Showing papers in "Journal of Physics D in 1990"
TL;DR: In this paper, the authors discussed the stabilisation of a glow discharge at atmospheric pressure which was attained by controlling the following three conditions: the use of a high-frequency source, the usage of He gas for dilution and the insertion of a dielectric plate between electrodes.
Abstract: Some reasons are discussed for the stabilisation of a glow discharge at atmospheric pressure which was attained by controlling the following three conditions: the use of a high-frequency source, the use of He gas for dilution and the insertion of a dielectric plate between electrodes. The three conditions interact: the dielectric plate in a plasma forms the pulsed discharge from a low-frequency source, the fast duration of pulse current prevents a transition to an arc style discharge and a large volume of metastable atomic helium aids ionisation or dissociation near the electrode plate and in the flowing gas. The measurements of discharge-maintaining voltage at several hundred volts provide evidence that this is really a glow plasma at atmospheric pressure. The changes of the emission intensities of metastable helium prove indirectly that some dissociation occurs as a result of the action of the helium atom.
287 citations
TL;DR: In this article, a solution-cast polyethylene oxide (PEO) complexed with ammonium perchlorate (NH4ClO4) has been established using optical microscopy, XRD, DTA, IR, coulometry, transient ionic current and electrical conductivity studies.
Abstract: Proton transport in solution-cast films of polyethylene oxide (PEO) complexed with ammonium perchlorate (NH4ClO4) has been established using optical microscopy, XRD, DTA, IR, coulometry, transient ionic current and electrical conductivity studies. The solubility of NH4ClO4 in PEO is found to be limited to a maximum concentration NH4+/EO ratio of 0.167. The highest conductivity ( approximately 1.05*10-5 S cm-1) is for the film with NH4+/EO=0.02-0.1. The H+ ion transference number, tH+, and mobility, mu H+, are 0.85 and 1.7*10-4 cm2 V-1 s-1, respectively. The movement of ClO4- ions also contributes slightly to the overall charge transport.
217 citations
TL;DR: Extensions of the electrostatic probe technique to situations with negative ions, both theoretical and experimental, are described in this article, where Charged particle distributions and the plasma-sheath boundary are discussed in relation to probe measurements.
Abstract: Extensions of the electrostatic probe technique to situations with negative ions, both theoretical and experimental, are described. Charged particle distributions and the plasma-sheath boundary are discussed in relation to probe measurements. Plasmas with negative ions, their occurrence and interest, particularly situations where the negative ion density becomes comparable to or exceeds the electron density are described. Some data in negative ion containing plasmas are shown and discussed.
185 citations
TL;DR: In this paper, the performance of a class of irreversible Carnot refrigeration cycles operating between two heat reservoirs at a low temperature TL and a high temperature TH, for which the only irreversibility results from the finite rate of heat conduction, is studied.
Abstract: The performance of a class of irreversible Carnot refrigeration cycles operating between two heat reservoirs at a low temperature TL and a high temperature TH, for which the only irreversibility results from the finite rate of heat conduction, is studied. The relation between the optimal rate of refrigeration and the coefficient of performance of these cycles is derived, based on a general heat transfer law. Moreover, the optimal performance of these cycles is discussed and the effect of different heat transfer laws on the optimal performance is investigated. Consequently, some new and useful results for refrigeration cycles are obtained.
149 citations
TL;DR: In this paper, an atmospheric-pressure glow discharge plasma method was developed for surface treatment and deposition on insulating surfaces for purposes of large-scale system treatment, but this method was not able to treat metallic substrates.
Abstract: Recently the authors developed an atmospheric-pressure glow discharge plasma method which can be applied to surface treatment and deposition on insulating surfaces for purposes of large-scale system treatment. However, this method was not able to treat metallic substrates. Consequently, they have improved the upper electrode to enable metal substrates to be treated. Some organic films were polymerised by the atmospheric-pressure method. Comparison of results from the atmospheric-pressure glow plasma method with those obtained by the low-pressure glow plasma method showed no differences in the chemical structures of plasma-polymerised films.
148 citations
TL;DR: In this article, the effects of high temperature and pre-irradiation annealing on the pre-dose thermal activation curves are examined, and it is shown that if a quartz sample is only partially 'fired', i.e. heated only to moderate temperatures (300-450 degrees C, rather than the usual 950-1000 degrees C), then a large sensitivity increase is observed during the thermal activation curve measurement which is not due to pre-dosing sensitisation.
Abstract: In the authors' previous work data have been presented which indicate that thermoluminescence (TL) at 110 degrees C in crystalline quartz is due to the recombination of electrons released from (GeO4)- centres with holes trapped at (AlO4)0 centres and at unidentified hole traps. In this paper new results are presented which identify the latter defect with (H3O4)0 centres. These defects are seen to anneal in exactly the same fashion as the (AlO4)0 centres during the production of TL at 110 degrees C, and are seen to sensitise slightly when pre-exposed to radiation and subsequently heated to near 400 degrees C. The effects of high temperature and pre-irradiation annealing on the pre-dose thermal activation curves are also examined. The data show that if a quartz sample is only partially 'fired', i.e. heated only to moderate temperatures (300-450 degrees C, rather than the usual 950-1000 degrees C), then a large sensitivity increase is observed during the thermal activation curve measurement which is not due to pre-dose sensitisation . This effect may have important consequences in pre-dose dating and dosimetry.
128 citations
TL;DR: The Langmuir-Blodgett technique is a way of making ultrathin organic films with a controlled layer structure, which have many possible applications in technology for signal processing and transformation.
Abstract: The Langmuir-Blodgett technique is a way of making ultrathin organic films with a controlled layer structure, which have many possible applications in technology for signal processing and transformation. Recent research has shown that their characteristics are strongly influenced by the highly anisotropic, essentially two-dimensional organisation of their constituent molecules. Novel effects in charge transport at the molecular scale ( approximately 1 nm) appear to be connected with very strong electron-phonon interactions, but are still not understood.
123 citations
TL;DR: In this article, a two-dimensional stochastic model of electrical treeing in solid dielectrics has been examined using 'fractal' analysis and statistical methods, and it is found that simulated trees display remarkably similar behaviour to that found experimentally.
Abstract: A two-dimensional stochastic model of electrical treeing in solid dielectrics has been examined using 'fractal' analysis and statistical methods. It is found that simulated trees display remarkably similar behaviour to that found experimentally. A distribution of dimensions is found and simulated failure probability is well described by the two-parameter Weibull distribution. Several methods of assessing fractal dimension are critically compared and correlations are found between different methods. The influence of model parameters on tree growth behaviour is also examined.
118 citations
TL;DR: In this paper, the autograph method was used to investigate the arc spot motion over a virgin tungsten cathode under a magnetic field of H=0.1-0.7 T in the current range 2-50 A. The cathode spot (CS) has been found to start dividing at a current of a few amperes.
Abstract: The autograph method was used to investigate the arc spot motion over a virgin tungsten cathode under a magnetic field of H=0.1-0.7 T in the current range 2-50 A. The cathode spot (CS) has been found to start dividing at a current of a few amperes. The current density measured at the moment of CS death is (1.2+or-0.5)*1011 A m-2 for a cold cathode and (3+or-1)*1010 A m-2 for a hot one. The CS lifetime is 25-50 ns for a cold cathode and it increases to 150-200 ns for a heated one. Neither the current density nor the CS lifetime depends on current. Estimates have shown that the erosion rate decreases with current and increases with temperature. The backflow electron current from the CS plasma is invoked to account for the experimental evidence.
114 citations
TL;DR: In this paper, the complex permittivities (dielectric properties) of two plastics, Rexolite 1422 and Kynar, were measured at frequencies of 2.45, 11.5 and 22.0 GHz at 25 degrees C by the short-circuited waveguide technique.
Abstract: The complex permittivities (dielectric properties) of solid and pulverised samples of two plastics, Rexolite 1422 and Kynar, were measured at frequencies of 2.45, 11.5 and 22.0 GHz at 25 degrees C by the short-circuited waveguide technique. Several dielectric mixture equations and extrapolation of functions of the dielectric constants and loss factors that are linear with bulk density were then used to estimate the permittivities at solid-material densities from measurements on the pulverised samples. For these materials, the best estimates of the permittivities were provided by extrapolations that are consistent with the complex refractive index and Landau and Lifshitz, Looyenga mixture equations. The Bottcher mixture equation often gave values very close to the Landau and Lifshitz, Looyenga equation, and the Bruggeman-Hanai, Rayleigh and Lichtenecker mixture equations gave increasingly larger permittivity estimates in that order.
106 citations
TL;DR: In this article, a number of statistical models are developed and discussed with the aid of experimental data and the general trends obtained can be used to aid the interpretation of the engineers' data.
Abstract: The engineers' approach to dielectric breakdown has traditionally been one of testing leading to life prediction and material comparison. On the other hand, the scientist has attempted to understand the mechanism of specific breakdown processes. It is shown here that the former approach is prone to ambiguity and that a need exists to understand not just the physics of breakdown processes but also their resulting statistics. A number of statistical models are developed and discussed with the aid of experimental data. Finally it is shown how the general trends obtained can be used to aid the interpretation of the engineers' data.
TL;DR: In this paper, the tin disulphide (SnS2) was chemically deposited for the first time from an acidic bath, using sodium thiosulphate (Na2S2O3) as a sulphur source, onto glass, tin oxide-coated glass and titanium substrates.
Abstract: Thin films of tin disulphide (SnS2) have been chemically deposited for the first time from an acidic bath, using sodium thiosulphate (Na2S2O3) as a sulphur source, onto glass, tin oxide-coated glass and titanium substrates. Their electrical, optical and photoelectrochemical properties have been studied. The chemically deposited SnS2 films are n-type semiconductors and the optical band gap is 2.35 eV. The room temperature resistivity is of the order of 103-104 Omega cm. As-deposited SnS2 films showed photovoltaic activity.
TL;DR: In this paper, the safety and cost and the optimisation of chemically deposited PbS thin films for solar control applications are presented. But the results of the analysis are limited to the case of 3 mm thick clear glass with a shading coefficient of approximately 50%.
Abstract: Assessments of safety and cost and the optimisation of chemically deposited PbS thin films for solar control applications are presented. The maximum integrated infrared reflectance, 44%, is obtained at a PbS thin film thickness of approximately=95 nm. The corresponding value of the solar control parameters (AM2 case) are: integrated infrared transmittance, 45%; integrated visible transmittance, 17% (yellowish appearance); integrated visible reflectance, 21% (purple appearance); and integrated solar absorptance, 36%. The total solar radiation and heat transfer into the building through a glazing with such a PbS coating is less than 44%, as compared with the approximately=84% of 3 mm thick clear glass, giving a shading coefficient of approximately=50%. A film thickness of 95 nm is obtainable with a deposition time of 50 min from a bath (at 24 degrees C) containing Pb2+ ions and thiourea in the 1:3 molar ratio. However, molar ratios up to 1:5 may be employed, thereby enabling the reduction of deposition time to 35 min. Analyses of the safety and the cost of these coatings have shown excellent promise for their application as medium-efficiency low-cost solar control coatings appropriate for small-scale industrial and 'do-it-yourself' production of the coatings.
TL;DR: In this article, the time dependence of discharge processes in dielectric bounded voids of 40 mm have been studied under power frequency voltage and fast oscilloscopic techniques were used to observe the pulse shape of single discharges or clusters of discharges.
Abstract: The time dependence of the discharge processes in dielectric bounded voids of 40 mm have been studied under power frequency voltage. Fast oscilloscopic techniques were used to observe the pulse shape of single discharges or clusters of discharges. Synchronous optical registration of discharge images was performed using a highly sensitive video system. At least two distinct discharge types were registered as a function of time. A 'streamerlike' discharge regime is gradually replaced by a more diffuse 'Townsendlike' discharge regime. This transition could be recognized in the shape of the discharge pulses and in the pattern of the optical image. A key parameter governing the transition is the surface resistance of the void-dielectric interfaces. This surface resistance was seen to decrease gradually due to discharge by-products. In its turn, a low surface resistance strongly favours the transition from 'streamerlike' to 'Townsendlike' discharges.
TL;DR: In this article, a molecular approach is taken to describe charge transport and charge injection in insulating polymers, which satisfactorily predicts low and high-field conductivities and is compatible with electrostatic contact-charging phenomena.
Abstract: A molecular approach is taken to describe charge transport and charge injection in insulating polymers. Localized acceptor and donor states are shown to develop from the energy bands of a regular polymer chain when polymer morphology is taken into account. Charge transport then requires resonance tunnelling between reduced and oxidized states and an important factor is the reorganization energy accompanying localization. The same processes, which are of an electrochemical nature, are used to describe electron transfer across electrode-polymer interfaces. The approach satisfactorily predicts low- and high-field conductivities and is compatible with electrostatic contact-charging phenomena. It also illuminates the likely initiatory stages of electrical and water tree formations at breakdown fields. A satisfying result is that similar models may be used to describe both insulating and 'synthetic metal' polymers at opposite ends of the conductivity spectrum.
TL;DR: The analysis of the Doppler profile of the Balmer Halpha line in the cathode sheath and negative glow of a hydrogen glow discharge shows an important concentration of anisotropic energetic atoms as mentioned in this paper.
Abstract: The analysis of the Doppler profile of the Balmer Halpha line in the cathode sheath and negative glow of a hydrogen glow discharge shows an important concentration of anisotropic energetic atoms. This translational energy is regarded as mainly resulting from reactions including ions accelerated by the cathode sheath electric field. The mechanisms involved are gas-phase charge-exchange collisions producing fast atoms moving toward the cathode and simultaneous neutralisation and backscattering of the ions at the cathode surface leading to energetic atoms moving in the other direction. Quantitative analysis shows that most of the emission of the fast atoms results from excitation directly produced by these ion impact reactions.
TL;DR: In this paper, a 2.2 kV beam is used to inject a short pulse of charge into the free surface of a thin film of polystyrene and a second electron beam monitors the surface potential of the film.
Abstract: The energy distribution of localized states in monodisperse polystyrene (37000 MWt) has been studied by observing the detrapping of electrons from the polymer. The states are populated by means of an electron beam. A 2.2 kV beam is used to inject a short pulse of charge into the free surface of a thin film of the polymer and a second electron beam monitors the surface potential of the film. The surface potential is proportional to trapped charge density, and the time derivative of the potential is a measure of the current flow, which is related to the release kinetics of the electrons trapped in the polymer. The release of electrons from traps is analyzed in terms of a demarcation energy, Em. Following Simmons and Tam's analysis of the isothermal discharge this energy is so defined that the release of the excess electrons from traps of depth Em occurs in a time equal to the elapsed time from the injection event. The energy Em is then related to elapsed time through the equation Em=kT ln ( nu 0t), and the density of occupied states at Em is proportioned to tdV/dt. From the temperature dependence of the appearance time of peaks in the density of localized states, the attempt frequency nu 0 can be calculated. Based on such measurements, at temperatures from 30 to 90 degrees C, the author estimates the attempt frequency to be about 1011 s-1.
TL;DR: The preparation and properties of K2Ca2(SO4)3 doped with Eu are described in this article, where it is claimed that this phosphor can replace CaSO4:Dy.
Abstract: The preparation and properties of K2Ca2(SO4)3 doped with Eu are described. The phosphor is five times more sensitive than CaSO4:Dy. It has a linear response, simple glow curve, emission peaking at 415 nm, negligible fading and excellent reusability. It is claimed that this phosphor can replace CaSO4:Dy.
TL;DR: In this paper, it is shown how streamers and tree-like structures develop; how, on the surface of these primary streamers, instabilities initiate fast growing secondary streamers; and how these events lead to the establishment of a conducting channel.
Abstract: The phenomenon of electrical breakdown in condensed matter has been the subject of many studies. While the ultimate result is relatively easy to observe and study, attempts to uncover its initial phases that lead to the short circuit as evidenced by light and acoustical emissions defied discovery. In the past decades some of the initial phases of the breakdown process have been elucidated with the help of sophisticated devices that permit registration on photographic film and/or on transient digitizing instruments. The progress made in this field is summarized and an attempt is made to establish the significance of these observations. Starting with the events occurring at the metal surface, it is shown how streamers and tree-like structures develop; how, on the surface of these primary streamers, instabilities initiate fast growing secondary streamers; and how these events lead to the establishment of a conducting channel. These stages are examined in the light of published information. The implications of these findings in terms of the performance of actual systems are also considered.
TL;DR: In this paper, a method is described whereby ion implantation profiles in amorphous materials may be accurately represented by Pearson frequency distribution curves, and the type of Pearson distribution to be used depends upon the implantation conditions but it is shown that the three main types, I, IV and VI, together with the transition types II, III, V, VII and the Gaussian are all suitable representations.
Abstract: A method is described whereby ion implantation profiles in amorphous materials may be accurately represented by Pearson frequency distribution curves. The type of Pearson distribution to be used depends upon the implantation conditions but it is shown that the three main types, I, IV and VI, together with the transition types II, III, V, VII and the Gaussian are all suitable representations. Previous attempts to fit Pearson curves to implantation profiles have often failed due to semi-infinite moments being used instead of infinite moments. This approximation is only valid when the surface concentration of implanted ions is negligibly small.
TL;DR: In this article, a correlation between the IH/ICH intensity ratio and the bulk electron density measured by double probes has been found, but no correlation was found between the emission intensities of various species and the deposition rates.
Abstract: Methane plasmas excited at 25 kHz and 13.56 MHz used for a-C:H deposition have been studied by optical emission spectroscopy. At 25 kHz the emitted bands and lines, namely CH (431.4 nm), H (486.1 nm) and H2 (463.4 nm), have been found to result from dissociative excitation of the CH4 molecule under electron impact. It is supposed that the fast electron beam formed by the accelerated secondary electrons is predominant. In this discharge a correlation between the CH emission and the deposition rate is found. In contrast to the 13.56 MHz discharge the Hbeta emission appears to result from both dissociative excitation from CH4 and electron impact excitation of H atoms present in the bulk of the discharge. A correlation between the IH/ICH intensity ratio and the bulk electron density measured by double probes has been found. However, no correlation has been found between the emission intensities of various species and the deposition rates. It is thought that processes in the vicinity of the RF electrode on which deposition occurs are predominant.
TL;DR: In this article, a new evolution equation with new transport parameters, which are obtained directly from the arrival-time spectra, is introduced, and relations between the longitudinal transport coefficients and the new parameters are also presented.
Abstract: Arrival-time spectra of the evolution of swarms in the hydrodynamic regime have been studied theoretically starting from the Boltzmann equation and its eigenvalue problem. In order to express the development of the number density of the one-dimensional pulse swarm, a new evolution equation with new transport parameters, which are obtained directly from the arrival-time spectra, is introduced. Relations between the longitudinal transport coefficients and the new parameters are also presented. By means of this theory, it is shown that the distribution functions for the different types of experiments (steady-state Townsend or pulsed Townsend) are distinguished from each other in non-conservative cases, and drift velocities defined by different principles have in general their own values even if the kind of gas and the value of E/N are the same.
TL;DR: In this article, a transformer model for discharge and induction coil is derived from the Maxwell's equations and applied to a low-pressure argon-mercury discharge excited between 3 and 8 MHz.
Abstract: A method is described for the determination of current, power, electrical conductivity and the electric and magnetic field strengths in electrodeless inductive low-pressure gas discharges. A transformer model for discharge and induction coil is derived from Maxwell's equations. The method is applied to a low-pressure argon-mercury discharge excited between 3 and 8 MHz.
TL;DR: In this paper, cross sections of RF sputtered MoS2 thin films are investigated using lattice resolution transmission electron microscopy and electron diffraction, and the results are compared with X-ray diffraction measurements.
Abstract: Cross sections of RF sputtered MoS2 thin films are investigated using lattice resolution transmission electron microscopy and electron diffraction. The results are compared with X-ray diffraction measurements. The films have a (001) texture (type II) in the first nanometres near the interface and a conventional (100) texture (type I) in the upper part.
TL;DR: In this article, low-frequency (approximately 500-approximately 2000 Hz) oscillations are detected in a double-plasma device in association with double layers in which the potential drop somewhat exceeds the ionisation potential of the gas.
Abstract: Low-frequency ( approximately 500- approximately 2000 Hz) oscillations are detected in a double-plasma device in association with double layers in which the potential drop somewhat exceeds the ionisation potential of the gas. The oscillations are interpreted as ion-acoustic waves excited by an ionisation instability. A simple theory of the instability is presented and its results are compared with observations.
TL;DR: In this paper, a comparison of two different theoretical approaches to model kinetic processes in N2 discharges is presented and discussed, and the conclusions drawn from both models are qualitatively in agreement as to the important role of the coupling between the electron and the vibrational kinetics.
Abstract: A comparison of two different theoretical approaches reported in the literature to model kinetic processes in N2 discharges is presented and discussed. One of these approaches is directly concerned with steady-state conditions and the other analysis with the evolution of the properties of the medium from a cold gas situation up to nearly equilibrium conditions as time evolves. Both approaches are based on solutions to the coupled system of the electron Boltzman equation and the kinetic equations for the N2(X,v) vibrational levels, but they differ by the approximations used to model atomic recombination processes and by the choice of collisional data. The conclusions drawn from both models are qualitatively in agreement as to the important role of the coupling between the electron and the vibrational kinetics. However, due to the different data and recombination models used different results are obtained for equilibrium conditions, namely for that concerning the rate of dissociation, the degree of vibrational excitation, and the electron rate coefficients. In particular, the present analysis shows that a deeper knowledge of atomic recombination processes is necessary in order to improve the reliability of both models.
TL;DR: In this paper, a narrow size distribution of irregular aluminium particles was blended into power cable insulation grade polyethylene, and some batches of the resulting material were then melt-filtered to reduce the size of particles present and narrow the distributions further.
Abstract: A narrow size distribution of irregular aluminium particles was blended into power cable insulation grade polyethylene. Some batches of the resulting material were then melt-filtered to reduce the size of particles present and narrow the distributions further. The failure statistics of the loaded polymers were then determined under AC ramped stress. The data have been fitted to extreme value statistics, and trends with size and density of defect can clearly be identified. In addition, for the filtered material, a minimum breakdown field can be associated with a given filter size: a result of commercial importance. Some indications exist to suggest that different modes of failure operate at high and low fields. Candidates for these modes are analysed and discussed in terms of the distributions of defects present. Local field enhancement due to the included flaws were calculated using finite-element techniques. The results are compared with a percolation model of breakdown. Predictions are found to quantify accurately the reduction in the characteristic strength of the material over the narrow range of defect concentrations examined.
TL;DR: In this paper, the analysis of several parameters for recognizing patterns of partial discharges in a dielectric was carried out using different statistical operators such as skewness, kurtosis and modified cross correlation.
Abstract: In recent years investigations of the use of digital evaluation of partial discharges have become increasingly important Such methods of evaluation greatly improve the recognition of discharge patterns and the correlation of these patterns with various types of defects Conventional methods of oscillographic observation provide a limited recognition of defects causing discharges A powerful interpretation of the discharge signals can be achieved when a large number of discharge quantities are measured simultaneously, making use of their stochastic character A computer-aided discharge analyser has been built for continuous and multiparameter registration This paper concentrates on the analysis of several parameters for recognizing patterns of partial discharges in a dielectric A combination of statistical and discharge parameters was studied to discriminate between different types of cavities Two phase-angle quantities, pulse counts and mean pulse height distributions as a function of phase angle, were processed, using different statistical operators such as skewness, kurtosis and modified cross correlation The tests on samples with different internal defects have shown that significant differences exist in the behaviour of discharge parameters Three of these parameters provide a good description of discharge and offer a good discrimination between different internal defects
TL;DR: In this paper, the arrangement of cells in undifferentiated vegetable tissues of five different species was studied and the distribution of the number of sides, the average area (an), perimeter (pn), and side length (ln) of n-sided cells were determined.
Abstract: The authors study the arrangement of cells in undifferentiated vegetable tissues of five different species The distribution of the number of sides, the average area (an), perimeter (pn) and side length (ln) of n-sided cells are determined as well as the correlation between the number of sides of a cell and of its neighbours The results show that vegetable cellular nets obey Aboav-Weaire's law They also discuss Lewis' law and a possible relation between (pn) and n The analysis of these structures provides a different example of random cellular structures and helps to show general aspects of the ideal one
TL;DR: In this article, the behavior of polyethylene under the influence of high electric fields was investigated and it was shown that if two sets of traps are assumed, not only the thermodynamic equilibrium occupation but also the dynamic capture and escape processes must be taken into consideration for the deep ones and anomalies found experimentally under the presence of high electrical field strengths in the region of more than 30 kV mm-1 can be explained.
Abstract: The paper presents results of experiments undertaken to elucidate the behaviour of polyethylene under the influence of high electric fields. Especially when using virgin samples, some 'anomalies' occur that are a result of a slow transition of the polymer to a preloaded state. It is shown that if two sets of traps are assumed, not only the thermodynamic equilibrium occupation but also the dynamic capture and escape processes must be taken into consideration for the deep ones and anomalies found experimentally under the influence of high electric field strengths in the region of more than 30 kV mm-1 can be explained. A numerical simulation program leads to qualitatively correct results.