scholarly journals The Bennett pinch for non-relativistic electrons

2018 ◽  
Vol 84 (6) ◽  
Author(s):  
J. E. Allen ◽  
L. Simons
Keyword(s):  
Electrostatic Field ◽  
Magnetic Force ◽  
Relativistic Electrons ◽  
Positive Ions ◽  
Basic Physics

A theory of the Bennett pinch is presented for the case of non-relativistic electrons. In this way the basic physics of the phenomenon can be clearly demonstrated. The magnetic force acting on the electrons is transmitted to the positive ions via an electrostatic field.

Effects of Space Charge on ESEM Gas Amplification

1997 ◽  
Vol 3 (S2) ◽  
pp. 609-610 ◽  
Author(s):  
B.L. Thiel ◽  
M.R. Hussein-Ismail ◽  
A.M. Donald
Keyword(s):  
Electric Field ◽  
Electrostatic Field ◽  
Secondary Electron ◽  
Sample Surface ◽  
Cascade Process ◽  
Secondary Electrons ◽  
Positive Ions ◽  
Space Charges ◽  
Cascade Amplification ◽  
Environmental Sem

We have performed a theoretical investigation of the effects of space charges in the Environmental SEM (ESEM). The ElectroScan ESEM uses an electrostatic field to cause gas cascade amplification of secondary electron signals. Previous theoretical descriptions of the gas cascade process in the ESEM have assumed that distortion of the electric field due to space charges can be neglected. This assumption has now been tested and shown to be valid.In the ElectroScan ESEM, a positively biased detector is located above the sample, creating an electric field on the order of 105 V/m between the detector and sample surface. Secondary electrons leaving the sample are cascaded though the gas, amplifying the signal and creating positive ions. Because the electrons move very quickly through the gas, they do not accumulate in the specimen-to-detector gap. However, the velocity of the positive ions is limited by diffusion.

Is Atmospheric Superoxide Vitally Necessary? Accelerated Death of Animals in a Quasi-Neutral Electric Atmosphere

1997 ◽  
Vol 52 (5-6) ◽  
pp. 396-404 ◽  
Author(s):  
Naum Goldstein ◽  
Tatyana V. Arshavskaya
Keyword(s):  
Premature Infants ◽  
Electrostatic Field ◽  
Ambient Air ◽  
Ultrastructural Changes ◽  
Pituitary Insufficiency ◽  
Human Beings ◽  
Air Ions ◽  
Positive Ions ◽  
Acrylic Glass ◽  
Glass Surfaces

Abstract To estimate the necessity of air ions (AIs) as a natural source of atmospheric gaseous superoxide for mammalia the effect of air ion deprivation on mice and rats was investigated. Ambient air deionization inside an experimental acrylic glass cage (AGC) was performed by electrostatic field, built up by acrylic glass surfaces. Under these conditions, four hours after the animals were placed into the AGC, the concentration of negative AIs was not detectable, the concentration of positive ions was (mean ± SD) 77 ± 18 ionsxcm-3. The negative and positive AI concentrations in identical silicate glass cages (control) were 482 ± 128 ionsxcm-3 and 660 ± 148 ionsxcm-3 respectively. It was found that the prolonged deficiency of AIs in ambient air leads to accelerated death of the animals. The life span of the deprived mice and rats was 16.2 ± 0.9 and 23.0 ± 1.1 days respectively. The pathological symptoms and ultrastructural changes in the adeno-and neurohypophysis in deprived animals observed strongly suggest that animal death is related to disturbances in neurohormonal regulation and pituitary insufficiency. The possible physiological need of AIs and atmospheric superox­ide, and its role in the development of environmental stress in human beings and in particular in premature infants is discussed.

Dissipation by thermal forces in quantum plasmas

1984 ◽  
Vol 32 (3) ◽  
pp. 369-385
Author(s):  
R. R. Burman ◽  
D. E. McClelland
Keyword(s):  
Magnetic Force ◽  
Mass Density ◽  
Fluid Velocity ◽  
Relativistic Electrons ◽  
Neutron Star Matter ◽  
Dilute Gas ◽  
Protons And Neutrons ◽  
Heat Flux Vector ◽  
Frictional Forces ◽  
Partially Ionized Plasmas

This paper deals with degenerate Fermi–Dirac plasmas in which transport is by quasi-particles that form a dilute gas described by the Boltzmann equation. The off-equilibrium part of the distribution function of each species is estimated by expanding it in terms of the fluid velocity of the species, relative to the plasma, and its relative heat flux vector. Expressions for the frictional forces acting between the species, consisting of a relaxation-model force and a thermal force, are obtained. These are used in a plasma dissipation formalism, yielding, for ternary partially ionized plasmas, a generalized Ohm law and an ambipolar diffusion law. The results are applied to neutron star matter, consisting of thermally ultra-relativistic electrons and non-relativistic protons and neutrons, with the mass density dominated by the neutrons. The dissipation formalism is used to obtain an expression for the magnetic force on this material.

A New AID for Interpolating and Assessing Collision Strengths and Rate Coefficients

1988 ◽  
Vol 102 ◽  
pp. 107-110
Author(s):  
A. Burgess ◽  
H.E. Mason ◽  
J.A. Tully
Keyword(s):  
Significant Loss ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation ◽  
Graphical Display ◽  
Practical Procedure ◽  
Positive Ions ◽  
Allowed Transition ◽  
Computational Errors ◽  
Existing Data

AbstractA new way of critically assessing and compacting data for electron impact excitation of positive ions is proposed. This method allows one (i) to detect possible printing and computational errors in the published tables, (ii) to interpolate and extrapolate the existing data as a function of energy or temperature, and (iii) to simplify considerably the storage and transfer of data without significant loss of information. Theoretical or experimental collision strengths Ω(E) are scaled and then plotted as functions of the colliding electron energy, the entire range of which is conveniently mapped onto the interval (0,1). For a given transition the scaled Ω can be accurately represented - usually to within a fraction of a percent - by a 5 point least squares spline. Further details are given in (2). Similar techniques enable thermally averaged collision strengths upsilon (T) to be obtained at arbitrary temperatures in the interval 0 < T < ∞. Application of the method is possible by means of an interactive program with graphical display (2). To illustrate this practical procedure we use the program to treat Ω for the optically allowed transition 2s → 2p in ArXVI.

Instrumentation for detecting channelling radiation in the high-voltage electron microscope

1983 ◽  
Vol 41 ◽  
pp. 318-319
Author(s):  
J. H. Butler ◽  
C. J. Humphreys
Keyword(s):  
Monochromatic Light ◽  
Incident Beam ◽  
Laboratory Frame ◽  
Relativistic Electrons ◽  
Voltage Electron ◽  
Dipole Emission ◽  
Sinusoidal Oscillations ◽  
Pass Through ◽  
Incident Beam Energy ◽  
Increasing Function

Electromagnetic radiation is emitted when fast (relativistic) electrons pass through crystal targets which are oriented in a preferential (channelling) direction with respect to the incident beam. In the classical sense, the electrons perform sinusoidal oscillations as they propagate through the crystal (as illustrated in Fig. 1 for the case of planar channelling). When viewed in the electron rest frame, this motion, a result of successive Bragg reflections, gives rise to familiar dipole emission. In the laboratory frame, the radiation is seen to be of a higher energy (because of the Doppler shift) and is also compressed into a narrower cone of emission (due to the relativistic “searchlight” effect). The energy and yield of this monochromatic light is a continuously increasing function of the incident beam energy and, for beam energies of 1 MeV and higher, it occurs in the x-ray and γ-ray regions of the spectrum. Consequently, much interest has been expressed in regard to the use of this phenomenon as the basis for fabricating a coherent, tunable radiation source.

Luminescence from individual dislocations in II-VI and III-V semiconductors

1991 ◽  
Vol 49 ◽  
pp. 834-835
Author(s):  
J W Steeds
Keyword(s):  
Group Iv ◽  
Luminescence Properties ◽  
Carrier Recombination ◽  
Transmission Electron ◽  
Wide Range ◽  
Basic Physics ◽  
Semiconducting Compounds ◽  
Diamond Group ◽  
Non Destructive ◽  
Technological Significance

There is a wide range of experimental results related to dislocations in diamond, group IV, II-VI, III-V semiconducting compounds, but few of these come from isolated, well-characterized individual dislocations. We are here concerned with only those results obtained in a transmission electron microscope so that the dislocations responsible were individually imaged. The luminescence properties of the dislocations were studied by cathodoluminescence performed at low temperatures (~30K) achieved by liquid helium cooling. Both spectra and monochromatic cathodoluminescence images have been obtained, in some cases as a function of temperature.There are two aspects of this work. One is mainly of technological significance. By understanding the luminescence properties of dislocations in epitaxial structures, future non-destructive evaluation will be enhanced. The second aim is to arrive at a good detailed understanding of the basic physics associated with carrier recombination near dislocations as revealed by local luminescence properties.

Creating a standard method of controlling digital microscopes: the microscope access protocol (map)

1995 ◽  
Vol 53 ◽  
pp. 16-17
Author(s):  
T. A. Dodson ◽  
E. Völkl ◽  
L. F. Allard ◽  
T. A. Nolan
Keyword(s):  
Data Storage ◽  
Storage Systems ◽  
Digital Systems ◽  
Data Networks ◽  
Digital Microscopy ◽  
Command Language ◽  
Access Protocol ◽  
Analog To Digital ◽  
Basic Physics ◽  
Scanning Electron

The process of moving to a fully digital microscopy laboratory requires changes in instrumentation, computing hardware, computing software, data storage systems, and data networks, as well as in the operating procedures of each facility. Moving from analog to digital systems in the microscopy laboratory is similar to the instrumentation projects being undertaken in many scientific labs. A central problem of any of these projects is to create the best combination of hardware and software to effectively control the parameters of data collection and then to actually acquire data from the instrument. This problem is particularly acute for the microscopist who wishes to "digitize" the operation of a transmission or scanning electron microscope. Although the basic physics of each type of instrument and the type of data (images & spectra) generated by each are very similar, each manufacturer approaches automation differently. The communications interfaces vary as well as the command language used to control the instrument.

Influence of unbalanced magnetic force on shaft deflection in permanent magnet synchronous motor with fractional slot concentrated windings

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1461-1468
Author(s):  
Ting Dong ◽  
Juyan Huang ◽  
Bing Peng ◽  
Ling Jian
Keyword(s):  
Permanent Magnet ◽  
Magnetic Force ◽  
Permanent Magnet Synchronous Motor ◽  
Operational Reliability ◽  
Topology Structure ◽  
Permanent Magnet Synchronous Motors ◽  
Synchronous Motors ◽  
Shaft Deflection ◽  
Large Length ◽  
Fractional Slot

The calculation accuracy of unbalanced magnetic forces (UMF) is very important to the design of rotor length, because it will effect the shaft deflection. But in some permanent magnet synchronous motors (PMSMs) with fractional slot concentrated windings (FSCW), the UMF caused by asymmetrical stator topology structure is not considered in the existing deflection calculation, which is very fatal for the operational reliability, especially for the PMSMs with the large length-diameter ratio, such as submersible PMSMs. Therefore, the part of UMF in the asymmetrical stator topology structure PMSMs caused by the choice of pole-slot combinations is analysized in this paper, and a more accurate rotor deflection calculation method is also proposed.

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