Axial heating of magnetically confined plasma with CO2 lasers

1977 ◽  
Vol 55 (5) ◽  
pp. 412-418 ◽  
Author(s):  
A. A. Offenberger
Keyword(s):  
Wave Propagation ◽  
Laser Intensity ◽  
Laser Energy ◽  
Ion Heating ◽  
Intensity Parameter ◽  
Order Unity ◽  
Ion Energy ◽  
Magnetically Confined ◽  
Laser Heated ◽  
Heating Wave

The coupled electron–ion heating equations, neglecting losses, in a CO2 laser heated solenoid are solved for a laser intensity varying with time as I = I0t2/3. An analytical solution, without restriction on the ratio of electron-to-ion temperatures Te/Ti is found, showing Te,i ~ t2/3.The heating wave which propagates along the solenoid is found to be supersonic having a velocity independent of time and varying as I03/5. Low intensity heating is found to maximize Ti/Te and minimize plasma length and laser energy requirements. The heating wave propagation is found to be consistent with an optical thickness of order unity in the heated plasma column. Considerations of electron–ion energy transfer, supersonic heating wave propagation, and laser beam trapping lead to an optimum laser intensity parameter [Formula: see text].

On the axial heating of magnetically confined plasma with CO2 lasers

1977 ◽  
Vol 55 (21) ◽  
pp. 1868-1870
Author(s):  
C. S. Lai ◽  
M. P. Madan
Keyword(s):  
Magnetic Field ◽  
Plasma Column ◽  
Laser Intensity ◽  
Confinement Time ◽  
Co2 Lasers ◽  
Ion Heating ◽  
Magnetically Confined ◽  
Laser Heated

The equations governing the electron–ion heating in a CO2 laser heated plasma column confined by a solenoidal magnetic field are solved for a laser intensity law I = I0t2/3. It is shown that in addition to a set of solutions obtained by Offenberger, one more set of solutions exists, which is of considerable interest if shorter confinement time is desirable.

scholarly journals A simple model for soft X-ray conversion efficiency from laser-irradiated gold disk targets

1984 ◽  
Vol 2 (3) ◽  
pp. 303-307 ◽  
Author(s):  
P. H. Y. Lee ◽  
H. G. Ahlstrom
Keyword(s):  
Heat Conduction ◽  
Simple Model ◽  
Conversion Efficiency ◽  
Laser Light ◽  
Laser Intensity ◽  
Laser Energy ◽  
High Irradiance ◽  
X Rays ◽  
X Ray ◽  
Laser Heated

Simple arguments are used to construct a model to explain the conversion efficiency of absorbed laser energy into soft X-rays from laser-irradiated targets. In this model, we postulate that the energy available for conversion is bounded at some low irradiance limit by heat conduction away from the laser heated spot, while at some high irradiance limit it is bounded by the energy lost in plasma blowoff. Consequently, at some appropriate laser intensity, where the sum energy of the conduction and blowoff losses is at a minimum, the X-ray conversion efficiency should reach a maximum. A specific example for gold disk targets irradiated by 0·53 μm laser light will be treated. Simple heuristic scalings of blowoff and conduction as functions of laser intensity are obtained.

scholarly journals Constraints on ion versus electron heating by plasma turbulence at low beta

2019 ◽  
Vol 85 (3) ◽  
Author(s):  
A. A. Schekochihin ◽  
Y. Kawazura ◽  
M. A. Barnes
Keyword(s):  
Spatial Scales ◽  
Low Frequency ◽  
Larmor Frequency ◽  
Energy Partition ◽  
Ion Distribution ◽  
Ion Heating ◽  
Order Unity ◽  
Ion Cyclotron Waves ◽  
Laboratory Plasmas ◽  
Density Perturbations

It is shown that in low-beta, weakly collisional plasmas, such as the solar corona, some instances of the solar wind, the aurora, inner regions of accretion discs, their coronae and some laboratory plasmas, Alfvénic fluctuations produce no ion heating within the gyrokinetic approximation, i.e. as long as their amplitudes (at the Larmor scale) are small and their frequencies stay below the ion-Larmor frequency (even though their spatial scales can be above or below the ion Larmor scale). Thus, all low-frequency ion heating in such plasmas is due to compressive fluctuations (‘slow modes’): density perturbations and non-Maxwellian perturbations of the ion distribution function. Because these fluctuations energetically decouple from the Alfvénic ones already in the inertial range, the above conclusion means that the energy partition between ions and electrons in low-beta plasmas is decided at the outer scale, where turbulence is launched, and can be determined from magnetohydrodynamic (MHD) models of the relevant astrophysical systems. Any additional ion heating must come from non-gyrokinetic mechanisms such as cyclotron heating or the stochastic heating owing to distortions of ions’ Larmor orbits. An exception to these conclusions occurs in the Hall limit, i.e. when the ratio of the ion to electron temperatures is as low as the ion beta (equivalently, the electron beta is order unity). In this regime, slow modes couple to Alfvénic ones well above the Larmor scale (viz., at the ion inertial or ion sound scale), so the Alfvénic and compressive cascades join and then separate again into two cascades of fluctuations that linearly resemble kinetic Alfvén and ion-cyclotron waves, with the former heating electrons and the latter ions. The two cascades are shown to decouple, scalings for them are derived and it is argued physically that the two species will be heated by them at approximately equal rates.

scholarly journals Characterisation and Modelling of Ultrashort Laser-Driven Electromagnetic Pulses

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Kwinten Nelissen ◽  
Máté Liszi ◽  
Massimo De Marco ◽  
Valeria Ospina ◽  
István Drotár ◽  
...  
Keyword(s):  
Pulse Energy ◽  
Large Scale ◽  
Laser Intensity ◽  
Laser Energy ◽  
Laser System ◽  
Intense Laser ◽  
Electron Interaction ◽  
Laser Target ◽  
Electromagnetic Pulses ◽  
Target Holder

AbstractRecent advances on laser technology have enabled the generation of ultrashort (fs) high power (PW) laser systems. For such large scale laser facilities there is an imperative demand for high repetition rate operation in symbiosis with beamlines or end-stations. In such extreme conditions the generation of electromagnetic pulses (EMP) during high intense laser target interaction experiments can tip the scale for the good outcome of the campaign. The EMP effects are several including interference with diagnostic devices and actuators as well as damage of electrical components. The EMP issue is quite known in the picosecond (ps) pulse laser experiments but no systematic study on EMP issues at multi-Joule fs-class lasers has been conducted thus far. In this paper we report the first experimental campaign for EMP-measurements performed at the 200 TW laser system (VEGA 2) at CLPU laser center. EMP pulse energy has been measured as a function of the laser intensity and energy together with other relevant quantities such as (i) the charge of the laser-driven protons and their maximum energy, as well as (ii) the X-ray Kα emission coming from electron interaction inside the target. Analysis of experimental results demonstrate (and confirm) a direct correlation between the measured EMP pulse energy and the laser parameters such as laser intensity and laser energy in the ultrashort pulse duration regime. Numerical FEM (Finite Element Method) simulations of the EMP generated by the target holder system have been performed and the simulations results are shown to be in good agreement with the experimental ones.

scholarly journals Simulation of femtosecond laser absorption by metallic targets and their thermal evolution

2017 ◽  
Vol 35 (3) ◽  
pp. 415-428 ◽  
Author(s):  
A. Suslova ◽  
A. Hassanein
Keyword(s):  
Femtosecond Laser ◽  
Laser Intensity ◽  
Laser Energy ◽  
Absorption Efficiency ◽  
Optical Parameters ◽  
Temperature Dependent ◽  
Simulation Code ◽  
Laser Absorption ◽  
Plasma State ◽  
Wide Range

AbstractThe interaction of femtosecond laser with initially cold solid metallic targets (Al, Au, Cu, Mo, Ni) was investigated in a wide range of laser intensity with focus on the laser energy absorption efficiency. Our developed simulation code (FEMTO-2D) is based on two-temperature model in two-dimensional configuration, where the temperature-dependent optical and thermodynamic properties of the target material were considered. The role of the collisional processes in the ultrashort pulse laser–matter interaction has been carefully analyzed throughout the process of material transition from the cold solid state into the dense plasma state during the pulse. We have compared the simulation predictions of the laser pulse absorption with temperature-dependent reflectivity and optical penetration depth to the case of constant optical parameters. By considering the effect of the temporal and spatial (radial) distribution of the laser intensity on the light absorption efficiency, we obtained a good agreement between the simulated results and available experimental data. The appropriate model for temperature-dependent optical parameters defining the laser absorption efficiency will allow more accurate simulation of the target thermal response in the applications where it is critical, such as prediction of the material damage threshold, laser ablation threshold, and the ablation profile.

scholarly journals Ion energy enhancement from TNSA plasmas obtained from advanced targets

2014 ◽  
Vol 32 (3) ◽  
pp. 383-389 ◽  
Author(s):  
L. Torrisi
Keyword(s):  
Electric Field ◽  
Double Layer ◽  
Laser Intensity ◽  
Laser Wavelength ◽  
Rear Side ◽  
Energetic Ions ◽  
Ion Energy ◽  
Fast Electrons ◽  
Surface Reflection ◽  
Laser Absorption

AbstractLaser generated plasmas from target normal sheath acceleration produce energetic ions from the rear side of the target due to the formation of a high directive electric field. Fast electrons are ejected from the rear side of the target and a successive Coulomb explosion is driven by the fast electrons generating a high electric field of double layer. The ion acceleration is mainly controlled by the laser intensity and by the square of the laser wavelength. Literature reports that at intensities of the order of 1018 W/cm2 and at wavelengths of about 1 µm the ion energy is of the order of 5 MeV/nucleon. The use of advanced targets realized with the aim to reduce the surface reflection, to increase the laser absorption coefficient and, with an optimal thickness, to increase the electric field of the double layer, permits to enhance the ion energy acceleration, so that the energy of 5.0 MeV per charge state can be reached at about 1016 W/cm2, as it will be presented and discussed.

Anomalous ion heating in a laser heated plasma

1973 ◽  
Vol 15 (1) ◽  
pp. 21-27 ◽  
Author(s):  
S E Bodner ◽  
G F Chapline ◽  
J DeGroot
Keyword(s):  
Ion Heating ◽  
Laser Heated

scholarly journals Experiments with laser-irradiated cylindrical targets

1991 ◽  
Vol 9 (3) ◽  
pp. 725-747 ◽  
Author(s):  
C. Stöckl ◽  
G. D. Tsakiris
Keyword(s):  
Light Propagation ◽  
Energy Transport ◽  
Laser Light ◽  
Laser Energy ◽  
Axial Direction ◽  
Radiative Energy ◽  
Capillary Length ◽  
Inner Diameter ◽  
Laser Heated ◽  
Good Agreement

Results of novel experiments with laser-heated capillary targets are presented. In these experiments the interior of gold capillaries having a 200- or 700-μm inner diameter and a 2–12-mm length was axially irradiated by injection of the laser energy through one of the end openings. A frequency-doubled Nd:glass laser (λ = 0.53 μm) was employed, delivering 8-J energy in 3 ns. The experiments showed no significant backreflection of laser light. Depending on the capillary diameter and length, most of the laser energy is either transmitted or absorbed inside the capillary. The transmission of laser light was measured as a function of capillary length and found to be in good agreement with the predictions of a simple theoretical model. Two extreme cases could be identified. Capillaries with a 700-μm diameter show uninhibited laser light propagation due to multireflections off the inner wall. In contrast, at the entrance of capillaries with a 200-μm inner diameter a plasma plug forms that absorbs most of the laser energy. In both cases significant energy transport was observed to occur in the axial direction. A stable and strongly radiating plasma column is formed along the capillary axis by the collision of the radially imploding plasma. During the collision, part of the hydrodynamic energy of the plasma is converted into radiative energy. In a special case-a lower limit of ≊7% could be inferred for the conversion efficiency from laser light into X-ray radiation emitted from the rear opening of the capillary.

Dynamics of CO2 laser heated solenoids

1982 ◽  
Vol 60 (9) ◽  
pp. 1247-1256 ◽  
Author(s):  
D. C. D. McKen ◽  
W. Tighe ◽  
R. Fedosejevs ◽  
A. A. Offenberger
Keyword(s):  
Laser Energy ◽  
Plasma Temperature ◽  
Wave Model ◽  
Hydrogen Gas ◽  
Pressure Balance ◽  
Scaling Models ◽  
Simple Scaling ◽  
Gas Breakdown ◽  
Long Pulse ◽  
Laser Heated

Experimental results are reported for long pulse CO2 laser production and heating of magnetically confined plasma columns. The plasma column is produced by an ionizing and heating wave propagation along the axis of a linear magnetic solenoid when laser radiation is focused into hydrogen gas contained inside the solenoid. The axial behavior is found to be reasonably well described by a "bleaching" wave model which predicts column length as a function of time. Radial behavior, following a transient ionization and expansion phase, is determined by a balance of ion thermal conduction and inverse bremsstrahlung laser heating. A finite ionization time is observed at the gas breakdown front. Energy balance measurements indicate that most of the incident laser energy is effectively coupled to ionization and heating of the plasma. Temperature measurements show good agreement with predictions of simple scaling models from which pressure balance gives a density value in agreement with experiment.

scholarly journals Simultaneous measurements of the two-dimensional distribution of infrared laser intensity and temperature in a single-sided laser-heated diamond anvil cell

2019 ◽  
Vol 351 (2-3) ◽  
pp. 286-294 ◽  
Author(s):  
Kamil M. Bulatov ◽  
Pavel V. Zinin ◽  
Yulia V. Mantrova ◽  
Aleksey A. Bykov ◽  
Maksim I. Gaponov ◽  
...  
Keyword(s):  
Diamond Anvil Cell ◽  
Laser Intensity ◽  
Infrared Laser ◽  
Two Dimensional ◽  
Simultaneous Measurements ◽  
Dimensional Distribution ◽  
Diamond Anvil ◽  
Laser Heated
Sign in / Sign up

Export Citation Format

Share Document