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In this paper, we describe the design and development of helical cut smooth wall mode launcher for high frequency and high power Gyrotron. A Vlasov-type helical cut mode launcher for converting TE 22,6 mode to a Gaussian mode has been designed for 120 GHz, 1 MW Gyrotron. The initial design of mode launcher has been optimized using LOT/SURF-3D software. The mode launcher diameter and length are optimized considering the minimum return loss and the minimum insertion loss by using CST microwave studio. The return loss (S 11 ) and insertion loss (S 21 ) performance of helical cut smooth wall mode launcher have been obtained using CST-Microwave Studio. The fabrication of Vlasov-type helical cut mode launcher for 120 GHz Gyrotron has also been carried out. [ABSTRACT FROM AUTHOR]

A triode-type magnetron injection gun (MIG) for a 42 GHz, 200 kW gyrotron was designed by two commercial codes: EGUN and TRAK. An in-house code MIGANS was used as the post-processor of the EGUN. Some basic equations relevant to the problem available in literature were used while using the EGUN code for the purpose. The results on the design output parameters obtained by these two codes were found to be in close agreement. [ABSTRACT FROM AUTHOR]

This letter presents a simple and general fabrication method for helical groove waveguides (HGWs) with successful fabrication of a number of novel HGWs such as the hole-gap-shaped groove HGW, the swallow-tailed groove one, the trapezoid groove one and the ridge-loaded rectangular one. Also, measurements on these structures have been carried out to determine their dispersion properties. The experimental results agree well with the theoretical results and demonstrate the large influence of groove shape on the dispersion characteristics of the structures. [ABSTRACT FROM PUBLISHER]

A review on the sub-THz/THz gyrotrons is performed in this manuscript. The present development status of gyrotrons can be divided into three streams for the sake of better understanding: 1. low frequency (<35 GHz), medium power (<100 kW), small size and easy to handle gyrotrons for industrial applications, 2. very high power (1 MW or more), medium frequency (100–200 GHz) gyrotrons for plasma fusion applications, 3. low power (few tens of watt to kW), high frequency (>200 GHz) gyrotrons for various innovative applications. In this manuscript, the third stream of gyrotron development is reviewed. In last few decades several innovative applications are searched in sub-THz/THz band where the gyrotrons could be used as an efficient source of RF radiation. The applications of sub-THz/THz gyrotrons including the futuristic scope of the device are also discussed in this article. Further, several criticalities arise in the design and development when the gyrotron operation shifts toward the high frequency band. Various such design and technological challenges are also discussed here. Finally the development status of sub-THz/THz gyrotrons as per the use in various scientific and technological applications is also discussed. [ABSTRACT FROM AUTHOR]

The design study of dual frequency gyrotron operating at 42/84 GHz frequencies with output power ∼500 kW is presented in this article. TE 10,4 and TE 6,2 are selected as the operating modes for 84 and 42 GHz operations of the device, respectively. The beam-wave interaction simulations are performed by using the Particle-in-Cell algorithm to evaluate the growth of RF power and frequency. Magnetically tunable magnetron injection gun is also designed to launch the electron beam at the radius of 6.2 mm (84 GHz) and 7.3 mm (42 GHz) in the interaction cavity. The CVD diamond RF window is also designed, which must be transparent for 42 GHz and 84 GHz frequencies. The design results of the dual frequency gyrotron confirm the growth of ∼500 kW power at 42/84 GHz. [ABSTRACT FROM AUTHOR]

Highlights: [•] Design of triple frequency MW gyrotron. [•] The mode selection process for three frequency operation of MW gyrotron. [•] Design of magnetically tunable magnetron injection gun. [•] CVD diamond window design for triple frequency operation of gyrotron. [Copyright &y& Elsevier]

Abstract: The design work of 95 GHz, 100 kW gyrotron for Active Denial System (ADS) application is reported in this manuscript. The mode selection is performed considering the various technical constraints. Particle-in-Cell code and indigenously developed code based on the generalized non-linear formalism are used in the beam–wave interaction computation and cavity design. Both the codes show good similarity in results. In addition, the design of electron beam source of 364 kW beam power, beam tunnel, depressed collector and RF window are also discussed. The design results confirm the RF power >100 kW with ≈50% tube efficiency. [Copyright &y& Elsevier]

Highlights: [•] The complete electrical design of 42GHz, 200kW gyrotron is presented. [•] Un-depressed collector and axial output system for RF power is selected. [•] Various commercially available design tools as well as in-house developed computer codes are used in the design process. [•] The experimental results of cold cavity analysis are also presented. [•] The design results show more than 200kW power with 40% interaction efficiency at 42GHz frequency. [Copyright &y& Elsevier]

Highlights: [•] Numerical analysis of gyrotron cavity geometry effect on Q value, ohmic wall heating and field profile. [•] Experimental analysis of gyrotron cavity geometry effect on Q value, ohmic wall heating and field profile. [•] Effect of gyrotron cavity geometrical parameters on the start oscillation current. [•] Effect of gyrotron cavity geometrical parameters on the beam–wave interaction efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] Electrical design of single stage depressed collector for high power gyrotron tube. [•] Efficiency enhancement by collecting spent beam. [•] Optimization of geometry and magnetic field for optimized beam spread. [•] Optimization of cooling duct system for better thermal management. [Copyright &y& Elsevier]

Abstract: The beam tunnel, equipped with the high lossy ceramics, is designed for 95GHz gyrotron. The geometry of the beam tunnel is optimized considering the maximum RF absorption (ideally 100%) and the suppression of parasitic oscillations. The excitation of parasitic modes is a concerning problem for high frequency, high power gyrotrons. Considering the problem of parasitic mode excitation in beam tunnel, a detail analysis is performed for the suppression of these kinds of modes. Trajectory code EGUN and CST Microwave Studio are used for the simulations of electron beam trajectory and electromagnetic analysis, respectively. [Copyright &y& Elsevier]

Abstract: The electrical design of different components of 1MW, 170GHz gyrotron such as, magnetron injection gun, cylindrical interaction cavity and collector and RF window is presented in this article. Recently, a new project related to the development of 170GHz, 1MW gyrotron has been started for the Indian Tokamak. TE34,10 mode is selected as the operating mode after studied the problem of mode competition. The triode type geometry is selected for the design of magnetron injection gun (MIG) to achieve the required beam parameters. The maximum transverse velocity spread of 3.28% at the velocity ratio of 1.34 is obtained in simulations for a 40A, 80kV electron beam. The RF output power of more than 1MW with 36.5% interaction efficiency without depressed collector is predicted by simulation in single-mode operation at 170GHz frequency. The simulated single-stage depressed collector of the gyrotron predicted the overall device efficiencies>55%. Due to the very good thermal conductivity and very weak dependency of the dielectric parameters on temperature, PACVD diamond is selected for window design for the transmission of RF power. The in-house developed code MIGSYN and GCOMS are used for initial geometry design of MIG and mode selection respectively. Commercially available simulation tools MAGIC and ANSYS are used for beam–wave interaction and mechanical analysis respectively. [Copyright &y& Elsevier]

Abstract: This paper presents the numerical simulation of a double-beam magnetron injection gun (DB-MIG) and beam-wave interaction for 60GHz, 500kW gyrotron. The beam-wave interaction calculations, power and frequency growth estimation are performed by using PIC code MAGIC. The maximum output power of 510kW at 41.5% efficiency, beam currents of 6A and 12A, electron beam velocity ratios of 1.41 and 1.25 and beam voltage of 69kV are estimated. To obtain the design parameters, the DB-MIG with maximum transverse velocity spread less than 5% is designed. The computer simulations are performed by using the commercially available code EGUN and the in-house developed code MIGANS. The simulated results of DB-MIG design obtained by using the EGUN code are also validated with another trajectory code TRAK, which are in good agreement. [Copyright &y& Elsevier]

Abstract: The design of weakly tapered interaction cavity for 0.3THz, 4kW gyrotron operating at the fundamental cyclotron harmonic is presented in this paper. The interaction cavity design and the beam-wave interaction computation are carried out for TE0,6 mode by using the Particle-in-Cell (PIC) electromagnetic simulation approach. The operating mode is selected by using the code GCOMS, in which various mode selection parameters and start oscillation current are calculated. Further, the power and frequency estimation are performed to finalize the cavity and electron beam parameters. The sensitivity analysis is done to finalize the tolerance limit in various parameters. Finally, the thermal and structural analyses are performed for the designed interaction cavity for the effective cooling. [Copyright &y& Elsevier]

Abstract: A single stage depressed collector has been designed to dissipate the spent electron energy of 45 keV. This results in an increase of overall efficiency of 42 GHz, 200 kW gyrotron from 33% to 57%. The design of depressed collector has taken into account the performance on several sectors such as maximum beam spread, minimum power dissipation including the effect of high voltage and thermal efficiency. Different computer codes have been used in order to design this particular collector. The simulated efficiency of the single stage depressed collector is 63%. [Copyright &y& Elsevier]

Abstract: This paper describes the design of a large sized diamond window for 1MW, 170GHz gyrotron. The diameter and the thickness of the diamond window are 80mm and 1.482mm, respectively, whose edge is directly cooled by water. The CST microwave studio has been used for the S-parameter, and finite element analysis code ANSYS has been used for the thermal and the structural simulation. The return loss (S 11) and insertion loss (S 21) of the 170GHz gyrotron window have been found −39.80dB and −0.011dB, respectively. The thermal and structural analysis of RF window the 397K temperature at disk center and maximum displacement 0.01mm has been found in the window disk during the thermal analysis. [Copyright &y& Elsevier]

Abstract: In this paper, the three-dimensional simulation of triode-type magnetron injection gun (MIG) for 120GHz, 1MW gyrotron is presented. The operating voltages of the modulating anode and the accelerating anode are 57kV and 80kV respectively. The high order TE22,6 mode is selected as the operating mode and the electron beam is launched at the first radial maxima for the fundamental beam-mode operation. The initial design is obtained by using the in-house developed code MIGSYN. The numerical simulation is performed by using the commercially available code CST-Particle Studio (PS). The simulated results of MIG obtained by using CST-PS are validated with other simulation codes EGUN and TRAK, respectively. The results on the design output parameters obtained by using these three codes are found to be in close agreement. [Copyright &y& Elsevier]

Abstract: The design and the numerical simulation of the interaction cavity for 120GHz, 1MW gyrotron is presented. The optimizations of the cavity parameters are carried out by using the Particle-in-Cell, 3D-electromagnetic simulation code MAGIC. The co-rotating TE22,6 mode is selected by using the in-house developed code GCOMS. The cold cavity and the beam–wave interaction analyses are carried out to analyze the eigenmode, eigenfrequency and the output power performance. The output power more than 1MW is achieved at the magnetic field of 4.82T. The sensitivity analyses of the output power and the frequency with respect to the various interaction cavity parameters are also performed. [Copyright &y& Elsevier]

Abstract: The design of the interaction cavity of a 170 GHz gyrotron operating in the TE34,10 mode is presented in this article. An in-house developed code GCOMS and Particle-in-Cell (PIC) code MAGIC are used for the mode selection and beam–wave interaction simulations, respectively. The cold cavity analysis and beam–wave interaction computation are carried out to analyze the eigenmode and output power, respectively. A thorough parametric analysis of the interaction cavity geometry and electron beam parameters is also carried out with respect to the output power and frequency. The results show the capability of the interaction cavity, designed for the TE34,10 mode, to produce more than 1 MW of RF power of a gyrotron at the operating frequency of 170.03 GHz. [Copyright &y& Elsevier]

Abstract: This paper presents experimental results for cold testing a gyrotron open resonator. Experiments were accomplished to measure resonant frequency and their particular quality factor for TE mode at the operating frequency. The perturbation technique was used to determine the axial, radial and azimuthal electric field profile for identification of TE031 mode at operating frequency 42GHz. The good agreement between experimental and theoretical was found. The results were quite good and suitable for suppression the undesired modes in the specific gyrotron cavity. [Copyright &y& Elsevier]