Influence of background gas ionization on oscillations in a virtual cathode with a retarding potential

Abstract

The effect of mobile ion background on the dynamics of a planar virtual cathode with retarding field is investigated. The ions appear in the diode gap due to ionization of a neutral gas by the electron beam. Detailed examination of the self-consistent processes of the virtual cathode dynamics, gas ionization, and ions motion is performed using the particle-in-cell simulation. It is shown that the presence of ions leads to the virtual cathode neutralization, its displacement, and subsequent anew formation. The microwave generation has the form of a sequence of pulse packets, whose duration depends on the value of the retarding potential and the kind of gas.

Beam discharge excited by distributed virtual cathode

“…Figure 10 shows the dynam ics of the total number of particles of each type in the cavity in time, corresponding to such a repeated mode of VC formation. A similar mode was previously observed in [22,49,50] in the system with one beam VC.…”

“…Thus, the VC moves casting plasma in its path; the VC velocity increases with the gas pressure. The VCBD was theoretically studied in [19][20][21][22]. This discharge type can be used in ultrahigh vacuum meters [23,24], pumping of active media of gas discharge lasers [25], and collective acceleration of intense ion beams [26][27][28].…”

Subterahertz Chaos Generation by Coupling a Superlattice to a Linear Resonator

“…We believe that the phenomena of linear resonators described here are applicable to other NDC solid-state devices, including Gunn diodes [42]. The chaotic high-frequency oscillations observed in our experiments may have technological applications in, for example, nonlinear antennas, broadband radar [43][44][45][46][47][48], and chaos-based logic [49,50]. The latter also plays a crucial role in modern chaos-based communication systems [30,31].…”

Effect of self-magnetic fields on the nonlinear dynamics of relativistic electron beam with virtual cathode

“…The oscillating VC is known to appear in an electron beam when the beam current exceeds a certain critical value, I cr (space charge limiting (SCL) current) 1,19 , and the beam space charge is strong enough in order to form a potential barrier (VC) which reflects the electrons back to the injection plane. The mechanisms of the VC formation have been investigated in detail in case of the one-dimensional (1D) electron beam motion (fully magnetized beam) 7,12,[20][21][22] , with the critical beam current value being analytically defined for this case in Ref. 19 .…”