The effects of electron thermal radiation on laser ablative shock waves from aluminum plasma into ambient air

2016 ◽  
Vol 23 (5) ◽  
pp. 053107 ◽  
Author(s):  
S. Sai Shiva ◽  
Ch. Leela ◽  
P. Prem Kiran ◽  
C. D. Sijoy ◽  
S. Chaturvedi
Keyword(s):  
Shock Waves ◽  
Thermal Radiation ◽  
Ambient Air ◽  
Aluminum Plasma

Investigation of the State of Local Thermodynamic Equilibrium of a Laser-Produced Aluminum Plasma

2005 ◽  
Vol 59 (4) ◽  
pp. 529-536 ◽  
Author(s):  
Olivier Barthélemy ◽  
Joëlle Margot ◽  
Stéphane Laville ◽  
François Vidal ◽  
Mohamed Chaker ◽  
...  
Keyword(s):  
Excited States ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Short Pulse ◽  
Ambient Air ◽  
Laser Induced Plasma ◽  
Laser Systems ◽  
Aluminum Plasma ◽  
Long Pulse ◽  
Xecl Excimer Laser

In this work, the assumption of local thermodynamic equilibrium (LTE) for a laser-induced plasma in ambient air is examined experimentally using two different laser systems, namely an infrared short-pulse Ti:Sapphire laser and an ultraviolet long-pulse XeCl excimer laser. The LTE assumption is investigated by examining the plasma produced at a laser fluence of 10 J/cm2 from aluminum targets containing iron and magnesium impurities. The excitation temperature is deduced from Boltzmann diagrams built from a large number of spatially integrated neutral iron lines distributed from 3.21 to 6.56 eV. It is shown that at any time after the end of the laser pulse, the neutral excited states are in excellent Boltzmann equilibrium. Detailed investigation of Boltzmann equilibrium further validates previous temperature measurements using less accurate diagrams. However, observations of ion lines provide some evidence that the ionized species do not obey Saha equilibrium, thereby indicating departure from LTE. This could be explained by the fact that the plasma cannot be considered as stationary for these species.

Distilled shock conditions for ideal magneto-acoustic shock waves in an optically thick medium

2012 ◽  
Vol 79 (5) ◽  
pp. 457-465
Author(s):  
D. ONIĆ
Keyword(s):  
Shock Waves ◽  
Thermal Radiation ◽  
Total Pressure ◽  
Fixed Ratio ◽  
Black Body ◽  
Black Body Radiation ◽  
Ideal Gas ◽  
Specific Heats ◽  
Special Case ◽  
Thick Medium

AbstractThe shock waves are important features in the analysis of transonic magnetohydrodynamical (MHD) flows where thermal radiation could also be significant. In this paper the effects of black-body radiation on non-relativistic shock waves in an ideal radiation MHD model for the optically thick case are discussed. Distilled shock conditions were derived and discussed for the case of a fixed ratio of specific heats of an ideal gas (γ) and ratio of gas to total pressure (b). The special case, when jumps in γ and/or b are allowed, was also considered.

scholarly journals Relativistic jets and non-thermal radiation from collapse of stars to black holes

2006 ◽  
Vol 2 (S238) ◽  
pp. 395-396
Author(s):  
V. Kryvdyk ◽  
A. Agapitov
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Shock Waves ◽  
Electric Field ◽  
Thermal Radiation ◽  
Radiation Flux ◽  
Thermal Emission ◽  
Charged Particles ◽  
Particle Spectrum ◽  
Relativistic Jets

AbstractThe formation of the relativistic jets and a non-thermal emission from the collapsing magnetized stars with dipole magnetic fields and the heterogeneous particles distribution are investigated. These polar jets are formed when the stellar magnetosphere compress during collapse its magnetic field increases considerable. The electric field is produced in magnetosphere, which the charged particles will be accelerated. As follow from the calculation, the jets can be formed from collapsing stars already the explosion of supernova stars without shock waves. These jets will generate the non-thermal radiation. The radiation flux depends on the distance to the star, its magnetic field and the particle spectrum in the magnetosphere. This flux can be observed near Earth by means of modern telescopes in the form of the radiation pulse with duration equal to time collapse.

Generalized Equation for Thermal Conductivity of MLI at Temperatures From 20K to 300K

2003 ◽  
Author(s):  
Lixing Gu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Radiation ◽  
Thermal Performance ◽  
Ambient Air ◽  
Liquid Hydrogen ◽  
Heat Fluxes ◽  
Layer By Layer ◽  
Storage Tanks ◽  
Thermal Conductivities

Multilayer insulation (MLI) has the lowest thermal conductivity of any currently used insulation in high vacuum environments and is used in cryogenic insulation system to minimize heat leaks in liquid hydrogen storage tanks. MLI consists of highly reflective radiation shields separated by spacers or insulation. The thermal conductivity of MLI varies with both temperature and vacuum level. Most published apparent thermal conductivities were measured for temperatures between 80K and 300K; some of the published data were for temperatures between 20K and 80K. Since the temperature of liquid hydrogen is 20K and the storage tanks are exposed to ambient air, it is essential to know the thermal performance of MLI for the temperature range of 20K to 300K. In addition, in order to provide a detailed temperature distribution and to optimize insulation systems with respect to the number of layers of MLI, layer density, insulation weight, and separator configuration, the layer-by-layer thermal performance of MLI has to be established for efficient storage tank design. A general equation for thermal conductivity was developed based on heat transfer principles for a wide range of temperature differences and vacuum levels. The equation consists of four heat transfer modes: 1) thermal radiation between two adjacent reflectors, 2) thermal radiation absorbed by spacers 3) gas conduction, and 4) solid spacer conduction. The equation can be applied for the temperature ranges of liquid hydrogen up to ambient, and for pressure ranges between 1.33 mPa to 1.33 kPa (0.01 millitorr and 10 torr). The predicted layer-by-layer temperatures, heat fluxes and apparent thermal conductivities using the developed thermal conductivity equation show very good agreement with measured data between the temperatures of 80K and 300K at the various pressure levels. When the equation was applied for a temperature of 20K, heat fluxes increased due to the larger temperature difference, while apparent thermal conductivities decreased due to the lower cold side temperature.

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