Improving the work function of the niobium surface of SRF cavities by plasma processing

Tyagi, Puneet; Doléans, M.; Hannah, Brian; Afanador, Ralph; McMahan, Christopher; Stewart, Steve; Mammosser, J.; Howell, M.; Saunders, Jeffrey; DeGraff, B.; Kim, Sang-ho

doi:10.1016/j.apsusc.2016.02.030

Cited by 21 publications

(10 citation statements)

References 13 publications

(11 reference statements)

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“…Plasma mineralization with volume DBD showed spots of inhomogeneity in the distribution of carbon. [44][45][46] Therefore, work function of the mesoporous TiO 2 coating could be affected by the carbon concentration of the surface, which was efficiently influenced by plasma mineralization with both DBDs. After plasma mineralization with volume DBD, the difference between the maximum and the minimum of the carbon concentration was approx.…”

Section: Resultsmentioning

confidence: 99%

“…Generally, plasma surface modification can affect the morphology and chemistry of the surface by etching, contamination removal, and incorporation of functional groups onto the surface. [44][45][46] Therefore, work function of the mesoporous TiO 2 coating could be affected by the carbon concentration of the surface, which was efficiently influenced by plasma mineralization with both DBDs. The coplanar DBD led to a lower carbon concentration and thus a higher work function.…”

Section: Resultsmentioning

confidence: 99%

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Mineralization of flexible mesoporous TiO₂ photoanodes using two low‐temperature dielectric barrier discharges in ambient air

Shekargoftar

Dzik

Ďurašová

et al. 2018

Contributions to Plasma Physics

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Two types of dielectric barrier discharges (DBDs), volume DBD (called Industrial Corona) and coplanar DBD, were used for low temperature (70 • C) atmospheric pressure plasma mineralization of mesoporous methyl-silica/titanium dioxide nanocomposite photoanodes. The photoanodes with a thickness of approx. 300 nm were inkjet-printed on flexible polyethylene terephthalate (PET) foils. Plasma treatments of both DBDs led to changes in the chemical stoichiometry and morphology of the mesoporous photoanodes, resulting in a significant increase of the work function from approx. 4.0 to 4.3 eV and 4.8 eV, after plasma mineralization with volume DBD and coplanar DBD, respectively. We also studied the effect of plasma mineralization on the photoelectrochemical properties of the flexible mesoporous TiO 2 photoanodes. Plasma mineralization with volume DBD and coplanar DBD showed different effects on the generated photocurrent in the photoanodes. Although the plasma mineralization with volume DBD showed only a minor effect on the photocurrent, plasma mineralization with coplanar DBD led to significantly higher photocurrents. We found that the enhancement of the photoelectrochemical properties was related to the homogeneity of the plasma-treated surfaces-arising from different spatial properties of the plasma between volume and coplanar DBDs. Furthermore, the results showed that plasma mineralization using coplanar DBD can effectively change the energy levels of the surface. This resulted in the enhancement of the work function and the photoelectrochemical properties of the mesoporous TiO 2 photoanodes. This contribution shows that coplanar arrangement of electrodes in DBDs generates plasma of higher efficacy compared with standard volume DBD that is currently often used in industrial processes. KEYWORDSdielectric barrier discharge (DBD), homogeneity of the treated surface, low-temperature plasma, mesoporous photoanodes, plasma mineralization INTRODUCTIONTitanium nanoparticles (TiO 2 NPs) are among the most widely used semiconductors in various applications such as water splitting, [1] photocatalysis, and energy-conversion processes. [2][3][4] TiO 2 NPs are in use as photoanodes in dye-synthesized solar cells (DSSCs), [5] and recently porous and/or compact TiO 2 layers are utilized in perovskite solar cells (PSCs).[6] TiO 2 NPs have been deposited using a variety of techniques, including deposition from vapour and liquid phases. [7][8][9] As the deposited NPs possess a large absorbing area, the TiO 2 layer is often contaminated by the adventitious organic impurities from the ambient

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Mineralization of flexible mesoporous TiO₂ photoanodes using two low‐temperature dielectric barrier discharges in ambient air

Shekargoftar

Dzik

Ďurašová

et al. 2018

Contributions to Plasma Physics

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“…On the other hand, when Ar/O 2 mixed plasma was used, the work function increased quickly from 4.0 to 5.2 eV after 30 s of plasma cleaning, then leveled off, indicating that the addition of O 2 can accelerate the removal of hydrocarbon pollutants and may further oxidize the niobium surface when compared to pure Ar plasma cleaning. To further demonstrate that chemical reactions occurred on the surface following Ar/O 2 mixed plasma treatment, EQP was used to monitor CO 2 and CO [ 23,24 ] as byproducts in the plasma cleaning process, as shown in Figure 2B. The EQP test plays a monitoring role.…”

Section: Treatment Mechanism Of Multicomponent Plasmamentioning

confidence: 99%

Interfacial properties of multicomponent plasma‐modified high‐performance fiber‐reinforced composites: A review

et al. 2022

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This study reveals the interfacial properties of multicomponent plasma with four aspects, including cleaning, etching, functionalization, and polymerization. Particles formed by plasma ionization collide to form volatile groups, which can interact with the surface to form volatile substances that clean the surface. The multicomponent plasma etching effect on the surface is significant, and O 2 and N 2 may interact to improve oxidation capacity. Inert gas argon (Ar) can be combined with reactive gases O 2 , N 2 , and NH 3 to introduce hydroxyl and amine groups and other active groups to change the surface's chemical structure. When a multicomponent plasma polymerizes, a film forms on the surface, changing the chemical composition. The cross-linking of gases has a positive effect on the properties of the deposited layer as well. The treatment of various fiber materials, nanoparticles, polymer films, and matrix materials with multicomponent plasma is summarized. The multicomponent plasma significantly improves surface wettability and roughness, and oxygen species aid in the etching of nanomaterials, which improves interface properties. The gas types determine the groups introduced to the surface and the surface attachment site.

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“…In-situ processing of SRF cavities in the tunnel has been identified as an important area of research to improve the performances of SNS SRF cavities while minimizing the impact on machine operation and reducing cost for the improvements. R&D for in-situ processing using plasma has successfully demonstrated that the accelerating gradients in operating cavities can be increased by 2 MV/m or higher on average [31,32]. The plasma processing developed at the SNS mainly focuses on removal of residual hydro-carbons using low density reactive oxygen plasma at room temperature.…”

Section: Srf Cavity Performance Improvementmentioning

confidence: 99%

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

Kim

Afanador

Barnhart

et al. 2017

Nuclear Instruments and Methods in Physics Research Section A:

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The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenance activities for cryomodules are introduced.

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Improving the work function of the niobium surface of SRF cavities by plasma processing

Cited by 21 publications

References 13 publications

Mineralization of flexible mesoporous TiO₂ photoanodes using two low‐temperature dielectric barrier discharges in ambient air

Mineralization of flexible mesoporous TiO₂ photoanodes using two low‐temperature dielectric barrier discharges in ambient air

Interfacial properties of multicomponent plasma‐modified high‐performance fiber‐reinforced composites: A review

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

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Improving the work function of the niobium surface of SRF cavities by plasma processing

Cited by 21 publications

References 13 publications

Mineralization of flexible mesoporous TiO2 photoanodes using two low‐temperature dielectric barrier discharges in ambient air

Mineralization of flexible mesoporous TiO2 photoanodes using two low‐temperature dielectric barrier discharges in ambient air

Interfacial properties of multicomponent plasma‐modified high‐performance fiber‐reinforced composites: A review

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

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Mineralization of flexible mesoporous TiO₂ photoanodes using two low‐temperature dielectric barrier discharges in ambient air

Mineralization of flexible mesoporous TiO₂ photoanodes using two low‐temperature dielectric barrier discharges in ambient air