Influence Of Ion Dynamics Research Articles

The influence of ion dynamics on the breaking of plane electron oscillations

The influence of ion dynamics on the breaking of plane relativistic electron oscillations is studied by numerical modeling. An algorithm in Euler’s variables for finite-difference simulation is developed, and preliminary analytical study is performed. A new type of breaking of long-lived oscillations, different from the earlier-known one, is presented. Part of the computations were performed on the Chebyshev supercomputer (Lomonosov Moscow State University).

Experimental research into the influence of ion dynamics when measuring theelectron density from the Stark broadening of the Hα and Hβlines

In this work we have performed experimental research into theinfluence of ion dynamics on the profiles of the Hα and Hβlines of the hydrogen Balmer series. In order to understand this influence the electrondensity of a microwave plasma column at atmospheric pressure is measured fromthe Stark broadening of both lines. However, in this case Kepple–Griem’s theoryis not used, as usual, but a new computational model based on the μ-ion modelthat includes the effect of the ion dynamics on the profiles. The results obtained show thatthe difference between the electron density values from both the Hα and Hβlines is about 3%. So, it is possible to use the Hα line for thediagnosis of the electron density in those cases in which it is not possible to use the Hβline; for example, when the Hβ lineis not intense enough.

Influence of ion dynamics on the shape of neutral-atom spectral lines

Influence of ion dynamics on the shape of neutral-atom spectral lines

Influence of ion dynamics on the width and shift of isolated He I lines in plasmas. II.

Stark widths and shifts of the He i 7065-, 6678-, 5016-, 4713-, and 3188-\AA{} lines are measured in hydrogen-helium plasma. A repetitively pulsed low-pressure arc is used as a plasma source, while the signal averaging technique is employed to record the line profiles. The electron densities in the range of (2.5\char21{}5.9)\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ are measured by 10.6-\ensuremath{\mu}m laser interferometry. The electron temperatures ranging from 19 300 to 23 600 K are determined from the ratio of the ${\mathrm{H}}_{\ensuremath{\gamma}}$ line intensity to the underlying continuum, while the gas temperatures from 5000 to 12 600 K are measured from the Doppler component of the He i line profiles. The experimental Stark widths and shifts are compared with the theoretical results obtained from the three sets of semiclassical calculations of Stark broadening parameters by using the quasistatic and ion-dynamic treatment of the ions. Inclusion of ion dynamics in the width and shift calculations improves the consistency in the comparison between the theory and the experiment and shows the systematic discrepancy between three semiclassical calculations. These results suggest the possibility of high precision electron-density diagnostics.

Influence of ion dynamics on the width and shift of isolated He I lines in plasmas.

We report measured Stark widths and shifts of the neutral helium lines 3889 and 5876 A in hydrogen-helium, pure helium, and argon-helium plasmas. A pulsed low-pressure arc is used as a plasma source. Electron densities of (2--10){times}10{sup 16} cm{sup {minus}3} are measured by laser interferometry, electron temperatures in the range from 31 000 to 42 000 K are determined from the intensity ratio of O II impurity lines, and the gas temperature is determined from the Doppler component of the O II line profile. Experimental Stark widths and shifts are compared with theoretical results obtained from three sets of semiclassical calculations of Stark-broadening parameters using quasistatic and ion-dynamic treatment of the ions. Inclusion of ion dynamics in the calculation of widths and shifts considerably improves the agreement between theory and experiments. The results of the comparison show a constant systematic discrepancy between three semiclassical calculations and the experiment. These results suggest the possibility of plasma-electron-density diagnostics with a precision in the range 3--5 %.

Ion mobility influence on stimulated Raman scattering in homogeneous laser-irradiated plasma

1½ D computer simulations have been performed to illustrate the influence of ion dynamics on stimulated Raman scattering in laser irradiated plasmas. A flat density profile has been used. Backward and forward scatter and heated electron distribution have been studied as a function of ion mass and ion temperature. The results show clearly that the lighter the ions, the more inhibited the Raman scatter and associated fast electron production. Futhermore, when ions are cold enough to allow Brillouin scattering release, Raman scatter, as well as associated suprathermal electrons is even more reduced. These observations evidence the complex non-linear coupling of the electron plasma waves driven by the Raman instability and the ion fluctuations which can exist in the plasma.