| Paper | Title | Page |
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| WEPWB053 | Simulation of the Dynamics of Gas Mixtures during Plasma Processing in the C75 Cavity | 696 |
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Funding: The work is supported by SC Nuclear Physics Program through DOE SC Lab funding announcement DE-FOA-0002670 & is authored by JSA, LLC under U.S. DOE Contract No. DE-AC05- 06OR23177 Plasma processing using a mixture of noble gas and oxygen is a technique that is currently being used to reduce field emission and multipacting in accelerating cavities. Plasma is created inside the cavity when the gas mixture is exposed to an electromagnetic field that is generated by applying RF power through the fundamental power or higher-order mode couplers. Oxygen ions and atomic oxygen are created in the plasma which breaks down the hydrocarbons on the surface of the cavity and the residuals from this process are removed as part of the process gas flow. Removal of hydrocarbons from the surface increases the work function and reduces the secondary emission coefficient. This work describes the initial results of plasma simulation, which provides insight into the ignition process, distribution of different species, and interactions of free oxygen and oxygen ions with the cavity surfaces. The simulations have been done with an Ar/¿2 plasma using COMSOL® multiphysics. These simulations help in understanding the dynamics and control of plasma inside the cavity and the exploration of different gas mixtures. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB053 | |
| About • | Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 29 June 2023 | |
| Cite • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | |
| WEPWB054 | In Situ Plasma Processing of Superconducting Cavities at JLab, 2023 Update | 701 |
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Jefferson Lab has an ongoing R&D program in plasma processing which just completed a round of production processing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient. Unlike helium processing which relies on ion bombardment of the field emitters, plasma processing uses free oxygen produced in the plasma to break down the hydrocarbons on the surface of the cavity. The initial focus of the effort was processing C100 cavities by injecting RF power into the HOM coupler ports. Results from processing cryomodules in the CEBAF accelerator as well as vertical test results will be presented. The goal will be to improve the operational gradients and the energy margin of the linacs. This work will describe the systems and methods used at JLAB for processing cavities using an argon-oxygen gas mixture as well as a helium-oxygen gas mixture. Before and after plasma processing results will also be presented.
Funding provided by SC Nuclear Physics Program through DOE SC Lab funding announcement DE-FOA-0002670. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB054 | |
| About • | Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 01 July 2023 | |
| Cite • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | |