Analysis of a Disc-Loaded Circular Waveguide for Interaction Impedance of a Gyrotron Amplifier

Propagation Characteristics of a Variant of Disc-Loaded Circular Waveguide

“…Clearly, in the said model, one may consider, the region I (disc free region) supporting propagating and the regions II and III (disc occupied regions) supporting standing waves. The axial magnetic and azimuthal electric field intensities in various considered regions are, respectively [27][28][29][30][31][32][33][34][35]: In region I:…”

“…and even in the vacuum electronic devices, such as, linear/particle accelerators [11,12], backward-wave oscillators (BWOs) [13], magnetrons [14], coupledcavity and helix travelling-wave tubes (TWTs) [15][16][17][18][19], cyclotron masers [20,21], gyrotron sources [21][22][23][24] and amplifiers [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39], etc.. In these devices, one may see the periodic beam-wave interaction structures holding either azimuthal or axial periodicity [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]…”

“…The azimuthal periodicity in interaction structure may be seen, for example: in travelling-wave magnetrons [14] for π-mode operation, in gyrotrons [21][22][23][24] for mode rarefaction, in conventional helixTWTs [17] for broadbanding, in gyro-travelling wave tubes (gyroTWTs) [25,26] for higher interaction impedance and, in turn, for higher device-gain. The axial periodicity in interaction structure may be seen, for example, in conventional helix-TWT [17] for higher device-gain, in coupled-cavity TWT [17] for getting fundamentalmode backward-wave characteristics, and in gyro-TWT [27][28][29][30][31][32][33][34][35][36][37][38][39] for broadbanding.…”

“…The axial-periodicity in the interaction structure of a gyro-TWT promises the broadbanding through dispersion shaping that allows wideband coalescence between the beam-and waveguide-mode dispersion characteristics and, in turn, the broadband gain-frequency response [27][28][29][30][31][32][33][34][35][36][37]. Choe and Uhm [36] analyzed the infinitesimally thin disc-loaded circular waveguide ignoring the higher order stationaryand propagating-wave modes in the field matching technique and presented the dispersion shaping by changing the structure parameters.…”

“…Choe and Uhm [36] analyzed the infinitesimally thin disc-loaded circular waveguide ignoring the higher order stationaryand propagating-wave modes in the field matching technique and presented the dispersion shaping by changing the structure parameters. Kesari et al [27][28][29][30] improved the analysis of Choe and Uhm [26] considering higher order stationary-and propagating-wave modes, first for infinitesimally thin disc-loaded waveguide [27,28] and then for thick disc-loaded waveguide [28][29][30]. Kesari [31,32] also proposed the coaxial-disc-loaded circular waveguide interaction structure, such that in one configuration metal discs radially projecting inward from the metallic wall, and in second configuration metal discs radially projecting outward from the coaxial insert, for the beamabsent [31] and the beam-present [32] cases, and demonstrated the second configuration a better interaction structure.…”