Current Pulse Generator Research Articles

Generation of microwave current pulses in the erosion plasma of a metallic target by two-frequency laser radiation

When IR laser radiation that is intensity-modulated at a frequency of 1.1 GHz is incident on a conducting target in a rarified gas at a pressure of 0.1 torr, microwave modulation of the current pulses generated in the erosion plasma is observed. A microwave signal with a voltage amplitude of 2 V is obtained at a laser intensity of 100 GW/cm2. The efficiency of the conversion of laser energy to the microwave band at an intensity of 10 GW/cm2 is 2.5 ? 10?7.

High current pulse generator for gain switching semiconductor lasers

A high current, nanosecond pulse generator using step recovery diodes is described. This generator is useful for driving low impedance loads such as laser diodes. A unique pulsed biasing scheme is employed to provide a pulse generator with very flexible pulse parameters.

Somatosensory, visual and motor evoked potentials in anaesthetized patients

The electroencephalogram (EEG) represents the electrical activity of the cerebral cortex recorded between two electrodes placed on the scalp. This signal is filtered through the skull; it represents the potential difference between the two electrodes and may be of the order of 100-150 txV. If a stimulus, such as a light flash, is applied, then a sensory potential is evoked over the area of the brain which processes that signal. For example, the visual potential is evoked over the occipital cortex. However, the potential is very small in amplitude, commonly about 2 ~xV. A sensory evoked potential is, in contrast to the relatively randomly varying nature of the EEG, relatively stable in morphology. It is, therefore, amenable to acquisition by repeated stimulation and averaging of the signal. In the case of the visual evoked potential, which occurs approximately 60 ms after stimulus, the visual stimulus is repetitively applied and the resultant EEG is averaged for a period of, say, 100 ms. Averaging the resultant EEG will, as the number of averages increase, gradually remove the non-stimulus related, randomly varying background EEG and leave the specific sensory evoked potential (thus increasing the signal to noise ratio). Three modalities--visual, somatosensory and auditory--are commonly used for evoking cortical potential during surgery and anaesthesia. The visual stimulus is provided by means of a light flash. This may be applied via light-emitting diodes embedded in swim goggles at a rate of approximately 2 Hz. Higher rates result in the production of more complex wave-forms. Somatosensory evoked potentials are obtained by stimulating a convel~ient nerve, usually the median nerve but alternatively the posterior tibial nerve, with a constant current pulse generator. This is set at 150% of motor threshold, thus ensuring a supramaximal sensory stimulus. The third method of recording cortical potentials is to provide an auditory stimulus, usually clicks provided by headphones. Auditory evoked responses are dealt with in Chapter 7 and are not considered further here. For the measurement of anaesthetic effects, sensory or auditory evoked potentials are generally considered to be more reliable than visual evoked potentials. Flash evoked visual potentials have a relatively high degree of intertrial variability in the

High current pulser for transmural and field stimulation

The determination of the requirements and the design of a constant current pulse generator with low internal resistance capable of providing the high currents required for transmural and field stimulation of biologic tissues are described. It is concluded that direct measurement of current flowing and voltage applied to electrodes is the best way of monitoring stimulus parameters.

Experimental determination of internal parameters of capacitive current pulse generators working into an inductive load

Experimental determination of internal parameters of capacitive current pulse generators working into an inductive load

Generation of rapidly varying current and voltage pulses as a result of interaction of a train of laser pulses with a target in the atmosphere

A study was made of the generation of electric voltage and current pulses as a result of interaction of a train of laser pulses with a target in a gas under a variety of focusing conditions and at different gas pressures. It was found that at atmospheric pressure the voltage and current pulses appeared on repeated laser exposures, which was due to the formation of a heated layer of a low-density gas at the target surface, the expansion of which occurred in a time comparable with a period between laser pulses in a train. The rapid variation of the response in the form of the current and voltage pulses to laser radiation made it possible to reproduce the modulation of such radiation at frequencies 30 MHz.

A method to reduce deflection aberrations in electron-beam lithography systems.: W Knauer, J Vac Sci Technol, 19 (4), 1981, 1042–1047

A pulsed magnetron sputtering discharge at different modes of discharge ignition and a large range of duty cycles and pulse rates from single pulses to 50kHz was investigated. A 2kV vacuum pentode modulator was used for the generation of current pulses with amplitudes up to 2A and target power densities up to 145W/cm2.Ignition of a pulsed discharge occurs with some delay, but still at the rise of the voltage pulse, if in the inter-electrode gap either a starting-up discharge with a current of some tens of milliamperes is sustained or if the residual concentration of charged particles after a previous pulse is still high enough. A spike of electron current to the substrate with energies up to 100eV is generated at the current front of the high-current discharge when the voltage drops to its equilibrium value. These electrons are presumably secondary electrons. The effective cathode secondary emission and gas ionization take place at the current front when the voltage drop at the gap is higher than the equilibrium value. Therefore, the duration of the current front lasts only some microseconds and an excess concentration of charged particles is generated in the gap.During the high-current discharge stage the plasma expands with the velocity of ambipolar diffusion from the near-target region. The ion current to substrate reaches its maximum value after some tens of microseconds. For this reason, the pulse duration should not be lower than 20–40μs for ion-assisted deposition.In the afterglow period deionization of the post-discharge plasma takes place. Due to the surplus ion conductivity of the plasma the starting-up discharge is suppressed. With delay in self-restoring the starting-up discharge is some tens of microseconds. This time determines the duration of maximum pauses between the control pulses without the starting-up discharge. Thus, work in the middle-frequency range of pulse rates allows to exclude a starting-up discharge and to obtain the lowest delay for establishing the magnetron discharge at each of the following pulses.

Effect of rate of current rise in the output windings on the space-time distribution of the electron beam in a betatron

This article reports results of a study of the effect of the rate of current rise in the output windings of a betatron on the parameters of the resultant electron beam. It is shown that the rate of current rise in the windings only changes the duration of the radiation pulse associated with the beam and its delay relative to the initiation of the current pulse in the windings. The spatial distribution of the beam is determined mainly by the distribution of the magnetic field of the betatron. The findings obtained from the study made it possible to simplify the current pulse generator in the output-winding supply circuit of the PMB-6E betatron, reduce its size, and make it more reliable.

Acoustically derived auditory nerve action potential evoked by electrical stimulation: an estimation of the waveform of single unit contribution.

An experimental study of the electrical stimulation of the guinea pig cochlea is made using an electrode on the round window for both stimulation and recording. The neural response is separated from the electrical artifact with a masking procedure combined with a low amplification, "statistical" averaging method [Charlet de Sauvage et al., Hear. Res. 2, 343-346 (1980)]. The high electrical impedance required for recording physiological responses implies the use of a current pulse generator. Monitoring of evoked potentials from the auditory cortex provides evidence that the effects of electrical stimulation (and of masking noise) are of auditory origin. The electrically evoked round window response is of very short latency (less than 0.2 ms). There is a response threshold for both electrical stimulus and masking noise. The response amplitude varies monotonically as a function of masking noise or electrical stimulus intensity. Experiments with high-pass noise masking suggest that the electrical stimulus is mainly acting on basal fibers. The response latency and waveform are independent of electrical stimulus intensity, repetition rate, masker level, or spectrum. Little intersubject variation is noted. Our experiments (reciprocal forward masking by electrical and acoustic stimuli) suggest that a direct, instantaneous electrical stimulation of the fibers occurs. We believe that this response to electrical stimulation represents the mean unit response of the auditory nerve fibers. This approach may be useful in the separate study of cochlear and VIIIth nerve functions and in the analysis (deconvolution) of the acoustically evoked compound AP.

The Need for Standards Limiting the Power System Disturbance Caused by Pulse-Burst Modulation Control

This paper reviews the types of disturbances caused by Pulse Burst Modulation Control and explains a number of remedial methods which help eliminate or reduce the undesirable d.c. injection in the power network and the generation of current pulses within the neutral wire. The need for adequate standards is emphasized.

Electrical characteristics of a transversely pulse-initiated hydrogen fluoride laser

Measurements of the discharge V-I characteristics of a pulsed HF laser initiated by a Blumlein circuit indicate that the discharge is attachment dominated operating at a reduced field magnitude E/N constant with the normalised current density J/N. A simple model of the combined circuit-discharge network is developed which is capable of accurately describing the pressure dependence of peak current and discharge resistance and the conditions to be verified for an efficient energy transfer into the laser plasma. Experimental results are given that strongly support the model used for the analysis, which therefore should prove useful in the design and optimisation of current-pulse generation networks.

Generation and measurement of ultrashort current pulses with Josephson devices

Experimental demonstration of an ultrashort-pulse generator and a novel sampling technique to measure its pulse shape is reported. The pulse generator, which uses Josephson interferometers, is designed to be dc powered and self-resetting. Its pulses are measured to be 26 ps in duration at a simulated maximum frequency of 2.5 GHz. The sampling technique is useful for measuring general fast waveforms with unprecented sensitivity and resolution extendable to subpicosecond time scale.

A one million bit bubble memory solution

Intel Magnetics is offering for sale a one million bit magnetic bubble memory package plus the LSI support circuits to build a complete memory subsystem compatible with the standard Intel microcomputer bus structures [1]. A manufacturable 2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . one megabit chip was realized with an 11.2 × 11.2 square micrometer storage cell and with block replicate and swap gates for control functions. A binary organization was chosen so that useable data storage is organized as 2048 bit blocks of 512 bits each. A minimum system of 128k Bytes can be contained in 14 square inches of board space and requires only +12 volt and +5 voH power supplies and maximum power of 5 watts. The system is easily expandable to 1 M Byte. Product features offered include error correction on each 256 bit block segment and a leadless bubble memory package with a matching socket. The LSI support devices include a Current Pulse Generator, a Coil Driver, A Coil Predriver, a Formatter/Sense Amplifier and a Bubble Memory Controller.

電解放電加工の基礎的研究 電解液中の放電現象および電解放電加工における電解除去量について

Electric discharge phenomena in electrolyte and the electro-chemical metal removal in electrochemical discharge machining (ECDM) are studied experimentally to make clear the working mechanism of ECDM. The results obtained are as follows:(1) Discharge in electrolyte has some appearances by various electrode voltages and the unstable arc discharge is utilized for ECDM.(2) When the electrode gap is rather wide (about 0.2mm and more) discharge takes place between the electrode and the electrolyte, but in the usual ECDM of small working gap (less than 0.1mm) discharge seems to occur between the two electrodes.(3) In the single discharge by a rectangular wave pulse current generator an ignition delay of long duration is found out which suggests that the discharge occurs after the electrode surface has been covered by the gas evoluted in the electrochemical process.(4) Chemical analysis of iron ion in the drainage of ECDM shows that electrochemical removal in ECDM is nearely equal to the maximum rate of electrochemical removal even if the total removal rate changes.

Generation of coherent current pulses and delayed switching in relaxation GaAs p+-iν-n diodes

In GaAs p+-ν-n diodes prepared from high-resistivity Cr-doped GaAs, generation of coherent current pulses (CCP) has been observed in the forward bias region Vth?V&amp;lt;Vsw and delayed switching in the region V≳Vsw, where Vth is a threshold voltage for the CCP and Vsw is a threshold voltage for the switching. Coexistence of multiple components of the CCP with different interpulse times and pulse heights has been observed, which indicates that the CCP is caused by the periodic formation and annihilation of the filamentary current path. A double-pulse experiment of the delayed switching has been performed using first and second identical pulses with varying pulse-separation time. For pulse heights slightly larger than Vsw, the delay time of the second pulse (td2) is larger than that of the first pulse (td1). Experimental results show that this peculiar relation td2≳td1 is due to an electronic process. These new nonlinear transport phenomena are closely related to each other. A model based on the concept of the relaxation semiconductor is proposed, taking into account the relationship between the dielectric relaxation time and the diffusion length lifetime in a transient state of the system involving two types of defect centers. Numerical estimations based on the model agree with the experimental values.

A stabilized high current pulse generator (for n.m.r. spectrometers)

A current pulse generator is described which has been developed for use in connection with a pulsed nuclear magnetic resonance (NMR) spectrometer. It is capable of producing current regulated pulses in the range 30-120 A at pulse widths of 0.1-10 ms. Twin pulse separations of 0.1 ms at repetition frequencies of 3 Hz have been achieved. Typical rise times into resistive loads are of the order of mu s( approximately 80%) for a 120 A pulse.

The safe use by divers of a high current pulse generator in studies of the behaviour of marine fish in electric fields

The safe use by divers of a high current pulse generator in studies of the behaviour of marine fish in electric fields

A Precision Current Pulse Generator for NMR Self-Diffusion Measurements by the Pulsed Gradient Technique

An apparatus is described for delivering controlled pulses of current into an inductive load. Digital logic is utilized for control of the pulse duration, and current feedback is used to control the magnitude of the pulse. The apparatus was designed to enable NMR self-diffusion measurements to be obtained by the pulsed gradient technique, and diffusion results are shown for number 15 white mineral oil using pulse durations of 10 msec and magnitudes of over 25 A.

Anomalous Photocurrents in Low-Power Epitaxial Transistors

In this paper, we give additional experimental results concerning the anomalous photocurrent problem. Anomalous photocurrents were observed in various epitaxial NPN transistors for different operating modes and bias voltages. It is particularly shor that the devices switch on a stable I(V) characteristic that agrees closely with that given by the avalanche injection mode obtained experimentally with a fast rising high current pulse generator. The triggering mechanism is investigated and emitter injection is found to be a necessary condition. This experimental approach allows us to predict accurately the anomalous photocurrent value without radiation tests and seems to be quite useful in hardening studies.

Measurement of p-n junction second breakdown characteristics†

A current pulse generator suitable for performing non-destructive measurements of the second breakdown characteristics of p-n diodes and bipolar transistors has been developed. The generator permits second breakdown measurements up to a maximum current of 0-8 A with current rise times of less than 1 μsec.