Production of short microwave pulses with a peak power exceeding the driving electron beam power

Abstract

This article presents results of theoretical and experimental studies on the production of ultrashort~a few RF cycles duration! microwave pulses of gigawatt peak powers based on superradiance from high-current electron beams. With the Cherenkov backward-wave-electron-beam interaction in a low-dispersion slow-wave structure, microwave pulses with a peak power greater than the peak power of the driving electron beam have been produced for the first time. In an experiment using the SINUS-150 compact high-current electron accelerator, with a 2.6-kA injected beam current and a 330-kV electron energy, microwave pulses of 1.2 GW peak power and ;0.5 ns duration~FWHM! were generated in the X-band. Production of superradiance pulses in a repetitive regime~3500 Hz! in the Ka-band has been demonstrated using a compact hybrid SOS-modulator. The effect of spatial accumulation of microwave energy in extended slow-wave structures with substantially nonuniform coupling has been demonstrated. In an experiment using the SINUS-200 compact accelerator, X-band pulses of ;3 GW peak power and 0.6-0.7 ns width~FWHM! were produced with a power conversion efficiency of 150-180% and an energy efficiency of ;15%.Calculations performed with various D J values have shown the following: With any value of j k . . 1, the optimum value of D J must be such~D J opt ; exp~Ϫj k !! that the region where the amplitude of the RF current saturates due to the non-188 A. A. Eltchaninov et al.

Generation, Amplification, and Nonlinear Self-Compression of Powerful Superradiance Pulses

“…In the range of moderate electron energies ∼300-500 keV the conversion factor can slightly exceed unity K ∼ 1.2a n dK reaches a maximum value ∼1.4 for nonrelativistic energies [21].…”

“…It is beneficial to realize a situation where despite the linearly growing energy and power of the microwave pulse, as it propagates through the system, the electric field strength in the synchronous harmonic acting upon the electrons is a constant. The impedance profile satisfying the above condition may be presented in the form [21] where the parameter p 0 characterizes the relative impedance variation. The evolution of the radiation power |a (τ, Z )| 2 in the case of a tapered coupling impedance for p 0 = 90 and Z 0 = 0.93L are shown in Fig.…”

“…The next step is the use of nonuniform SWS with coupling impedance that increased toward the collector end [21]- [25]. The first experiments using nonuniform SWS are performed in the X-band [21].…”

Relativistic microwave oscillators with high power flux in a free space and interaction zone

“…As a result of a single-pass, high gain amplification of initial electromagnetic (EM) perturbation, the power of SR pulse may exceed the power of the driving beam [2]. This is also because of SR pulse is shorter than the electron beam (in space) and less than its propagation time throughout the entire SWS.…”

“…[1][2][3][4][5][6] and citation therein). For generation of HPM pulses with duration of units of nanosecond and less influence of microwave breakdowns of electrodynamics systems, expansion of cathode and collector plasmas, and electron beam structure distortions becomes insignificant.…”