Considerations of the effect of space-charge in the magnetron

1940 ◽  
Vol 36 (1) ◽  
pp. 94-100 ◽  
Author(s):  
E. B. Moullin
Keyword(s):  
Magnetic Field ◽  
Space Charge ◽  
Cylindrical Symmetry ◽  
Potential Difference ◽  
Anode Current ◽  
Pronounced Decrease ◽  
Field Parallel ◽  
Image Position ◽  
The Magnetic Field

When a diode thermionic tube, having cylindrical symmetry, is placed in a magnetic field parallel to its axis it is commonly called a magnetron. If there is a given potential difference between the anode and cathode of the tube, and if the magnetic field is steadily increased, a sharp and pronounced decrease of anode current occurs when the field reaches a certain value. It is easy to show that, if electrons leave without velocity from a cathode of radius b, they will just graze a concentric anode of radius a at potential V when the magnetic field H has the value given by

The cut-off characteristic of the single anode magnetron

1939 ◽  
Vol 35 (4) ◽  
pp. 637-651
Author(s):  
A. F. Harvey
Keyword(s):  
Magnetic Field ◽  
Uniform Magnetic Field ◽  
Axial Magnetic Field ◽  
Present Discussion ◽  
A Value ◽  
Field Parallel ◽  
Concentric Cylinders ◽  
Image Position ◽  
The Magnetic Field

For the purpose of the present discussion the magnetron will be defined as a diode thermionic tube, having concentric cylinders as electrodes, in which there is a uniform magnetic field parallel to the axis of the electrodes. An electron emitted from the cathode travels towards the anode in a path which is bent by the action of the magnetic field. If the anode has radius a and is at potential V with respect to the cathode of radius b, then it is well known that electrons emitted without velocity from the cathode will just graze the anode when the uniform and axial magnetic field has a value H such that

scholarly journals Влияние параллельного слоям магнитного поля на фототок в GaAs/AlAs p-i-n-структурах

2022 ◽  
Vol 56 (1) ◽  
pp. 107
Author(s):  
И.А. Ларкин ◽  
Ю.Н. Ханин ◽  
Е.Е. Вдовин
Keyword(s):  
Magnetic Field ◽  
Wavelength Range ◽  
Strong Dependence ◽  
Diffusion Current ◽  
Radiation Wavelength ◽  
Quantization Level ◽  
Dimensional Quantization ◽  
Field Parallel ◽  
The Magnetic Field

The behavior of the photocurrent in GaAs / AlAs p-i-n heterostructures is studied in a magnetic field parallel to the heterolayers in the wavelength range from 395 to 650 nm. A strong dependence of the non-oscillating component of the photocurrent on the radiation wavelength associated with the suppression of the diffusion current by the magnetic field was found. It is shown that the behavior of the oscillating component of the photocurrent in a magnetic field does not depend on the wavelength of light and is determined by the transfer of electrons through the dimensional quantization level in a triangular near-barrier well. It is shown that the suppression of the oscillating component by the magnetic field is due to the smearing of the level in the triangular well due to the motion of electrons parallel to the walls of the well and perpendicular to the magnetic field.

scholarly journals Study of the Magnetic Field of the Galaxy using Correlation Functions of the Intensity of Synchrotron Background Radio Emission

1996 ◽  
Vol 169 ◽  
pp. 615-616
Author(s):  
V.R. Shoutenkov
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Correlation Functions ◽  
Theoretical Calculations ◽  
Angular Separation ◽  
Field Studies ◽  
Position Angle ◽  
The Galaxy ◽  
Image Position ◽  
The Magnetic Field

The possibility to study magnetic field of the Galaxy calculating correlation or structure functions of synchrotron background radio emission have been known long ago (Kaplan and Pikel'ner (1963); Getmantsev (1958)). But this method had not been as popular as other methods of magnetic field studies. However theoretical calculations made by Chibisov and Ptuskin (1981) showed that correlation functions of intensity of synchrotron background radio emission can give a lot of valuable information about galactic magnetic fields because of the intensity of synchrotron background radio emission depends on H⊥. According to this theory correlation C(θ, φ) and structure S(θ, φ) functions of intensity, as functions of angular separation θ between two lines of sight and position angle φ on the sky between this two lines of sight, can be presented as a sum of isotropic (not dependent from angle φ) and anisotropic parts:

Optimization of magnetic hat for quartz flexible accelerometer

Sensor Review ◽  
2016 ◽  
Vol 36 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Cuo Wang ◽  
Xingfei Li ◽  
Ke Kou ◽  
Chunguo Long
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Cylindrical Symmetry ◽  
Air Gap ◽  
Magnetic Sensors ◽  
Magnetic Field Distribution ◽  
Navigation Systems ◽  
Pole Piece ◽  
Content Type ◽  
The Magnetic Field

Purpose – This study aims to ameliorate the strength and uniformity of the magnetic field in the air-gap of quartz flexible accelerometers. Quartz flexible accelerometers (QFAs), a type of magneto-electric inertial sensors, have wide applications in inertial navigation systems, and their precision, linearity and stability performance are largely determined by the magnetic field in operation air-gap. To enhance the strength and uniformity of the magnetic field in the air-gap, a magnetic hat structure has been proposed to replace the traditional magnetic pole piece which tends to produce stratiform magnetic field distribution. Design/methodology/approach – Three-dimensional analysis in ANSYS workbench helps to exhibit magnetic field distribution for the structures with a pole piece and a magnetic hat, and under the hypothesis of cylindrical symmetry, two-dimensional finite element optimization by ANSYS APDL gives an optimal set of dimensions of the magnetic hat. Findings – Three structures of the QFA with a pole piece, a non-optimized magnetic hat and an optimized magnetic hat are compared by the simulation in ANSYS Maxwell and experiments measuring the electromagnetic rebalance force. The results show that the optimized hat can supply stronger and more uniform magnetic field, which is reflected by larger and more linear rebalance force. Originality/value – To the authors ' knowledge, the magnetic hat and its dimension optimization have rarely been reported, and they can find significant applications in designing QFAs or other similar magnetic sensors.

Superconductors With Structured Surfaces: Fields and Currents

1987 ◽  
Vol 101 ◽  
Author(s):  
Z.C. Wu ◽  
Daniel A. Jelski ◽  
Thomas F. George
Keyword(s):  
Magnetic Field ◽  
The Other ◽  
Ginzburg Landau ◽  
Landau Model ◽  
Structured Surfaces ◽  
Field Parallel ◽  
First Case ◽  
The Magnetic Field ◽  
Effect Of Structure ◽  
Effect Of Surface

ABSTRACTThis paper discusses the behavior of currents and fields along a structured superconductor. First the effect of surface structure on supercurrents is investigated. Then the effect of structure on the critical nucleation field is discussed in two cases, one with the magnetic field parallel to the ripples and the other with the field parallel to the grating wavenumber. In the first case, it is found that the critical field is reduced as a function of grating height, whereas in the latter case it is increased. Finally, the relevance of this work for laser-induced chemistry above a superconducting surface is discussed. The Ginzburg-Landau model is used throughout.

A Circular Magneto-Hydrodynamic (MHD) Micropump With Electrolyte Solution

2004 ◽  
Author(s):  
Weidong Shen
Keyword(s):  
Magnetic Field ◽  
Cross Section ◽  
Closed Loop ◽  
Pressure Head ◽  
Electrolyte Solutions ◽  
Electrolyte Composition ◽  
Potential Difference ◽  
Copper Electrodes ◽  
Straight Conduit ◽  
The Magnetic Field

Linear and circular magneto-hydrodynamic (MHD) micro-pumps that operate with electrolyte solutions were studied experimentally. Each pump consisted of a conduit with a square cross-section. The linear pump consisted of a straight conduit with its inlet and an outlet subjected to different pressures. The circular pump consisted of a conduit bent into a loop. Copper electrodes were aligned along the two opposite walls of the conduits. Experiments were carried out with various electrolyte solutions such as NaCl, FeCl2/FeCl3, and CuSO4 at various concentrations. The device was placed in a uniform magnetic field and a potential difference was applied across the electrodes. The resulting current interacted with the magnetic field to produce a Lorenz force that propelled the liquid. The electric current and the flow rate were measured as functions of the imposed potential difference across the electrodes, the electrolyte composition and concentration, and the adverse pressure head. The feasibility of using the closed-loop MHD pump to transfer heat from a heat source to a heat sink was also explored.

BEHAVIOR OF CHARGED PARTICLE MOTION IN A MAGNETIC FIELD AND A RETARDING POTENTIAL II – OBSERVATIONS OF THE EXISTENCE OF "FORBIDDEN STATES" AND AHARANOV-BOHM ANALOG IN CLASSICAL MECHANICAL DOMAIN

1993 ◽  
Vol 08 (40) ◽  
pp. 3823-3834 ◽  
Author(s):  
R. K. VARMA ◽  
A. M. PUNITHAVELU
Keyword(s):  
Magnetic Field ◽  
Charged Particle ◽  
Particle Motion ◽  
Electron Gun ◽  
Anode Current ◽  
Forbidden States ◽  
Bohm Effect ◽  
Charged Particle Motion ◽  
The Magnetic Field ◽  
Grid Potential

The observations made earlier1 on the existence of discrete 'forbidden' (and allowed) states in a classical mechanical system of charged particle motion in a magnetic field are extended to include the region where the applied retarding potential exceeds the potential equivalent of the electron energy. The electron current flowing to the ground from the anode of the electron gun is found to exhibit strong dips as the potential on the grid of the detector system kept at a distance along the magnetic field, is swept from a large negative value to zero. The observed anode current 'dips' are quite enigmatic since the electrons under the conditions (grid potential far exceeding the cathode potential) are unable to reach the grid, yet they respond to the grid potential changes in quite an unexpected manner. This observation is thus reminiscent of the Aharanov-Bohm effect in quantum mechanics. The dips are moreover found to fit a relation, a modified form of that given in the earlier reported results.

An experimental study of transverse ionizing MHD shock waves

1968 ◽  
Vol 2 (4) ◽  
pp. 633-652 ◽  
Author(s):  
Charlles F. Stebbins ◽  
George C. Vlases
Keyword(s):  
Magnetic Field ◽  
Shock Waves ◽  
High Speed ◽  
Initial Conditions ◽  
Easy Access ◽  
Low Speed ◽  
Wide Range ◽  
Image Position ◽  
Shock Jump Relations ◽  
The Magnetic Field

The jump conditions across a transverse ionizing MHD shock wave, where the magnetic field is in the plane of the shock, are examined. The conservation laws, in conjunction with Maxwell's laws and the equation of state, yield three jump equations in four unknowns. To uniquely describe jumps across an ionizing wave requires an additional descriptive relationship. The theory of Kulikovskii & Lyubimov and, later, Chu, in which the internal structure of the shock itself supplies the missing relationship, is examined. In particular, Kulikovskii & Lyubimov show, for appropriate ratios of thermal to magnetic diffusivities, that for low-speed waves the magnetic field compression across the shock is unity and the jump equations reduce to the ordinary Rankine—Hugoniot relations. For high-speed shock waves, the magnetic field compression, B2/B1, equals the gas compression across the wave, p2/p1, and the jump equations become the magnetohydrodynamic shock jump relations. Furthermore, intermediate speed shocks induce magnetic field compressions between 1 and p2/p1. An experiment was performed in an inverse pinch where E behind the shock, the shock and piston velocities, and the magnetic field compression across the shock, were measured over a wide range of initial conditions and shock velocities in hydrogen. The jump relations were written with B2/B1 as a parameter and programmed into a digital computer. The program was written for real, equilibrium hydrogen. The program provided easy access to a unique solution of the jump equations for any B2/B1. The experiment tends to confirm the Kulikovskii—Lyubimov—Chu theory. Ordinary shock waves were observed at low speeds and near-MilD shocks were observed at high speeds. Further, the relation was verified for the plasma behind the shock for low-speed shock waves, and was verified to within experimental accuracy for the intermediate class of shock waves.

scholarly journals 5. The axisymmetric case in hydromagnetics

1958 ◽  
Vol 6 ◽  
pp. 46-49
Author(s):  
S. Chandrasekhar ◽  
Kevin H. Prendergast
Keyword(s):  
Magnetic Field ◽  
Recent Work ◽  
Hydrodynamic Equation ◽  
Azimuthal Angle ◽  
Unit Vector ◽  
Velocity Fields ◽  
Laplacian Operator ◽  
Axis Of Symmetry ◽  
Image Position ◽  
The Magnetic Field

Recent work at the Yerkes Observatory has been concerned with the study of configurations in which the magnetic and velocity fields possess a common axis of symmetry. In those cases where the density ρ may be assumed constant, it has proved advantageous to employ a representation suggested by Lüst and Schlüter[1]: in cylindrical co-ordinates (ω, ϕ, z) let and where is a unit vector and T, P, V, and U are independent of the azimuthal angle Φ. The hydrodynamic equation may then be replaced by the pair of equations (cf. Ghandrasekhar [2]) and where Δ5 is the Laplacian operator in 5 dimensions. The equation for the magnetic field, may similarly be replaced by the pair of equations and

scholarly journals A Storage Process of the Magnetic Energy in the Space Active Regions and Stellar Atmosphere

1990 ◽  
Vol 140 ◽  
pp. 17-19
Author(s):  
Li Zhongyuan
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Free Field ◽  
Stellar Atmosphere ◽  
Mhd Equations ◽  
Static Force ◽  
Specific Expression ◽  
Image Position ◽  
The Magnetic Field ◽  
Force Free Field

A few authors (Barnes and Sturrock, 1972; Ma, 1977; Svestka, 1977) have calculated the quantitative relationship between the static force-free field connecting the magnetic field and the twisting processes. They pointed out that the potential magnetic field without the current may be twisted into the force-free field with the enhanced current produced by the plasma rotation. Li et al. (1982) and Li and Hu (1984) have stated that the processes should be unsteady, and especially that they should not be static. The magnetic Reynold number is usually much larger than 100 in stellar atmosphere (Li et al., 1982). We adopt the following MHD equations: where the force - free factor α (t, r) depends on both, t and r. According to t h e kinematical momentum conservation, the following constraint is easily obtained: where V = (u, v, w) is the velocity field in the cylindrical coordinates. When studying the evolution of the kinematical force - free field, the in fluence of a reasonable flow on the variations of the magnetic field should be taken into account. After some reasonable simplification we deduce the specific expression of the variation law of the toroidal magnetic energy where J1 is the Bessel function of the first order. In the active region, magnetic energy including the term of a twisted effect f(t) is larger than that of the static force - free field.

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