A. N. Kuleshov

400-GHz Continuous-Wave Clinotron Oscillator

Experimental results of a 400-GHz clinotron, which is a modification of the backward-wave oscillator, are presented. Development of grating, focusing magnetic system, and electron gun is shown. The clinotron tube is designed to use a high-perveance electron gun and thereby enhance the output power and efficiency. An output power of 43 mW is demonstrated at 385 GHz.

Development of the 75-GHz planar gyrotron with transverse energy extraction

The opportunity of generating ribbon-shaped polyhelical electron beams intended to excite oscillations in the new type of gyrotrons is investigated via particle-in-cell simulation. Its distinctive features are the planar geometry of an interaction space and transverse energy extraction (with respect to the direction of translational motion of a helical electron beam). The electrode configuration has been found in the gyrotron with an operating frequency 75 GHz, where the formed electron beam has a velocity spread of ∼10%, the rotational energy fraction is 50%, and the beam profile is weakly distorted. When the voltage is 12 kV and the beam current is 1 A, the electron beam under study is demonstrated to excite the single-mode generation with an efficiency of up to 15% in the gyrotron’s operating space produced by the planar waveguide.

Low-Voltage Cyclotron Resonance Maser

The gyrotron, which is the most powerful cyclotron resonance maser (CRM), is an extremely effective device to generate high-power microwave radiation. It is used in microwave heating of thermonuclear plasma, radar, and other industrial applications. However, the gyrotron has one basic problem. It requires relativistic (very high energy) electrons. These require very high voltages to produce, and, in turn, relativistic electrons produce intense and dangerous X-rays in the collector region. In this paper, we discuss an alternate method of operation that does not require high voltages. We have also constructed a low-voltage CRM that operates at 2.2 kV and produces 8 GHz at a magnetic field of 0.3 T. In principle, the device should operate at even lower voltages.

Research Results and Applications of Torch Discharge in the Goubau Line

The waveguide-coaxial microwave setup for an excitation of erosion torch discharge at the end of a single-conductor Goubau line in open air has been developed. Properties of erosion torch discharge and surface wave propagation in the Goubau line have been investigated. Two modes of the setup operation when the line acts as a spike antenna and also as surface waveguide supporting microwave energy transmission to plasmoid were considered. Aspects of setup application for refractory metal thin-film spattering, utilization of natural gases, and coal-water mixture firing were discussed.

A novel THz-band double-beam gyrotron for high-field DNP-NMR spectroscopy

We present the first experimental results of the study on a novel second harmonic THz-band double-beam gyrotron. The tube has demonstrated a stable single-mode operation with output parameters that are appropriate for the next-generation 1.2 GHz dynamic nuclear polarization-nuclear magnetic resonance spectroscopy. Besides the design mode (TE8,5), a series of other fundamental and second harmonic modes have been excited. This makes the new gyrotron a versatile radiation source, which can be used also in other applications of the high-power science and technologies.

Development of compact CW clinotrons for DNP-NMR spectroscopy

Numerical simulations of the electromagnetic systems for both 130 GHz and 263 GHz CW clinotrons have been performed. Experimental results of the 130 GHz CW clinotron hot-testing are presented. Potentials of significant output power magnification and extension of operating frequency range in clinotrons has been shown by increasing the electron beam current up to 150 mA.

Sub-THz CW clinotron oscillators with increased output power

The parameters of sub-THz CW clinotrons developed in IRE NAS of Ukraine are presented. The output power increase is achieved using optimized magnetic focusing system. Multiple-stage grating is proposed as a part of clinotron electromagnetic structure to provide the feedback by hybrid surface-volume modes that results in ohmic losses decrease in THz range. Comparison of simulation and experimental results of the interaction of the intense ribbon electron beam with hybrid surface-volume modes of sub-THz clinotron oscillator have been resented and discussed.

Long-Living Plasma Excited by Electric Discharge in Water

Excitation of long-living plasmoids in open air is a very interesting phenomenon due to its physical origins and possible applications for energy conservation and lossless transmission. This paper describes the experimental setup for the excitation of long-living plasma formations under the action of electrical discharge in water. It also provides the measured characteristics of the plasmoids and the discussion of the physical model.

Excitation and observation of ball-lightning type spherical formations

Experimental research results of discharge processes in liquids are presented. Excitation conditions of spherical plasma formation are met on the water-air boundary. Theoretical model of complex wave excited in layer media, is proposed to explain the plasmoid existence. It is shown that such structure can be formed by standing acoustic wave, which occurs during electrical discharge in water container.

Adiabatic Magnetron Injection Gun for Low-Voltage Gyrotron

Adiabatic magnetron injection gun for low-voltage gyrotron is developed and the test results are presented in this paper. MIG was developed for operation in anode range from 2 to 6 kV and electron current upto 300 mA with pinch parameter varying from 2 to 4. Experiments on optimization of both gun and cavity parameters for a low-voltage gyrotron oscillator are carried out.