Search results for "MAGNETIC FIELD"

QUANTITATIVE SPECTROSCOPY OF Rb ATOMS IN STRONG MAGNETIC FIELD BASED ON SUBMICRON THIN VAPOUR.

2010

The energy levels of atoms placed in an external magnetic field undergo frequency shifts and changes in their transition probabilities. It is demonstrated that using fluorescence spectra from a submicron thin vapour cell (STC) with the thickness L = λ/2, it is possible to efficiently study the above mentioned changes (“half-λ Zeeman technique” (HLZT)). The circularly polarized beam of extended-cavity diode laser (λ = 794 nm, laser bandwidth γL < 1 MHz) resonant with 87Rb D1 transition, after passing through Faraday isolator is directed onto the Rb STC with the thickness L = λ/2. The temperature of the STC is 120 °C, corresponding to N ~ 1013 atom/cm3. STC was provided by a special oven with…

Cosmological origin of anomalous radio background

2012

The ARCADE 2 collaboration has reported a significant excess in the isotropic radio background, whose homogeneity cannot be reconciled with clustered sources. This suggests a cosmological origin prior to structure formation. We investigate several potential mechanisms and show that injection of relativistic electrons through late decays of a metastable particle can give rise to the observed excess radio spectrum through synchrotron emission. However, constraints from the cosmic microwave background (CMB) anisotropy, on injection of charged particles and on the primordial magnetic field, present a challenge. The simplest scenario is with a greater than or similar to 9 GeV particle decaying i…

3D MHD MODELING of TWISTED CORONAL LOOPS

2016

We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube, in the solar atmosphere extending from the high-beta chromosphere to the low-beta corona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ~30 km. We obtain an overall evolution typical of loop models and realistic loo…

A fast multi-dimensional magnetohydrodynamic formulation of the transition region adaptive conduction (TRAC) method

2021

We have demonstrated that the Transition Region Adaptive Conduction (TRAC) method permits fast and accurate numerical solutions of the field-aligned hydrodynamic equations, successfully removing the influence of numerical resolution on the coronal density response to impulsive heating. This is achieved by adjusting the parallel thermal conductivity, radiative loss, and heating rates to broaden the transition region (TR), below a global cutoff temperature, so that the steep gradients are spatially resolved even when using coarse numerical grids. Implementing the original 1D formulation of TRAC in multi-dimensional magnetohydrodynamic (MHD) models would require tracing a large number of magne…

Energy Storage: Giant Enhancement in the Supercapacitance of NiFe–Graphene Nanocomposites Induced by a Magnetic Field (Adv. Mater. 28/2019)

2019

Unconventional behavior of superconducting nanostructures

2000

Abstract Various aluminium nanostructures have been studied experimentally. Unusual nonmonotonous dependence of the critical current on external magnetic field has been observed. Pronounced nonlocal interaction has been found to decay exponentially on a scale of the superconducting coherence length ξ(T).

Resistive state triggered by vortex entry in YBa 2 Cu 3 O 7−δ nanostructures

2014

We have realized YBa2Cu3O7-delta nanowires and nano Superconducting Quantum Interference Devices (nanoSQUID). The measured temperature dependence of the wire resistances below the superconducting transition temperature has been analyzed using a thermally activated vortex entry model valid for wires wider than the superconducting coherence length. The extracted zero temperature values of the London penetration depth, lambda(0) similar or equal to 270 +/- 15 nm, are in good agreement with the value obtained from critical current modulations as a function of an externally applied magnetic field in a nanoSQUID implementing two nanowires.

Effect of boron doping in the microwave surface resistance of neutron irradiated melt-textured Y1.6Ba2.3Cu3.3O7−x samples

2012

We report on the microwave surface resistance of melt-textured Y_1.6Ba_2.3Cu_3.3O_7-x samples, doped with different amount of B_2O_3 and, subsequently, irradiated by thermal neutrons at the fluence of 1.476 \times 10^17 cm^-2. The microwave surface resistance has been measured as a function of temperature and DC magnetic field. The experimental results are quantitatively discussed in the framework of the Coffey and Clem theory, properly adapted to take into account the d-wave nature of cuprate superconductors. By fitting the experimental data at zero DC field, we have highlighted the effects of the induced defects in the general properties of the samples, including the intergranular region.…

Possibility of unconventional superconductivity of SrTiO3−δ

2003

Abstract SrTiO3−δ can show metallic behavior and superconductivity at T It is demonstrated that by variation of the annealing temperature in vacuum the transport properties of SrTiO3−δ can be tuned continuously from semiconducting to metallic. We present measurements of the upper critical field Bc2(T) which show near Tc a positive curvature. This unusual temperature dependence is consistent with a model of weakly interacting charged bosons which condense in the superconducting state (local pairing). However, measurements of current–voltage curves reveal only small critical currents of our samples. This observation is discussed in the framework of doping inhomogeneities.

Complex conductivity in high-Tc single crystal superconductors

1994

The electromagnetic surface impedance of single crystal high-T c superconductors has been examined within the framework of the two-fluid model and the hypothesis that the em field modulates the partial concentrations of both normal and condensate fluids. A comparison with experimental data is reported