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We suggest to use the effect of cyclotron resonance absorption for modulation of microwave signals. Stationary signal transforms into the sequence of soliton-like pulses during interaction with rectilinear electron beam. For operating frequency of 250 GHz output pulses can possess subnanosecond durations.
The development of a 2 MW, 170 GHz short-pulse coaxial-cavity gyrotron pre-prototype for electron cyclotron heating and current drive (ECRH&CD) of magnetically confined plasmas in upcoming fusion devices is in progress at Karlsruhe Institute of Technology (KIT). Significant design modifications have been done recently. First experimental tests of a modified setup show two important unwanted effects...
We describe the project for the construction of a Terahertz (THz) beamline to be called TeraFERMI at the seeded FERMI Free Electron Laser (FEL) facility in Trieste, Italy.
A technique for controlling electric field distribution in the near-cathode region of a magnetron-injection gun has been developed. The possibility to improve the quality of the helical electron beam by regulated non-uniformity of electric field is studied experimentally and using computer modelling. This technique is applied to enhance the efficiency of a 74.2 GHz, 100 kW gyrotron.
We investigate, by numerical simulations, the effects of a misaligned (i.e. shifted with respect to the resonator axis) electron beam on the beam-wave interaction in a 170 GHz, 2 MW coaxial gyrotron. The correlation of the simulations results with the experimental findings, which motivated the present study, is discussed.
Within the quasi-optical approach, we study evanescent waves propagation along a periodically corrugated surface and their excitation by a relativistic electron beam. The main features of amplifier and oscillators schemes are described including the increments, starting currents, electron efficiency and forming of self-consistent spatial structure of the radiation field. The feasibility of realization...
Numerical simulations have been conducted at the University of Strathclyde to study the spatial growth rate and emission topology of the cyclotron maser instability responsible for auroral magnetospheric radio emission from stars and planets and intense non-thermal radio emission in other astrophysical contexts. The results have significant bearing on the radiation propagation characteristics and...
The effect of the tilt of the electron beam axis on the gyrotron operation is investigated. It is commonly accepted that the tilt deteriorates the efficiency of cylindrical cavity gyrotrons. Our study showed that this deterioration can be mitigated by a proper displacement of the electron beam axis at the entrance. Also, in some cases, when the aftercavity interaction lowers the gyrotron efficiency,...
We report on the design and development of a PPM integrated 233 GHz staggered vane sheet beam TWTA [1, 2]. The permanent magnetic (NdFeB) based focusing lens structure for the sheet electron beam transport has been designed for a gun operated at 19 kV. For a beam tunnel of 830 µm * 160 µm, a transmitted current of ∼ 200 mA is achieved for > 40 mm length channel. For 19 kV operation, the TWTA circuit...
The possibilities to obtain efficient operation of sub-THz gyrotrons at cyclotron harmonics are analyzed and the evolution of gyrotron optimal parameters is presented. 3D PIC simulations of THz band gyrotrons have been performed. The reasonable agreement with experimental results is demonstrated, that allows one to analyze some effects resulting from ellipticity of cavities, non-uniform emission and...
The effect of the emitter surface roughness on the quality of an electron beam emitted by a gyrotron magnetron injection gun (MIG) has been studied. Several different shapes of microstructures (imperfections) have been modeled on the emitter surface. A modified version of the two-dimensional, finite-difference beam optics code ESRAY has been used for the numerical simulations. Results for the different...
Latest experimental developments of W-band gyro-devices with helically corrugated waveguides and a cusp electron gun are presented. The cusp generated a 40 keV, 1.5 A axis-encircling electron beam. Helical corrugated waveguides have ideal dispersive properties which improve the frequency tuning range of a gyrotron backward wave oscillator (gyro-BWO) whilst maintaining the already good efficiency of...
A new model of vacuum tube amplifier, designed to produce over 10 Watts at 263 GHz is in development at CPI Canada. This device uses CPI's Extended Interaction Klystron technology, which has previously demonstrated good results from 17 to 220 GHz. With recent completion of a 264 GHz CW tunable oscillator, the amplifier development will extend the demonstrated envelope for EIKs to a frequency and power...
Numerical 3D PIC code simulations show that Slow-Wave-Structures SWSs demonstrate excellent potential as a virtual dielectric in a Cherenkov based Backward Wave Oscillator (BWO). CST Microwave Studio confirms internal mode coupling between a volume TM0,6 and surface HE20,1 modes resulting in the creation of a high-Q cavity, necessary for the Cherenkov mechanism to be exploited. MAGIC 3D demonstrates...
A novel physical phenomenon is reported which may combine electronics and photonics to generate electromagnetic radiation. Surface plasmon polaritons (SPPs) are excited by a uniformly moving electron beam in a structure of nano-scale metal film with dielectric medium loading, and then are transformed into Cherenkov radiation with intensity enhancement. Surface Polariton Cherenkov Light Source (SPCLS)...
Communications and Power Industries (CPI) is currently developing megawatt-class gyrotrons for fusion plasma heating and current drive across a range of frequencies, for use at several different fusion research facilities. These gyrotrons are currently at different stages of development, fabrication, and test. Design features will be compared, available test data will be presented, and future plans...
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