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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 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]

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]

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]

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: 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: 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: 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]