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Title: Numerical simulations used for a validity check on the laser induced photo-detachment diagnostic method in electronegative plasmas

Abstract

Laser photo-detachment is used as a method to measure or determine the negative ion density and temperature in electronegative plasmas. In essence, the method consists of producing an electropositive channel (negative ion free region) via pulsed laser photo-detachment within an electronegative plasma bulk. Electrostatic probes placed in this channel measure the change in the electron density. A second pulse might be used to track the negative ion recovery. From this, the negative ion density and temperature can be determined. We study the formation and relaxation of the electropositive channel via a two-dimensional Particle-In-Cell/Mote Carlo collision model. The simulation is mainly carried out in a Hydrogen plasma with an electronegativity of α = 1, with a parametric study for α up to 20. The temporal and spatial evolution of the plasma potential and the electron densities shows the formation of a double layer (DL) confining the photo-detached electrons within the electropositive channel. This DL evolves into two fronts that move in the opposite directions inside and outside of the laser spot region. As a consequence, within the laser spot region, the background and photo-detached electron energy distribution function relaxes/thermalizes via collisionless effects such as Fermi acceleration and Landau damping. Moreover, the simulations showmore » that collisional effects and the DL electric field strength might play a non-negligible role in the negative ion recovery within the laser spot region, leading to a two-temperature negative ion distribution. The latter result might have important effects in the determination of the negative ion density and temperature from laser photo detachment diagnostic.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Laboratoire des plasmas de décharges, Centre de Développement des Technologies Avancées, Cité du 20 Aout BP 17 Baba Hassen, 16081 Algiers (Algeria)
  2. Istituto di Metodologie Inorganiche e dei Plasmi, CNR, via Amendola 122/D, 70126 Bari (Italy)
  3. Laboratoire d'Electronique Quantique, Faculté de Physique, USTHB, El Alia BP 32, Bab Ezzouar 16111, Algiers (Algeria)
  4. Laboratoire de Physique des Plasmas (CNRS, Ecole Polytechnique, Sorbonne Universités, UPMC Univ Paris 06, Univ Paris-Sud), École Polytechnique, 91128 Palaiseau Cedex (France)
Publication Date:
OSTI Identifier:
22304060
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANIONS; COMPUTERIZED SIMULATION; ELECTRON DENSITY; ELECTROSTATIC PROBES; ENERGY SPECTRA; LANDAU DAMPING; LASERS; PLASMA; PLASMA POTENTIAL

Citation Formats

Oudini, N., Taccogna, F., Bendib, A., and Aanesland, A. Numerical simulations used for a validity check on the laser induced photo-detachment diagnostic method in electronegative plasmas. United States: N. p., 2014. Web. doi:10.1063/1.4886144.
Oudini, N., Taccogna, F., Bendib, A., & Aanesland, A. Numerical simulations used for a validity check on the laser induced photo-detachment diagnostic method in electronegative plasmas. United States. https://doi.org/10.1063/1.4886144
Oudini, N., Taccogna, F., Bendib, A., and Aanesland, A. 2014. "Numerical simulations used for a validity check on the laser induced photo-detachment diagnostic method in electronegative plasmas". United States. https://doi.org/10.1063/1.4886144.
@article{osti_22304060,
title = {Numerical simulations used for a validity check on the laser induced photo-detachment diagnostic method in electronegative plasmas},
author = {Oudini, N. and Taccogna, F. and Bendib, A. and Aanesland, A.},
abstractNote = {Laser photo-detachment is used as a method to measure or determine the negative ion density and temperature in electronegative plasmas. In essence, the method consists of producing an electropositive channel (negative ion free region) via pulsed laser photo-detachment within an electronegative plasma bulk. Electrostatic probes placed in this channel measure the change in the electron density. A second pulse might be used to track the negative ion recovery. From this, the negative ion density and temperature can be determined. We study the formation and relaxation of the electropositive channel via a two-dimensional Particle-In-Cell/Mote Carlo collision model. The simulation is mainly carried out in a Hydrogen plasma with an electronegativity of α = 1, with a parametric study for α up to 20. The temporal and spatial evolution of the plasma potential and the electron densities shows the formation of a double layer (DL) confining the photo-detached electrons within the electropositive channel. This DL evolves into two fronts that move in the opposite directions inside and outside of the laser spot region. As a consequence, within the laser spot region, the background and photo-detached electron energy distribution function relaxes/thermalizes via collisionless effects such as Fermi acceleration and Landau damping. Moreover, the simulations show that collisional effects and the DL electric field strength might play a non-negligible role in the negative ion recovery within the laser spot region, leading to a two-temperature negative ion distribution. The latter result might have important effects in the determination of the negative ion density and temperature from laser photo detachment diagnostic.},
doi = {10.1063/1.4886144},
url = {https://www.osti.gov/biblio/22304060}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 6,
volume = 21,
place = {United States},
year = {Sun Jun 15 00:00:00 EDT 2014},
month = {Sun Jun 15 00:00:00 EDT 2014}
}