Investigation of thermodynamic equilibrium in laser-induced aluminum plasma using the Hα line profiles and Thomson scattering spectra

Abstract

We have studied isothermal equilibrium in the laser-induced plasma from aluminum pellets in argon at pressure of 200 mbar by using a method which combines the standard laser Thomson scattering and analysis of the Hα, Stark-broadened, line profiles. Plasma was created using 4.5 ns, 4 mJ pulses from a Nd:YAG laser at 1064 nm. While electron density and temperature were determined from the electron feature of Thomson scattering spectra, the heavy particle temperature was obtained from the Hα full profile applying computer simulation including ion-dynamical effects. We have found strong imbalance between these two temperatures during entire plasma evolution which indicates its non-isothermal character. At the same time, according to the McWhirter criterion, the electron density was high enough to establish plasma in local thermodynamic equilibrium.

Plasma local diagnostics by polarimetric method

“…In the modern plasma experiment, there is a clear desire for non-contact diagnostics of plasma. In this case, both passive diagnostics are developed-the electromagnetic field or corpuscular radiation emitted by the object under study is analyzed, and active diagnostics-the probing beam of radiation or particles scattered by the plasma is analyzed [3][4][5][6][7].…”

Polarimetric method of plasma diagnostics

“…In the modern plasma experiment, there is a clear desire for non-contact diagnostics of plasma. In this case, both passive diagnostics are developed -the electromagnetic field or corpuscular radiation emitted by the object under study is analyzed, and active diagnostics -the probing beam of radiation or particles scattered by the plasma is analyzed [3][4][5][6].…”

“…passive diagnostics are developed-the electromagnetic field or corpuscular radiation emitted by the object under study is analyzed, and active diagnostics-the probing beam of radiation or particles scattered by the plasma is analyzed [3][4][5][6][7].…”

Determination of excitation temperature in laser-induced plasmas using columnar density Saha-Boltzmann plot

“…The physical characterization of plasma and diagnostic approaches for the evaluation of plasma parameters have been the focus of several publications. It is well known that among the plasma parameters, plasma temperature plays an important role [17], [18], [19], [20], [21], [22], [23], [24]. The knowledge of plasma temperature has a great significance in describing other plasma characteristics such as the relative populations of energy levels and the velocity distribution of particles [16].…”