Conference papers

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Browsing Conference papers by Subject "gradient limits"

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    The problem of RF gradient limits
    (American Institute of Physics, 2010-03) Norem, J.; Insepov, Z.; Huang, D.; Mahalingam, S.; Veitzer, S.
    We describe breakdown in rf accelerator cavities in terms of a number of mechanisms. We divide the breakdown process into three stages: 1) we model surface failure using molecular dynamics of fracture caused by electrostatic tensile stress, 2) the ionization and plasma growth is modeled using a particle in cell code, 3) we model surface damage by assuming unipolar arcing. Although unipolar arcs are strictly defined with equipotential boundaries, we find that the cold, dense plasma in contact with the surface produces very small Debye lengths and very high electric fields over a large area, and these high fields produce strong erosion mechanisms, primarily self sputtering, compatible with crater formation.We compare this model with arcs in tokamaks, plasma ablation, electron beam welding, micrometeorite impacts, and other examples.
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    ItemOpen Access
    Vacuum arcs and gradient limits
    (Proceedings of 2011 Particle Accelerator Conference, New York, 2011) Norem, J.; Moretti, A.; Insepov, Z.
    We have been extending and refining our model of vacuum breakdown and gradient limits and describe recent developments. The model considers a large number of mechanisms, but finds that vacuum arcs can be described fairly simply and self-consistently, however simulations of individual mechanisms can be involved, in some cases. Although based on accelerator rf data, we believe our model of vacuum arcs should have general applicability. The paper explores breakdown in plasmas, and self-sputtering and damage by parasitic arcs.