Séminaire

Vendredi 22 Avril 2022 à 11h00.

Multi-scale multi-physics models for field emitters in the verge of thermal runaway and vacuum breakdown

''Field electron emission is crucial for the function of various types of electron sources: compact X-ray sources, electron microscopes, ion thrusters, etc. On the other hand, it plays a detrimental role as the precursor to vacuum breakdown in various devices that involve high electric fields: particle accelerators, vacuum switches, etc. When a field emitter is exposed to very high local fields (~10 GV/m) and the emission current density approaches a limiting scale (~1 μΑ/nm2), it enters into a thermal runaway process that typically leads to vacuum arcing and emitter destruction. Despite its importance, this phenomenon is still poorly described by existing theoretical models, mainly due to the extremely complex physics involved, especially for the case of semiconducting electron emitters. This seminar will give an overview of recent and on-going attempts to explain and prevent vacuum breakdown by developing multi-scale multi-physics computational models that describe the complex processes of field emitters under thermal runaway conditions. Our two in-house developed computational models, FEMOCS and GETELEC, concurrently couple and combine Molecular Dynamics, Finite Element and Particle-In-Cell methods, in an attempt to describe the complex dynamics of vacuum breakdown from metal, semiconducting and insulating field emitters.''