Atomistic self-sputtering mechanisms of rf breakdown in high-gradient linacs

Insepov, Z.; Norem, J.; Veitzer, Seth

doi:10.1016/j.nimb.2009.12.016

Cited by 18 publications

(15 citation statements)

References 30 publications

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“…Selfsputtering produces a flux of neutral atoms that can raise the plasma density and also fuel the plasma, permitting long plasma lifetimes [5]. Numerical simulations of sputtering yields show that this mechanism is very sensitive to the sheath potential, ion charge distribution, surface (melting) temperature [29], and even grain orientation [30].…”

Section: B Materials Dependencementioning

confidence: 99%

Sheath parameters for non-Debye plasmas: Simulations and arc damage

Морозов

Norman

Insepov

et al. 2012

Phys. Rev. ST Accel. Beams

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This paper describes the surface environment of the dense plasma arcs that damage rf accelerators, tokamaks, and other high gradient structures. We simulate the dense, nonideal plasma sheath near a metallic surface using molecular dynamics (MD) to evaluate sheaths in the non-Debye region for high density, low temperature plasmas. We use direct two-component MD simulations where the interactions between all electrons and ions are computed explicitly. We find that the non-Debye sheath can be extrapolated from the Debye sheath parameters with small corrections. We find that these parameters are roughly consistent with previous particle-in-cell code estimates, pointing to densities in the range 10 24 -10 25 m À3 . The high surface fields implied by these results could produce field emission that would short the sheath and cause an instability in the time evolution of the arc, and this mechanism could limit the maximum density and surface field in the arc. These results also provide a way of understanding how the properties of the arc depend on the properties (sublimation energy, for example) of the metal. Using these results, and equating surface tension and plasma pressure, it is possible to infer a range of plasma densities and sheath potentials from scanning electron microscope images of arc damage. We find that the high density plasma these results imply and the level of plasma pressure they would produce is consistent with arc damage on a scale 100 nm or less, in examples where the liquid metal would cool before this structure would be lost. We find that the submicron component of arc damage, the burn voltage, and fluctuations in the visible light production of arcs may be the most direct indicators of the parameters of the dense plasma arc, and the most useful diagnostics of the mechanisms limiting gradients in accelerators.

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Section: B Materials Dependencementioning

confidence: 99%

Sheath parameters for non-Debye plasmas: Simulations and arc damage

Морозов

Norman

Insepov

et al. 2012

Phys. Rev. ST Accel. Beams

Self Cite

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“…6,9,[33][34][35][36] In addition, this approach is capable of accurate quantifying sputtering rates for organic materials and solids under bombardment with a variety of primary species, commonly used atomic ions and relatively new molecular and cluster ions, such as in Refs. 37, 38.…”

Section: Examplementioning

confidence: 99%

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

Baryshev

Erck

Moore³

et al. 2013

JoVE

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In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.Specifically, we will discuss: i. Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion. ii. Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions. iii. Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained. Video LinkThe video component of this article can be found at

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“…The details of the calculations can be found in our previous papers [11][12][13] where the obtained calculated yields were compared with the existing experimental and simulation results [20][21][22].…”

Section: Self-sputtering Of Solid and Liquid Copper Surfacesmentioning

confidence: 99%

“…Energetic ion collisions with solid targets are an important area of research in basic science [1][2][3][4][5][6][7][8], as well as in numerous industrial applications [9][10][11][12][13][14][15][16][17][18][19]. Self-sputtering processes are also of fundamental interest in the development of high-gradient rf accelerators [1].…”

Section: Introductionmentioning

confidence: 99%

Ion Solid Interaction And Surface Modification At RF Breakdown In High-Gradient Linacs

Insepov¹,

Norem²,

Veitzer³

2011

AIP Conference Proceedings

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Abstract. Ion solid interactions have been shown to be an important new mechanism of unipolar arc formation in high-gradient rf linear accelerators through surface self-sputtering by plasma ions, in addition to an intense surface field evaporation. We believe a non-Debye plasma is formed in close vicinity to the surface and strongly affects surface atomic migration via intense bombardment by ions, strong electric field, and high surface temperature. Scanning electron microscope studies of copper surface of an rf cavity were conducted that show craters, arc pits, and both irregular and regular ripple structures with a characteristic length of 2 microns on the surface. Strong field enhancements are characteristic of the edges, corners, and crack systems at surfaces subjected to rf breakdown.

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Atomistic self-sputtering mechanisms of rf breakdown in high-gradient linacs

Cited by 18 publications

References 30 publications

Sheath parameters for non-Debye plasmas: Simulations and arc damage

Sheath parameters for non-Debye plasmas: Simulations and arc damage

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

Ion Solid Interaction And Surface Modification At RF Breakdown In High-Gradient Linacs

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