Susceptibility of DC breakdown in dielectric-loaded systems

Summary form only given. This work presents a novel theory of breakdown susceptibility for dielectric-loaded systems in DC, targeting multipactor as the lowest-order effect. Models from [1] are simulated with 2D particle-in-cell (PIC) using the method of [2], and susceptibility limits are developed employing the theory of [3]. Considering secondary electrons near the dielectric surface have a lifetime defined by the perpendicular (to the surface) electric field and an impact energy defined by the parallel field, a lower limit, (E_⊥/E_∥)₁, and an upper limit, (E_⊥/E_∥)₂, in E_⊥/E_∥-space can be formulated for multipactor in vacuum under quasi-static conditions neglecting space charge: (E_⊥/E_∥)_1,2 = 2ν_⊥0/(ν_∥0-(√(2W_1,2/m_e^- -ν_⊥0²))) ν_||0 and ν_⊥0 are parallel and perpendicular initial velocities of an emitted secondary, respectively, and W₁ and W₂ are the first-crossover and second-crossover energies, respectively [3]. The evolution of the surface fields tracked via simulation can be plotted against these limits in E_⊥/E_||-space to determine multipactor-breakdown characteristics. The effects of secondary-emission energy and angle, applied voltage, space charge, and dielectric characteristics will be discussed. The effect of gases on susceptibility will also be discussed, targeting argon and air. As described in [4], gaseous breakdown in DC develops oscillatory behavior as a result of space-charge coupling between charged species and the charged dielectric surface. Near-surface ionization electrons will be involved in early-transient multipactor, influencing the drive to saturation depending on impact characteristics. Increased pressure will non-linearly affect secondary impact characteristics as a result of increased space-charge and accelerated sheath formation. Gas species will also influence breakdown saturation and periodicity via interaction cross-sections, inertia, and drift characteristics via field interactions. Methods for incorporating these various parameters into the theory of susceptibility will be discussed.