It is shown that in an electrokinetic acoustoelectric transducer, when a constant DC electric field (pump voltage) is applied during reception of an acoustic signal, it becomes possible to retransmit the initial external acoustic field. This is due to the presence of simultaneously reverse electrokinetic phenomena in the transducer: electroosmosis and flow potential. The necessary theoretical substantiation of this phenomenon is presented. The data of a full-scale experiment confirming the theory are presented. Keywords: acoustoelectric conversion, electrokinetic phenomena, current potential, energy pumping, electrokinetic repeater.

A mathematical model of an acoustoelectric transducer based on the use of the electrokinetic phenomenon of the flow potential is proposed. It is shown theoretically that the flow potential increases in proportion to the strength of the constant electric pumping field, which is confirmed experimentally. The described converter has variable sensitivity. Rather large values of the sensitivity of an electrokinetic microphone have been obtained experimentally. The results of the work can be used in the design of acoustoelectric transducers. Keywords: Acoustoelectric conversion, Electrokinetic phenomena, Current potential, Flow potential hydrodynamics, Energy pumping. Electrokinetic microphone sensitivity.

A mathematical model of operation of an acoustoelectric converter, based on the electrokinetic phenomenon of flow potential, is proposed. It is shown theoretically that the flow potential increases in proportion to the strength of the pumping dc electric field. This is also confirmed experimentally. It is shown that the described converter exhibits variable sensitivity. The presence of saturation in this process, caused by the physics of the process (its nonlinearity and occurrence of turbulent liquid motion in the converter body), is revealed experimentally. The acoustoelectric-converter theory, based on the electrokinetic phenomenon of flow potential, is identical to the electroacoustic transformation theory, based on the electrokinetic phenomenon of electro-osmosis, which is inverse to the flow potential. The measured converter sensitivity exceeds those of analogs. The results can be used in theory and in practice in designing reversible electroacoustic and acoustoelectric converters.

Показано, что в электрокинетическом акустоэлектрическом преобразователе при приложении постоянного электрического поля (напряжения накачки) в процессе приема акустического сигнала возникает возможность ретрансляции исходного внешнего акустического поля. Это происходит вследствие наличия в преобразователе одновременно обратных электрокинетических явлений: электроосмоса и потенциала течения. Приведены необходимые теоретические обоснования этого явления. Представлены данные натурного эксперимента, подтверждающие теорию. Ключевые слова: акустоэлектрическое преобразование, электрокинетические явления, потенциал течения, накачка энергии, электрокинетический ретранслятор.

The paper presents the results of measuring the cross section of the spin-exchange broadening of the magnetic resonance line in the Zeeman structure of the ground state of cesium. The analysis of the influence of measurement errors of parameters on the result was carried out, the values of the concentration of cesium vapors were refined by independent measurements.

The cross section of spin-exchange broadening of the magnetic-resonance line in the Zeeman structure of the cesium ground state has been measured. The influence of the error in measuring the parameters on the obtained result has been analyzed, and the cesium-vapor concentrations have been refined using independent measurements.

The paper theoretically and experimentally investigates the fundamental limitations imposed by spin (or atomic) quantum projection noise on the sensitivity of optical quantum sensors based on thermal atoms (this class of devices includes frequency standards, magnetometers, and gyroscopes using optical detection of electron paramagnetic resonance). The effect of increasing the rms amplitude of the projection noise in the magnetometric scheme under the influence of strong optical pumping is demonstrated, its explanation is proposed and experimentally tested - it is shown that in a wide range of pump intensities this effect is explained by the invariance of the projection noise integral power with respect to the magnetic resonance line width. An experimental study of the parameters of projection noise in a magnetometric quantum sensor was carried out, recommendations were given for optimizing the sensor parameters.

We demonstrate the possibility of using vertical-cavity surface emitting lasers with intracavity contacts and a rhomboidal oxide current aperture for creating compact optically pumped 133 Cs atomic magnetometer operating in non-zero magnetic fields, which is promising to use in magnetoencephalographic systems. The magnetic resonance parameters were studied in a two-beam MX optically pumped magnetic field sensor scheme based on the effect of the magnetic resonance line narrowing at high laser pumping and high concentrations of alkali-metal atoms. The ultimate sensitivity of OPM was estimated by the ratio of the magnetic resonance steepness to the probe light shot noise level. It is shown that a magnetic sensor based on the vertical-cavity surface emitting lasers and a compact (0.125 cm 3 volume) Cs vapor cell can achieve a shot noise-limited sensitivity better than 15 fT in 1 Hz bandwidth. Developed intracavity contacted VCSELs suitable for use in compact atomic magnetometers for magnetoencephalographic systems.

Spin exchange is one of the effective processes for obtaining spin-polarized atoms. Such mechanism of spin polarization is usually used to transmit and observe the longitudinal (along magnetic field) component magnetization of atoms. However, spin-exchange collisions can also lead to the transfer of the transverse component of magnetization, which occurs when the atoms involved in the collisions are exposed to an alternating resonant magnetic field. This article describes experiments to observe the transmission of transverse magnetization between alkali metal atoms Cs-133 and Rb-85 in spin-exchange collisions. The calculation of the spin exchange in a mixture of Cs and Rb under magnetic resonance conditions gave a qualitative agreement with the experimental results.

A method is proposed for precise measurement of the deflection of the magnetic field vector. This method does not require the use of artificially created magnetic fields; a scheme of an all-optical quantum sensor based on this method has been experimentally tested. The proposed method does not involve the use of radiofrequency field, since it is based on measuring the polarization properties of an oriented paramagnetic medium and does not use the phenomenon of magnetic resonance. However, the inclusion of a resonant radiofrequency field into the proposed scheme allows the information about the angle of the magnetic field vector to be supplemented with information about its module. The proposed method maintains operability and provides the same angular sensitivity of the order of tens of angular milliseconds in a wide range of magnetic fields, from hundreds of nT to hundreds of µT and above.

We consider the effect of the polarization characteristics of probe light on the signal of optically detected magnetic resonance in quantum sensors, including quantum magnetometers based on the phenomenon of electron paramagnetic resonance and quantum gyroscopes employing both the electron and nuclear magnetic resonance. Relationships between the magnetic resonance signal magnitude and parameters of the optical system elements, which are based on the Stokes–Mueller formalism, are derived and verified. It is found that the main destructive influence in the signal in a standard two-beam scheme is produced by phase delays introduced by both metallic and dielectric mirrors. Methods for compensation of this destructive influence are proposed and verified.

Using the experimental setup that allows the Earth's magnetic field to be screened up to 1-100 nT, we found features of the microscopic fungi growth pattern, namely, the appearance of spiral growth instead of fractal. A hypothesis was put forward on the participation of a charged protein cluster - Spitzenkorper, located in the apical zone of cells, in the reorganization of fungal growth.

AbstractAn experiment on the observation of the effect of transmitting the transverse spin magnetization in spin-exchange collisions of cesium atoms with optically aligned rubidium atoms is described.

The principal possibility of creating optically pumped compact magnetic sensor for MEG operating in a wide magnetic field range is experimentally proved.

The optical orientation of the angular momenta of alkali atoms in the presence of a buffer gas (molecular nitrogen) has been studied experimentally. It has been shown that, even at a low concentration of molecular nitrogen in the cell, the excitation of 133 Cs atoms from the lower hyperfine level with F = 3, which belongs to the ground 2 S 1/2 state, results in a larger amplitude of the magnetic resonance than the excitation from the hyperfine level with F = 4. This result has been theoretically explained under the assumption that the spin state of the alkali atomic nucleus does not change at collision with a nitrogen molecule, which is accompanied by a nonradiative transition of the alkali atom from the excited 2 P 1/2 state to the ground 2 S 1/2 state.

An experiment on the observation of the effect of transmitting the transverse spin magnetization in spin-exchange collisions of cesium atoms with optically aligned rubidium atoms is described.

The paper reports the results of an experiment on searching for the neutron electric dipole moment (EDM), performed on the ILL reactor (Grenoble, France). The double-chamber magnetic resonance spectrometer (Petersburg Nuclear Physics Institute (PNPI)) with prolonged holding of ultra cold neutrons has been used. Sources of possible systematic errors are analyzed, and their influence on the measurement results is estimated. The ways and prospects of increasing accuracy of the experiment are discussed.

This paper discusses the indirect orientation of Cs atoms, which was observed for the first time in our early works in a helium–cesium plasma discharge with use of an indirect registration method. We propose an explanation for the unusually small ratio of the magnetic resonance signals from Cs and metastable He atoms under condition of optical orientation of He atoms.

A research program aimed at studying fundamental interactions by means of ultracold and polarized cold neutrons at the GEK-4-4′ channel of the PIK reactor is presented. The apparatus to be used includes a source of cold neutrons in the heavy-water reflector of the reactor, a source of ultracold neutrons based on superfluid helium and installed in a cold-neutron beam extracted from the GEK-4 channel, and a number of experimental facilities in neutron beams. An experiment devoted to searches for the neutron electric dipole moment and an experiment aimed at a measurement the neutron lifetime with the aid of a large gravitational trap are planned to be performed in a beam of ultracold neutrons. An experiment devoted to measuring neutron-decay asymmetries with the aid of a superconducting solenoid is planned in a beam of cold polarized neutrons from the GEK-4′ channel. The second ultracold-neutron source and an experiment aimed at measuring the neutron lifetime with the aid of a magnetic trap are planned in the neutron-guide system of the GEK-3 channel. In the realms of neutrino physics, an experiment intended for sterile-neutrino searches is designed. The state of affairs around the preparation of the experimental equipment for this program is discussed.

We are the first to have observed magnetic resonance signals from atoms of 85Rb and 87Rb isotopes when using the indirect optical orientation in conditions of helium–rubidium gas discharge plasma. An anomalously small ratio of magnetic resonance signals from isotopes of rubidium and metastable helium upon optical orientation of 4Не atoms has been detected. The experimental results have been considered theoretically, and an explanation of the observed anomaly in the signals is presented.Z