Measurement of atmospheric pressure microplasma jet with Langmuir probes

Abstract

A radio frequency argon microplasma jet at atmospheric-pressure is characterized using Langmuir probes. While optical methods are the typical diagnostic for these small scale plasmas, the simplicity and low cost of Langmuir probes makes them an attractive option. The plasma density and electron temperature are measured using existing high-pressure Langmuir probe theories developed for flames and arcs. The density and temperature vary from 1 × 1016 to 1 × 1019 m−3 and 2.3 to 4.4 eV, respectively, depending on the operating condition. The density decreases while the electron temperature increases with axial distance from the jet exit. The applicability of the probe theories as well as the effect of collisionality and jet mixing is discussed.

Measurement of electron temperature in a non-equilibrium discharge of atmospheric pressure supported by focused microwave radiation from a 24 GHz gyrotron

“…In this case, the measured electron temperature may differ from the temperature in the plasma volume. [20] This cooling should be taken into account if Equation 1 is fulfilled:…”

Optical Emission Spectroscopic (OES) analysis for diagnostics of electron density and temperature in non-equilibrium argon plasma based on collisional-radiative model

“…This is because the assumption of collisionless sheath, as a prerequisite condition for the probe analysis, does not hold in the atmospheric-pressure plasmas due to a short mean free path of electrons. Hence, theoretical analysis of the probe data under atmospheric-pressure condition becomes too complicated to apply for practical measurement [31,32]. Before that, the size of the atmospheric-pressure plasmas is generally very small, and consequently, it is sometimes difficult to insert the probe-electrode.…”

Use of thermocouples and argon line broadening for gas temperature measurement in a radio frequency atmospheric microplasma jet

“…The plasma density for this source ranges from 10 10 to 10 14 cm 3 . 15 Therefore, only instrument, Doppler, and van der Waals broadening are considered.…”

“…Data from prior experiments with the linear-field configuration were used for the expected electron temperature and density. 15 A simplified formula to calculate the Stark broadening component is given in Eq. (4), 5 ∆λ…”

“…Past experiments with the linear-field configuration provided electron temperature and density values between 3.05 and 3.45 eV and 5.0 × 10 10 -2.5 × 10 12 cm 3 , respectively. 15 In order to simulate conditions where the Stark component would be at its maximum value, which corresponds to the point of the highest electron temperature and density, the values of 3.45 eV and 2.5 × 10 12 cm 3 were used.…”