to correct probe-laser absorption. At low laser intensity, nonsaturated absorption profiles were measured to correct fluorescence reabsorption. Saturation broadening at the measurement point was corrected using a ratio of saturated to non-saturated broadening. Observed LIF broadening and corresponding translational temperature without correction were, respectively,2.20±0.05 GHz and2510±100 K and corrected broadening and temperature were, respectively,1.96±0.07 GHz and1990±150 K. Although this correction is applicable only at the center of symmetry, the deduced temperature agreed well with that obtained by LAS with Abel inversion.
APA, Harvard, Vancouver, ISO, and other styles
28

TAKAHARA, F., K. ASANO, and S. IWAMOTO. "A WIEN FIREBALL MODEL OF RELATIVISTIC OUTFLOWS IN AGNs." International Journal of Modern Physics D 17, no. 09 (September 2008): 1651–60. http://dx.doi.org/10.1142/s0218271808013261.

Full text
Abstract:
A new mechanism for the production and acceleration of relativistic outflows in active galactic nuclei is presented. When copious pair production occurs in a hot accretion plasma, optically thin to absorption but optically thick to scattering, the free energy per electron or positron can exceed its rest mass. Then, if pairs can escape, they produce a powerful outflow of a large bulk Lorentz factor. We show analytically and numerically that this picture holds for spherically symmetric flows of pure pairs and radiation. We further simulate the generation process of a pair outflow from a hot plasma with normal proton-electron composition. Using a multifluid approximation and a Monte Carlo method of radiative transfer, we obtain spherically symmetric steady solutions of radiation and pair outflows, taking Coulomb friction into account. We show that a powerful and moderately relativistic flow is realized and discuss several possibilities to realize a highly relativistic flow.
APA, Harvard, Vancouver, ISO, and other styles
29

Rodríguez, R., R. Florido, J. M. Gil, J. G. Rubiano, P. Martel, and E. Mínguez. "RAPCAL code: A flexible package to compute radiative properties for optically thin and thick low and high-Z plasmas in a wide range of density and temperature." Laser and Particle Beams 26, no. 3 (July 22, 2008): 433–48. http://dx.doi.org/10.1017/s026303460800044x.

Full text
Abstract:
AbstractRadiative properties are fundamental for plasma diagnostics and hydro-simulations. For this reason, there is a high interest in their determination and they are a current topic of investigation both in astrophysics and inertial fusion confinement research. In this work a flexible computation package for calculating radiative properties for low and high Z optically thin and thick plasmas, both under local thermodynamic equilibrium and non-local thermodynamic equilibrium conditions, named RAPCAL is presented. This code has been developed with the aim of providing accurate radiative properties for low and medium Z plasmas within the context of detailed level accounting approach and for heavy elements under the detailed configuration accounting approach. In order to show the capabilities of the code, there are presented calculations of some radiative properties for carbon, aluminum, krypton and xenon plasmas under local thermodynamic and non-local thermodynamic equilibrium conditions.
APA, Harvard, Vancouver, ISO, and other styles
30

Kondo, Yoji. "Mass Flow in Interacting Binaries Observed in the Ultraviolet." International Astronomical Union Colloquium 107 (1989): 79–84. http://dx.doi.org/10.1017/s0252921100087686.

Full text
Abstract:
AbstractRecent satellite observations of close binary systems show that practically all binaries exhibit evidence of mass flow and that, where the observations are sufficiently detailed, a fraction of the matter flowing out of the mass-losing component is accreted by the companion and the remainder is lost from the binary system. The mass flow is not conservative. During the phase of dynamic mass flow, the companion star becomes immersed in optically-thick plasma and the physical properties of that star elude close scrutiny.
APA, Harvard, Vancouver, ISO, and other styles
31

AKSENOV, A. G., R. RUFFINI, I. A. SIUTSOU, and G. V. VERESHCHAGIN. "DYNAMICS AND EMISSION OF MILDLY RELATIVISTIC PLASMA." International Journal of Modern Physics: Conference Series 12 (January 2012): 1–9. http://dx.doi.org/10.1142/s2010194512006204.

Full text
Abstract:
Initially optically thick (with τ = 3⋅107) spherically symmetric outflow consisting of electron-positron pairs and photons is considered. We do not assume thermal equilibrium, and include the two-body processes that occur in such plasma: Möller and Bhabha scattering of pairs, Compton scattering, two-photon pair annihilation, two-photon pair production, together with their radiative three-body variants: bremsstrahlung, double Compton scattering, and three-photon pair annihilation, with their inverse processes. We solve numerically the relativistic Boltzmann equations in spherically symmetric case for distribution functions of pairs and photons. Three epochs are considered in details: a) the thermalization, which brings initially nonequilibrium plasma to thermal equilibrium; b) the self-accelerated expansion, which we find in agreement with previous hydrodynamic studies and c) decoupling of photons from the expanding electron-positron plasma. Photon spectra are computed, and appear to be non thermal near the peak of the luminosity. In particular, the low energy part of the spectrum contain more power with respect to the black body one.
APA, Harvard, Vancouver, ISO, and other styles
32

Coleman, Colin S. "A novel interpretation of the cosmic conspiracy in AGNs." Symposium - International Astronomical Union 119 (1986): 421–23. http://dx.doi.org/10.1017/s007418090015315x.

Full text
Abstract:
The flat radio spectra of core dominated AGNs are often attributed to a superposition of optically thick synchrotron components. This is known as the cosmic conspirac A radio index pr ∼0 is not a natural consequence of this model, and an alternative model proposed here interprets the source components as regions in which relativistic electrons stream along a magnetic field. Stream collimation is determined by plasma instabilities, and components are assumed to be optically thin, with cyclotron turnover at low frequencies. An appealing feature of this model is that radio photon index depends only upon electron energy distribution, which may be obtained from the photon index above the turnover frequency. An energy power-law with index s≥3 is typical for these sources, and implies a flat radio spectrum with pr = (4/3)-p ∼0.
APA, Harvard, Vancouver, ISO, and other styles
33

MUCCINO, M., C. L. BIANCO, L. IZZO, A. V. PENACCHIONI, and R. RUFFINI. "GRB 090227B: A FIRST EXAMPLE OF A GENUINE SHORT GRB." International Journal of Modern Physics: Conference Series 23 (January 2013): 248–53. http://dx.doi.org/10.1142/s2010194513011392.

Full text
Abstract:
In the context of the Fireshell scenario Gamma-Ray Bursts (GRBs) find a natural explanation in the values of three main parameters: the energy of the emitting e± plasma [Formula: see text], the baryon load B, and the density of the Circum-Burst Medium (CBM) nCBM. For B≲10-5, the GRB consists of a spike-like emission without any afterglow: a genuine short burst. GRB 090227B is the first recognized genuine short GRB. Its analysis reveals that the transparency emission is not a pure thermal process, owing to a non-gradual transition between the optically thick and the optically thin phases. Within our theory we have recovered the original thermal spectrum of the e± plasma, namely the effective Black body (BB); we indeed have determined the parameters of the Fireshell model, including the redshift. Setting a baryon load B = 10-6, we obtain the effective temperature [Formula: see text], the Lorentz factor at transparency Γ = 12852, and the total energy [Formula: see text]. The estimated redshift is z = 4.07±0.36.
APA, Harvard, Vancouver, ISO, and other styles
34

Aller, L. H., and C. D. Keyes. "Some Statistics of Nebular Chemical Compositions." Symposium - International Astronomical Union 131 (1989): 219. http://dx.doi.org/10.1017/s0074180900138318.

Full text
Abstract:
Data from a survey of 51 planetary nebulae (PN) observed with the image tube scanner on Shane Telescope at Lick Observatory are combined with those for a comparable number of objects previously reported. For nearly all of the PN included in the later program, it was possible to obtain adequately accurate plasma diagnostics and line intensities to derive ionic concentrations for He, N, O, Ne, S, Cl, and Ar. To get ionization correction factors we calculated theoretical nebular models to fit the excitation level and the intensities of individual important lines. Final model parameters include the stellar radius, emergent flux, Fv(*), from Husfeld et al. (1984, Astron. Astrophys., 134, 139), nebular size, the optical depth at the hydrogenic Lyman limit, and chemical abundances. Many PN do not appear to be optically very thick in the Lyman continuum.
APA, Harvard, Vancouver, ISO, and other styles
35

Kim, Jae-Young, Sang-Sung Lee, Jeffrey A. Hodgson, Juan-Carlos Algaba, Guang-Yao Zhao, Motoki Kino, Do-Young Byun, and Sincheol Kang. "Long-term millimeter VLBI monitoring of M 87 with KVN at milliarcsecond resolution: nuclear spectrum." Astronomy & Astrophysics 610 (February 2018): L5. http://dx.doi.org/10.1051/0004-6361/201732421.

Full text
Abstract:
We study the centimeter- to millimeter-wavelength synchrotron spectrum of the core of the radio galaxy M 87 at ≲0.8 mas ~ 110Rs spatial scales using four years of fully simultaneous, multi-frequency VLBI data obtained by the Korean VLBI Network (KVN). We find a core spectral index α of ≳−0.37 (S ∝ ν+α) between 22 and 129 GHz. By combining resolution-matched flux measurements from the Very Long Baseline Array (VLBA) at 15 GHz and taking the Event Horizon Telescope (EHT) 230 GHz core flux measurements in epochs 2009 and 2012 as lower limits, we find evidence of a nearly flat core spectrum across 15 and 129 GHz, which could naturally connect the 230 GHz VLBI core flux. The extremely flat spectrum is a strong indication that the jet base does not consist of a simple homogeneous plasma, but of inhomogeneous multi-energy components, with at least one component with the turn-over frequency ≳ 100 GHz. The spectral shape can be qualitatively explained if both the strongly (compact, optically thick at >100 GHz) and the relatively weakly magnetized (more extended, optically thin at <100 GHz) plasma components are colocated in the footprint of the relativistic jet.
APA, Harvard, Vancouver, ISO, and other styles
36

Shrivastava, V., A. K. Patidar, and R. K. Pensia. "A stability analysis of a self-gravitating optically thick magnetized quantum plasma including the effects of black body radiation." QScience Connect, no. 2014 (January 2014): 16. http://dx.doi.org/10.5339/connect.2014.16.

Full text
APA, Harvard, Vancouver, ISO, and other styles
37

MATSUI, Makoto, and Ryo MORITA. "Development of High-Sensitivity Laser Absorption Spectroscopy System for Number Density Measurement of Atomic Oxygen in Optically Thick Plasma." TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 19, no. 3 (2021): 447–51. http://dx.doi.org/10.2322/tastj.19.447.

Full text
APA, Harvard, Vancouver, ISO, and other styles
38

Hansen, Katherine, Melissa Cardona, Amartya Dutta, and Chen Yang. "Plasma Enhanced Atomic Layer Deposition of Plasmonic TiN Ultrathin Films Using TDMATi and NH3." Materials 13, no. 5 (February 27, 2020): 1058. http://dx.doi.org/10.3390/ma13051058.

Full text
Abstract:
Transition metal nitrides, like titanium nitride (TiN), are promising alternative plasmonic materials. Here we demonstrate a low temperature plasma-enhanced atomic layer deposition (PE-ALD) of non-stoichiometric TiN0.71 on lattice-matched and -mismatched substrates. The TiN was found to be optically metallic for both thick (42 nm) and thin (11 nm) films on MgO and Si <100> substrates, with visible light plasmon resonances in the range of 550–650 nm. We also demonstrate that a hydrogen plasma post-deposition treatment improves the metallic quality of the ultrathin films on both substrates, increasing the ε1 slope by 1.3 times on MgO and by 2 times on Si (100), to be similar to that of thicker, more metallic films. In addition, this post-deposition was found to tune the plasmonic properties of the films, resulting in a blue-shift in the plasmon resonance of 44 nm on a silicon substrate and 59 nm on MgO.
APA, Harvard, Vancouver, ISO, and other styles
39

Melon Fuksman, J. D., L. Becerra, C. L. Bianco, M. Karlica, M. Kovacevic, R. Moradi, M. Muccino, et al. "Evolution of an electron-positron plasma produced by induced gravitational collapse in binary-driven hypernovae." EPJ Web of Conferences 168 (2018): 04009. http://dx.doi.org/10.1051/epjconf/201816804009.

Full text
Abstract:
The binary-driven hypernova (BdHN) model has been introduced in the past years, to explain a subfamily of gamma-ray bursts (GRBs) with energies Eiso ≥ 1052 erg associated with type Ic supernovae. Such BdHNe have as progenitor a tight binary system composed of a carbon-oxigen (CO) core and a neutron star undergoing an induced gravitational collapse to a black hole, triggered by the CO core explosion as a supernova (SN). This collapse produces an optically-thick e+e- plasma, which expands and impacts onto the SN ejecta. This process is here considered as a candidate for the production of X-ray flares, which are frequently observed following the prompt emission of GRBs. In this work we follow the evolution of the e+e- plasma as it interacts with the SN ejecta, by solving the equations of relativistic hydrodynamics numerically. Our results are compatible with the Lorentz factors estimated for the sources that produce the flares, of typically Γ ≲ 4.
APA, Harvard, Vancouver, ISO, and other styles
40

Gornushkin, I. B., N. Omenetto, B. W. Smith, and J. D. Winefordner. "Determination of the Maximum Temperature at the Center of an Optically Thick Laser-Induced Plasma Using Self-Reversed Spectral Lines." Applied Spectroscopy 58, no. 9 (September 2004): 1023–31. http://dx.doi.org/10.1366/0003702041959398.

Full text
APA, Harvard, Vancouver, ISO, and other styles
41

He, Jian, Qingguo Zhang, and Haili Zhao. "Analysis of the intensity of Cu I 465.11 nm spectral line under optically thick conditions for laser induced copper plasma." Optik 126, no. 9-10 (May 2015): 999–1001. http://dx.doi.org/10.1016/j.ijleo.2015.02.019.

Full text
APA, Harvard, Vancouver, ISO, and other styles
42

Lu, Wenbin, and E. Sterl Phinney. "Imprint of local environment on fast radio burst observations." Monthly Notices of the Royal Astronomical Society 496, no. 3 (June 12, 2020): 3308–13. http://dx.doi.org/10.1093/mnras/staa1679.

Full text
Abstract:
ABSTRACT When fast radio burst (FRB) waves propagate through the local (${\lesssim}\rm 1\, pc$) environment of the FRB source, electrons in the plasma undergo large-amplitude oscillations. The finite-amplitude effects cause the effective plasma frequency and cyclotron frequency to be dependent on the wave strength. The dispersion measure and rotation measure should therefore vary slightly from burst to burst for a repeating source, depending on the luminosity and frequency of the individual burst. Furthermore, free–free absorption of strong waves is suppressed due to the accelerated electrons’ reduced energy exchange in Coulomb collisions. This allows bright low-frequency bursts to propagate through an environment that would be optically thick to low-amplitude waves. Given a large sample of bursts from a repeating source, it would be possible to use the deficit of low-frequency and low-luminosity bursts to infer the emission measure of the local intervening plasma and its distance from the source. Information about the local environment will shed light on the nature of FRB sources.
APA, Harvard, Vancouver, ISO, and other styles
43

Jmerik, V. N., T. V. Shubina, D. V. Nechaev, A. N. Semenov, D. A. Kirilenko, V. Yu Davydov, A. N. Smirnov, I. A. Eliseev, G. Posina, and S. V. Ivanov. "Site-controlled growth of GaN nanorods with inserted InGaN quantum wells on mu-cone patterned sapphire substrates by plasma-assisted MBE." Физика и техника полупроводников 52, no. 5 (2018): 526. http://dx.doi.org/10.21883/ftp.2018.05.45870.59.

Full text
Abstract:
AbstractWe report on a new approach to fabricate regular arrays of GaN nanorods (NRs) with InGaN QWs by plasma-assisted molecular-beam epitaxy (PA MBE) on micro-cone patterned sapphire substrates (μ-CPSSs). A two-stage PA MBE fabrication process of GaN NRs has been developed, starting with a high temperature nucleation layer growth at metal-rich conditions to aggregate selectively GaN nucleus on c-oriented areas of the μ-CPSSs and followed by growth of 1-μm-thick GaN NRs at strongly nitrogen-rich conditions exactly on the cone tips. These results are explained by energetically favorable GaN growth on the (000-) oriented sapphire surface. Both micro-photoluminescence and micro-cathodoluminescence confirm the formation of regular array of optically and spectrally isolated NRs without usage of any nanolithography.
APA, Harvard, Vancouver, ISO, and other styles
44

Labrosse, N., J. C. Vial, and P. Gouttebroze. "Diagnostics of active and eruptive prominences through hydrogen and helium lines modelling." Annales Geophysicae 26, no. 10 (October 15, 2008): 2961–65. http://dx.doi.org/10.5194/angeo-26-2961-2008.

Full text
Abstract:
Abstract. In this study we show how hydrogen and helium lines modelling can be used to make a diagnostic of active and eruptive prominences. One motivation for this work is to identify the physical conditions during prominence activation and eruption. Hydrogen and helium lines are key in probing different parts of the prominence structure and inferring the plasma parameters. However, the interpretation of observations, being either spectroscopic or obtained with imaging, is not straightforward. Their resonance lines are optically thick, and the prominence plasma is out of local thermodynamic equilibrium due to the strong incident radiation coming from the solar disk. In view of the shift of the incident radiation occuring when the prominence plasma flows radially, it is essential to take into account velocity fields in the prominence diagnostic. Therefore we need to investigate the effects of the radial motion of the prominence plasma on hydrogen and helium lines. The method that we use is the resolution of the radiative transfer problem in the hydrogen and helium lines out of local thermodynamic equilibrium. We study the variation of the computed integrated intensities in H and He lines with the radial velocity of the prominence plasma. We can confirm that there exist suitable lines which can be used to make a diagnostic of the plasma in active and eruptive prominences in the presence of velocity fields.
APA, Harvard, Vancouver, ISO, and other styles
45

van der Straaten, Trudy, and Mark J. Kushner. "A Monte-Carlo model of xenon resonance radiation transport in a plasma display panel cell: Transition from optically thick to thin regimes." Journal of Applied Physics 87, no. 6 (March 15, 2000): 2700–2707. http://dx.doi.org/10.1063/1.372244.

Full text
APA, Harvard, Vancouver, ISO, and other styles
46

Marcel, G., J. Ferreira, P. O. Petrucci, G. Henri, R. Belmont, M. Clavel, J. Malzac, et al. "A unified accretion-ejection paradigm for black hole X-ray binaries." Astronomy & Astrophysics 615 (July 2018): A57. http://dx.doi.org/10.1051/0004-6361/201732069.

Full text
Abstract:
Context. X-ray binaries display cycles of strong activity during which their luminosity varies across several orders of magnitude. The rising phase is characterized by a hard X-ray spectrum and radio emission due to jets (hard state), whereas the declining phase displays a soft X-ray spectrum and no jet signature (soft state). The origin of these correlated accretion-ejection and spectral hysteresis cycles is still under investigation. Aims. We elaborate on the previously described paradigm, where the increase and decrease in the disk accretion rate is accompanied by a modification of the disk magnetization μ, which in turn determines the dominant torque allowing accretion. For μ greater than some threshold, the accretion flow produces jets that vertically carry away the disk angular momentum (jet-emitting disk, or JED mode), whereas for smaller μ, the turbulence transfers the disk angular momentum outward in the radial direction (standard accretion disk, or SAD mode). The goal of this paper is to investigate the spectral signatures of the JED configurations. Methods. We have developed a two-temperature plasma code that computes the disk local thermal equilibria, taking into account the advection of energy in an iterative way. Our code addresses optically thin/thick transitions, both radiation and gas supported regimes, and computes in a consistent way the emitted spectrum from a steady-state disk. The optically thin emission is obtained using the BELM code, which provides accurate spectra for bremsstrahlung and synchrotron emission processes as well as for their local Comptonization. Results. For a range in radius and accretion rates, JEDs exhibit three thermal equilibria, one thermally unstable and two stable: a cold (optically thick and geometrically thin) and a hot (optically thin and geometrically thick) equilibrium. From the two thermally stable solutions, a hysteresis cycle is naturally obtained. However, standard outbursting X-ray binary cycles cannot be reproduced. Another striking feature of JEDs is their ability to reproduce luminous hard states. At high accretion rates, JEDs become slim, where the main cooling is advection. Conclusions. When the loss of angular momentum and power in jets is consistently taken into account (JED mode), accretion disks have spectral signatures that are consistent with hard states, up to high luminosities. When no jet is present (SAD mode), the spectral signature is consistent with the soft state. These two canonical spectral states of black hole binaries can be explained in terms of two completely different dynamical solutions, namely JED and SAD. The observed spectral cycles can therefore be directly understood in terms of dynamical transitions from one accretion mode to another. These transitions must involve states where some regions emit jets and others do not, however, which argues for hybrid disk configurations.
APA, Harvard, Vancouver, ISO, and other styles
47

RUFFINI, REMO, FEDERICO FRASCHETTI, LUCA VITAGLIANO, and SHE-SHENG XUE. "OBSERVATIONAL SIGNATURES OF AN ELECTROMAGNETIC OVERCRITICAL GRAVITATIONAL COLLAPSE." International Journal of Modern Physics D 14, no. 01 (January 2005): 131–41. http://dx.doi.org/10.1142/s0218271805006146.

Full text
Abstract:
We present theoretical predictions for the spectral, temporal and intensity signatures of the electromagnetic radiation emitted during the process of the gravitational collapse of a stellar core to a black hole, during which electromagnetic field strengths rise over the critical value for e+e- pair creation. The last phases of this gravitational collapse are studied, leading to the formation of a black hole with a subcritical electromagnetic field, likely with zero charge, and an outgoing pulse of initially optically thick e+e--photon plasma. Such a pulse reaches transparency at Lorentz gamma factors of 102–104. We find a clear signature in the outgoing electromagnetic signal, drifting from a soft to a hard spectrum, on very precise time-scales and with a very specific intensity modulation. The relevance of these theoretical results for the understanding of short gamma-ray bursts is outlined.
APA, Harvard, Vancouver, ISO, and other styles
48

Brown, Alexander, H. R. E. Tjin A. Djie, P. F. C. Blondel, G. M. Harper, P. D. Bennett, and S. L. Skinner. "HST GHRS Observations of the Herbig Ae Star HD104237: First UV Observations of a Hot Disk Wind from a Pre-Main Sequence Star." International Astronomical Union Colloquium 163 (1997): 448–52. http://dx.doi.org/10.1017/s0252921100043013.

Full text
Abstract:
AbstractWe have obtained ultraviolet spectra of the Herbig Ae star HD104237 using the Goddard High Resolution Spectrograph (GHRS) on HST. The high temperature emission and absorption lines show remarkable outflow absorption features, which have very similar profiles that are essentially independent of formation temperature. The profiles are not those expected from a spherically-symmetric stellar wind but have optically-thick absorption to −280 km s−1 and a high velocity plateau extending to −375 km s−1. The profile shape is a manifestation of the nonspherical geometry of the flow. The observed UV emission is too strong to be associated with the hot X–ray emitting plasma seen by ASCA and probably is generated by the interaction of the innermost part of an accretion disk with the corotating outermost magnetospheric field. The outflow is almost certainly the inner part of a biconical disk wind.
APA, Harvard, Vancouver, ISO, and other styles
49

Salmi, Tuomo, Valery F. Suleimanov, Joonas Nättilä, and Juri Poutanen. "Magnetospheric return-current-heated atmospheres of rotation-powered millisecond pulsars." Astronomy & Astrophysics 641 (September 2020): A15. http://dx.doi.org/10.1051/0004-6361/202037824.

Full text
Abstract:
We computed accurate atmosphere models of rotation-powered millisecond pulsars in which the polar caps of a neutron star (NS) are externally heated by magnetospheric return currents. The external ram pressure, energy losses, and stopping depth of the penetrating charged particles were computed self-consistently with the atmosphere model, instead of assuming a simplified deep-heated atmosphere in radiative equilibrium. We used exact Compton scattering formalism to model the properties of the emergent X-ray radiation. The deep-heating approximation was found to be valid only if most of the heat originates from ultra-relativistic bombarding particles with Lorentz factors of γ ≳ 100. In the opposite regime, the atmosphere attains a distinct two-layer structure with an overheated optically thin skin on top of an optically thick cool plasma. The overheated skin strongly modifies the emergent radiation: It produces a Compton-upscattered high-energy tail in the spectrum and alters the radiation beaming pattern from limb darkening to limb brightening for emitted hard X-rays. This kind of drastic change in the emission properties can have a significant impact on the inferred NS pulse profile parameters as performed, for example, by Neutron star Interior Composition ExploreR. Finally, the connection between the energy distribution of the return current particles and the atmosphere emission properties offers a new tool to probe the exact physics of pulsar magnetospheres.
APA, Harvard, Vancouver, ISO, and other styles
50

Ruiqin, Ding, Geoffry Kolbe, and D. D. Burgess. "The propagation of a laser pulse through an optically thick hydrogen plasma-an examination of the collisional radiative models of the atomic hydrogen system." Chinese Physics Letters 4, no. 2 (February 1987): 93–95. http://dx.doi.org/10.1088/0256-307x/4/2/012.

Full text
APA, Harvard, Vancouver, ISO, and other styles
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography