Shaping of X-ray Pulses via Dynamical Control of Their Interaction with a Resonant Medium

2020 ◽  
pp. 45-52
Author(s):  
T. Akhmedzhanov ◽  
V. Antonov ◽  
X. Zhang ◽  
K. C. Han ◽  
E. Kuznetsova ◽  
...  
Keyword(s):  
Resonant Medium ◽  
X Ray ◽  
Dynamical Control

scholarly journals Генерация аттосекундного импульса на основе коллективного спонтанного излучения слоя трехуровневых атомов, возбуждаемых парой униполярных импульсов

2020 ◽  
Vol 128 (11) ◽  
pp. 1723
Author(s):  
Р.М. Архипов ◽  
М.В. Архипов ◽  
И. Бабушкин ◽  
А.В. Пахомов ◽  
Н.Н. Розанов
Keyword(s):  
Hydrogen Atom ◽  
Key Words ◽  
Spontaneous Emission ◽  
Coherent Control ◽  
Generation Mechanism ◽  
Resonant Medium ◽  
Atomic Polarization ◽  
Short Pulses ◽  
X Ray ◽  
Free Polarization

Recently, for the generation of extremely short pulses, a method was proposed for coherent control of the polarization of a medium, based on the excitation of atomic polarization oscillations and their subsequent arrest using a pair of ultra short pulses. The so-called stopped pulse of polarization of the medium, which appears in the interval between its excitation and de-excitation, can be a source of an extremely short radiation pulse. In this paper, the indicated possibility of generating an isolated attosecond ultraviolet pulse in a three-level resonant medium, the parameters of which correspond to a hydrogen atom excited by a pair of unipolar X-ray pulses, is considered theoretically. In this case, the generation mechanism is "antenna", that is, it is caused by the collective spontaneous emission of pre-phased atoms in the absence of a noticeable decay of their free polarization. Key words: collective spontaneous emission, coherent control of atomic polarization, attosecond pulses, unipolar pulses, X-ray pulses, hydrogen atom.

scholarly journals A self-terminating X-ray amplifying medium: Kinetics of K-shell photoionization and stimulated emission

2000 ◽  
Vol 18 (1) ◽  
pp. 49-57
Author(s):  
F.N. CHUKHOVSKII ◽  
U. TEUBNER ◽  
I. USCHMANN ◽  
E. FÖRSTER
Keyword(s):  
Emission Cross Section ◽  
Input Pulse ◽  
Stimulated Emission ◽  
Resonant Medium ◽  
Photon Flux ◽  
Stage Model ◽  
Two Stage ◽  
Effective Lifetime ◽  
X Ray ◽  
Amplifying Effect

A two-stage model for achieving X-ray amplifying action on photoionized K-transitions pumped by the soft X-ray broadband flux from laser-produced plasma is treated. A simple pumping criterion is considered by the analysis of the positive gain-length product for the two-stage model of innershell transitions (0) → (3) and (2) → (1). The incident photon flux integrated over the effective lifetime T21 of an innershell transition (2) → (1) is related to the photoionization coefficient μ03(ph), stimulated emission cross section σ21(stim), and the effective gainlength L(eff) ≃ 0.63/μ03(abs), where μ03(abs) is the absorption coefficient of a pump soft X-ray radiation. Numerical estimates for the feasibility of K-shell X-ray amplification are given for C, F, Na, Ti, and Sn. For the example of an exponential X-ray carrier pulse (XCP) propagating through a resonant medium, an amplifying effect depending on the ratio of the input pulse temporal bandwidth τband to the effective lifetime T21 is investigated. It is shown that for an XCP with a finite bandwidth τband the logarithm of an energy gain, ln[U(z)], falls below a linear relation with z and thus, from the viewpoint of maximum amplifying effect bandwidths τband with τband/T21 > 1 are preferable. The requirements for achieving X-ray K-shell photoionization amplification for C are discussed in more detail. PACS numbers: 32.80.Hd, 42.50.Md, 42.55.Vc, 42.65.Re, 52.25.Nr.

scholarly journals Temporal and spectral control of the X-ray pulses in a resonant medium with a modulated transition frequency

2021 ◽  
Author(s):  
Farit Vagizov ◽  
Vladimir Antonov ◽  
Ilias Khairulin ◽  
Yevgeny Radeonychev ◽  
Kyong-Chol Han ◽  
...  
Keyword(s):  
Transition Frequency ◽  
Resonant Medium ◽  
X Ray ◽  
Spectral Control

Space and Time Distribution of Hard X-Ray Emission in a Loop at the Beginning of a Flare

1994 ◽  
Vol 144 ◽  
pp. 275-277
Author(s):  
M. Karlický ◽  
J. C. Hénoux
Keyword(s):  
Time Distribution ◽  
Electron Bombardment ◽  
Spatial Evolution ◽  
Superthermal Electrons ◽  
Flare Loop ◽  
X Ray ◽  
Superthermal Electron ◽  
Flare Loops ◽  
Chromospheric Evaporation ◽  
Temporal And Spatial

AbstractUsing a new ID hybrid model of the electron bombardment in flare loops, we study not only the evolution of densities, plasma velocities and temperatures in the loop, but also the temporal and spatial evolution of hard X-ray emission. In the present paper a continuous bombardment by electrons isotropically accelerated at the top of flare loop with a power-law injection distribution function is considered. The computations include the effects of the return-current that reduces significantly the depth of the chromospheric layer which is evaporated. The present modelling is made with superthermal electron parameters corresponding to the classical resistivity regime for an input energy flux of superthermal electrons of 109erg cm−2s−1. It was found that due to the electron bombardment the two chromospheric evaporation waves are generated at both feet of the loop and they propagate up to the top, where they collide and cause temporary density and hard X-ray enhancements.

Some Problems in Understanding the Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 1-9
Author(s):  
A. H. Gabriel
Keyword(s):  
Solar Corona ◽  
Solar Atmosphere ◽  
Theoretical Modelling ◽  
Total System ◽  
Major Advance ◽  
X Ray ◽  
Proper Perspective ◽  
Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Iron K-Line Emission from X-Ray Binaries

1988 ◽  
Vol 102 ◽  
pp. 47-50
Author(s):  
K. Masai ◽  
S. Hayakawa ◽  
F. Nagase
Keyword(s):  
Accretion Disk ◽  
Radiative Recombination ◽  
Characteristic Temperature ◽  
Line Emission ◽  
Ionization Front ◽  
Continuum Radiation ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx> 10 keV is likely due to fluorescence outside the He II ionization front.

Diagnostics of Gold Laser Plasmas

1988 ◽  
Vol 102 ◽  
pp. 357-360
Author(s):  
J.C. Gauthier ◽  
J.P. Geindre ◽  
P. Monier ◽  
C. Chenais-Popovics ◽  
N. Tragin ◽  
...  
Keyword(s):  
Experimental Results ◽  
Pure Gold ◽  
Electronic Temperature ◽  
X Ray ◽  
Laser Plasmas ◽  
Collisional Radiative Model ◽  
Radiative Model

AbstractIn order to achieve a nickel-like X ray laser scheme we need a tool to determine the parameters which characterise the high-Z plasma. The aim of this work is to study gold laser plasmas and to compare experimental results to a collisional-radiative model which describes nickel-like ions. The electronic temperature and density are measured by the emission of an aluminium tracer. They are compared to the predictions of the nickel-like model for pure gold. The results show that the density and temperature can be estimated in a pure gold plasma.

Axial Observation of X-Ray Spectra from a Beam-Foil Source

1988 ◽  
Vol 102 ◽  
pp. 339-342
Author(s):  
J.M. Laming ◽  
J.D. Silver ◽  
R. Barnsley ◽  
J. Dunn ◽  
K.D. Evans ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Heavy Ion ◽  
Ion Beams ◽  
Beam Axis ◽  
Doppler Broadening ◽  
X Ray ◽  
Beam Foil

AbstractNew observations of x-ray spectra from foil-excited heavy ion beams are reported. By observing the target in a direction along the beam axis, an improvement in spectral resolution, δλ/λ, by about a factor of two is achieved, due to the reduced Doppler broadening in this geometry.

Observed and Theoretical Spectra in the 10–100Å Interval

1988 ◽  
Vol 102 ◽  
pp. 259-261
Author(s):  
W.A. Brown ◽  
M.E. Bruner ◽  
L.W. Acton
Keyword(s):  
Sounding Rocket ◽  
Full Spectrum ◽  
X Ray

AbstractThe soft x-ray spectra recorded in two sounding rocket flights in 1982 and 1985 are compared with with predicted spectra. The poster presents the processed densitometer trace of the full spectrum together with the new spectrum from the 1985 experiment. This note compares the intensities of the lines with predictions.

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