Evolution of the magnetic-field profile inTl2Ba2CuO6:Consequences for the second magnetization peak

1999 ◽  
Vol 59 (21) ◽  
pp. 13635-13638 ◽  
Author(s):  
S. Anders ◽  
Ming Xu ◽  
H. M. Jaeger ◽  
T. W. Li ◽  
D. G. Hinks
Keyword(s):  
Magnetic Field ◽  
Field Profile ◽  
Magnetic Field Profile ◽  
The Magnetic Field ◽  
Second Magnetization Peak

Dependence of the a-Si:H Defect Density of States on the Magnetic Field Profile of an Electron Cyclotron Resonance Microwave Plasma

1992 ◽  
Vol 258 ◽  
Author(s):  
F.S. Pool ◽  
J.M. Essick ◽  
Y.H. Shing ◽  
R.T. Mather
Keyword(s):  
Magnetic Field ◽  
Density Of States ◽  
Cyclotron Resonance ◽  
Electron Cyclotron Resonance ◽  
Microwave Plasma ◽  
Defect Density ◽  
Electron Cyclotron ◽  
Field Profile ◽  
Magnetic Field Profile ◽  
The Magnetic Field

ABSTRACTThe magnetic field profile of an electron cyclotron resonance (ECR) microwave plasma was systematically altered to determine subsequent effects on a-Si:H film quality. Films of a-Si:H were deposited at pressures of 0.7 mTorr and 5 mTorr with a H2/SiH4 ratio of approximately three. The mobility gap density of states ND, deposition rate and light to dark conductivity were determined for the a-Si:H films. This data was correlated to the magnetic field profile of the plasma, which was characterized by Langmuir probe measurements of the ion current density. By variation of the magnetic field profile ND could be altered by more than an order of magnitude, from 1×1016 to 1×1017 at 0.7 mTorr and 1×1016 to 5×1017 at 5 mTorr. Two deposition regimes were found to occur for the conditions of this study. Highly divergent magnetic fields resulted in poor quality a-Si:H, while for magnetic field profiles defining a more highly confined plasma, the a-Si:H was of device quality and relatively independent of the magnetic field configuration.

scholarly journals Non-stationarity of the quasi-perpendicular bow shock: comparison between Cluster observations and simulations

2011 ◽  
Vol 29 (2) ◽  
pp. 263-274 ◽  
Author(s):  
H. Comişel ◽  
M. Scholer ◽  
J. Soucek ◽  
S. Matsukiyo
Keyword(s):  
Magnetic Field ◽  
Bow Shock ◽  
Field Profile ◽  
Mass Ratio ◽  
Poynting Flux ◽  
Magnetic Field Profile ◽  
Low Mass ◽  
Low Mass Ratio ◽  
The Waves ◽  
The Magnetic Field

Abstract. We have performed full particle electromagnetic simulations of a quasi-perpendicular shock. The shock parameters have been chosen to be appropriate for the quasi-perpendicular Earth's bow shock observed by Cluster on 24 January 2001 (Lobzin et al., 2007). We have performed two simulations with different ion to electron mass ratio: run 1 with mi/me=1840 and run 2 with mi/me=100. In run 1 the growth rate of the modified two-stream instability (MTSI) is large enough to get excited during the reflection and upstream gyration of part of the incident solar wind ions. The waves due to the MTSI are on the whistler mode branch and have downstream directed phase velocities in the shock frame. The Poynting flux (and wave group velocity) far upstream in the foot is also directed in the downstream direction. However, in the density and magnetic field compression region of the overshoot the waves are refracted and the Poynting flux in the shock frame is directed upstream. The MTSI is suppressed in the low mass ratio run 2. The low mass ratio run shows more clearly the non-stationarity of the shock with a larger time scale of the order of an inverse ion gyrofrequency (Ωci): the magnetic field profile flattens and steepens with a period of ~1.5Ωci−1. This non-stationarity is different from reformation seen in previous simulations of perpendicular or quasi-perpendicular shocks. Beginning with a sharp shock ramp the large electric field in the normal direction leads to high reflection rate of solar wind protons. As they propagate upstream, the ion bulk velocity decreases and the magnetic field increases in the foot, which results in a flattening of the magnetic field profile and in a decrease of the normal electric field. Subsequently the reflection rate decreases and the whole shock profile steepens again. Superimposed on this 'breathing' behavior are in the realistic mass ratio case the waves due to the MTSI. The simulations lead us to a re-interpretation of the 24 January 2001 bow shock observations reported by Lobzin et al. (2007). It is suggested that the high frequency waves observed in the magnetic field data are due to the MTSI and are not related to a nonlinear phase standing whistler. Different profiles at the different spacecraft are due to the non-stationary behavior on the larger time scale.

Challenges in Circumferential Magnetisation II: A FEA Point of View

2006 ◽  
Author(s):  
R. C. Ireland ◽  
C. R. Torres
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Wall Thickness ◽  
Pipe Wall ◽  
Point Of View ◽  
Field Profile ◽  
Pipe Wall Thickness ◽  
Magnetic Field Profile ◽  
Background Magnetic Field ◽  
The Magnetic Field

In order to design a Magnetic Flux Leakage (MFL) tool, knowledge of the magnetic field profile both within the pipe wall and around the sensor locations is required. The former is important since the magnitude of a defect signature will be maximised when the pipe wall is magnetically saturated. The latter is important for the reason that the background magnetic field profile will determine the sensor bias level for a given defect. Previous research using the Finite Element (FE) technique has investigated the magnetic field profile within the pipe wall for a generic circumferential MFL tool and showed how it varied depending upon the pipe wall thickness and tool speed. It was found that as the pipe wall thickness and tool speed increased, a plume of magnetic flux formed behind the tool. Furthermore, it was observed that as the pipe wall thickness increased, outer regions of the pipe wall exhibited substantially reduced levels of magnetic flux. A reduction of magnetic flux in these outer regions of the pipe wall suggests defects located here may be harder to detect and resolve compared to defects located closer to the inner pipe wall. This paper briefly reviews the previous research and extends the numerical analysis by considering the magnitude of the magnetic field profile for locations within the inner and outer pipe wall and possible sensor positions. It is shown how these profiles change with pipe wall thickness and tool speed and demonstrates the complex and non-linear nature of the magnetic field. The information obtained can be combined with previous research and will be useful for determining the optimal sensor location and yield predictions for background magnetic field magnitudes. The full complexity of magnetic materials is not incorporated into the modelling, however, the results obtained give a theoretical indication of operational limitations of the circumferential MFL technique.

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