Dynamics of a virtual cathode oscillator driven by a pinched diode

Abstract

A new method is demonstrated for extracting radiation from a virtual cathode oscillator in transverse electric (TE) waveguide modes. The dominant radiation mechanism occurs in the region of the virtual cathode, and is not due to reflexing of electrons. Microwave radiation occurs simultaneously or just after beam pinching in the diode. Electrostatic signals show simultaneous occurrence of the virtual cathode and microwave radiation. At the same time, the electron population divides into a beam population and a reflexing electron population. Inhibition of pinching by an axial guide field suppresses microwave radiation.

Investigation of the chaotic dynamics of an electron beam with a virtual cathode in an external magnetic field

“…Moreover, a study was also made of experimental models of a vircator without an external focusing magnetic field [5,9,12,24]. In addition, the vircator radiation spectra calculated in 1D models are in rather poor agreement with the data of physical experiments.…”

“…As above, the energy of the transverse and longitudinal coherent structures is determined by analyzing the eigenvalues corresponding to the KL modes in Eq. (9). Figure 6 displays how the energy W n (in percentage terms) of five highest-energy transverse and longitudinal coherent structures depends on the focusing magnetic field strength (the gyrofrequency ω c ) for the beam current I = 1.5I 0 .…”

“…In this way, coherent structures can be conveniently singled out by using the Karunen-Loev (KL) orthogonal decomposition of the spatiotemporal data [20]. The problem of singling out the KL modes reduces to that of solving the integral equation (9) the kernel of which has the form (10) where the symbol 〈…〉 t stands for the time averaging. It is possible to choose a zero-mean set of spatiotemporal distributions of any physical quantity as the function ξ(z, t).…”

“…Numerous experimental and theoretical investigations of VC-based devices (which are usually called vircators [7]) give evidence of the complicated unsteady dynamics of radiation from beams with a VC in such systems [3,[8][9][10][11][12]. In particular, such investigations revealed some regular features of the chaotic generation of radiation in vircators [5,6,[12][13][14][15][16][17], provided insight into the onset of spatiotemporal structures in an electron beam and on their interaction with a VC [16][17][18][19][20][21], and showed a close relationship between the complication of the spectral content of radiation from a vircator and the formation of electron structures in an overcritical-current electron beam [16,[18][19][20]22].…”

A Plasma Expansion Model Based on the Full Euler–poisson System

“…Such a problem arises in the study of high current diodes mentioned in Ref. 27, in electrical discharges on satellite solar panels, see Ref. 6 or in high current injectors for ion accelerators, see Ref.…”