Study of RF Window for High Frequency Gyrotron

Bhomia, V and Alaria, MK and Sinha, AK (2011) Study of RF Window for High Frequency Gyrotron. In: National Conference on Innovative Developments in Electronics Arena (IDEA-2011), February 19-20, 2011, Arya Institute of Engineering and Trchnology, Jaipur. (Submitted)

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Abstract

Gyrotron is a high power microwave tube, which emits coherent radiation at approximately the electron cyclotron frequency or its harmonics. Gyrotron is widely used in Plasma fusions, ECRH heating, Industrial heating and Material processing. The need for high power, high frequency rf sources for the magnetic fusion research experiments has provided much of the impetus for the development of present day gyro oscillators. The desired features of an ideal window are minimum reflection, minimum insertion loss, and high power handling capability, wide bandwidth, excellent mechanical strength, high thermal conductivity and vacuum tightness. Types of window have been suggested in literature for high power mm wave applications and in Gyrotrons, these are single disc with edge cooling, single disc with surface cooling by gas, and double disc with surface cooling by liquid. The double disc face cooled structure causes power loss in two discs. In addition, loss in the coolant also can be taken into account. For high power CW Gyrotrons at millimeter wavelengths, advanced materials such as sapphire, chemical vapour deposited (CVD) diamond, Silicon nitride composite, BeO, Au-doped silicon etc. have to be used. Design of CVD diamond, sapphire or other dielectric based high-power window operating at more than hundred GHz and capable of handling average power of one mega watt. The study of RF window for 10 GHz Gyrotron has been carried out using Ansoft HFSS. In 35 GHz Gyrotron single disc of diameter 70 mm and thickness 4.02 mm alumina window has been used in the simulation. The return loss (S11) and insertion loss (S21) of the 35 GHz Gyrotron window have been found -45.3 dB and -0.04 dB respectively. The simulation of RF window for 120 GHz and 170GHz Gyrotron has been carried out using the Ansoft HFSS and CST microwave studio. The return loss (S11) and insertion loss (S21) of the 120 GHz and 170 GHz Gyrotron window have been found -27.0 dB and -0.04 dB respectively. The specifications of RF window for the Gyrotron of 2 MW average power operating at frequency 170 GHz are VSWR ≤ 1.2 and Insertion loss ≤ 0.1 dB. In this paper describes the computational analysis of RF window for high power and high frequency Gyrotron. In 170 GHz Gyrotron single disc diamond window have been used in the simulation. The diameter of the diamond disk is 96 mm and thickness of the disc is 2.2 mm. In this analysis, the medium quality diamond disc (tanδ=1.3 x10-4) has been used. The single disc windows from BeO, SiC, and PACVD diamond material have also been studied.

Item Type:	Conference or Workshop Item (Paper)
Subjects:	?? TK ?? Microwave Tubes > Gyrotrons
Divisions:	Microwave Tubes
Depositing User:	Mr. Rabin Chatterjee
Date Deposited:	23 May 2013 08:55
Last Modified:	23 May 2013 08:55
URI:	http://ceeri.csircentral.net/id/eprint/74

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