The team takes a high-speed image at Los Alamos National Lab
The optical setup for imaging. Light leaves the sources, hits a mirror at the end of the tunnel, and bounces back to the telescope to record the image.
UMD’s MSE Koeth Research Group is excited to share a sampling of our high-speed imaging of the formation of Lichtenberg Figures in PMMA (acrylic). For decades, Lichtenberg Figures, sometimes called beam trees, have been made as artwork and scientific mementos. Since making his first one 20 years ago, Prof. Koeth has dreamed of seeing Lichtenberg Figures form up close. In the past few years, the Koeth Research Group assembled a team to accomplish this feat, forming a joint collaboration between talented graduate students, staff, and Los Alamos National Laboratory.
Our team is proud to have developed groundbreaking techniques to image dielectric breakdown, and as a result, are the first to have seen this phenomenon unfold up close. For more information on the new imaging techniques pioneered in our research, please see Noah Hoppis et. al.
During this investigation, our group also discovered a heretofore unclassified mode of electrical discharge that we named “Ivy Type.” Propagating at speeds greater than 10 million meters per second in the PMMA, Ivy-type discharge is the fastest known physical phenomenon observed in a solid material. Our findings were published in Science on July 19th, 2024. For more on this please see Kate Sturge, et. al.
2022:
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Shot 5 Branch Type Our very first successful high-speed imaging, which was of a 4inch wide, 12-inch-long, 1 inch thick slab of PMMA. The discharge was initiated with an exploding bridge wire (EBW) synchronized with the high-speed camera. Each frame was spaced 200ns apart. This immediately revealed that the channels being formed, which ultimately become the permanent Lichtenberg Figure, are in fact the discharge current paths, propagating much faster than the speed of sound. |
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Shot 9 Branch Type Similar to shot 5, except each frame was spaced 150ns. |
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Shot 55 Branch Type Using a SIM-X camera with 3ns exposure time, interframe spacing of 32ns, for frame steps of 35ns. |
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Shot 56 Branch Type Using a SIM-X camera with 3ns exposure time, interframe spacing of 32ns, for frame steps of 35ns. |
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Shot 61 Branch Type 3ns exposure time, interframe spacing of 17ns, for frame steps of 30ns. |
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Shot 78 Branch Type This used a special high-speed imaging technique where we back-lit the sample with a laser while the camera viewed the sample with a notch filter at the laser light. Therefore, none of the discharge light was captured–just the shadow of the damage was observed. Only a “long time” after the channel (damage) has formed do we observe the shockwave radiating away. This was the unequivocal demonstration that damage occurs hundreds of times faster than the speed of sound. The camera settings were 3ns exposure time with 97ns interframe spacing, for frame steps of 100ns. |
2023:
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Shot 84 Branch and Ivy Type This shot captures the high-speed Ivy Type transitioning into the relatively slower Branch Type before discharge cessation. The exposure time was 3ns, interframe spacing 7ns, for frame steps of 10ns. Note the distance the Ivy type travels in just four frames compared to the Branch Type. |
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Shot 97 Branch Type 3ns exposure time, 0ns interframe spacing, for 3ns frame steps. |
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Shot 75 Ivy Type An example of extreme high-speed channel formation occurring at a rate of 10 million meters per second. The camera settings pushed the SIM-X to its limits with a 3ns exposure time, interframe spacing of -2ns, for frame steps of 1ns (this implies 2ns overlap between adjacent frames). |
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Shot 77 Combined Branch and Ivy Type Shows both Branch Type and Ivy Type discharges. Note the Branch Type slowly growing from the discharge point compared to the fantastic rate by which Ivy Type grows throughout the material. The camera settings again pushed the SIM-X to its limits with a 3ns exposure time, interframe spacing of -2ns, for frame steps of 1ns (this implies 2ns overlap between adjacent frames). |