A. A. Levchenko

Quasiadiabatic decay of capillary turbulence on the charged surface of liquid hydrogen.

We study the free decay of capillary turbulence on the charged surface of liquid hydrogen. We find that decay begins from the high frequency end of the spectral range, while most of the energy remains localized at low frequencies. The apparent discrepancy with the self-similar theory of nonstationary wave turbulent processes is accounted for in terms of a quasiadiabatic decay wherein fast nonlinear wave interactions redistribute energy between frequency scales in the presence of finite damping at all frequencies. Numerical calculations based on this idea agree well with experimental data.

Excitation and Detection of Nonlinear Waves on a Charged Surface of Liquid Hydrogen

A new technique for exciting nonlinear waves on a charged surface of liquid hydrogen is described. Methods of optical detection of surface oscillations in experiments on capillary turbulence at frequencies of up to 10 kHz are discussed. The results of a study of capillary waves on the surface of liquid hydrogen are presented.

Measurement of the boundary frequency of the inertial interval of capillary wave turbulence at the surface of liquid hydrogen

The boundary frequency was experimentally measured for the upper edge of an inertial interval corresponding to the Kolmogorov spectrum for energy distribution over the oscillation frequencies at the surface of liquid hydrogen. It is shown that the dependence of boundary frequency ωb on the wave amplitude ηp at the pump frequency ωp is well described by the power law ωb∼ηp4/3ωp23/9.

The turbulence of capillary waves on the surface of liquid hydrogen

It is experimentally demonstrated that the surface excitation of liquid hydrogen at a low frequency results in the turbulent mode in a system of capillary waves. The experimental results are in good agreement with the theory of weak wave turbulence. The pair correlation function of the surface deviations is described by the exponential function ωm. The exponent m decreases in magnitude from m=−3.7±0.3 to −2.8±0.2 when the pumping at a single resonant frequency changes to broadband noise excitation. Measurements are made of the dependence of the boundary frequency ωb of the upper edge of the inertial range in which the Kolmogorov spectrum is formed on the wave amplitude ηp at the pumping frequency. It is demonstrated that the obtained data are well described by a function of the form ωb∝ηp4/3ωp23/9.

Static phenomena at the charged surface of liquid hydrogen

Evolution of the shape of the equipotentially charged surface of the liquid hydrogen layer covering the lower plate of a horizontally arranged flat diode in increasing external stretching electric fields has been studied experimentally for the first time. Reconstruction of a flat charged surface (formation of a stationary hump) at voltages higher than a certain critical value Uc1 is observed under conditions of total compensation of the electric field in the bulk of the liquid by a surface charge. It is shown that the transition of the flat charged surface to the reconstructed state is a phase transition close to a second-order transition. The height of the hump is found to increase with voltage, the reconstructed surface loses its ability at a voltage Uc2>1.2Uc1, and a streamed discharge is observed. Evolution of the shape of a charged droplet of constant volume suspended from the upper plate of a diode is studied with increasing electric field under the conditions when the forces of gravity and stretchi...

Negative charges in liquid hydrogen and deuterium

The temperature and pressure dependence of the mobilities of negative charges injected into liquid hydrogen and deuterium have been measured. We propose the existence of two types of charge carriers in liquid parahydrogen. One is a bubble with an electron inside while the other has higher mobility. Relaxation of the current through liquid hydrogen was observed. It is suggested that in liquid and solid hydrogen under β-irradiation neutral complexes are created which can trap the negative charges and have a lifetime of about 10 hours.

Structural transitions in ice samples at low temperatures and pressures

The structure of ice samples formed in the decay of a water impurity gel at temperatures above 4 K and atmospheric pressure has been examined. The X-ray diffraction analysis indicates that three phases coexist in the initial sample at temperatures of 85–110 K. These phases are amorphous ice occupying up to 30% of the sample volume, cubic-phase ice Ic metastable at low pressures (∼60%), and normal hexagonal ice Ih (≤6%). The characteristic sizes of crystals of the cubic and hexagonal phases are about 6 and 30 nm, respectively. The amorphous phase at annealing above 110 K is gradually transformed to the crystalline phase both cubic and hexagonal. This transition is accompanied by two processes, including a fast increase in the sizes of cubicphase nanocrystals and the partial transition of the cubic phase Ic to the hexagonal one Ih. Hexagonal ice Ih prevails in the bulk of the sample above 200 K.

Evolution of a turbulent cascade on the surface of liquid hydrogen under a change in the spectral characteristic of an exciting force

The modification of the turbulent cascade in a system of capillary waves on the surface of liquid hydrogen under a change in the spectral width of exciting noise has been experimentally studied. The correlation function Iω of the deviations of the surface of liquid hydrogen from equilibrium under broadband excitation is a monotonically decreasing function of frequency. The distribution Iω in the inertial range is well described by the power function ω−m with the exponent m close to 17/6. In the presence of narrowband excitation, a chain of peaks appears on the cascade Iω; the positions of the peaks are described by a power function of frequency with the exponent m = 3.8 ± 0.1.

Suppression of High-Frequency Turbulent Oscillations of the Fluid Surface by Additional Low-Frequency Pumping

The dynamics of establishing steady-state turbulent cascade has been studied in a system of capillary waves on the surface of liquid hydrogen after additional pumping whose frequency is lower than the frequency of the main pumping is switched off/on. It has been found that, when the additional low-frequency pumping is switched on, the amplitude of waves in the high-frequency part of the turbulent spectrum decreases, which gives rise to the narrowing of the inertial frequency range. The experimental data qualitatively agree with the numerical calculations performed in the kinetic-equation approximation including the viscous damping of waves.

Generation of a vortex flow by waves on the surface of a liquid

The formation of a vortex flow in a vessel with a liquid undergoing harmonic oscillations in a vertical direction has been studied experimentally. It has been found that the vortex flow does not occur in a cylindrical vessel until the amplitude of the oscillations exceeds a threshold value, at which the Faraday parametric instability develops and azimuthal modes emerge on the surface. The vortices appear in a square vessel and in a cylindrical vessel with broken symmetry at amplitudes below the parametric instability threshold. The formation of a vortex flow is presumably caused by the interaction of surface waves propagating at an angle with respect to each other.