A combined system for generating a uniform magnetic field and its application in the investigation of Efimov physics

We propose a scheme to produce a uniform magnetic field with a system comprising a pair of coils and an atom chip.After optimizing the parameters of the chip wires, we improve the homogeneity of the magnetic field by two orders of magnitude. We exhibit that this method can be applied in the investigation of Efimov physics in ~(87)Rb-~(40)K mixture.     

A new method for the antiferromagnetic Ising model's properties at any temperature and any magnetic field on the infinite square lattice

Since the introduction of the Ising model on the square lattice, many hundreds of articles have dealt with several properties of the ferromagnetic Ising model, but very few articles had included the antiferromagnetic Ising model. We have known that the Ising antiferromagnetism on a bipartite lattice is not zero in a considerable area of the magnetic field, H, and temperature, T. Now we present the dimensionless specific heat, C, and susceptibility, χ, per vertex using a new method to obtain the data in about 10,000 points in the interesting (T,H) area. Our last four figures show the contours and the smooth hills and valleys of C and of χ.     

Optimization of the parameters of a two-coil magnetic system for the generation of a uniform field with power supply from the line or a capacitor bank

Physical experiments often require the generation of a short-lived magnetic field with specified limits of nonuniformity. Various energy storage units, specifically capacitor banks, are used to supply pulsed power to the magnetic system. The simplest configuration of such a magnetic system is formed by two identical coaxial electromagnetic coils. In this work the parameters of this system configuration are optimized, subject to field uniformity requirements. Zh. Tekh. Fiz. 67, 101–106 (April 1997)     

A simple electromagnetic method of cyclic loss measurement for superconducting wires in a combined alternating transverse magnetic field and transport current

We measured cyclic losses in a superconducting wire, carrying alternating transport current, simultaneously exposed to an alternating transverse magnetic field. Samples of Bi-2223 Ag-sheathed tapes have configuration of a double-layer non-inductive coil, which itself is a pickup coil to measure the AC losses. Potential taps were attached to both terminals of the sample coil. The external field was applied along the axis of the sample coil. In this procedure, we can estimate an averaged Poynting's vector on a cylindrical surface between the two layers by means of signals from a pair of the potential taps and from pickup coils for the external magnetic field and the transport current. We can also measure a magnetization and an extended transport-current components of AC losses in addition to a total cyclic loss for a combined alternating external field and transport current. Obtained results are compared with numerical predictions of the critical state model taking into account the magnetic field dependence of critical current density.     

A reliable treatment of the homotopy analysis method for viscous flow over a non-linearly stretching sheet in presence of a chemical reaction and under influence of a magnetic field

The similarity solution for the steady two-dimensional flow of an incompressible viscous and electrically conducting fluid over a non-linearly semi-infinite stretching sheet in the presence of a chemical reaction and under the influence of a magnetic field gives a system of non-linear ordinary differential equations. These non-linear differential equations are analytically solved by applying a newly developed method, namely the Homotopy Analysis Method (HAM). The analytic solutions of the system of non-linear differential equations are constructed in the series form. The convergence of the obtained series solutions is carefully analyzed. Graphical results are presented to investigate the influence of the Schmidt number, magnetic parameter and chemical reaction parameter on the velocity and concentration fields. It is noted that the behavior of the HAM solution for concentration profiles is in good agreement with the numerical solution given in reference [A. Raptis, C. Perdikis, Int. J. Nonlinear Mech. 41, 527 (2006)].      

Ground states of the hydrogen molecule and its molecular ion in the presence of a magnetic field using the variational Monte Carlo method

ABSTRACT

By using the variational Monte Carlo (VMC) method, we calculated the 1sσ_g-state energies, the dissociation energies, and the binding energies of the hydrogen molecule and its molecular ion in the presence of an aligned magnetic field regime between 0 and 10?a.u. The present calculations are based on using two types of compact and accurate trial wave functions, which are put forward for consideration in calculating energies in the absence of a magnetic field. The obtained results are compared with the most recent accurate values. We conclude that the applications of the VMC method can be successfully extended to cover the case of molecules under the effect of a magnetic field.     

Dynamic magnetic behavior of the mixed spin （2, 5/2） Ising system with antiferromagnetic/antiferromagnetic interactions on a bilayer square lattice

Using the mean-field theory and Glauber-type stochastic dynamics, we study the dynamic magnetic properties of the mixed spin （2, 5/2） Ising system for the antiferromagnetic/antiferromagnetic （AFM/AFM） interactions on the bilayer square lattice under a time varying （sinusoidal） magnetic field. The time dependence of average magnetizations and the thermal variation of the dynamic magnetizations are examined to calculate the dynamic phase diagrams. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and the effects of interlayer coupling interaction on the critical behavior of the system are investigated. We also investigate the influence of the frequency and find that the system displays richer dynamic critical behavior for higher values of frequency than that of the lower values of it. We perform a comparison with the ferromagnetic/ferromagnetic （FM/FM） and AFM/FM interactions in order to see the effects of AFM/AFM interaction and observe that the system displays richer and more interesting dynamic critical behaviors for the AFM/AFM interaction than those for the FM/FM and AFM/FM interactions.     

A solution to the problem of the skin effect with a bias current in the Maxwell plasma by the method of expansion in eigenfunctions

A problem of the skin effect in the Maxwell plasma is solved analytically by the method of expansion in eigenfunctions based on the Vlasov–Maxwell kinetic equation with a self-consistent electric field. Specular electron reflection from the boundary is used as a boundary condition. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 33–38, February, 2009.     

Experimental and theoretical study of density,potential, and current structures of a helium plasma in front of an radio frequency antenna tilted with respect to the magnetic field lines

Potential and density structures in the vicinity of an radio frequency (RF) electrode/antenna in a magnetized plasma are investigated using an RF-compensated cylindrical Langmuir probe. These measurements were performed in the ALINE plasma device in which only electrons can be considered well magnetized. Very precise 2-D maps of the plasma parameters are drawn thanks to a 3-D automatic manipulator on which the probe is mounted. The effect of the tilted magnetic angle between the RF-biased surface and the magnetic lines is also studied thanks to a tilting electrode. Comparison of several simplistic models with the experiments proved the reliability of simple Langmuir probe measurements in such an RF and magnetized environment (space potential vs. tilting angle of the antenna with respect to magnetic field lines and recovery of the floating potential structure using measured currents). A fluid model based on total current density and ion diffusion equations over the biased flux tube provides the same density structures in front of the electrode as the measurements. Those density structures display a “bunny ears” shape and can be explained using transverse RF and collisional current behaviour: In front of the antenna, the transverse ion currents deplete the magnetized flux tube, while at the edge of the biased flux tube, the same currents increase the density.     

A general assignment method for oriented sample (OS) solid-state NMR of proteins based on the correlation of resonances through heteronuclear dipolar couplings in samples aligned parallel and perpendicular to the magnetic field

The acquisition and different appearances observed for wide bandwidth solid-state MAS NMR spectra of low-γ nuclei, using (14)N as an illustrative nucleus and employing two different commercial spectrometers (Varian, 14.1T and Bruker, 19.6T), have been compared/evaluated and optimized from an experimental NMR and an electronic engineering point of view, to account for the huge differences in these spectra. The large differences in their spectral appearances, employing the recommended/standard experimental set-up for the two different spectrometers, are shown to be associated with quite large differences in the electronic design of the two types of preamplifiers, which are connected to their respective probes through a 50Ω cable, and are here completely accounted for. This has led to different opportunities for optimum performances in the acquisition of nearly ideal wide bandwidth spectra for low-γ nuclei on the two spectrometers by careful evaluation of the length for the 50Ω probe-to-preamp cable for the Varian system and appropriate changes to the bandwidth (Q) of the NMR probe used on the Bruker spectrometer. Earlier, we reported quite distorted spectra obtained with Varian Unity INOVA spectrometers (at 11.4 and 14.1T) in several exploratory wide bandwidth (14)N MAS NMR studies of inorganic nitrates and amino acids. These spectra have now been compared/evaluated with fully analyzed (14)N MAS spectra correspondingly acquired at 19.6T on a Bruker spectrometer. It is shown that our upgraded version of the STARS simulation/iterative-fitting software is capable of providing identical sets for the molecular spectral parameters and corresponding fits to the experimental spectra, which fully agree with the electronic measurements, despite the highly different appearances for the MAS NMR spectra acquired on the Varian and Bruker spectrometers.     

A method for calculating the surface tension of a droplet in a lattice-gas model with long-range interaction

Since the droplet of the lattice-gas model with long-range interaction is not circular and is determined by the Wulff construction due to surface tension anisotropy, a calculation method of the surface tension of the droplet is proposed in this paper. The calculated surface tension is in good agreement with the surface tension measured by using the Laplace's formula in consideration of the surface thickness. Received 15 March 2000 and Received in final form 31 May 2000