Operation Characteristics of 12-Cavity Relativistic Magnetron With Single-Stepped Cavities

The possibility of using single-stepped cavities to replace the common tapered cavities was studied using particle-in-cell simulations in an A6 magnetron with diffraction output (MDO). The replacing of the tapered cavities by the single-stepped cavities in a 12-cavity MDO increases the interaction space where the charged particles interact with the induced RF waves. The electronic efficiency of the 12-cavity MDO with single-stepped cavities driven by the transparent cathode
[2]
of GW output power level can be as high as 73% for
$\alpha=18.2^{\circ}$
, 74% for
$\alpha=17.5^{\circ}$
, and 72% for
$\alpha=12.5^{\circ}$
at
$\beta=32^{\circ}$
, where
$\alpha$
is the angle between the outer wall and
$z$
-axis, and
$\beta$
is the angle between the inner wall and
$z$
-axis. The depth of single-stepped cavities is changed when
$\alpha$
is changed, which results in different frequency range of magnetron operating modes. When a 400-kV voltage pulse of 10-ns duration is applied to a transparent cathode or a solid cathode, the output power can be as high as 1 GW. Without loss of generality, for
$\alpha=12.5^{\circ}$
at
$\beta=32^{\circ}$
, the peak efficiency around 70% of 12-cavity MDO with single-stepped cavities design occurs at the voltage
$(V\sim 400\pm 50~{\rm kV})$
. The results presented in this paper provide references for relativistic magnetron mode selection or mode switching experiments when choosing the input parameters (magnetic field and accelerating voltage) allowing the magnetron to operate in the desired operation mode.