Comparison of simulation and experimental results for a radially symmetric transit-time oscillator

Summary form only given, as follows. The transit-time effect in a coaxial structure has been proposed by Arman (1996) as a mechanism to develop low impedance high power microwave devices using no externally-generated magnetic fields and having no confining foils. The major advantages seen for this type of device include: (1) a low device impedance due to the radial geometry; (2) reduced X-ray emission and associated shielding due to the low operating voltage; (3) elimination of magnets normally used in RF oscillators to stabilize the electron beam; and, (4) simplified coupling of the device output to the RF extraction structure (waveguide of antennas). The two-dimensional particle-in-cell code MAGIC has been used to design a prototype device: the redial acceletron. In the prototype device, an electron beam propagates radially within an annular anode-cathode (A-K) gap. Interaction between the electron beam self-generated electric and magnetic fields, non-linear (with gap voltage) cathode current emission, and electron transit time across the A-K gap generates a self-sustaining RF oscillation. Due to the complex internal geometry of the prototype device, simulation is not straightforward. The prototype design has been fabricated and tested.