Analysis of Ohmic Quality Factor of Circumferentially Corrugated Circular Cavities
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Analysis of Ohmic Quality Factor of Circumferentially Corrugated Circular Cavities Vishal Kesari & Neetesh Purohit & M. Thumm
Received: 24 June 2009 / Accepted: 23 November 2009 / Published online: 11 December 2009 # Springer Science+Business Media, LLC 2009
Abstract A general analytical approach was proposed to estimate the ohmic quality factor of circumferentially corrugated cavities having a finite-single-valued and continuous radius-profile in circular symmetry within the boundary of its length. In the present paper, two field profiles, namely, the sinusoidal and the Gaussian one, and four radius profiles, namely, the sinusoidal, the cosinusoidal, the triangular-sinusoidal and the triangular-cosinusoidal, of the cavity were considered and the results were presented in order to demonstrate the helpfulness of the proposed approach. Out of the eight cavity versions considered, the minimum and the maximum ohmic quality factors were obtained for the cavity with sinusoidal field profile and triangular-sin radius profile and for the cavities with Gaussian field profile with sinusoidal and cosinusoidal radius profiles. It has been found that for higher values of the cavity-length to corrugation-period ratio (≥3), the ohmic quality factor performances of the cavities in sinusoidal and cosinusoidal radius profiles overlap. Keywords Cavity resonator . Microwave resonator . Corrugated wall cavity . Resonator quality factor Abbreviation CCCCS Circumferentially corrugated cavities in circular symmetry
V. Kesari Microwave Tube Research and Development Centre, Bangalore, India e-mail: [email protected] N. Purohit (*) Indian Institute of Information Technology, Allahabad, India e-mail: [email protected] M. Thumm Karlsruhe Institute of Technology (KIT), IHE and IHM, Karlsruhe, Germany e-mail: [email protected]
J Infrared Milli Terahz Waves (2010) 31:510–520
511
1 Introduction Corrugated cavities and waveguides have proved their applications as the interaction structure in vacuum-electron oscillators, such as gyrotron, backward-wave oscillator, magnetron, etc. [1–5] and amplifiers, such as travelling-wave tube, gyro-travelling-wave tube, etc. [5–14] as well as in linear accelerators [12, 13]. An axial corrugation on the wall of an open-ended cavity may reduce the problem of mode-competition [1–5] in gyrotrons, similar corrugation on waveguide-wall and on barrel-wall may produce higher device gain of gyro-travelling-wave tubes [6, 7] and wider device bandwidth of helix-travelling-wave tubes [8], respectively. On the other hand, an azimuthal corrugation on the waveguide-wall may increase the gain as well as the bandwidth of gyro-travelling-wave tubes [9, 10], however, increase the gain, but not the bandwidth of travelling-wave tubes [11–13]. Helical corrugations on the waveguide-wall with various groove cross-sections may increase the bandwidth of gyro-travelling-wave tubes [14]. However, for such high-power devices, thermal considerations and the power dissipation in the wall of the cavities / waveguides limi
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