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Design Studies of a 3-MW, Multifrequency (170/204/236 GHz) DEMO Class Triangular Corrugated Coaxial Cavity Gyrotron
摘要： In this paper, the design studies of a triple frequency (170/204/236 GHz) coaxial cavity gyrotron are carried out which is suitable for plasma heating application in a commercial fusion demonstration (DEMO) tokamak class prototype reactor. To reduce the spatial and maintenance requirements in the heating system of the DEMO tokamak, the output power of the proposed gyrotron is targeted at ≈3 MW for all the three operating frequencies. The cavity modes are selected by considering various physical and technical constraints of the multifrequency gyrotron. The dimensions of the interaction cavity are optimized for the chosen modes at the desired frequencies through cold-cavity calculations. Mode competition studies are then performed to understand the effect of the parasitic modes on the desired modes around the operating frequencies. A triangular corrugated coaxial insert is considered for reducing the problem of localized heating. Initial optimization of beam parameters and magnetic ?eld is carried out using single-mode calculations for the maximum output ef?ciency. A triode-type coaxial magnetron injection gun is designed for supporting this multifrequency operation. Startup calculations are carried out with beam space-charge neutralization at all the three operating frequencies. These studies predict that a 3-MW, continuous-wave operation is possible at the desired frequencies of the proposed DEMO class gyrotron.
关键词： demonstration (DEMO) class gyrotron,multifrequency operation,triangular corrugated insert,space-charge neutralization,Coaxial cavity gyrotron,startup calculation
更新于2025-09-10 09:29:36
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Analysis of the Methods of Discrete and Smooth Frequency Tuning in Gyrotrons for Spectroscopy, on the Example of a Generator Operated in the 0.20–0.27 THz Frequency Range
摘要： We consider the main features of a low-power frequency-tunable gyrotron with an oversized cavity, which is designed for the purposes of nuclear magnetic resonance spectroscopy and other applications and operates in the 0.20–0.27 frequency range producing an output power of 200 W. We study the possibilities of wideband output frequency tuning by exciting a sequence of modes with similar caustics using magnetic-?eld variations and smooth tuning due to the excitation of modes with a great number of longitudinal variations. Aiming at widening the frequency tuning range, we also analyzed the possibility of smooth frequency tuning determined by controlled variations of the cavity temperature. Speci?c features of the electron-optical system of such a gyrotron is discussed, along with the possibility of increasing its e?ciency by means of single-stage recovery of the residual energy of the electron beam.
关键词： gyrotron,frequency tuning,nuclear magnetic resonance spectroscopy,electron-optical system,efficiency
更新于2025-09-10 09:29:36
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Developments of Equipment for sub- THz Collective Thomson Scattering in LHD
摘要： Equipment for collective Thomson scattering diagnostics in the Large Helical Device has been developed. The probe beam source is a 303 GHz Gyrotron. It operates in a pulse mode. No parasitic mode is excited during the whole pulse width including the turn-on and turn-off phases. Single mode oscillation at several frequencies has been confirmed. For power transmission, a 3.5 inch corrugated waveguide line installed for electron heating with lower frequency gyrotrons will be used. The test with the 303 GHz gyrotron has shown a sufficiently low transmission loss.
关键词： Gyrotron,collective Thomson scattering,corrugated waveguide,sub-THz,Large Helical Device
更新于2025-09-10 09:29:36
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[IEEE 2016 IEEE International Vacuum Electronics Conference (IVEC) - Monterey, CA, USA (2016.4.19-2016.4.21)] 2016 IEEE International Vacuum Electronics Conference (IVEC) - Investigation on mode eigenvalue limits for stable 236 GHz, 1 MW-class gyrotron operation
摘要： In order to find the upper limit for mode eigenvalues for stable 1 MW-class gyrotron operation, the behavior of a 236 GHz cylindrical (hollow) cavity gyrotron design is theoretically analyzed for operation with even higher order modes (eigenvalues between 100 and 145). In this frame, two independent methods are used to determine the effect of neighboring modes on mode stability and to estimate the eigenvalue limit for stable operation. With consideration of realistic electron beam parameters (velocity spread and beam width) and a diode start-up regime, the results of both methods suggest that mode eigenvalues smaller than 125 should be selected to ensure the stability of operation.
关键词： high order modes,DEMO,mode eigenvalue,gyrotron,limits of gyrotron operation
更新于2025-09-09 09:28:46
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Design, Development & Functional Validation of Magnets system in support of 42 GHz Gyrotron in India
摘要： A multi institutional initiative is underway towards the development of 42 GHz, 200 kW gyrotron system in India under the frame work of Department of Science and Technology, Government of India. Indigenous realization comprising of design, fabrication, prototypes and functional validations of an appropriate Magnet System is one of the primary technological objective of these initiatives. The 42 GHz gyrotron magnet system comprises of a warm gun magnet, a NbTi/Cu based high homogenous superconducting cavity magnet and three warm collector magnets. The superconducting cavity magnet has been housed inside a low loss cryostat. The magnet system has been designed in accordance with gyrotron physics and engineering considerations respecting highly homogenous spatial field profile as well as maintaining steep gradient as per the compression and velocity ratios between the emission and resonator regions. The designed magnet system further ensures the co-linearity of the magnetic axis with that of the beam axis with custom winding techniques apart from a smooth collection of beam with the collector magnet profiles. The designed magnets have been wound after several R & D validations. The superconducting magnet has been housed inside a low loss designed cryostat with in-built radial and axial alignment flexibilities to certain extent. The cryostat further houses liquid helium port, liquid nitrogen ports, current communication ports, ports for monitoring helium level and other instrumentations apart from over-pressure safety intensive burst disks etc. The entire magnet system comprising of warm and superconducting magnets has been installed and integrated in the Gyrotron test set-up. The magnet system has been aligned in both warm and when the superconducting cavity magnet is cold. The integrated geometric axes have been experimentally ensured as well as the field profiles have been measured with the magnets being charged. Under experimental conditions, all magnets including the superconducting magnet have been charged to their nominal values with appropriate protection measures against the quench. This is the first time in India that a gyrotron specific magnet system with superconducting magnet has been realized.
关键词： India,Superconducting Magnet,42 GHz Gyrotron,Gyrotron Test Set-up,Magnet System
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 17th International Conference on Mathematical Methods in Electromagnetic Theory (MMET) - Kiev (2018.7.2-2018.7.5)] 2018 IEEE 17th International Conference on Mathematical Methods in Electromagnetic Theory (MMET) - Validity of Surface Impedance Model for Electromagnetic Analysis of a Corrugated Gyrotron Cavity
摘要： An approximate surface impedance model (SIM) is the widely used electromagnetic properties of corrugated RF structures. According to this model, the corrugated walls are replaced by a homogeneous surface with averaged anisotropic impedance, which depends on the corrugation parameters. In this study, the SIM validity is investigated for TE waves of a circular waveguide with longitudinal wall corrugations. The investigation is based on the full-wave approach, which accounts for the coupling between the fundamental and higher space harmonics. It is shown that this coupling may invalidate the results of the surface impedance model, even though the widely accepted condition of SIM validity is fulfilled.
关键词： space harmonic,gyrotron,eigenvalue,corrugations
更新于2025-09-09 09:28:46
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[IEEE 2017 14th IEEE India Council International Conference (INDICON) - Roorkee (2017.12.15-2017.12.17)] 2017 14th IEEE India Council International Conference (INDICON) - Design of a Magnetron Injection Gun for a 4 MW, 170 GHz, Coaxial Cavity Gyrotron
摘要： In this paper, design of a Magnetron Injection Gun (MIG) for a 4 MW, 170 GHz coaxial cavity gyrotron is presented. The operating mode is chosen as TE52,31. A triode configured coaxial MIG is designed for the generation of the annular electron beam with the desired beam parameters. The supporting magnetic guidance system is also designed. The initial gun design parameters are obtained using our in-house code Gyrotron Design Suite version 4.1 2016 (GDSv4.1 2016) and the geometry of the MIG is finally optimized through particle trajectory code ESRAY.
关键词： Coaxial Cavity Gyrotron,Magnetron Injection Gun (MIG),Magnetic Guidance System
更新于2025-09-09 09:28:46
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[Lecture Notes in Electrical Engineering] Recent Trends in Communication, Computing, and Electronics Volume 524 (Select Proceedings of IC3E 2018) || Magnetic Field Sensitivity in Depressed Collector for a Millimeter-Wave Gyrotron
摘要： The electron beam trajectories were simulated in a single-stage depressed collector for a millimeter-wave gyrotron. This collector was designed to handle the spent beam obtained after beam-wave interaction in the 100 kW gyrotron (accelerating voltage 55 kV and beam current 5 A). Similar to other high-power gyrotrons, this collector has larger volume considered at ground potential. The cathode and the beam-wave interaction cavity were considered at ?40 kV and +15 kV, respectively. The collector sees the depression of 15 kV. The geometry of the collector is considered as three sections: (i) the open entrance conical section, (ii) the smooth cylindrical section, and (iii) the closed conical section. In order to simulate the beam trajectory from nonlinear taper to collector, the electron trajectories and spent beam power distribution data obtained from large-signal analysis have been fed at the entrance of mode converter of the gyrotron with required potentials applied. The collector geometry and the magnetic ?eld are pro?led to ensure the landing of the gyrating electrons to the wider smooth cylindrical section for better thermal management. The sensitivity of the magnetic ?eld pro?le is studied and observed that for ±5% variation in the magnetic ?eld pro?le would not shift the electron beam landing to conical sections, and the spent electron beam has no interception. The power dissipation on the collector is found to be 80.55 kW. The collector ef?ciency is calculated as ~48% for 120 kW RF output. The maximum thermal loading on collector inner surface is estimated as 0.38 kW/cm2.
关键词： Millimeter-wave gyrotron,Electron trajectory simulation,W-band gyrotron,Depressed collector
更新于2025-09-04 15:30:14
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Development of the Full Package of Gyrotron Simulation Code
摘要： A complete code-package for gyrotron simulation to analyze its performance is under development in UNIST, Korea. We first time report the present status of the code-package named as UNIST Gyrotron Design Tool (UGDT). It can perform design simulations for gyrotron’s interaction cavity, RF window, and the essential mode calculations including the study of mode competition. We will discuss about its salient features, theory, numerical implementation, and its calculation result for 95 GHz UNIST Gyrotron. Moreover, we will validate its capability to perform the mode competition calculation for fundamental and second harmonic modes.
关键词： Harmonic operation,Mode competition,Gyrotron design code,Gyrotron
更新于2025-09-04 15:30:14
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Generation of Electromagnetic Rogue-Waves in Submillimeter-Band Gyrotrons
摘要： Rogue-waves in gyrotrons represent sporadically emitted ultrashort electromagnetic pulses with intensities significantly greater than the average radiation power and, in optimal conditions, higher than the power of the driving electron beams. In this paper within the framework of the average approach and direct 3D PIC (particle-in-cell) simulations, we study the possibility of rogue wave generation in submillimeter-band gyrotrons operating at high-order modes. It is demonstrated that in a 500 GHz fundamental cyclotron harmonic gyrotron excited by the 30 kV/50 A helical electron beam the peak power of generated picosecond electromagnetic spikes at TE61 mode can reach 5 MW that more than three times exceeds the power of the driving beam.
关键词： Rogue waves,Submillimeter-wave radiation,Gyrotron
更新于2025-09-04 15:30:14