Experimental results of the generation of microwaves from a static electric field by an ionization front in a gas-filled capacitor array

Summary form only given. Experimental results of the generation of electromagnetic radiation from a gas-filled, laser-ionized capacitor array are presented. Within the capacitor array, an alternating static electric field (/spl omega/=0) with a specific spatial wavenumber (k=k/sub 0/) is established when a voltage is applied. The electromagnetic radiation is generated by upshifting this static electric field to a frequency of /spl omega//spl ap//spl omega//sub p//sup 2//2k/sub 0//sup c/(/spl omega//sub p//sup 2/=4/spl pi/n/sub 0/e/sup 2//m/sub e/, where n/sub 0/ is the plasma density and m/sub e/ the mass of the electron in CGS units) by temporally varying the dielectric properties of the gas medium with an ionization front. The ionization front is created by the propagation of a high-power short-duration laser pulse in the gas. The frequency of the radiation can be tuned by either the gas density (therefore the plasma density) and/or the capacitors spacing. This scheme has been called an "electromagnetic accordion" because the static electric field is squeezed into a shorter but similar propagating waveform. The device can potentially provide coherent pulses of high-power (MW) radiation that can be tuned over orders of magnitude in frequency. In this presentation a brief theoretical review is given, followed by the experimental results. In the proof-of-principle experiment, microwave radiation in the range of 6 to 21 GHz has been detected. The status of some improved designs for future research is presented. These designs incorporate waveguide structures in various geometries.