Speaker
Description
See the full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P1.3020.pdf
Microwave Pulse Compressor (MPC) is an high power microwave device designed for generation of 100's of MW's thru amplification. The amplification is based upon time compression of an initial Microwave (RF) pulse characterized by a long (µsec) duration to a short (ns) output pulse, ideally increasing the RF power by the duration ratio of the pulses.
In order to accumulate RF power and radiate it outside a pressurized RF resonator we use a Qswitch method based on laser induced plasma channel. The RF pulse initiate a discharge in the gas, pre-ionization using microwave pulse, where a short (ns) laser pulse induce breakdown by a thin plasma channel which switch the resonator from a storage phase to a release phase, i.e. sufficient to reduce the Q factor of the resonator.
We demonstrate experimentally an efficient way to cause a discharge in the pressurized gas by focusing a short 2ns laser pulse inside the MPC volume. We have investigated the evolution of the plasma channel by means of gated MCP intensified CCD framing camera of ~1.5ns exposure time (4quikE camera). We found that as the accumulated energy inside the resonator increases, the time delay between lasing and switching decreases. Furthermore, stronger initiative RF pulse results in a stronger and spatially larger luminesce of the plasma channel. Using a spatialtemporal processing of the plasma luminesce imaging we were able to simulate this phenomenon by 2D-Lsp hybrid PIC modeling where we assume that the resonator is pressurized with gas, uniformly distributed background electron density of 10^3cm^-3 and seed electrons density occupying the laser focal region. Electron impact ionization develops self consistently with the oscillating RF field which eventually creates a plasma channel sufficient for the MPC switching. We fitted the seed electron density and the volume of the focal region to match the experimental results.
