Optical diagnostics of a dielectric surface discharge in the triggered vacuum gap using various dielectric materials

High-speed imaging and visible light stereomicroscopy were applied to do researches, which allowed us to find out differences in a dielectric surface discharge behavior in the triggered vacuum gap, when various dielectric materials (mica, muscovite and corundum-type ceramics) were used. Images of the discharge and the erosion in the electrode systems were analized to reveal that at the discharge on the ceramics surface a material of electrodes was mostly involved as a plasma-forming matter and on the mica it is the dielectric material.

The discharge initiation in vacuum gap by moderate intensity optical range radiation

The hypothesis of discharge initiation in vacuum gap by optical range radiation based on previously obtained experimental data. During the laser pulse interaction with electrode erosion products the glow discharge has ignited. In result of ioniza-tion-overheating instability the discharge has had current channel contraction and has transferred to arc. The dependences of material of target thermo dynamical parameters on the minimal and threshold laser pulse energy have demonstrated. The threshold laser pulse energy – the energy which enough to effective impact on the laser plasma.

Semiconductor thermionics for next generation solar cells: photon enhanced or pure thermionic?

Semiconductors have been used in solar energy conversion for decades based on the photovoltaic effect. An important challenge of photovoltaics is the undesired heat generated within the device. An alternative approach is thermionics, which uses the thermal excitation of electrons from an emitter to a collector across a vacuum gap. If the emitter is a p-type semiconductor, the photogeneration-induced quasi-Fermi level splitting can reduce the effective barrier for electron emission—a mechanism used by a photon enhanced thermionic emission device. Here, we evaluate the prospects of this alternative solar conversion technology considering different semiconductor materials and thermionic device configurations. We also reveal that whether such a device operates in the photon enhanced or purely thermionic mode, depends on the complex interplay among materials properties, device physics and solar concentration level.