Utilization of RADFET sensors for x-ray undulators: experiential considerations on magnetic field profile before commissioning

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.

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Simulation of bunched electron-beam acceleration by the cylindrical TE113 microwave field

International Journal of Modern Physics A ◽

10.1142/s0217751x19420302 ◽

2019 ◽

Vol 34 (36) ◽

pp. 1942030

Author(s):

E. A. Orozco ◽

J. D. González ◽

J. R. Beltrán ◽

V. E. Vergara

Keyword(s):

Magnetic Field ◽

Electron Beam ◽

Microwave Field ◽

Inhomogeneous Magnetic Field ◽

X Ray ◽

Particle In Cell ◽

Magnetic Field Profile ◽

Detailed Simulation ◽

The Magnetic Field ◽

Particle Approximation

We report a detailed simulation of a bunched electron-beam accelerated in a TE[Formula: see text] cylindrical cavity immersed in a static inhomogeneous magnetic field using a relativistic full electromagnetic particle-in-cell (PIC). This type of acceleration concept is known as Spatial AutoResonance Acceleration (SARA) in which the magnetic field profile is such that it keeps the electron-beam in the acceleration regime along their trajectories. In this work, the numerical experiments are carried out including a bunched electron-beam with the concentrations in the range [Formula: see text]–[Formula: see text][Formula: see text]cm[Formula: see text] in a TE[Formula: see text] cylindrical microwave field, at a frequency of 2.45 GHz and an amplitude of 15 kV/cm. The electron energy reaches values up to 250 keV without significant unfocusing effect that can be used as a basis to produce hard X-ray. Additionally, a comparison between the data obtained from the full electromagnetic PIC simulations and the results derived from the relativistic Newton–Lorentz equation in a single particle approximation is carried out.

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Generation of a Large Swelling in the Spatial Magnetic Field Profile near the Coil Axis of a Theta Pinch

Japanese Journal of Applied Physics ◽

10.1143/jjap.26.1727 ◽

1987 ◽

Vol 26 (Part 1, No. 10) ◽

pp. 1727-1732

Author(s):

Sukeomi Ogi ◽

Masaharu Shiratani ◽

Yukio Watanabe

Keyword(s):

Magnetic Field ◽

Field Profile ◽

Magnetic Field Profile ◽

Theta Pinch ◽

Coil Axis

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Influence of the magnetic field profile on ITER conductor testing

Superconductor Science and Technology ◽

10.1088/0953-2048/19/8/016 ◽

2006 ◽

Vol 19 (8) ◽

pp. 783-791 ◽

Cited By ~ 1

Author(s):

A Nijhuis ◽

Y Ilyin ◽

H H J ten Kate

Keyword(s):

Magnetic Field ◽

Field Profile ◽

Magnetic Field Profile ◽

The Magnetic Field

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

Annales Geophysicae ◽

10.5194/angeo-29-263-2011 ◽

2011 ◽

Vol 29 (2) ◽

pp. 263-274 ◽

Cited By ~ 16

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.

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