rf mode switching in a relativistic magnetron with diffraction output

Abstract

The relativistic magnetron with diffraction output (RMDO) has demonstrated nearly 70% efficiency in recent simulations. This letter reports a rapid mode switching technique in the RMDO using a low power, short-pulse, external single frequency signal. The MAGIC electromagnetic finite-difference-time-domain particle-in-cell code used in simulations demonstrated that an input signal of 300 kW is sufficient to switch neighboring modes in a gigawatt output power A6 RMDO with a transparent cathode, whereas for the original A6 magnetron configuration with radial extraction driven by a transparent cathode 30 MW is required. This frequency agility adds additional versatility to this high power microwave source.

Hysteresis dependence of mode separation on time-varying applied voltage in a magnetron with diffraction output

“…Since it is impossible to account for the real noise level in simulations, we use more realistic results for M-l/ H OO = 2% when controlled mode switching from one pulse to the next in a gigawatt magnetron can be realized using a short (�10 ns) single frequency weak (�10 5 W) RF signal, whereas during one voltage pulse it is impossible to achieve mode switching using a weak RF signal [14]. This result will be refined in forthcoming experiments.…”

“…Using common properties of dynamical systems with two stable states separated by an unstable saddle point [13] it was shown [14] that the closer the axial magnetic field value is to the boundary (critical value), the weaker is the RF signal that is needed to switch modes. This does not imply that we can choose the axial field Hoz so close to the critical value Hoo that we can use an arbitrarily small signal to achieve mode switching.…”

“…The region of synchronous interaction for each mode with cyclic frequency OJ and phase velocity v ph is determined by the relation [14] OJ OJ ----Le < :r , ve vph (6) where L e = v e T e is the azimuthal pathlength of electrons during their lifetime T e . The relation (6) means that electrons that are in the favorable phase of the operating wave do not escape this phase during their drift to the anode.…”

Injection locking of a two-mode electron oscillator with close frequencies

“…5,6 Also, a low-power external driving of a high-power oscillator may result in the fast frequency step tuning owing to the mode switching effect. [7][8][9] Nevertheless, the fundamentals of the mode switching are still poorly understood. In Refs.…”

A high-efficiency tunable TEM-TE11 mode converter for high-power microwave applications

“…Many high power microwave (HPM) devices such as virtual cathode oscillator (VCO), 1,2 relativistic magnetron (RM) [3][4][5][6][7] and the magnetically insulated transmission line oscillator (MILO), [8][9][10] can generate symmetric azimuthally output modes including TM 01 circular waveguide mode and coaxial transverse electromagnetic (TEM) mode. Both modes will be consequentially transformed either to TE 11 circular waveguide or to TE 11 coaxial waveguide in order to get directed radiation.…”