Generation of Electromagnetic Fields of Extremely High Intensity by Coherent Summation of Cherenkov Superradiance Pulses

Abstract

We demonstrate both theoretically and experimentally the possibility of correlating the phase of a Cherenkov superradiance (SR) pulse to the sharp edge of a current pulse, when spontaneous emission of the electron bunch edge serves as the seed for SR processes. By division of the driving voltage pulse across several parallel channels equipped with independent cathodes we can synchronize several SR sources to arrange a two-dimensional array. In experiments carried out, coherent summation of radiation from four independent 8-mm wavelength band SR generators with peak power 600 MW resulted in the interference maximum of the directional diagram with an intensity that is equivalent to radiation from a single source with power 10 GW. Numerous scientific and technological applications stimulate interest in the generation of ultra-high power coherent radiation. Approaches that can be suggested to achieve this goal include the generation of radiation by a single source with an oversized electrodynamic system. In this case special methods (for example, 2D distributed feedback [1,2]) are required to produce spatially coherent radiation. Another method is the synchronization of a large number of moderate-power sources using a master oscillator [3][4][5]. DOIAt the same time for short-pulse sources, in particular, for sources based on Cherenkov superradiance (SR) of extended electron bunches moving in a slow wave structure (SWS) [6,7], there is an alternative opportunity, associated with the correlating the phase of a radiated pulse to the sharp edge of a current pulse. In fact, spontaneous emission of the bunch edge serves as the seed for SR processes. It gives rise to the stimulated emission including electron self-bunching and subsequent radiation of the short high-power electromagnetic pulse. If identical current pulses are sent simultaneously to several channels, identical SR pulses will be generated and the coherent summation of their amplitudes is possible. For two channel radiation sources such a possibility has been experimentally demonstrated in Ref. [8]. However the physical model describing the transformation of spontaneous Cherenkov radiation (i.e. the radiation from the unperturbed moving particles without the reverse effect of the field [9]) to stimulated radiation is still missing. The

Progress in microwave to sub-THz sources at Strathclyde

“…Ginzburg et al [12] have successfully demonstrated the coherent summation of Cherenkov sources, which provides a pathway to achieving very high intensity fields by combining several sources.…”

Concepts for a short wavelength rf gun

“…There are high-power, high-efficiency rf sources with controllable phase at frequencies above X-band [1][2][3][4]. These sources can have output powers from tens of megawatts to gigawatts, pulse length varying from nanoseconds to microseconds, and repetition rates the might reach the kilohertz level.…”

“…There are nanosecond, GW power level, rf Cherenkov sources driven by relativistic beams with repetition rate up to 1 kHz [3,4]. Rf phase is controllable by either a low power master-source (in amplifiers) or by precise synchronization with the voltage front (in oscillators).…”

Efficient power combiner for THz radiation

“…The reason is that TE 11 mode is the lowest mode which is propagating in an oversize waveguide. The TE 11 − ⊥, ∥ directions according to waveguide wall with angle θ each plane makes with parallel axis. k sin θ = k ⊥ and k cos θ = β z = k ∥ (propagation constant inside waveguide).…”

“…Also, in Ref. 11 it was demonstrated that by dividing the driving voltage pulse across several parallel channels equipped with independent cathodes, four synchronized superradiant sources in the form of a 2D array can be achieved which can generate fields of extremely high intensity.…”