Voltage Pulse Generator Research Articles

Design of High Voltage Pulse Generator and Receiver Circuit for Ultrasonic velocity and Absorption Measurements In liquids

Design of High Voltage Pulse Generator and Receiver Circuit for Ultrasonic velocity and Absorption Measurements In liquids

Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80–90 ns, and a pulse repetition rate of up to 16 Hz.

Time-Domain Optoelectronic Vector Network Analysis on Coplanar Waveguides

The development of a one-port laser-based vector network analyzer (VNA) is described. Measurements are carried out in the time domain using a femtosecond laser for the generation and detection of ultrashort voltage pulses on a coplanar waveguide (CPW). The accurate separation of voltage signals propagating in forward and backward directions, being one of the key tasks of vector network analysis, is achieved by measuring voltage pulses at different positions on the CPW. This separation technique even works in the case of temporally overlapping forward and backward propagating signals. With this laser-based VNA, a frequency spacing of 500 MHz, a measurement bandwidth of approximately 500 GHz, and a dynamic range of more than 40 dB are obtained. As an application example, the laser-based VNA is used to realize an ultra-broadband voltage pulse standard.

Evolution of electrical discharge channel in isopropyl alcohol solution

Evolution of the spark channel created by the high voltage pulse generator in 15% isopropyl alcohol solution in tap water was investigated experimentally. Fast camera images show the start of spark discharge channel with the anode region glowing, which is due to ionization-overheating instability near the surface of anode electrode. Measured propagation velocity is about 4 m/s and points to thermal process of channel evolution. Partial discharges in gas bubbles near the spark channel were observed. When the channel bridges the gap the cathode flash of lightning occurs which is much brighter than anode glowing and channel one. After destruction of the spark channel the cathode glowing stays for a longer period than anode one.

A video based feedback system for control of an active commutator during behavioral physiology.

BackgroundTo investigate the relationship between neural function and behavior it is necessary to record neuronal activity in the brains of freely behaving animals, a technique that typically involves tethering to a data acquisition system. Optimally this approach allows animals to behave without any interference of movement or task performance. Currently many laboratories in the cognitive and behavioral neuroscience fields employ commercial motorized commutator systems using torque sensors to detect tether movement induced by the trajectory behaviors of animals.ResultsIn this study we describe a novel motorized commutator system which is automatically controlled by video tracking. To obtain accurate head direction data two light emitting diodes were used and video image noise was minimized by physical light source manipulation. The system calculates the rotation of the animal across a single trial by processing head direction data and the software, which calibrates the motor rotation angle, subsequently generates voltage pulses to actively untwist the tether. This system successfully provides a tether twist-free environment for animals performing behavioral tasks and simultaneous neural activity recording.ConclusionsTo the best of our knowledge, it is the first to utilize video tracking generated head direction to detect tether twisting and compensate with a motorized commutator system. Our automatic commutator control system promises an affordable and accessible method to improve behavioral neurophysiology experiments, particularly in mice.Electronic supplementary materialThe online version of this article (doi:10.1186/s13041-015-0152-8) contains supplementary material, which is available to authorized users.

Electrical resistance of human soft tissue sarcomas: an ex vivo study on surgical specimens.

This paper presents a study about electrical resistance, which using fixed electrode geometry could be correlated to the tissue resistivity, of different histological types of human soft tissue sarcomas measured during electroporation. The same voltage pulse sequence was applied to the tumor mass shortly after surgical resection by means of a voltage pulse generator currently used in clinical practice for electrochemotherapy that uses reversible electroporation. The voltage pulses were applied by means of a standard hexagonal electrode composed by seven, 20-mm-long equispaced needles. Irrespective of tumor size, the electrode applies electric pulses to the same volume of tissue. The resistance value was computed from the voltage and current recorded by the pulse generator, and it was correlated with the histological characteristics of the tumor tissue which was assessed by a dedicated pathologist. Some differences in resistance values, which could be correlated to a difference in tissue resistivity, were noticed according to sarcoma histotype. Lipomatous tumors (i.e., those rich in adipose tissue) displayed the highest resistance values (up to 1700 Ω), whereas in the other soft tissue sarcomas, such as those originating from muscle, nerve sheath, or fibrous tissue, the electrical resistance measured was between 40 and 110 Ω. A variability in resistance was found also within the same histotype. Among lipomatous tumors, the presence of myxoid tissue between adipocytes reduced the electrical resistance (e.g., 50-100 Ω). This work represents the first step in order to explore the difference in tissue electrical properties of STS. These results may be used to verify whether tuning electric field intensity according to the specific STS histotype could improve tissue electroporation and ultimately treatment efficacy.

Implementation of an Economical and Compact Single MOSFET High Voltage Pulse Generator

The high voltage load applications need very compact generators for the production of fast rising high voltage pulses and are invited in many applications including plasma soft X-ray, ion beam, PEF technology and microwave generators. From the right beginning several technologies have been introduced, Pulse Forming Networks, up to Marx generators. This paper also presents such type of square pulse generator based on power semiconductor device which simplifies the size of the conventional pulse generators. The high electric field intensity square pulses varying in magnitudes in the range of kilovolts with ms to µs pulse widths have been successfully used in many research fields. The advancements in power semiconductor devices, such as power MOSFETs, IGBTs are becoming most suitable for high switching speed high voltage pulse generators. These semiconductor devices are more reliable to control high voltages and currents when implemented in typical circuits. The voltage and current capabilities are increased by connecting the power switches in series and parallel respectively which need aided circuit for protection, equal voltage distributions. This paper presents the design and implementation of such a compact, portable high voltage µs pulse generator based on single power MOSFETs thus avoiding auxiliary circuits. A single CoolMOSTM RF Power MOSFET IXZR08N120B is selected as main switch in this work to produce the high voltage square pulses and is triggered using the suitable high-speed driver DEIC420 with low jitter at higher frequencies. The designed high voltage pulse generator which has variable pulse widths ranging from 2µs to 200μs with a variable pulse magnitude of 1kV is implemented in our laboratory. Keywords: CoolMOSTM Device, High Speed Driver DEIC420, Power Switch, Pulse Generator, RF Power MOSFET, Schmitt Trigger

High repetition rate multi-channel source of high-power rf-modulated pulses.

This paper presents the results of testing a high voltage pulse generator based on parallel gyromagnetic nonlinear transmission lines filled with saturable ferrite. The generator is capable of producing almost identical stable rf-modulated nanosecond high voltage pulses in each of the two, or four, parallel output channels. The output voltage amplitude in each channel can reach -285 or -180 kV, respectively, with a rf modulation depth of up to 60%. Drive pulses were produced as the packets of duration 1-5 s at a pulse repetition frequency of 800 Hz using a driver equipped with all-solid-state switches. Splitting the driver pulse provided electric field strengths in the channels which were below the breakdown field strength of the transmission lines. As a result, the use of nonlinear transmission lines of reduced diameter made it possible to increase the center frequency of the excited rf oscillations to ∼2 GHz.

A control unit of the cold-cathode thyratron with a high pulse repetition rate

A compact high-voltage pulse generator is designed for control of TDI thyratrons in grounded-cathode thyratron-switching circuits. The unit is the part of the pulse voltage generator for charging a double forming line of the frequency electron accelerator. The unit is controlled from the GZI-6 external generator with a maximal repetition rate of 50 s−1. The unit produces negative-polarity firing voltage pulses with a ∼18-kV/μs rate of pulse rise and allows one to fire simultaneously two TDI4-100k/75PD thyratrons. The scatter of amplitudes of currents of thyratrons, connected in parallel without additional current-dividing circuits, does not exceed 1%. The efficiency factor of the control unit is approximately 85%. The active elements of the control unit are the thyristor and the TGI-500/16 low-power pulse hydrogen thyratron.

Magnetohydrodynamic effects of heterogeneous spray detonation

Electrical power on the board of an aircraft with a liquid-fuel pulse-detonation engine is proposed to be produced by a magnetohydrodynamic (MHD) generator placed at the outlet of the jet nozzle. MHD effects of the pulsed heterogeneous (spray) detonation of n-heptane–oxygen mixtures with addition of a potassium carbonate aqueous solution (ionizing additive) to the detonation products are studied. The MHD channel electrodes are demonstrated to steadily generate voltage pulses with an amplitude of up to 3 V. Three types of shape of individual pulses are observed: single pulses, double pulses, and double pulses with a shortterm change in the sign of the voltage. Increasing the frequency of operation of the PDE from 20 to 40 Hz does not affect the amplitude and shape of the voltage pulse. Reducing the magnetic induction from 0.6 to 0.3 T decreases the amplitude of the voltage pulse across the MHD channel electrodes, but the shape of individual pulses remains virtually unchanged. Leaning the fuel mixture reduces the generated voltage. Addition of mechanoactivated Mg-MoO3 energetic nanocomposite to the fuel mixture does not cause significant changes in the shape and amplitude of voltage pulses.

Neuromorphic Hardware System for Visual Pattern Recognition With Memristor Array and CMOS Neuron

This paper presents a neuromorphic system for visual pattern recognition realized in hardware. A new learning rule based on modified spike-timing-dependent plasticity is also presented and implemented with passive synaptic devices. The system includes an artificial photoreceptor, a Pr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -based memristor array, and CMOS neurons. The artificial photoreceptor consisting of a CMOS image sensor and a field-programmable gate array converts an image into spike signals, and the memristor array is used to adjust the synaptic weights between the input and output neurons according to the learning rule. A leaky integrate-and-fire model is used for the output neuron that is built together with the image sensor on a single chip. The system has 30 input neurons that are interconnected to 10 output neurons through 300 memristors. Each input neuron corresponding to a pixel in a 5 × 6 pixel image generates voltage pulses according to the pixel value. The voltage pulses are then weighted and integrated by the memristors and the output neurons, respectively, to be compared with a certain threshold voltage above which an output neuron fires. The system has been successfully demonstrated by training and recognizing number images from 0 to 9.

Optically isolated, 2 kHz repetition rate, 4 kV solid-state pulse trigger generator.

This paper presents the design and operation characteristics of a solid-state high voltage pulse generator. Its primary utilization is aimed at triggering a gaseous spark gap with high repeatability. Specifically, the trigger generator is designed to achieve a risetime on the order of 0.1 kV/ns to trigger the first stage, trigatron spark gap of a 10-stage, 500 kV Marx generator. The major design components are comprised of a 60 W constant current DC-DC converter for high voltage charging, a single 4 kV thyristor, a step-up pulse transformer, and magnetic switch for pulse steepening. A risetime of <30 ns and pulse magnitude of 4 kV is achieved matching the simulated performance of the design.

Energy balance in a double forming line operated in the bipolar pulse mode

The analysis of the energy balance in a double forming line that operates into a resistive load and an ion diode with self-magnetic insulation is presented. The studies were performed using a TEMP-4M accelerator, which consists of a capacitive storage—a pulse-voltage generator (PVG), a double forming line (DFL), and a vacuum ion diode with self-magnetic insulation of electrons (or a resistive load). The accelerator forms double pulses of opposite polarities: the first pulse is negative (300–600 ns, 150–200 kV), and the second is positive (120 ns, 250–300 kV). The energy losses in the forming line caused by the leakage current in water during the line charging and generation of an ion beam were determined, as well as the energy loss in gas-filled gaps. The performed studies showed that the total energy transferred from the PVG to the DFL is equal to the sum of the energy stored in the DFL and the energy loss in the load. The loss due to the leakage in water and in the gas-filled gap was within 4%. The efficiency of the energy transfer from the DFL to the load (a resistive load or a diode) and in the short-circuiting mode was analyzed. It was obtained that 90% of the energy that was stored in the DFL is transferred to the diode, and 90% of this energy is fed to the diode during the beam generation. The main energy loss (9–10%) occurs in gas-filled gaps. In this case, the efficiency of the energy transfer from the DFL to the load is independent of the energy stored in the DFL.

Marble Characterization by Ultrasonic Methods

Ultrasonic techniques are increasingly being used in various fields such as mining, geotechnical, civil engineering, because they are non-destructive and easy to apply. These techniques are usually employed both in situ and in laboratory to characterize and determine the dynamic and physical properties of rocks. In cultural heritage, the characterization of marble statue by acoustic wave is a well-known non-destructive method. This paper undertakes a study of the Carrara marble that composes the statues exposed in the Château de Versailles gardens, in order to better understand the processes of deterioration affecting them. For this, 10cm side square plates of Carrara marble are artificially aged through heating/cooling thermal cycles performed on one face of the samples. Acoustic waves such as compressive, shear and Rayleigh are generated by 1MHz central frequency contact transducers exited by a voltage pulse generator. A laser vibrometry detection method is used in the case of Rayleigh wave detection. The transmission measurements point out a strong decrease of the wave speed as well as a dramatic decrease of the maximum frequency transmitted in conjunction with the weathering. The velocity of ultrasonic waves depends on the physical and mechanical properties of the stone (such as density, porosity, elastic constants, and structure), Therefore, correlating the changes in these properties with the measured ultrasonic velocity helps to provide classification schemes for evaluating the degree of stone deterioration Köhler (1991). Some classical tests such as drilling resistance and water absorption (contact sponge method and water drop test) were also performed in order to complete the results obtained by ultrasonic velocity method.

A self-triggering system for a cold-cathode thyratron in a pulse voltage generator

A triggering scheme of the ТДИ high-voltage high-current switch of the pulse voltage generator for powering the vacuum diode of the Astra frequency electron accelerator is described. Its special feature is the automatic triggering mode of the switch, which is synchronized to the charging process of the high-voltage capacitive storage. The energy required for producing control pulses (1 J) is extracted in the process of charging the high-voltage capacitive storage using a pulse current transformer. The processes are synchronized by a peak transformer connected to the storage charging circuit. The components of the circuit are intended for the continuous operation with a repetition rate of up to 100 s−1.

Discharge in the saline solutions in a vicinity of the threshold voltages

This paper deals with the discharge in saline solution (0.9 % NaCl) in coaxial electrode system at voltages up to several hundred volts. The discharge was powered by bipolar pulsed generator with a pulse repetition rate of 100 kHz and by a generator of negative voltage pulses. At voltages less than a threshold value (less than 300 V)' different types of gas microcavities are formed at the surface of active electrode: the microbubble' the conglomerates of microbubbles (thin gas layers) and a macrobubble with diameter of about 1 mm and less. In a vicinity of threshold voltage the breakdown in the gas cavities occur. For negative polarity at the metal electrode the discharge burns in a form of microsparks of short duration. At positive voltage pulses' the glow-type discharge is sustained in the microcavities.

Optimization of the vacuum insulator stack of the MIG pulsed power generator

The MIG multi-purpose pulsed power machine is intended to generate voltage pulses of amplitude up to 6 MV with electron-beam loads and current pulses of amplitude up to 2.5 MA and rise time '00 ns with inductive loads like Z pinches. The MIG generator is capable of producing a peak power of 2.5 TW. Its water transmission line is separated from the vacuum line by an insulator stack. In the existing design of the insulator, some malfunctions have been detected. The most serious problems revealed are the vacuum surface flashover occurring before the current peaks and the deep discharge traces on the water-polyethylene interface of the two rings placed closer to the ground. A comprehensive numerical simulation of the electric field distribution in the insulator of the MIG generator has been performed. It has been found that the chief drawbacks are nonuniform voltage grading across the insulator rings and significant enhancement of the electric field at anode triple junctions. An improved design of the insulator stack has been developed. It is expected that the proposed modification that requires no rearrangement of either the water line or the load-containing vacuum chamber will provide higher electric strength of the insulator.

ESD on GaN-based LEDs: An analysis based on dynamic electroluminescence measurements and current waveforms

This work presents an extensive study on the effects of Electrostatic Discharges (ESD) on state-of-the-art GaN based LEDs, based on optical and electrical measurements carried out during the ESD events. ESD events were simulated through a Transmission Line Pulser (TLP) which generates voltage pulses with a duration of 100ns and increasing amplitude: during each pulse, spatially-resolved electroluminescence measurements were carried out through an high speed EMCCD camera. These measurements allowed to identify the chip region where the discharge is localized and the change in the damaged area induced by consecutive ESD events. Also the current and voltage waveforms at the LED terminal were monitored during the tests; this analysis provided important information about modifications the impedance of the devices. The analysis was carried out on different types of commercially available low-power GaN-based LEDs with several differences in the manufacturing technology. Thanks to these tests we have identified two different failure behaviours during a destructive ESD event, clearly related to the different defects in the semiconductor lattice and to structure of the chip.

Removal of Organic Pollutants from Reverse Osmosis Concentrate by Electro-Fenton Process

The RO concentrate containing non-degradation organic pollutants was treated by electro-Fenton process. The high voltage pulse generator was used as discharge power. The effects of pulsed electric field parameters, aeration rate and pH on COD removal rate was investigated. The results indicate that the COD removal rate is up to 80.71% when pulsed voltage, pulsed frequency, treatment time, aeration rate and pH are 30000 V, 5 Hz, 240 s, 1.0 m3/h and 10, respectively.

Generation and radiation of ultra-wideband electromagnetic pulses with high stability and effective potential

AbstractAn ultra-wideband radiation source based on the excitation of a 64-element array of combined antennas by a generator of bipolar voltage pulses with the length of 1 ns, amplitude of 200 kV and pulse repetition rate of 100 Hz has been designed and studied. The peak power of the voltage pulse was 3.2 GW. The effective potential of the ultra-wideband source radiation reached 4.3 MV.