Mathematical simulation of an inclined neutralization channel for a plasma source of neutral beams

An earlier developed model for a neutralization channel of a plasma source of neutral beams is applied to the case of an inclined neutralization channel. The energy and angular characteristics of the output beam are presented together with the neutralization factor as a function of the length and inclination angle of the channel. Strong angular separation of ions and fast neutral particles is observed in the sources of this design. Under a restricted range of angles of the output beam, this effect allows one to efficiently remove a considerable part of the ions from the output beam, thus increasing the neutralization factor.     

Radiation from a magnetic ring source encircling a drifting plasma column

The problem of radiation from a magnetic ring source encircling a plasma column drifting uniformly with a relativistic velocity is treated. In order to know the effect of the motion of the plasma on the radiation, first the radiation pattern for the ring source is investigated. From the numerical examples it is found that the lobe of the radiation pattern shifts in the direction of the plasma motion. Secondly the properties of the surface waves, which propagate along the plasma column, are investigated in detail. It is shown that the dispersion curve exhibits the characteristic natures which do not appear in the case of stationary plasma; in the case of drifting plasma the surface waves are generally excited to higher frequency extent, having no cut-off frequency.     

Radiation propagating transverse to the external magnetic field from an electromagnetic source in an unbounded plasma

The radiation characteristics of a line source of magnetic current embedded in an unbounded plasma are investigated for the case in which a uniform magnetic field is impressed externally throughout the medium in the direction of the source. The plasma is assumed to be a homogeneous and macroscopically neutral mixture of compressible gas of electrons and ions. A two-fluid continuum theory of plasma dynamics is employed. It is shown that it is possible to define three suitable wave functions which satisfy separately simple wave equations whose solutions are written down by inspection. These wave functions specify the three possible modes which are identified, respectively, to be the modified forms of the electromagnetic, the electron plasma and the ion plasma modes. The limiting behavior of these modes are discussed for the following two cases: 1) infinite source frequency and 2) vanishing external magnetic field. The dispersion relations for the three modes are examined in detail for the general case using a perturbation procedure. It is shown that the modified ion plasma (MIP) mode propagates for all frequencies whereas both the modified electron plasma (MEP) mode and the modified electromagnetic (MEM) mode have a low-frequency cutoff. Explicit expressions for the cutoff frequencies are obtained. The power radiated in each of the three modes is also evaluated. It is found that the power radiated in the MEM mode is always lower than that due to the line source in free space, whereas the power radiated in the two plasma modes is higher than that value for certain ranges of frequency.     

Measurement of magnetic fields radiated from ESD using fieldsensors

The goal of this paper is to show that commercial sensors, whose frequency response is not specifically designed, can be effectively used to measure very fast transient fields applying a proper reconstructing procedure based on the knowledge of the sensor transfer function. To do this, it is necessary to characterize a structure supporting a transverse electromagnetic (TEM) field, that will be used to set up a calibration procedure for elementary magnetic field sensors. The approach is completely analytical and allows us to know rigorously the field inside the structure. From the knowledge of this field, the transfer function of the sensor, in amplitude and phase, is evaluated up to 2 GHz. The complete characterization of the sensor allows us to reconstruct the sensed field from its output voltage waveform. The calibration procedure is carried out in time domain and therefore the fast Fourier transform (FFT) algorithm is used to achieve the sensor transfer function, as well as an inverse FFT (IFFT) is necessary to retrieve the transient impinging field. An experimental validation of the procedure shows the consistency of the approach     

Production and analysis of one-dimensional magnetic deflection fields

An experimental yoke consisting of four sets of independently excited coils has been made. The field distribution of the experimental yoke can be controlled to approximate the theoretically calculated ideal fields, which produce minimum aberrations for certain specified working distances, field coverage, and beam convergence angle. The aberrations that would be produced by the experimental yoke are calculated and compared with those of the ideal field.     

Radiation in a warm plasma from an electric dipole with a cylindrical column of insulation

The radiation in a warm plasma due to an axially oriented electric dipole on the axis of a cylindrical column of insulation of infinite length is studied using the linearized continuum plasma theory, and approximate boundary conditions. Two types of surface waves are excited along the cylindrical column of free space immersed in a plasma and their dispersion and power relations are examined. The uncoupled electromagnetic (EM) and the plasma (P) space waves are excited. The radiation pattern and the normalized radiation resistance of the EM and the P modes are studied both as a function of frequency and as the radius of the insulating column. The effect of the insulating column is found to be very significant only in the case of the P mode. It is found that the power transfer into the P mode becomes less at higher frequencies and larger thickness of the insulation. The results of this investigation may be used to predict in a crude manner the effect of the "ion sheath" that is formed around the antenna in the ionosphere.     

Low-frequency dosimetry of inhomogeneous magnetic fields using the coil source model and the household appliance

In this paper, the magnetic field properties and the dosimetry at ELF (50 Hz) are investigated using a coil model, which is prescribed in the European standard EN50366 (CENELEC) as a substitute source model for real household appliances. The accuracy of magnetic field vectors and values of the induced current density, which is achieved with the coil model, were compared with the results of two test appliances (a drilling machine and a hand mixer) obtained from the equivalent source model. It was demonstrated that the magnetic fields obtained (dominant component and strength) using the coil model and the real appliance show an agreement with each other with a maximum difference of 5 dB. The calculated induced current densities in the numerical human body models (homogeneous and anatomical body models) and the real appliances also show a good agreement with each other with a maximum difference by a factor of 1.6 (by the anatomical body model). Furthermore, the values of both field vectors and induced current density values calculated using the coil model were shown to be higher than those calculated in the case of the real appliances. Based on these results, the applicability of the coil model prescribed in EN50366 confirms that of the two applied test appliances.     

Effect of a strong axial magnetic field in the plasma recombinationand extreme ultraviolet emission from a highly-ionized capillarydischarge

The effect of an externally applied 70-100-kG axial magnetic field in the temporal evolution of the extreme ultraviolet emission from a 500-μm-diameter highly ionized LiH capillary discharge is studied. In the absence of external magnetic confinement, strong emission from ionic transitions excited by collisional recombinations is observed at the end of the current pulse. The externally applied magnetic field is observed to reduce the intensity of the recombination lines by decreasing the rate of plasma cooling by electron heat conduction to the capillary walls. In contrast, the self-generated magnetic field of the discharge aids to the generation of an initially hot plasma, and allows rapid conduction cooling at the end of the current pulse. The results are discussed in relation to a proposed capillary-discharge-excited extreme ultraviolet recombination laser scheme     

Simulation and experimental investigation of a multi-pole multi-layer magnetorheological brake with superimposed magnetic fields

This paper presents comprehensive investigations on a new multi-pole multi-layer magnetorheological (MR) brake. This unique design features MR working gaps set between two-layer individual coils. Independent current supply was proposed to generate more flexible braking torque and lower power consumption. In this article, an exploded-view drawing of the proposed MR brake was presented, and theoretical analyses of the braking torque and temperature characteristic were conducted. Then, finite element analysis was performed to verify the effect of the magnetic field superposition. A prototype MR brake was fabricated and tested to evaluate the magnetic field superposition, preliminary dynamic behavior, temperature and the performance of individual input current. The results show that the magnetic field superposition has much influence on the braking torque, and individual current supply results in different power consumption and torque ranges. Moreover, the dynamic response performance of this brake is less affected by the slip speed. Furthermore, the maximum steady-state slip power of the proposed brake is about 160 W, and the greater the slip power is, the faster the temperature increases. The results also have verified the correctness of the structure and magnetic circuit design.     

Detection of DC and low-frequency AC magnetic fields using an all single-mode fibre magnetometer

A technique for the determination of weak DC and low-frequency AC magnetic fields using a single-mode-fibre magnetometer is described. The technique utilises the dependence between the AC responsitivity and bias field to detect small changes in the bias field. Detection sensitivities in the milli-gauss/metre region have been obtained using a bulk nickel magnetostrictive element with microgauss sensitivities predicted for certain types of metallic glass.     

Evaluation of electron temperature in transverse and axial magnetic fields in an arc plasma by diffusion voltage measurement

The diffusion voltage in a mercury arc plasma has been measured for arc currents from 2.5 A to 5 A in transverse and axial magnetic fields from zero to 1.1 kG. Assuming the radial distribution of charged particles proposed by Ghosal et al, (1978) and utilizing the method of Sen et al. (1983), the ratio of electron temperatures with and without a magnetic field has been evaluated. It becomes a maximum in an axial field and then decreases, whereas it shows a minimum in a transverse field and then increases. An expression for the ratio of the electron temperature with and without a field has been deduced that explains these results. Quantitative agreement between experiment and theory is fairly satisfactory.     

Intersubband far-infrared emission and magnetotransport of 2D hole gas in a strong in-plane electric field and transverse magnetic fields

We observe FIR emission and magnetotransport phenomena of modulation doped p-GaAs/AlGaAs multi-quantum wells structures of different well width in a streaming regime. This FIR emission originates from radiative transitions between the upper quantum subbands, where hot holes are trapped by the emission of LO-phonons and the ground quantum state. The importance of the light-heavy states mixing with an increase of confinement effect is shown experimentally. The magnetoresistance in a strong in-plane electric field applied along the [110] crystallographic direction is found to be negative, which is explainedDby strong warping of the constant hole energy surfaces in two-dimensional quantum wells.     

Hydrogen passivation of PolySilicon MOSFET's from a plasma Nitride source

Improvements in polysilicon grain-boundary passivation techniques have made polysilicon MOSFET's increasingly attractive, as vertically stackable circuit components in applications, where high mobility is not a primary requirement. A simple method for the "last step" passivation of grain boundaries in polysilicon MOSFET's is presented. The method involves diffusion of atomic hydrogen at 450°C from a plasma-deposited compressive silicon nitride layer for reaction at silicon grain-boundary dangling bond sites. By use of this technique, ON/OFF current ratios of greater than 10⁶can be achieved with drive currents that are sufficient for many circuit applications.     

Estimation of wave fields of incident beams in a transmission electron microscope by using a small selected-area aperture

The direction of an electron beam in a nanometer-sized area is measured directly by utilizing a selected-area aperture. By the measurements at several areas in a beam, the wavefront curvature and thus the defocus value of the beam are detected. From the defocus value, the wave field at the specimen plane is also reproduced in consideration of the influences of the condenser aperture and spherical aberration of the illumination lens. The result shows that phase deviation of 2π is caused only at about 10?nm apart from the beam center in a beam with a typical diameter for high-resolution transmission electron microscopy. Based on the defocus value, the convergence angle of the beam is also estimated to be about 6?mrad without being influenced by the partial coherence, that is, independently of the type of the electron gun. Measuring the defocus values for only two beam diameters enables us to determine geometrical parameters peculiar to the illumination system, based on which wave fields of any beam diameters by any condenser aperture sizes can be estimated. The technique proposed in this paper is effective in evaluating the influence of wavefront curvature of incident beams on various kinds of precise measurements conducted in transmission electron microscopes.     

Motion of a charged particle in electric and magnetic fields

The motion of a charged particle in time-varying uniform electric and magnetic fields has been determined exactly by writing the Lorentz force equation in a matrix form. The general solution is obtained by solving the ordinary first-order linear differential equation.     

Instability regions of an electron beam in superimposed periodic and uniform magnetic fields

The stability of an electron beam in a superimposed sinusoidal and uniform magnetic field is theoretically and experimentally investigated. The first instability region degenerates to a point within the first well-known passband for a zero uniform field component, whereas the second instability region coincides with the first stopband of the sinusoidal field. These considerations are of practical significance for periodic magnetically-focused electron beams.     

Tunnel emission of electrons in photo-field detectors and in an auger transistor in very strong electric fields

The effect of a strong electric field [(5–7)×10⁷ V cm^?1] on the electron emission from a semiconductor to vacuum in photo-field detectors and in MIS structures with a tunnel-transparent insulator layer (Al-SiO₂-n-Si Auger transistor) has been studied. It is shown for the first time that the existence of deep self-consistent quantum wells on the semiconductor surface in a strong electric field provides a possibility of controlling the energy of fast electrons responsible for the impact ionization near the base of the Auger transistor and changes the photosensitivity of narrow-gap photo-field cathodes in the IR spectral range due to the formation of a transistor structure at the semiconductor-vacuum interface. It is also demonstrated that, both in photo-field detectors and in tunnel Al-SiO₂-n-Si transistor structures, only the electron tunnel current should be taken into account and the hole current, disregarded. The reason for this is that only the electron current exists in vacuum, and the tunneling of holes in Al-SiO₂-n-Si from the semiconductor into the metal is unlikely because of the large hole effective mass in the valence band of SiO₂.     

Efficiency of a stepped reflector when fed from an off-axis source

A correlation technique has been used to find the efficiency of a stepped reflector, given the focal-region field and the aperture field of the feed. The scanning properties of the antenna predicted by this theory agree well with existing experimental data.     

Theoretical investigation of an integrated all-opticalcontroller-modulator device using QCSE in a multiquantum wellphototransistor

Theoretical investigation of an all-optical controller-modulator device based on excitonic transitions for the purpose of a general logic implementation are discussed. The device is based on the quantum confined Stark effect of the heavy-hole excitonic transition in a multiquantum well. The device consists of three basic elements: modulator, controller, and load. The controller is a heterojunction phototransistor with multiquantum wells in the base-collector depletion region. This allows an amplified photocurrent-controlled voltage feedback with low light levels, allowing one to change the state of the modulator. A detailed analysis of the sensitivity of this device in various modes of operation (i.e. floating base and contacted base) is presented. Studies on the cascadability of the device as well as its integrating-threshold properties are also presented. Switching of the resistive load and optically active load with less than 10 μW total power is demonstrated to be feasible     

Radiation from an electromagnetic source in a half-space of compressible plasma-surface waves

The radiation characteristics of a line source of magnetic current are studied for the case in which the source is situated in a half-space of isotropic, compressible plasma which is bounded on one side by a perfectly conducting, rigid plane screen. In addition to the electromagnetic and plasma space waves, the line source excites a boundary wave. This boundary wave is a coupled wave. It has associated with it both a magnetic field component and the pressure term. This is in contrast to the space waves which can be decomposed into an electromagnetic (EM) mode with no pressure term and a plasma (P) mode with no magnetic field associated with it. The characteristics of this boundary wave are evaluated. The boundary wave propagates for all frequencies and the power carried by the boundary wave becomes smaller as the frequency is increased.