Plasma-induced surface cooling

TL;DR

This paper demonstrates that plasmas can cause transient cooling of material surfaces despite energetic flux, revealing complex physics involving chemical reactions and energy exchange that enable new cooling techniques.

Contribution

It uncovers the physics behind plasma-induced surface cooling and shows how energetic plasma species can transiently lower surface temperature, opening new avenues for thermal management.

Findings

Plasmas can induce local and transient cooling of surfaces.

Energy exchange involves chemical reactions, momentum transfer, and energy exchange.

Cooling occurs despite high energetic flux due to complex interplay of processes.

Abstract

Here we show that, despite a massive incident flux of energetic species, plasmas can induce transient cooling of a material surface. Using time-resolved optical thermometry in-situ with this plasma excitation, we reveal the novel underlying physics that drive this `plasma cooling' that is driven by the diverse chemical and energetic species that comprise this fourth state of matter. We show that the photons and massive particles in the plasma impart energy to different chemical species on a surface, leading to local and temporally changing temperatures that lead to both increases and decreases in temperature on the surface of the sample, even though energy is being imparted to the material. This balance comes from the interplay between chemical reactions, momentum transfer, and energy exchange which occur on different time scales over the course of picoseconds to milliseconds. Thus, we show that through energetically exciting a material with a plasma, we can induce cooling, which can lead to revolutionary advances in refrigeration and thermal mitigation with this new process that is not inhibited by the same limitations in the current state-of-the-art systems.