Plasma expansion produced by a long-pulse CO2 laser

1980 ◽  
Vol 58 (11) ◽  
pp. 1585-1588
Author(s):  
C. R. Neufeld ◽  
J. L. Lachambre
Keyword(s):  
Focal Spot ◽  
Laser Pulses ◽  
Plasma Expansion ◽  
Steady State Regime ◽  
Plasma Ions ◽  
Isothermal Expansion ◽  
State Regime ◽  
Expansion Model ◽  
Long Pulse ◽  
Aluminium Target

We have studied the plasma expansion produced when a 25 ns CO2 laser pulse is focussed onto a massive aluminium target. The maximum laser power density available was 2 × 1012 W cm−2 in a focal spot of approximately 250 μm in diameter. Charge collector measurements of the ions in the blow-off plasma indicate that an isothermal expansion model best describes the motion of the bulk of the plasma ions. Strong competing effects thus seem to inhibit the establishment of the steady-state regime expected for sufficiently long laser pulses, although faint indications of the beginnings of such a trend may be present.

Dissipative and Generative Fractional Electric Elements in Modeling RC and RL Circuits

2021 ◽  
Author(s):  
Kristian Haška ◽  
Stevan Cvetićanin ◽  
Dušan Zorica
Keyword(s):  
Asymptotic Behavior ◽  
Steady State ◽  
Constitutive Equation ◽  
Magnetic Flux ◽  
Electromotive Force ◽  
Constitutive Models ◽  
Steady State Regime ◽  
Power Type ◽  
State Regime ◽  
Transient And Steady State

Abstract Generalized capacitor (inductor) is constitutively modeled by expressing charge (magnetic flux) in terms of voltage (current) memory as a sum of instantaneous and power type hereditary contributions and it is proved to be a dissipative electric element by thermodynamic analysis. On the contrary, generalized capacitor (inductor) as a generative electric element is modeled using the same form of the constitutive equation, but by expressing voltage (current) in terms of charge (magnetic flux) memory. These constitutive models are used in transient and steady state regime analysis of the series RC and RL circuits subject to electromotive force, as well as in the study of circuits' frequency characteristics including asymptotic behavior.

MOLECULAR DYNAMICS SIMULATION OF PULSED LASER ABLATION

2011 ◽  
Vol 25 (04) ◽  
pp. 543-550 ◽  
Author(s):  
XIU-FANG GONG ◽  
GONG-XIAN YANG ◽  
PENG LI ◽  
YIN WANG ◽  
XI-JING NING
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Laser Pulses ◽  
Solid Surfaces ◽  
Dynamics Simulation ◽  
Angular Distributions ◽  
Adiabatic Expansion ◽  
Expansion Model

We have developed a simplified molecular-dynamical model for simulating ablation of solid surfaces by laser pulses, and specifically investigated expansion of Cu cloud in vacuum vaporized on the surface, showing that the angular distributions of the plume depend on the shape of the laser spot on the surface. In particular, experimentally observed flipover effects have been obtained, and an adiabatic constant determined from our simulations via an adiabatic expansion model agrees well with previous measurements.

scholarly journals On the mathematical model of combined rarefaction and compression waves in condensed matter

2021 ◽  
Vol 50 ◽  
pp. 104-107
Author(s):  
Alexander Alexandrovitch Samokhin ◽  
Pavel Aleksandrovich Pivovarov
Keyword(s):  
Shock Wave ◽  
Rarefaction Wave ◽  
Condensed Matter ◽  
Steady State Regime ◽  
Compression Waves ◽  
Momentum Fluxes ◽  
State Regime ◽  
The Mathematical Model ◽  
The Waves ◽  
Nonmetal Transition

Two waves model where shock wave is combined with rarefaction wave appearing in laser ablation due to metal-nonmetal transition effect is investigated using conservation laws for mass and momentum fluxes for the steady-state regime of the process. This approach permits to obtain the relation between front velocities of the waves which shows that the rarefaction wave can be rather slow compared with the generated shock wave.

scholarly journals Simulation of a two-dimensional binary gas mixture outflow into vacuum through a thin slit on the basis of direct solution of the Boltzmann kinetic equation

2021 ◽  
Vol 2056 (1) ◽  
pp. 012007
Author(s):  
S S Sitnikov ◽  
F G Tcheremissine ◽  
T A Sazykina
Keyword(s):  
Kinetic Equation ◽  
Boltzmann Kinetic Equation ◽  
Gas Mixture ◽  
Two Dimensional ◽  
Direct Solution ◽  
Steady State Regime ◽  
Collision Integrals ◽  
Flow Formation ◽  
Binary Gas Mixture ◽  
State Regime

Abstract Two-dimensional binary gas mixture outflow from a vessel into vacuum through a thin slit is studied on the basis of direct solution of the Boltzmann kinetic equation. For evaluation of collision integrals in the Boltzmann equation a conservative projection method is used. Numerical simulation of a two-dimensional argon-neon gas mixture outflow from a vessel into vacuum was performed. Graphs of mixture components flow rate dependence on time during the flow formation, as well as fields of molecular density and temperature for steady-state regime, were obtained.

scholarly journals Interferometric investigations of influence of target irradiation on the parameters of laser-produced plasma jets

2007 ◽  
Vol 25 (3) ◽  
pp. 425-433 ◽  
Author(s):  
A. Kasperczuk ◽  
T. Pisarczyk ◽  
S. Borodziuk ◽  
J. Ullschmied ◽  
E. Krousky ◽  
...  
Keyword(s):  
Focal Spot ◽  
Laser Energy ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Plasma Expansion ◽  
Third Harmonic ◽  
Fundamental Process ◽  
Laser Produced Plasma ◽  
Laser Facility ◽  
Planar Target

Our recent experimental results demonstrate that the formation of plasma jets is a fundamental process accompanying the laser produced plasma expansion, if a massive planar target with relatively high atomic number is irradiated by a defocused laser beam. In this paper some new results on the influence of target irradiation conditions on plasma jet parameters are presented. The experiment was carried out at the PALS iodine laser facility, with the third harmonic beam of the pulse duration of 250 ps (FWHM). The beam energies varied in the range of 13–160 J, the focal spot radii in the range of 35–600 µm. The planar massive targets used in the experiment were made of Cu, Ag and Ta. For measurements of the electron density evolution a three frame interferometric system was employed. The jets were observed in the whole range of the laser energy used. The initial velocities of the plasma jets produced in the reported experiment reached the value of up to 7·107 cm/s, the jets were up to 4 mm long including the jet pedestal and about 400 µm in diameter. Calculations of the efficiency of the plasma jet production show that it decreases with increasing the laser energy.

Integrated modelling of DEMO-FNS current ramp-up scenario and steady-state regime

2015 ◽  
Vol 55 (6) ◽  
pp. 063007 ◽  
Author(s):  
A.Yu. Dnestrovskij ◽  
B.V. Kuteev ◽  
A.S. Bykov ◽  
A.A. Ivanov ◽  
V.E. Lukash ◽  
...  
Keyword(s):  
Steady State ◽  
Integrated Modelling ◽  
Steady State Regime ◽  
Current Ramp ◽  
State Regime
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