Ultrafast X-ray provides new look at plasma discharge breakdown in water

Ultrafast X-ray provides new look at plasma discharge breakdown in water

Fig: (a) Diagram of the laser-triggered driving circuit with (b) voltage and current traces for a typical event. (c) Power and energy calculated from direct integration. 

Occurring faster than the speed of sound, the mystery behind the breakdown of plasma discharges in water is one step closer to being understood as researchers pursue applying new diagnostic processes using state-of-the-art X-ray imaging to the challenging subject.These diagnostic processes open the door to a better understanding of plasma physics, which could lead to advances in green energy production through methods including fusion, hydrocarbon reforming and hydrogen generation.

The team is working with LTEOIL on patented research into the use of multiphase plasma in carbon-free fuel reforming. The research is supported by the dynamic materials properties campaign (C2) and the advanced diagnostics campaign (C3) at Los Alamos National Laboratories through the Thermonuclear Plasma Physics group (P4) principal investigator, Zhehui (Jeph) Wang.Inertial confinement fusion—in which high temperature, high energy density plasmas are generated—is a specific focus of the project. To better understand the plasma physics involved in this type of fusion, Staack said the team is developing short timescale, high-speed imaging and diagnostic techniques utilizing a simple, low-cost plasma discharge system.

Additionally, they are seeking to better understand the phenomena that occur when plasma is discharged in liquid, causing a rapid release of energy resulting in low-density microfractures in the water that move at over 20 times the speed of sound.

Our goal is to experimentally probe the regions and timescales of interest surrounding this plasma using ultrafast X-ray and visible imaging techniques, thereby contributing new data to the ongoing literature discussion in this area. With a complete conceptual model, we could more efficiently learn how to apply these plasmas in new ways and also improve existing applications. Although they have made progress, Campbell said current methods are not yet sophisticated enough to collect multiple images of a single plasma event in such a short amount of time—less than 100 nanoseconds.

Even with the state-of-the-art techniques and fast framerates available at the Advanced Photon Source, we have only been able to image a single frame during the entire event of interest—by the next video frame, most of the fastest plasma processes have concluded. This work highlights several resourceful techniques we have developed to make the most of what few images we are able to take of these fastest processes.

Christopher Campbell et al, Ultrafast x-ray imaging of pulsed plasmas in water, Physical Review Research (2021). DOI: 10.1103/PhysRevResearch.3.L022021

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