Revealing Plasma-Surface Interaction at Atmospheric Pressure: Imaging of Electric Field and Temperature inside the Targeted Material

Abstract

The plasma-surface interaction is studied for a low temperature helium plasma jet generated at atmospheric pressure using Mueller polarimetry on an electro-optic target. The influence of the AC kHz operating frequency is examined by simultaneously obtaining images of the induced electric field and temperature of the target. The technique offers high sensitivity in the determination of the temperature variation on the level of single degrees. Simultaneously, the evolution of the electric field in the target caused by plasma-driven charge accumulation can be measured with the threshold of the order of 105 V/m. Even though a specific electro-optic crystal is used to obtain the results, they are generally applicable to dielectric targets under exposure of a plasma jet when they are of 0.5 mm thickness, have a dielectric constant greater than 4 and are at floating potential. Other techniques to examine the induced electric field in a target do not exist to the best of our knowledge, making this technique unique and necessary. The influence of the AC kHz operating frequency is important because many plasma jet designs used throughout the world operate at different frequency which changes the time between the ionization waves and hence the leftover species densities and stability of the plasma. Results for our jet show a linear operating regime between 20 and 50 kHz where the ionization waves are stable and the temperature increases linearly by 25 K. The charge deposition and induced electric fields do not increase significantly but the surface area does increase due to an extended surface propagation. Additionally, temperature mapping using a 100 μm GaAs probe of the plasma plume area has revealed a mild heat exchange causing a heating of several degrees of the helium core while the surrounding air slightly cools. This peculiarity is also observed without plasma in the gas plume.

Electrodeless atmospheric secondary induced ionization jet (EASII-jet): Dynamics and properties of a transferred helium plasma source

“…This is explained with the plasma surface interaction with the Pasteur pipette outer all. The value of T gas measured in the vicinity of the surface is consistent with the data published in the literature [38][39][40] . Regarding T gas in the plume of the SIIW, the latter is in agreement with prior measurements obtained in APPJ without interacting surface (free jet) 22 .…”

Towards plasma jet controlled charging of a dielectric target at grounded, biased, and floating potential

“…Therefore when a DC bias was applied, any charge detected at this time delay is defined as the continuous surface charge . This background also includes birefringence induced not by electric field but by internal strain in the BSO material caused by temperature gradients 23 , 24 . This background is now analyzed further.…”

Quantification of surface charging memory effect in ionization wave dynamics

“…A background is generally present within the birefringence relating to the temperature gradient along the material caused by (limited) heat transfer by the plasma 48 , 49 . This induces an internal strain that accumulates to the birefringence caused by the external electric field.…”