An Implication for Lasers of an Aspect of Interference at High Field Strengths

The theory for ionic conduction in solids based upon the homogeneous, field-assisted generation of defect pairs is developed in a general, three dimensional form, and its range of applicability is examined. At high field strengths the equations reduce to those of the so-called high field Frenkel defect theory, proposed originally by Bean, Fisher, and Vermilyea. At low field strengths, the steady-state expression reduces to the well-known conduction equation derived originally by Mott for ionic conduction in the alkali halides. At intermediate field strengths, more complicated relationships obtain. The homogeneous generation of defect pairs, whether field or current assisted, is shown to be inapplicable as a mechanism for the high field anodic oxidation of the valve metals, since either type of theory predicts unacceptable behavior for the mean free path of the mobile defects. Any such conduction mechanism can be acceptable only for the case of thick films (» 104 Å).

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Ultrafast Nonlinear Carrier Dynamics in n-Doped Ge at High Field Strengths

10.1109/irmmw-thz50926.2021.9566951 ◽

2021 ◽

Author(s):

A. Gupta ◽

V. Gupta ◽

A. Sharma ◽

Gy. Polonyi ◽

J. A. Fulop

Keyword(s):

High Field ◽

Carrier Dynamics ◽

Field Strengths

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Effect of Mineral Composition on Transverse Relaxation Time Distributions and MR Imaging of Tight Rocks from Offshore Ireland

Minerals ◽

10.3390/min10030232 ◽

2020 ◽

Vol 10 (3) ◽

pp. 232

Author(s):

Stian Almenningen ◽

Srikumar Roy ◽

Arif Hussain ◽

John Georg Seland ◽

Geir Ersland

Keyword(s):

Magnetic Field ◽

Relaxation Time ◽

Mr Imaging ◽

Field Strength ◽

High Field ◽

Transverse Relaxation Time ◽

Transverse Relaxation ◽

The Core ◽

Low Field ◽

Field Strengths

In this paper, we investigate the effect of magnetic field strength on the transverse relaxation time constant (T2) in six distinct core plugs from four different rock types (three sandstones, one basalt, one volcanic tuff and one siltstone), retrieved from offshore Ireland. The CPMG pulse-sequence was used at two different magnetic field strengths: high-field at 4.70 T and low-field at 0.28 T. Axial images of the core plugs were also acquired with the RAREst sequence at high magnetic field strength. Thin-sections of the core plugs were prepared for optical imaging and SEM analysis, and provided qualitative information on the porosity and quantification of the elemental composition of the rock material. The content of iron varied from 4 wt. % to close to zero in the rock samples. Nevertheless, the effective T2 distributions obtained at low-field were used to successfully predict the porosity of the core plugs. Severe signal attenuations from internal magnetic gradients resulted in an underestimation of the porosity at high-field. No definitive trend was identified on the evolution of discrete relaxation time components between magnetic field strengths. The low-field measurements demonstrate that NMR is a powerful quantitative tool for petrophysical rock analysis as compared to thin-section analysis. The results of this study are of interest to the research community who characterizes natural gas hydrates in tight heterogeneous core plugs, and who typically relies on MR imaging to distinguish between solid hydrates and fluid phases. It further exemplifies the importance of selecting appropriate magnetic field strengths when employing NMR/MRI for porosity calculation in tight rock.

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