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Y. Bliokh

Publications and source records attributed to Y. Bliokh.

9 recordsLinked to original sources
arXiv2025

The Brillouin flow in a smooth-bore magnetron fed by split cathode

Explosive emission from an axial cathode of a relativistic magnetron produces plasma, the radial expansion of which can cause pulse shortening. In a split cathode fed magnetron, the electron source and its explosive plasma are outside the space where the high power microwave producing interaction occurs. This electron source is a longitudinal annular electron column expanding radially. This expansion simulates the radial emission from an axial cathode. A mathematical model and numerical simulations are presented which enable to calculate the parameters of this electron column, its density, angular velocity, and potential distributions. The Hull Cutoff and Buneman-Hartree modified conditions applicable to the split cathode magnetron are formulated.

physics.plasm-ph↗
arXiv2024

Evolution of the electron distribution function during gas ionization by a sub-nanosecond microwave pulse of hundreds MW power

The electron velocity distribution function in the plasma, formed by gas ionization with a sub-nanosecond, hundreds of megawatts power level microwave pulse, is studied by a theoretical model and by numerical 3D simulations, the results of which agree well and show that the distribution varies along the pulse as a decreasing power-law function at the rear of the pulse. Experiments performed in a waveguide filled with helium gas confirm that energetic (from several keV to several tens of keV) electrons remain in plasma long after the pulse has crossed the experimental volume. These electrons continue the gas ionization over extended times up to tens of nanoseconds.

physics.plasm-ph↗
arXiv2022

Observation of the diocotron instability in a diode with split cathode

Diocotron instability has been observed in the pure electron plasma formed in a split cathode coaxial diode. This plasma consists of electrons, trapped in the longitudinal potential well between the two parts of the cathode. The mathematical model of the electron squeezed state, which allows calculation of the equilibrium plasma density, is presented. The model is applied in a comprehensive analysis of experimental data and the presence of the diocotron instability is unambiguously confirmed.

physics.plasm-ph↗
arXiv2021

Squeezed State of an Electron Cloud as a "Quasi-Neutral'' One-Component Plasma

We present a one-dimensional model which gives a novel physical interpretation to the specific state of an ensemble of electrons continuously injected into an electrostatic potential well immersed in a strong applied magnetic field preventing radial expansion. When the space-charge field of the electrons accumulated in the potential well compensates the external electrostatic field, a force-free steady-state of the electron cloud forms. This state of equilibrium is known in another context as a squeezed state of an electron beam. It is shown that the spatial distribution of the electron number density in this steady-state correlates with the shape of the potential well. Perturbations of the steady-state propagate along the electron cloud in the form of Trivelpiece-Gould modes.

physics.plasm-ph↗
arXiv2018

Temporal variation of the spectrum of continuously-pumped random fiber laser. Phenomenological model

A temporal variation of a spectrum of excited modes in a continuously pumped erbium-doped random fiber laser (RFL), based on randomly distributed Bragg gratings, is studied. Developed phenomenological theoretical model assumes hard excitation mechanism of the eigenmodes instability. The model explains qualitatively peculiarities of the spectrum variation, observed experimentally.

physics.optics↗
arXiv2016

Transmission Resonances Anomaly in 1D Disordered Quantum Systems

Connections between the electron eigenstates and conductivity of one-dimensional disordered electron systems is studied in the framework of the tight-binding model. We show that for weak disorder only part of the states exhibit resonant transmission and contribute to the conductivity. The rest of the eigenvalues are not associated with peaks in transmission and the amplitudes of their wave functions do not exhibit a significant maxima within the sample. Moreover, unlike ordinary states, the lifetimes of these `hidden' modes either remain constant or even decrease (depending on the coupling with the leads) as the disorder becomes stronger. In a wide range of the disorder strengths, the averaged ratio of the number of transmission peaks to the total number of the eigenstates is independent of the degree of disorder and is close to the value $\sqrt{2/5}$, which was derived analytically in the weak-scattering approximation. These results are in perfect analogy to the spectral and transport properties of light in one-dimensional randomly inhomogeneous media, which provides strong grounds to believe that the existence of hidden, non-conducting modes is a general phenomenon inherent to 1D open random systems, and their fraction of the total density of states is the same for quantum particles and classical waves.

cond-mat.mes-hall↗
arXiv2011

X-band microwave generation caused by plasma-sheath instability

It is well known that oscillations at the electron plasma frequency may appear due to instability of the plasma sheath near a positively biased electrode immersed in plasma. This instability is caused by transit-time effects when electrons, collected by this electrode, pass through the sheath. Such oscillations appear as low-power short spikes due to additional ionization of a neutral gas in the electrode vicinity. Herein we present first results obtained when the additional ionization was eliminated. We succeeded to prolong the oscillations during the whole time a positive bias was applied to the electrode. These oscillations could be obtained at much higher frequency than previously reported (tens of GHz compared to few hundreds of MHz) and power of tens of mW. These results in combination with presented theoretical estimations may be useful, e.g., for plasma diagnostics.

physics.plasm-ph↗
arXiv2004

Observation of a New Mechanism of Spontaneous Generation of Magnetic Flux in a Superconductor

We report the discovery of a new mechanism of spontaneous generation of a magnetic flux in a superconductor cooled through $T_c$. The sign of the spontaneous flux changes randomly from one cooldown to the next, and follows a Gaussian distribution. The width of the distribution increases with the size of the temperature gradient in the sample. Our observations appear inconsistent with the well known mechanisms of flux generation. The dependence on the temperature gradient suggests that the flux may be generated through an instability of the thermoelectric superconducting-normal quasiparticle counterflow.

cond-mat.supr-con↗