Configuration of the conventional P-band coaxial RBWO.
SWS model for the analytical model in Sec. II. The ripples on both the inner surface of the outer conductor and the outer surface of the inner conductor.
Quasi-TEM dispersion curves of the first wave mode in the coaxial SWS with and without an inner conductor ripple. The beam parameters are fixed, and the straight solid line which intersects with the dispersion curves is the electron beam Doppler line. (a) Effect of the inner conductor ripple on the operating frequency. (b) Effect of period length on the operating frequency.
(Color online) Temporal growth and spatial growth rates of coaxial RBWO with and without an inner conductor ripple. The beam parameters and other structure parameters are fixed. (a) Effect of the inner conductor ripple on the temporal growth rate. (b) Effect of the inner conductor ripple on the spatial growth rate.
Current (kA) versus the number of SWS periods. The diode voltage is 650 kV and other parameters are listed in Table I. The solid dots are the starting current (Ist); the solid squares are the space charge limited current (Iscl); the crosses are the critical current (Icr) of the overbunch instability; and the thick solid line are the region of single-frequency operation of the coaxial RBWO.
Simulation result of the beam current as a function of for the foilless diode, where γ0 is the relativistic factor.
(Color online) The beam-to-microwave efficiency versus the diode voltage (kV) for five cases of different SWS period numbers, viz. 2, 3, 4, 5, and 6. The geometry parameters of the diode are fixed and other parameters are listed in Table I.
(Color online) The output microwave power versus the diode voltage (kV) for five cases of different SWS period numbers, viz. 2, 3, 4, 5, and 6. The geometry parameters of the diode are fixed and other parameters are listed in Table I.
(Color online) Configuration of the compact P-band coaxial RBWO in Karat simulations. (a) Annual cathode, (b) Anode, (c) Collimator, (d) Outer conductor ripple, (e) Inner conductor ripple, (f) Coaxial extractor, and (g) Output cavity.
(Color online) The phase-space plots r-z (upper) and P z -z (lower) after saturation. P z is the z component of axial momentum, which is normalized to the electron mass (m) times the speed of light (c).
(a) Output power versus time for the compact device. (b) Saturated output power versus time and (c) the corresponding Fourier spectrum.
(Color online) Plot of the output microwave power, efficiency, and frequency versus diode voltage.
Some fixed parameters in the PIC simulations of the coaxial RBWO.
Comparison between the RBWO in Ref. 22 and RBWO in this paper.
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