Status of the development of X-band antenna-amplifier: design, simulations, and prototype experiments

Summary form only given. An antenna-amplifier, Cherenkov maser with a rod slow-wave structure operating in the non-axisymmetric HE₁₁ mode (fundamental mode of a dielectric rod antenna), can be a compact, controllable, high-power microwave source. In this work, new results obtained in the course of the development of the X-band antenna-amplifier are reported. The design of the proof-of-principle experiments on gain demonstration in the device assumes employing a microwave pulse compressor as a source of external signal, so that the RF drive pulse duration would be less than that of the operating voltage of the linear induction accelerator (LIA), a compact source of electron beam. Also, this allows one to increase the input microwave power up to ~1 MW. The results of numerical simulations using the 3-D version of the PIC code MAGIC show that the output power of ~30 MW is achievable with the operating voltage of ~290 kV and beam current of ~1.17 kA at the frequency of ~9.3 GHz. The prototype experiments included the annular beam transport with a dielectric rod inside (in the absence of input microwave signal) and the low-power microwave transmission (in the absence of the beam). The experiments on beam transport were aimed at estimating the density of plasma that can appear at the rod surface, since too dense plasma could prevent amplification in the device. It has been shown that one can avoid plasma formation to the degree inadmissible for an X-band device, when the density much exceeds 10¹² cm^-3; thus, the concept of the antenna-amplifier can be considered realizable. The dielectric rod antenna excitation has been studied using the microwave transmission system placed inside the LIA module (so that the antenna feed waveguide can serve also as a cathode holder). The antenna matching and radiation pattern have been measured, and it has been shown that the real geometry of the antenna-amplifier practically does not change the angular d- stribution of radiated power and its dependence on frequency in comparison with the case of isolated antenna