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This paper highlights the most important results achieved at the spherical tokamak Globus-M2 with a high magnetic field. This paper also covers the most important topics of fusion research: thermal energy confinement in regimes with neutral beam injection, toroidal Alfvén eigenmode and correspondent fast ions confinement issues, L-H transition, turbulence suppression and edge-localized modes' behavior, experimental and theoretical study of regimes with nitrogen seeding that allow to significantly reduce thermal loads on the divertor plates, and experiments and simulations of lower hybrid current drive. The research results provide the basis for the next step toward a fusion neutron source—the development of the Globus-3 spherical tokamak. [ABSTRACT FROM AUTHOR]

We determined the fundamental parameters and analysed the chemical composition for 20 G and K giants within 150 pc from the Sun, for which the magnetic fields B max from 0.3 to 98.6 G have been detected. Abundances of 18 chemical elements from lithium (Z = 3) to hafnium (Z  = 72) are derived. From infrared CN molecular lines, the nitrogen abundance and the carbon isotope ratio 12C/13C are determined. The low values 12C/13C = 7–26 for most of the giants prove that they were passed through the deep convecting mixing during the first dredge-up (FDU) evolutionary phase. Lithium is detected in spectra of 16 of 20 giants studied. The presence of lithium in atmospheres of giants passed through the deep mixing during the FDU phase contradicts the theory. The pronounced correlation between the [N/C] and [N/O] values is found, which has an evolutionary nature. A comparison of this relation with theoretical models calculated for rotating stars shows that it reflects mainly the dependence of these two values on the initial rotational velocity. The total C + N + O abundance that should be constant during the star's evolution is found to be correlated with [Fe/H]. This correlation can be explained partially by the known [O/Fe] versus [Fe/H] relation. The anticorrelation between the [El/Fe] and [Fe/H] values for rare earth (RE) elements is obtained. The relations for both the sum C + N + O and the RE elements reflect the initial chemical composition of the giants. No marked systematic differences in the element abundances are found between the magnetic and non-magnetic giants. [ABSTRACT FROM AUTHOR]

The thermal energy stored in plasma , normalized internal plasma inductance and current beta are calculated via the free-boundary equilibrium PET code. The equilibrium reconstruction algorithm is iterative method of minimizing two parameters, the distance between the reconstructed plasma boundary and that simulated by the PET code, as well as the difference between the plasma diamagnetic flux from PET and the experimental one. The discharges from the Globus-M2 tokamak with a toroidal magnetic field up to 0.9 T and a plasma current of 0.3–0.4 MA in a mode with auxiliary heating by two atomic injectors are analyzed. The possibility of using approximate formulas for estimating and is considered. The measured diamagnetic flux is used to determine and then to calculate . The normalized internal plasma inductance is additionally determined from the measured vertical magnetic field under the assumption that . [ABSTRACT FROM AUTHOR]

A multi-diagnostic study of the fast ion losses and redistribution during toroidal Alfvén eigenmodes at the Globus-M and Globus-M2 spherical tokamaks was performed. Mode amplitude and frequency evolution are discussed. Local energy-resolved spatial transport was examined using an active neutral particle analyzer. Losses and transport dependences on the mode amplitude were obtained. The change in the ion transport with the increase in plasma current and toroidal magnetic field is reported. The experimental data are compared with the modeling results. [ABSTRACT FROM AUTHOR]

Among the peripheral instabilities observed at the Globus-M2 tokamak, two types of edge localized modes (ELMs) are brought into focus: ELMs synchronized and desynchronized with the sawtooth oscillations. The desynchronized ELMs appear in regimes that are characterized by high values of pressure in the pedestal, pped ≥ 3 kPa, and they are observed in discharges with the toroidal magnetic field BT > 0.6 T and plasma current IP > 0.3 MA. The desynchronized ELMs belong to the type-III/V with the dominating effect of the peeling mode. The synchronized ELMs were observed in a wider range of discharge parameters, including at BT < 0.6 T and IP < 0.3 MA. Calculations of the stability of the peeling-ballooning (PB) mode showed that at pedestal width ψnorm = 0.09 and pped > 3.5 kPa, destabilization of PB modes is possible without additional influence. Experimental data shows that the microtearing mode plays a dominant role in the pedestal. The microtearing mode does not allow the pedestal at Globus-M2 tokamak to reach the state of the unstable kinetic ballooning mode (KBM), which explains the low predictive power of the EPED model at this tokamak. [ABSTRACT FROM AUTHOR]

The engineering part of the GLOBSYS code is presented, and the parameters of the Globus-3 facility, which is a development of the Globus program, are analyzed. The facility is primarily designed to provide a long pulse, a large toroidal magnetic field and strong heating. The concepts of searching for Globus-3 parameters under physical and engineering limitations are described. Obviously that reliable confinement and a large part of noninductive current are necessary to ensure existence of a plasma for a long time. Engineering constraints are involved in the choice of parameters in a more complex way: in some cases, it is overheating of the coils, in other cases, it is the total power supply, or the limit on the flux provided by the ohmic solenoid, or the strength of the constructions. The parameters of the Globus-3 spherical tokamak were preliminarily selected for the cases of a "warm" copper EMS (Electromagnetic system) and the EMS precooled to liquid nitrogen temperature. The exceeding of the duration of the plasma current plateau Δtplateau over the characteristic settling time of the plasma profiles τL/R was chosen as the key condition. At values of the toroidal magnetic field Bt0 = 3 T, the condition Δtplateau > τL/R cannot be attained even for precooled EMS. At Bt0 = 2 T, only options with precooled EMS can be considered acceptable, but the facility dimensions are fairly large. For the field Bt0 = 1.5 T, the options with "warm" EMS correspond to the duration of the plasma current plateau ~3 s (Δtplateau/τL/R ~ 1–1.5). In the case of precooled EMS, the duration of the plateau can increase to 12–13 s (Δtplateau/τL/R ~ 5). In the latter case, as a basis for further development of the Globus-3 facility, options with the following geometric dimensions are reasonable: R0 ~ 0.6–0.7 m, a ~ 0.35–0.4 m, А ≤ 1.7–1.8, k95 ~ 1.7–1.8. The minimum allowable value of the plasma current under the condition of effective absorption of the input power of neutral injection has been calculated. In the Globus-3 facility, Ip ≈ 0.8 MA was chosen as the base value. [ABSTRACT FROM AUTHOR]

This paper is devoted to a comprehensive study on a new type of microwave structures named magnetoelectric (ME) gradient structures. These structures are studied in this paper to understand the possibilities and application principles in feasible devices. The structure under study was calculated at different values of the applied electric field and different values of the relative permittivity of the artificial dielectric layer. The layered multiferroic structure in inhomogeneous electric and magnetic fields was calculated on the basis of the previously proposed mathematical model. The eigenwaves spectrum for several considered cases was the result of the performed calculation. The concept of using ME gradient structures in the design of electronically controlled microwave devices is formed on the basis of the results of a numerical experiment. Structures of this type will preferably be used in electronically controlled devices for the directional transmission of microwave signals, as it was shown in the theoretical part of the paper. [ABSTRACT FROM AUTHOR]

We present new information on the development of Alfvén modes on the Globus-M2 spherical tokamak. Data have been obtained using a V-band Doppler reflectometer with probing radiation frequencies from 50 to 75 GHz. Аs a multifrequency source of probing radiation, a microwave harmonic synthesizer has been used. As a result of using the new reflectometer, the toroidal Alfvén mode localization in a magnetic field of 0.5 T has been obtained. The spectral components of the Alfvén mode with Doppler frequency shifts caused by toroidal plasma rotation have been registered. In the central regions of the discharge, so-called "Alfvén cascades" have been investigated. [ABSTRACT FROM AUTHOR]

On the spherical tokamak Globus-M2 in discharges with toroidal magnetic field of 0.7 T by means of magnetic probes and a number of other diagnostics during neutral beam injection at the current ramp up stage, magnetic field oscillations in the range of 100–300 kHz having their frequency increasing in time, had been observed. Eigenmodes with wavenumbers n = 1–3 and m = 2–4 were being registered. These oscillations were identified as Alfvén cascades. By means of multi-channel fluctuation reflectometer, observed eigenmodes were found to be localized near the magnetic shear reversal radius. Application of MHD-spectroscopy technique allowed us to determine safety factor temporal evolution and experimental values are in well agreement with modelling results, provided by ASTRA transport code. [ABSTRACT FROM AUTHOR]

In this work, we report on the sensitivity of photo-electrical detection of magnetic resonances (PDMR) for magnetometry measurement using low density nitrogen vacancy (NV) ensembles in CVD-grown diamond. We demonstrate that the selection of the laser excitation wavelength is of importance for achieving optimal magnetic field sensitivity. The PDMR sensitivity obtained using a yellow-green (561 nm) laser surpasses the performances of a green laser (532 nm), by suppressing the photoionization of defects other than NV centers (such as P1 centers). It consequently allows to carry out the PDMR measurements at lower laser powers with increased magnetic resonance contrast. Noticeably for both the green and the yellow-green illuminations, PDMR leads to an improved sensitivity to magnetic fields in the selected conditions compared to optically detected magnetic resonance. [ABSTRACT FROM AUTHOR]

We present a theoretical investigation of the Goos-Häanchen effect upon light reflection from a heterostructure consisting of an electro-optic film deposited on a magneto-electric film grown on a nonmagnetic dielectric substrate. It is shown that the linear magneto-electric interaction leads to an increase of the lateral shift even in the absence of any applied electric field. The presence of the electro-optic layer enables the control of the Goos-Häanchen shift and of the position of its maximum (with respect to the angle of incidence) through a variation of the magnitude and orientation of an applied electric field. It is also demonstrated that applying an external magnetic field in order to reverse the magnetization in the magnetic layer results (under the influence of the magnetoelectric interaction in the system) in a sign reversal of the lateral shift but a nonreciprocal change of its amplitude. [ABSTRACT FROM AUTHOR]

In Globus-M2 ohmic discharges with low density, by means of Mirnov coils array, magnetic field oscillations with frequencies in 1 MHz range were detected. Frequency range of these oscillations significantly exceed the range of TAE and RSAE frequencies, which were previously observed on Globus-M and Globus-M2 tokamaks, and their amplitude, contrary, turned out to be up to an order of magnitude lower. It was found that high frequency oscillations are interrelated with suprathermal electron fraction. At the same time the observed instability seems to have Alfvenic nature, since its frequency correlates well with Alfven frequency scaling. It was also found that magnetic perturbation always forms standing wave with predominantly low toroidal wavenumbers, including n = 0 structure, which makes gap (e.g. TAE) mode excitation impossible. Frequency chirping during single bursts with is consistent with hole-clump model predictions. [ABSTRACT FROM AUTHOR]

Results of experimental studies of toroidal Alfvén eigenmodes (TAEs) in the Globus-M spherical tokamak (R = 36 cm, a = 24 cm) are reported. The experiments were carried out in a wide range of plasma parameters at a magnetic field of up to 0.5 T and plasma current of up to 250 kA. Auxiliary plasma heating was performed by tangential injection of a deuterium beam with a power of Pb= 0.75 MW and particle energy of Eb = 28 keV into deuterium plasma. The experiments have shown that the TAE-induced loss of fast particles decreases with increasing plasma current and magnetic field. Using multifrequency Doppler backscattering diagnostics, it is established that the TAEs are localized at the plasma periphery. Results of simulations of the Alfvén continuum and TAE structure by means of the modified KINX and CAXE codes agree satisfactory with the experimental data on the TAE frequencies and localization. [ABSTRACT FROM AUTHOR]

Globus-M2—a new 1-Tesla spherical tokamak—was recently launched. The main features and research directions of this machine in scope of fusion–fission reactor development are described. Main results of the first experimental campaign with toroidal magnetic field up to 0.73 T and plasma current up to 0.33 MA are discussed. Significant improvement of the discharge parameters as compared to Globus-M was achieved. Plasma total stored energy higher than 7 kJ was obtained. Energy confinement time increase was consistent with predictions by spherical tokamak scalings. Toroidal Alfvén eigenmode-induced losses decrease with increase of plasma current and toroidal magnetic field. For the first time, LHCD with the toroidal wave slowing-down was successfully used at a spherical tokamak. [ABSTRACT FROM AUTHOR]

The paper presents the latest results and summarizes the study of ion heat transport in the Globus-M spherical tokamak in regimes with neutral beam injection. Ion heat transport was investigated in discharges with various toroidal magnetic fields and plasma currents. Measurements of the ion temperature were carried out using charge-exchange recombination spectroscopy and a neutral particle analyzer. Plasma simulations using transport code ASTRA have shown that ion heat transport in Globus-M is predominantly neoclassical even for low collisionality range. The local transport analysis indicates that plasma core is stable to ion scale instabilities. [ABSTRACT FROM AUTHOR]

Aim. The synthesis of two degree of freedom robust two circuit system of active shielding of magnetic field with circular spacetime characteristic, generated by overhead power lines with «triangle» type of phase conductors arrangements for reducing the magnetic flux density to the sanitary standards level and to reducing the sensitivity of the system to plant parameters uncertainty. Methodology. The synthesis is based on the multi-criteria game decision, in which the payoff vector is calculated on the basis of the Maxwell equations quasi-stationary approximation solutions. The game decision is based on the stochastic particles multiswarm optimization algorithms. The initial parameters for the synthesis by system of active shielding are the location of the overhead power lines with respect to the shielding space, geometry and number of shielding coils, operating currents, as well as the size of the shielding space and magnetic flux density normative value, which should be achieved as a result of shielding. The objective of the synthesis is to determine their number, configuration, spatial arrangementand and shielding coils currents, setting algorithm of the control systems as well as the resulting of the magnetic flux density value at the shielding space. Results. Computer simulation and field experimental research results of two degree of freedom robust two circuit system of active shielding of magnetic field, generated by overhead power lines with «triangle» type of phase conductors arrangements are given. The possibility of initial magnetic flux density level reducing and system sensitivity reducing to the plant parameters uncertainty is shown. Originality. For the first time the synthesis, theoretical and experimental research of two degree of freedom robust two -circuit t system of active shielding of magnetic field generated by single-circuit overhead power line with phase conductors triangular arrangements carried out. Practical value. Practical recommendations from the point of view of the practical implementation on reasonable choice of the spatial arrangement of two shielding coils of robust two -circuit system of active shielding of the magnetic field with circular space-time characteristic generated by single-circuit overhead power line with phase conductors triangular arrangements are given. References 32, figures 17. [ABSTRACT FROM AUTHOR]

The magnetic fields of a subterranean source observed on the Earth's surface or from the orbit of a satellite are studied. We analyze the space of all harmonic functions g in the external spherical domain, which are defined as series in a standard basis. The functions decrease at infinity; their gradients are normal to the field of directions specified at a boundary sphere, and the field of directions is determined by the gradient of a basis function f. The results can be used in the solution of the general problem in which the functions f and g are assumed to be independent of two spherical coordinates on the boundary sphere. Specific calculations were made only under the assumption of the independence of both g and f of the longitude coordinate. The known results are refined for the case in which f is the dipole or quadrupole harmonic, and a new result is obtained for the case in which f is the octupole harmonic. [ABSTRACT FROM AUTHOR]

The 2/1 tearing mode instability during the plateau phase of the plasma current time evolution has been observed since the start of the Globus-M spherical tokamak operation. Because of a small amount of shots in a database, the poloidal beta dependence of the instability growth rate had been investigated with an insufficient accuracy. In this work, a more detailed analysis has been produced that proves the fact that the observed modes can be treated as neoclassical. The saturated island width as a function of poloidal beta has been obtained; a time evolution of the magnetic island has been calculated from the Mirnov magnetic coil signals and compared to the modified Rutherford theory, and the critical magnetic island width has been found for the neoclassical tearing mode (NTM) of the Globus-M tokamak. [ABSTRACT FROM AUTHOR]

Data on the dynamics of the plasma current quench in the Globus-M tokamak are presented. The main current quench characteristics at different toroidal magnetic fields are compared. The distribution of the toroidal current induced in the vessel wall is determined from magnetic measurements, and the electromagnetic loads acting on the vessel wall during the current quench are calculated. By extrapolating the experimental data, the additional pressure on the vessel wall during the current quench in the upgraded Globus-M2 tokamak is estimated. It is shown that the current quench results in the appearance of bending stresses in the vessel domes. Using numerical simulations, it is shown that the best agreement between the measured and calculated plasma current dynamics during the current quench corresponds to the linear (in time) influx of the carbon impurity. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) is increasingly employed as a core analysis technique by the oil and gas industry. In axial profiling of petroleum reservoir core samples and core plugs, the sample of interest may frequently be much longer than the natural field of view (FOV) defined by the radio frequency (RF) sensor and region of constant magnetic field gradient. Profiling such samples with a low field MRI will result in distorted, non-quantitative axial profiles near the edge of the FOV with data from outside the desired FOV folding back into the image, when the gradient magnetic field homogenity region is shorter than the region of RF excitation. The quality of MRI as a core analysis technique is increased if imaging can be performed on intact samples with the FOV reduced to the region of interest (ROI), either to increase the image resolution or to reduce the total time for imaging. A spatially selective adiabatic inversion pulse is applied in the presence of a slice selective magnetic field gradient to restrict the FOV to an ROI that is a small portion of a long sample. Slice selection is followed by a 1D centric-scan SPRITE measurement to yield an axial fluid density profile of the sample in the ROI. By employing adiabatic pulses, which are immune to RF field non-uniformities, it is possible to restrict the ROI to a region of homogeneous RF excitation, facilitating quantitative imaging. The method does not employ conventional selective excitation, but a subtraction based on images acquired with and without adiabatic inversion slice selection. The adiabatic slice selection lends itself to a selective T2 distribution measurement when a CPMG pulse sequence follows the slice selection. The inversion pulse selects a slice on the order of 1 cm at an arbitrary position. The local T2 distributions measured are of similar quality to bulk CPMG. This method is an alternative to MRI-based techniques for T2 mapping in short relaxation time samples in porous media when T2 is required to be measured at only a few positions along the sample, and a resolution of 1 cm is acceptable. [ABSTRACT FROM AUTHOR]

This paper presents the construction and operating principle of ME current sensors and its sensitivity investigation. Sensors presented here were designed for detecting AC and DC leakage currents. It is found that the sensor sensitivity depends on design and material parameters of the ME composite and some conditions such as bias magnetic field and the sensor way. It is defined that the additional bias magnetic field of the ME current sensor should be 10 Oe to obtain high sensitivity and linearity of the sensor. The sensitivity of the sensor is 340 mV/A. [ABSTRACT FROM AUTHOR]

An impressive linear influence of a magnetic field on optically generated trap-recharging waves (TRW) has been observed in InP:Fe and GaAs:Cr. The phenomenon appears for the particular orientation of $\vec{B}$ parallel to the samples’ surface and orthogonal to the direction of the electric field $\vec{E}$ and wave vector of the TRW $\vec{K}$ . The results are qualitatively explained taking into account the Lorentz force and a pronounced inhomogeneity of the charge transport and of the TRW parameters. [ABSTRACT FROM AUTHOR]

A three-dimensional lens with magnetic field control of the index of refraction and focal length has been designed and characterized over 2-18 GHz. The lens is made of a lattice of cross-wire resonators and ferrite cubes. For the lattice without the ferrite cubes, a refractive index n ≈ -1 is measured at 11.25 GHz. With the introduction of ferrite cubes in the lattice, n could be tuned over the range -1.2 to +1.8 for nominal bias magnetic fields H. The focal point for the lens with n ≈ -1, for example, could be displaced by 2 cm by tuning H from 4100 to 4125 Oe. Theoretical estimates of the lens characteristics are in agreement with the data. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2804–2807, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23847 [ABSTRACT FROM AUTHOR]

The paper describes a diagnostic system for studying MHD plasma perturbations in the Globus-M spherical tokamak (a major radius of 0.36 m, a minor radius of 0.24 m, and an aspect ratio of 1.5). The system includes a poloidal and a toroidal array consisting of 28 and 16 Mirnov probes, respectively, as well as a 32-channel proportional soft X-ray detector. Methods are described for calculating the poloidal and toroidal numbers of the dominant helical perturbations by using data from probe measurements. Results are presented of processing the experimental data from some tokamak discharges with a plasma current of 150–250 kA, an average electron density of up to 1020 m−3, and a toroidal magnetic field of 0.4 T. Specific features of MHD perturbations and their influence on the parameters of the plasma column in different stages of a discharge are briefly discussed. [ABSTRACT FROM AUTHOR]

Magnetic-field-induced circular polarization of the photoluminescence peak related to A(+) centers in quantum wells is measured for the first time. It is shown that, in a magnetic field of 4 T, the polarization degree is as high as 13%, while the peak splitting is virtually absent. A theory describing the behavior of the spin fine structure of A(+) centers in a magnetic field is developed. Experimental results agree well with the theoretical calculations. [ABSTRACT FROM AUTHOR]

A new type of plasma source with titanium hydride granules used as a hydrogen accumulator was employed to inject a dense, highly ionized plasma jet into the Globus-M spherical tokamak. The experiments have shown that the jet penetrates through the tokamak magnetic field and increases the plasma density, without disturbing the stability of the plasma column. It is found that, when the plasma jet is injected before a discharge, more favorable conditions (as compared to those during gas puffing) are created for the current ramp-up at a lower MHD activity in the plasma column. Plasma injection at the instant of maximum current results in a more rapid growth in the plasma density in comparison to gas puffing. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The effect of magnetic phase transition on the parameters of high-temperature conversion of pulse laser radiation into the acoustic field of surface waves (SAWs) was studied. For this purpose, an experimental setup was designed and assembled. [ABSTRACT FROM AUTHOR]

As an alternative to semiconductor sensor and sensor on hermetic contacts we present sensor based on magnetoelectric effect. In researches there are used the magnetoelectric bulk composites containing 95% of yttrium-iron garnet and 5% of lead zirconate titanate (PZT) and multilayer composite material consisting of PZT and Ni 0.5 Zn 0.5 Fe 2 O 4 . The magnetoelectric sensor represents the disk or plate from the magnetoelectric material with two electrodes for connecting to the voltage meter. The action of the sensor is based on magnetoelectric interaction. The experimental model was made for determining the basic parameters of the magnetoelectric sensor and optimization of its design. [ABSTRACT FROM AUTHOR]

An explanation is proposed for the gigantic magnetoacoustic effect that we observed in KMnF[sub 3] in previous work {Kh. G. Bogdanova, V. A. Golenishchev-Kutuzov, M. I. Kurkin et al., Zh. Eksp. Teor. Fiz. 112, 1830 (1997) [JETP 85, 1001 (1997)]}. The effect entails a tenfold amplitude reduction of an acoustic pulse in a magnetic field that varies over the range 0-8 kOe. It is shown that this effect is due to the interference of two nuclear magnetoelastic waves propagating in the sample under magnetoacoustic resonance conditions, if this resonance occurs in the region of strong spatial dispersion of nuclear spin waves. The effect is said to be gigantic because it exceeds in magnitude the magnetoacoustic effects observed previously in magnetically ordered materials even though it is due to nuclear magnetism, which is 10[sup 5] times weaker than electronic magnetism. We observe a concomitant anomalous dependence of the dispersion of the velocity of sound on the external magnetic field. [ABSTRACT FROM AUTHOR]

The NMR spectrum of the quasi-one-dimensional easy-plane antiferromagnetic CsMnBr[sub 3], which has trigonal spin lattice, is investigated in detail. The measurements were performed on a wide-band NMR decimeter microwave-band spectrometer over a wide range of magnetic fields at temperatures 1.3–4.2 K. All three branches of the NMR spectrum previously found by us [JETP Lett. 64, 225 (1996)] are severely distorted because of the dynamic interaction with the Goldstone mode in the antiferromagnetic resonance spectrum. The experimental results in fields up to 40 kOe are described satisfactorily by an equation obtained by Zaliznyak et al. [JETP Lett. 64, 473 (1996)]. Formulas are obtained in our work that agree very well with experiment at all fields up to the “collapse” field H[sub c] of all sublattices. The unbiased NMR frequency in CsMnBr[sub 3] is determined to be ν[sub n0]=416 MHz (T=1.3 K) in zero external magnetic field, and in this way the reduction in the spontaneous moment due to the quasi-one-dimensional nature of the system of Mn[sup 2+] spins, which according to our data amounts to 28%, is determined more accurately. The field dependences of the directions of the magnetic sublattices with respect to the magnetic field are obtained from the NMR spectra, confirming the equations of Chubukov [J. Phys. Condens. Matter 21, 441 (1988)]. The results on the field dependence of the width and intensities of the NMR lines are discussed, along with three observed anomalies: 1) a strong increase in the NMR frequency for nuclei in sublattices that are perpendicular to the magnetic field; 2) the nonmonotonic temperature dependence of the resonance field for the lower branch of the spectrum; 3) the presence of two branches of the NMR spectrum in large H[sub c] fields, in which the CsMnBr[sub 3] must be a quasi-one-dimensional antiferromagnetic. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The NMR of Mn[sup 55] nuclei is measured in the quasi-one-dimensional antiferromagnets CsMnBr[sub 3], RbMnBr[sub 3], and CsMnI[sub 3] in magnetic fields up to 8 T at temperatures in the range 1.3–4.2 K. The average moments of the magnetic sublattices and their field dependences, which turned out to be comparatively strong and different for magnetically nonequivalent Mn[sup 2+] ions, are determined from the hyperfine-field data obtained. As a result, the magnetizations of separate sublattices in an external magnetic field ∼8 T differ by more than 5%. The results obtained agree qualitatively with the theory of the suppression of quantum fluctuations by a magnetic field. © 1997 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The article is devoted to the theoretical and experimental study of a magnetoelectric (ME) current sensor based on a gradient structure. It is known that the use of gradient structures in magnetostrictive-piezoelectric composites makes it possible to create a self-biased structure by replacing an external magnetic field with an internal one, which significantly reduces the weight, power consumption and dimensions of the device. Current sensors based on a gradient bidomain structure LiNbO3 (LN)/Ni/Metglas with the following layer thicknesses: lithium niobate—500 μm, nickel—10 μm, Metglas—29 μm, operate on a linear section of the working characteristic and do not require the bias magnetic field. The main characteristics of a contactless ME current sensor: its current range measures up to 10 A, it has a sensitivity of 0.9 V/A, its current consumption is not more than 2.5 mA, and its linearity is maintained to an accuracy of 99.8%. Some additional advantages of a bidomain lithium niobate-based current sensor are the increased sensitivity of the device due to the use of the bending mode in the electromechanical resonance region and the absence of a lead component in the device. [ABSTRACT FROM AUTHOR]

We carry out microphotoluminescence measurements of an acceptor-bound exciton (A0X) recombination in the applied magnetic field with a single impurity resolution. In order to describe the obtained spectra we develop a theoretical model taking into account a quantum well (QW) confinement, an electron-hole and hole-hole exchange interaction. By means of fitting the measured data with the model we are able to study the fine structure of individual acceptors inside the QW. The good agreement between our experiments and the model indicates that we observe single acceptors in a pure two-dimensional environment whose states are unstrained in the QW plain. [ABSTRACT FROM AUTHOR]

Low-frequency and resonance magnetoelectric (ME) effects have been studied for a trilayer of permendur (alloy of Fe-Co-V) and lead zirconate titanate (PZT). The high permeability and high magnetostriction for permendur, key ingredients for magnetic field confinement, and ME response result in ME voltage coefficient of 23 V/cm Oe at low-frequency and 250 V/cm Oe at electromechanical resonance (EMR) for a sample with PZT fibers and inter-digital-electrodes. Theoretical ME coefficients are in agreement with the data. Measured magnetic noise floor of 25 pT/[Square_Root]Hz at 1 Hz and 100 fT/[Square_Root]Hz at EMR are comparable to best values reported for Metglas-PZT fiber sensors. [ABSTRACT FROM AUTHOR]

• Variation of 1/T 2 * was linear with B0 field for a range of rock core plug samples. • The optimal field based on SNR in SPRITE MRI measurements was predicted. • Implementation of the best field is facilitated by a variable field magnet. • The optimal field may be determined in three simple experimental steps. 1H relaxometry measurements of petroleum core plugs are commonly performed on low field magnets (<0.5 Tesla) to reduce the influence of magnetic susceptibility mismatch on measurements of the spin-spin relaxation time, T 2. The Signal to Noise Ratio (SNR) of the MR signal, however, generally decreases with lower magnetic fields. Higher magnetic fields (>3 Tesla) are typically employed in small animal MRI studies to improve SNR and image resolution. For many rock core plug samples, susceptibility mismatch effects can be severe at these higher fields leading to decreased T 2 and T 2 *. In this work we seek an answer to the general question of what is the best field for MRI of rock core plugs, anticipating that it will be both sample and measurement method dependent. Free Induction Decay (FID) relaxation time measurements were undertaken to investigate the conditions under which the SNR in Centric Scan SPRITE (Single Point Ramped Imaging with T 1 Enhancement) MRI measurements is maximized. The image SNR benefits from greater signal at higher fields, but is negatively impacted by the correspondingly shorter signal lifetimes. Depending on the noise regime of the sample, the maximum SNR may be predicted for Centric Scan SPRITE MRI with T 2 * being B 0 field dependent. In this work we describe a series of simple experimental considerations to determine the optimal B 0 field for SPRITE MRI. Selection of the best field is aided by a new generation of superconducting magnets which allows the experimentalist to readily vary the field strength. Such magnets allow one to experimentally control sample magnetization for high sensitivity MRI measurements of core plug samples, while controlling the effect of susceptibility mismatch on the signal lifetimes. [ABSTRACT FROM AUTHOR]