Anirban Bera

Design of interaction cavity for 42 GHz, 200 kW CW/long pulse gyrotron

A weakly tapered interaction cavity has been designed to excite TE03 operation mode at the fundamental harmonic number for 42 GHz, 200 kW gyrotron. A software code GCAVSYN has been developed to synthesize cavity geometry and selection of operating mode. The cold cavity analysis and beam-wave interaction were carried out using commercially available PIC code MAGIC. An axial output power above 200 kW has been achieved at guiding cavity magnetic field 1.61 T.

Design of MIG for 42GHz, 200kW Gyrotron

A triode type magnetron injection gun (MIG) shown in Fig. 1 for a 200 kW, 42 GHz gyrotron has been designed. Operating voltage of modulating anode is 29 KV and accelerating voltage is 65 KV. Operation mode of this gyrotron is TE03 and it would be used in a TOKAMAK system for plasma heating. This MIG is designed by using commercially available code EGUN and three in house developed software code MIGSYN, GINTMESH and MIGANS respectively.

SUNRAY-1D code for accurate and fast large signal analysis of a helix TWT

SUNRAY-1D code for large signal analysis of a helix TWT was developed. Effect of circuit loss, sever loss, backward and reflection waves are considered in this model. Higher order harmonics, spurious signals and intermodulation components are also considered in this model. This is fast and it takes less than one minute to find out saturation drive on a P-IV computer. It is also validated with experimental results of several helix TWTs. Agreement for saturated power is achieved within 0.5 dB and for saturated gain within 3 dB.

Design and development of Ku-band 140W space TWT

A Ku-band 140 W space TWT of gain (>55 dB), electronic efficiency (>24%), collector efficiency (>75%), overall efficiency (>55%), I/M components (<-12 dBc) for frequency 10.9-11.7 GHz has been designed and developed for satellite communication system. This paper presents critical design issues and approach related to different assemblies like electron gun, PPM focusing, helix SWS, input & output couplers, and 4-stage depressed collector in order to meet the stringent requirement of space TWTs.

Simulation of 2-section SWS for high gain, high efficiency helix TWT

A high efficiency 140W radiation-cooled Ku-band TWT has been designed successfully for communication satellite. This TWT with input coaxial coupler and output waveguide coupler was designed in 2-sections to achieve gain >55dB at MOW output power over the frequency range of 10.9-11.7GHz with high stability and high linearity.

Modeling of a multistage collector for a high efficiency space TWT

Two-dimensional package EGUN was used for the simulation of multistage collector. Based on this package a pre- and a post-processor have been developed which make the package user friendly and analyses the performance of the collector. In this article, we modelled the multistage collector for high efficiency space TWT.

A gyrating electron beam source for frequency tunable, 200 GHz gyrotron

Abstract Magnetron injection gun (MIG) is an important and critical part of any gyrotron. The overall performance of gyrotron deeply depends on the quality of gyrating electron beam. In this article, the design of triode type magnetron injection gun for 200 GHz frequency tunable gyrotron is discussed. It is planned to design and develop a 200 GHz gyrotron for 300 MHz DNP-NMR spectroscopy. The triode MIG is designed in such a way that it can be used in 200 GHz gyrotron of higher RF power for other applications also such as electron spin resonance, imaging. First, geometrical and electrical parameters of MIG are calculated using trade-off and scaling equations. Based on the calculated parameters, further, electron beam trajectory simulations are performed in EGUN. The geometry of electrodes are optimized through numerous simulation iterations to achieve the required beam parameters, such as, minimum spread in velocity and guiding center radius, an optimum value of velocity ratio (1.3–1.5), guiding center radius as per the maximum beam-wave coupling strength. The magnet system is designed to achieve the smooth Gaussian type of magnetic field profile with peak value of 7.35 T at cavity center. Further detail parametric analyses are performed which would be helpful in the frequency tuning and long-time stable operation of gyrotron device.

Design and development of RF window for high power Gyrotron

This paper describes design and development of single disc RF window for high power Gyrotron. The electrical design of edge cooled single-disc alumina window for 170 GHz, 1MW short pulse Gyrotron has been carried out using CST microwave studio. A diameter and thickness of the ceramic window are 90 mm and 3.16 mm, respectively, whose edge is directly cooled by water. The return loss (S11) and insertion loss (S21) of 170 GHz Gyrotron window have been obtained as - 47.5 dB and - 0.02 dB respectively. In this paper thermal analysis of RF window has also been carried out using ANSYS software. The disc center and disc edge temperature has been found as 385 K and 288 K, respectively. For the sake of experimental validation, a highly purity (99.5%) alumina window based upon design has been developed and cold characterization has also been carried out using Vector Network Analyzer (VNA).

Design of helix SWS for high efficiency, stable gain, Ku-band space TWT

In this paper helix SWS (slow wave structures) for Ku-band space TWT is presented to achieve RF output power 140 W with gain more than 50 dB over the frequency band 10.9 to 11.7 GHz with the optimum values of efficiency, linearity, stability, weight and size. The criteria of selecting both beam and circuit parameters are discussed. The simulated RF performance for space TWT are shown.