Some characteristics and observations of long diffuse discharges produced by the focussing of a TEA-CO2 pulse with an axicon

1980 ◽  
Vol 58 (10) ◽  
pp. 1477-1482 ◽  
Author(s):  
G. Roy ◽  
Y. d'Astous ◽  
M. Blanchard ◽  
R. Tremblay
Keyword(s):  
Experimental Study ◽  
Theoretical Model ◽  
Laser Pulse ◽  
Helium Plasma ◽  
Radial Expansion ◽  
Effective Volume ◽  
Breakdown Threshold ◽  
Electronic Density

A theoretical and an experimental study of long diffuse laser produced plasmas with axicon lenses is presented. It is shown that the heating of a helium plasma is strongly dependent on the nitrogen tail of the TEA-CO2 laser pulse when the initial electronic density (produced by photopreionization) is sufficiently high, but still below the breakdown threshold. Furthermore, a theoretical model is used to evaluate the radial expansion of the plasma in order to determine the effective volume of the plasma when dealing with rapidly evolving processes.

Dynamics of charge density wave phase-slips in mesoscopic samples

2002 ◽  
Vol 12 (9) ◽  
pp. 165-168
Author(s):  
S. N. Artemenko
Keyword(s):  
Experimental Study ◽  
Theoretical Model ◽  
Charge Density ◽  
Qualitative Agreement ◽  
Charge Density Wave ◽  
Temporal Evolution ◽  
Density Wave ◽  
Thermal Fluctuations ◽  
Charge Density Wave Phase ◽  
Phase Slips

Theoretical model of current conversion from normal to collective current in mesoscopic samples of CDW conductors is presented. The current conversion is described in terms of phase slips (PS) induced by strain of the CDW and stimulated by thermal fluctuations. Kernels of PS situated near contacts are surrounded by long-range perturbations of the CDW phase. If spacing between contacts is shorter than decaying length of these perturbations then temporal evolution of PS at different contacts becomes correlated, and PS voltage decreases with spacing between the contacts decreasing. The results are in qualitative agreement with experimental study of current conversion in submicron NbSe3 wires.

Improving the Technology for Producing Pressure Couplings of Bushing-Housing Parts by Using a Power Drive Made of an Alloy with the Shape Memory Effect

2021 ◽  
pp. 55-64
Author(s):  
O.V. Lomovskoy ◽  
R.S. Zagidullin
Keyword(s):  
Experimental Study ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Flow Diagram ◽  
Radial Expansion ◽  
Power Drive ◽  
Fmea Method ◽  
Contact Pressures

The article describes the technology of using a power drive made of an alloy with the shape memory effect to improve the quality of the pressure couplings of bushing-housing. A comprehensive assessment of the existing approaches to the production of a pressure coupling is performed. The risk analysis of the technological process of pressing by the FMEA method is carried out. The flow diagram of the proposed process and the results of an experimental study of the dependence of contact pressures on the radial expansion of a ring load-bearing element made of an alloy with the shape memory effect are presented.

scholarly journals Effect of self focusing on the prolongation of laser produced plasma channel

2009 ◽  
Vol 27 (1) ◽  
pp. 33-39 ◽  
Author(s):  
U. Verma ◽  
A.K. Sharma
Keyword(s):  
Theoretical Model ◽  
Time Delay ◽  
Laser Pulse ◽  
Density Profile ◽  
Plasma Channel ◽  
Ion Density ◽  
Pulse Technique ◽  
Recombination Time ◽  
Self Focusing ◽  
Gaseous Plasma

AbstractA theoretical model for the prolongation of lifetime of a gaseous plasma channel formed by two pulse technique at laser intensities below the tunnel ionization threshold is developed. The first laser pulse ionizes the gas completely on the axis and partially off the axis, causing self-defocusing of the pulse. After the passage of the pulse, the plasma expands radially, creating an atom/ion density profile with a minimum on the axis. Partial recombination also sets in. As the second pulse arrives, after a time delay of less than the recombination time (~ns), the electrons get heated, and the recombination rate is slowed down. The second pulse self focuses, enhancing the heating rate and lengthening the lifetime of the plasma channel.

scholarly journals Stopping power of a helium plasma under LTE or NLTE conditions

2018 ◽  
Vol 36 (4) ◽  
pp. 442-447
Author(s):  
Luis González-Gallego ◽  
Manuel D. Barriga-Carrasco ◽  
Juan Miguel Gil ◽  
Rafael Rodríguez ◽  
Guadalupe Espinosa
Keyword(s):  
Theoretical Model ◽  
Electron Temperature ◽  
Thermal Equilibrium ◽  
Stopping Power ◽  
Local Thermal Equilibrium ◽  
Helium Plasma ◽  
Slowing Down ◽  
Non Local ◽  
Argon Ions ◽  
Bound Electrons

AbstractIn this work, the stopping power of a partially ionized helium plasma due to its free and bound electrons is analyzed for an electron temperature and density in which local thermal equilibrium (LTE) or non-local thermal equilibrium (NLTE) regimes can be possible. In particular by means of collisional-radiative models, the average ionization of the plasma as well as the abundances of different helium species (HeI, HeII, and HeIII) are analyzed in both LTE and NLTE thermodynamic states. The influence of this ionization and of the different ion abundances on the stopping power of the helium plasma is shown to be quite significant. Finally, our theoretical model is compared with experimental results on slowing down of swift argon ions in helium plasma.

AN EXPERIMENTAL STUDY OF A DIVERGENT NUCLEAR REACTOR

1953 ◽  
Vol 31 (2) ◽  
pp. 182-188 ◽  
Author(s):  
J. G. Bayly
Keyword(s):  
Experimental Study ◽  
Theoretical Model ◽  
Experimental Error ◽  
Nuclear Reactor ◽  
Relaxation Times ◽  
Experimental Measurements ◽  
Zero Energy

Experimental measurements of the relaxation times of a nuclear reactor were compared with the theoretical relaxation times in the range 1.6 to 186 sec. The work was done with the Chalk River Zero Energy Experimental Pile, ZEEP, in 1947, and showed that agreement within the experimental error could be obtained if the theoretical model used to represent the reactor was of the age-velocity type with a correction for the effect of the reflector.

Radial Expansion of T5-6063 Aluminum Tubes: An Experimental Investigation and Numerical Simulation

2008 ◽  
Author(s):  
A. Al-Hajeri ◽  
A. C. Seibi
Keyword(s):  
Experimental Study ◽  
Finite Element ◽  
Stress Concentration ◽  
Failure Modes ◽  
Expansion Ratio ◽  
Radial Expansion ◽  
Drawing Force ◽  
Element Analysis ◽  
Aluminum Tubes ◽  
Zero Degree

This paper presents the design of an experimental set-up to mechanically expand T5-6063 aluminum tubes using conical hardened steel mandrels. The effect of the expansion ratio and mandrel angle on the tube wall thickness and drawing force required to expand the tubes as well as failure modes near embedded circular holes are investigated. The experimental study considered four radial expansion ratios of 1.5, 5, 7 and 10% and three mandrel angles of 10, 22.5, and 30 degrees. It was shown experimentally that most of the tubes failed at the 90 degrees position of the hole indicating that the maximum stress concentration takes place at that position as compared to the zero degree location. The experimental study was supplemented by finite element models reflecting the lab tests to determine the drawing force and study the stress concentration around the hole at zero and 90 degrees locations. The finite element analysis took into consideration various parameters such as expansion ratio and mandrel angle. The simulation results, which were calibrated through generated experimental data, confirmed the experimental observations when studying the stress concentration around the hole for various mandrel angles and expansion ratios at 90 degrees angle. The finite element results also showed that the stress concentration is much higher at 90 degrees position where failure occurred in all tested samples as compared to the zero degree angle.

Induction Electrohydrodynamic Pump in a Vertical Configuration: Part 2—Experimental Study

1989 ◽  
Vol 111 (3) ◽  
pp. 670-674 ◽  
Author(s):  
J. Seyed-Yagoobi ◽  
J. C. Chato ◽  
J. M. Crowley ◽  
P. T. Krein
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Theoretical Model ◽  
Natural Circulation ◽  
External Pressure ◽  
Temperature Profiles ◽  
Flow Rates ◽  
Present Apparatus ◽  
Circulation Velocity ◽  
Good Agreement

An induction electrohydrodynamic (EHD) pump in axisymmetric, vertical configuration was designed and built. The flow rates were measured for various temperature profiles and several values of frequency, voltage, wavelength, and electric conductivity. The experimental data are generally in good agreement with the theoretical model presented in Part 1. With the present apparatus at relatively low voltages, velocities four times higher than natural circulation velocity are easily obtained. The external pressure load and entrance temperature profile play important roles on the operation of the pump and must be considered carefully in the design.

A MATHEMATICAL FORMULATION FOR FREE SPIN DENSITY AND ELECTRONIC DENSITY OF STATES IN K2CuCl4 · 2H2O-TYPE CRYSTALS

2002 ◽  
Vol 16 (20) ◽  
pp. 751-756 ◽  
Author(s):  
M. A. GRADO-CAFFARO ◽  
M. GRADO-CAFFARO
Keyword(s):  
Theoretical Model ◽  
Spin Density ◽  
Molecular Orbital ◽  
Density Of States ◽  
Mathematical Formulation ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Electronic Density ◽  
Electronic Density Of States ◽  
Molecular Bonding

A theoretical model based upon molecular orbital theory for superexchange interaction in K 2 CuCl 4 · 2H 2 O -type crystals is presented; atomic d- and p-orbitals as well as molecular bonding and antibonding orbitals are considered. In particular, the free spin density and the electronic density of states are calculated.

scholarly journals An experiment to measure raindrop collection efficiencies: influence of rear capture

2014 ◽  
Vol 7 (5) ◽  
pp. 1321-1330 ◽  
Author(s):  
A. Quérel ◽  
P. Lemaitre ◽  
M. Monier ◽  
E. Porcheron ◽  
A. I. Flossmann ◽  
...  
Keyword(s):  
Experimental Study ◽  
Theoretical Model ◽  
Aerosol Particle ◽  
Aerosol Particles ◽  
Severe Accident ◽  
Radioactive Aerosol ◽  
Microphysical Parameter ◽  
Particle Collection ◽  
Modelling Studies

Abstract. In the case of severe accident with loss of containment in a nuclear plant, radionuclides are released into the atmosphere in the form of both gases and aerosol particles (Baklanov and Sørensen, 2001). The analysis of radioactive aerosol scavenged by rain after the Chernobyl accident highlights certain differences between the modelling studies and the environmental measurements. Part of these discrepancies can probably be attributed to uncertainties in the efficiencies used to calculate aerosol particle collection by raindrops, particularly drops with a diameter larger than one millimetre. In order to address the issue of these uncertainties, an experimental study was performed to close the gaps still existing for this key microphysical parameter. In this paper, attention is first focused on the efficiency with which aerosol particles in the accumulation mode are collected by raindrops with a diameter of 2 mm. The collection efficiencies measured for aerosol particle in the sub-micron range are quantitatively consistent with previous theoretical model developed by Beard (1974) and thus highlight the major role of rear capture in the submicron range.

An experimental study of self-focusing and self-defocusing of a TEA CO2 laser pulse in CDF3

1987 ◽  
Vol 42 (4) ◽  
pp. 225-231 ◽  
Author(s):  
Y. Beaudoin ◽  
P. Galarneau ◽  
A. Normandin ◽  
S. L. Chin
Keyword(s):  
Experimental Study ◽  
Laser Pulse ◽  
Co2 Laser ◽  
Tea Co2 Laser ◽  
Self Focusing
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