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Plasma Interactions and Electron Dynamics for Volumetrically Complex Materials.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Plasma Interactions and Electron Dynamics for Volumetrically Complex Materials./
作者:	Ottaviano, Angelica.
面頁冊數:	1 online resource (162 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
標題:	Fluid mechanics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30529738click for full text (PQDT)
ISBN:	9798379742188

Plasma Interactions and Electron Dynamics for Volumetrically Complex Materials.
Ottaviano, Angelica.

Plasma Interactions and Electron Dynamics for Volumetrically Complex Materials. - 1 online resource (162 pages)

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Thesis (Ph.D.)--University of California, Los Angeles, 2023.

Includes bibliographical references

Electron dynamics and plasma-infusion are crucial for understanding plasma and material recycling, cooling, and the plasma-material interactions (PMI) for plasma facing surfaces for applications such as fusion energy and space propulsion. Notably, we have shown that new materials such as volumetrically complex materials (VCMs) can improve plasma device performance and lifetime and may provide a versatile design space for plasma-facing components such as inner walls and high-power electrodes.The objective of this dissertation is to investigate the key PMI of VCMs by examining and characterizing the effects of electron dynamics occurring at the near-surface plasma region with focus on SEE and ion-induced sputtering. This work uses a combination of experimental, computational, and analytical methods. Much of this work uses reticulated foams as a representative material architecture to investigate PMI behavior across a wide range of the VCM design space.Secondary electron emission (SEE) yield analyses using a new scanning electron microscope (SEM) method revealed up to 43% suppression from foam compared with flat. Foam ligament-to-pore aspect ratio showed the presence of an optimal geometric configuration, which is in agreement with current and past analytical models. Using SEM techniques, the importance of sample transparency and backplate yield contributions on overall target yield in plasma-facing regimes was also established. These results showed that geometric transparency can be used to assess the effective transparency to plasma species. Angular dependence revealed multi-scale behavior in that foams with um features exhibit loss of angular dependence much like fuzzes, while large foams (mm) are directional much like fibers and velvets. Electron spectroscopy showed that backscattered electron suppression is 80% more than low energy SEE suppression in carbon foams, while low energy SE generation may be enhanced. An analytical model for ion-sputtering of foams was modified to employ SEE physics and calculate SEE yields, which were then compared with experimental results.A dedicated, compact, hollow-cathode generated plasma facility was developed to expose biased foam (100 - 600 V) to investigate plasma infusion regimes using electrostatic probing, optical emission spectroscopy, and in-situ sputter yield monitoring. A new diagnostic developed for real-time and in-situ surface profilometry is used to monitor the surface morphological evolution of foams during plasma exposure. Combined with ex-situ surface analysis techniques, plasma-foam experiments and analysis of inter-foam deposition and sputterant transport within pore layers have shown that plasma infusion is key for predicting back vs forward material sputtering. In addition, user facility was used in a collaboration project with UCLA Physics to investigate the effect of biased tungsten foams in a pulsed He plasma on material erosion and arcing in comparison with a planar surface. It was found that tungsten-based VCMs can withstand up to 600 V negative bias in a continuous and pulsed plasma environment, with significant reduction of arcing events when comparing to planar tungsten.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798379742188Subjects--Topical Terms:

528155
Fluid mechanics.
Subjects--Index Terms:

Electric propulsionIndex Terms--Genre/Form:

542853
Electronic books.

Plasma Interactions and Electron Dynamics for Volumetrically Complex Materials.
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504 $a Includes bibliographical references
520 $a Electron dynamics and plasma-infusion are crucial for understanding plasma and material recycling, cooling, and the plasma-material interactions (PMI) for plasma facing surfaces for applications such as fusion energy and space propulsion. Notably, we have shown that new materials such as volumetrically complex materials (VCMs) can improve plasma device performance and lifetime and may provide a versatile design space for plasma-facing components such as inner walls and high-power electrodes.The objective of this dissertation is to investigate the key PMI of VCMs by examining and characterizing the effects of electron dynamics occurring at the near-surface plasma region with focus on SEE and ion-induced sputtering. This work uses a combination of experimental, computational, and analytical methods. Much of this work uses reticulated foams as a representative material architecture to investigate PMI behavior across a wide range of the VCM design space.Secondary electron emission (SEE) yield analyses using a new scanning electron microscope (SEM) method revealed up to 43% suppression from foam compared with flat. Foam ligament-to-pore aspect ratio showed the presence of an optimal geometric configuration, which is in agreement with current and past analytical models. Using SEM techniques, the importance of sample transparency and backplate yield contributions on overall target yield in plasma-facing regimes was also established. These results showed that geometric transparency can be used to assess the effective transparency to plasma species. Angular dependence revealed multi-scale behavior in that foams with um features exhibit loss of angular dependence much like fuzzes, while large foams (mm) are directional much like fibers and velvets. Electron spectroscopy showed that backscattered electron suppression is 80% more than low energy SEE suppression in carbon foams, while low energy SE generation may be enhanced. An analytical model for ion-sputtering of foams was modified to employ SEE physics and calculate SEE yields, which were then compared with experimental results.A dedicated, compact, hollow-cathode generated plasma facility was developed to expose biased foam (100 - 600 V) to investigate plasma infusion regimes using electrostatic probing, optical emission spectroscopy, and in-situ sputter yield monitoring. A new diagnostic developed for real-time and in-situ surface profilometry is used to monitor the surface morphological evolution of foams during plasma exposure. Combined with ex-situ surface analysis techniques, plasma-foam experiments and analysis of inter-foam deposition and sputterant transport within pore layers have shown that plasma infusion is key for predicting back vs forward material sputtering. In addition, user facility was used in a collaboration project with UCLA Physics to investigate the effect of biased tungsten foams in a pulsed He plasma on material erosion and arcing in comparison with a planar surface. It was found that tungsten-based VCMs can withstand up to 600 V negative bias in a continuous and pulsed plasma environment, with significant reduction of arcing events when comparing to planar tungsten.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
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650 4 $a Plasma physics. $3 3175417
650 4 $a Electrical engineering. $3 649834
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653 $a Electrodes
653 $a Fusion energy
653 $a Plasma material interactions
653 $a Secondary electron emission
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