Vladislav Yu. Zaslavsky

Improvement of Stability of High Cyclotron Harmonic Operation in the Double-Beam THz Gyrotrons

A double-beam scheme of a short-wavelength gyrotron operating at the second cyclotron harmonic is studied both within the framework of the averaged self-consistent approach and using 3-D particle in cell simulations. The analysis shows that the introduction of an additional generating electron beam allows drastically increasing the operating current of a second-harmonic gyrotron with the simultaneous suppression of self-excitation of spurious modes at the fundamental harmonic. As a result, the radiated power of a double-beam gyrotron exceeds the power of a single-beam gyrotron by a factor of four. The developed concept makes it possible to realize high-power (several hundred watts) single-mode gyrotrons in the 0.7-1.0-THz frequency range.

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.

Cherenkov oscillators with two-dimensional distributed feedback

Possibility to use a 2D distributed feedback for generation of spatially coherent radiation by a rectilinear electron beams in Cherenkov type devises is discussed. Theoretical and experimental studies of a Ka-band coaxial BWO with external 2D Bragg structure which operates as a synchronizer are presented.

Quasi-optical theory of surface-wave oscillators with one- and two-dimensional periodic structures

Summary form only given. Within the frame of quasi-optical approach we develop a nonlinear theory of relativistic surface wave oscillators. Our theory provides a possibility to describe both linear and nonlinear stages of formation of evanescent slow-wave structure and include evaluation of threshold conditions, electron efficiency and output power.

Terahertz band superradaince of extended electron bunch moving above periodically corrugated surface

Summary form only given. Recently a significant progress has been achieved in generation of electromagnetic pulses in centimeter and millimeter waveband based on superradiance (SR) from high-current extended electron bunches formed by explosive emission cathodes [1]. Generated pulses are characterized by record-breaking (gigawatt) peak power and ultra-short (subnanosecond) duration. At particle energies up to 300 keV, current up to 1 kA and the bunch durations up to 1 ns the most effective mechanism of SR pulses generation is the Cherenkov one, when a rectilinearly moving electrons interacts with the backward wave propagating in a periodically corrugated waveguide with period and diameter ∼ λ. Advance of Cherenkov SR sources into short wave ranges needs fabrication of periodic micro- and nanostructures that can be fabricated based on modern technologies. Nevertheless in these wavebands waveguides with large oversized factor should be used, and process of SR needs special investigation.

FEM with high-selective Bragg resonator based on coupling of propagating and cutoff waves

Bragg FEM with a two-mirror resonator including advanced Bragg structure based on coupling of propagating and quasi-cutoff waves was studied. Implication of the cutoff wave into the feedback loop improves selectivity of the Bragg resonators over transverse coordinates and allows advance of FEM into short wavelengths up to THz-band. Operability of Bragg resonator of a novel type has been demonstrated in Ka-band JINR-IAP FEM.