Showing papers on "Rise time published in 2015"

16.7 A 20V 8.4W 20MHz four-phase GaN DC-DC converter with fully on-chip dual-SR bootstrapped GaN FET driver achieving 4ns constant propagation delay and 1ns switching rise time

Abstract: Recently, the demand for miniaturized and fast transient response power delivery systems has been growing in high-voltage industrial electronics applications. Gallium Nitride (GaN) FETs showing a superior figure of merit (R ds, ON X Q g ) in comparison with silicon FETs [1] can enable both high-frequency and high-efficiency operation in these applications, thus making power converters smaller, faster and more efficient. However, the lack of GaN-compatible high-speed gate drivers is a major impediment to fully take advantage of GaN FET-based power converters. Conventional high-voltage gate drivers usually exhibit propagation delay, t delay , of up to several 10s of ns in the level shifter (LS), which becomes a critical problem as the switching frequency, f sw , reaches the 10MHz regime. Moreover, the switching slew rate (SR) of driving GaN FETs needs particular care in order to maintain efficient and reliable operation. Driving power GaN FETs with a fast SR results in large switching voltage spikes, risking breakdown of low-V gs GaN devices, while slow SR leads to long switching rise time, t R , which degrades efficiency and limits f sw . In [2], large t delay and long t R in the GaN FET driver limit its f sw to 1MHz. A design reported in [3] improves t R to 1.2ns, thereby enabling f sw up to 10MHz. However, the unregulated switching dead time, t DT , then becomes a major limitation to further reduction of t de!ay . This results in limited f sw and narrower range of V IN -V O conversion ratio. Interleaved multiphase topologies can be the most effective way to increase system f sw . However, each extra phase requires a capacitor for bootstrapped (BST) gate driving which incurs additional cost and complexity of the PCB design. Moreover, the requirements of f sw synchronization and balanced current sharing for high f sw operation in multiphase implementation are challenging.

Impact of Damping on High-Speed Large Signal VCSEL Dynamics

Abstract: An investigation of the optimal relaxation oscillation damping for high-speed 850-nm vertical-cavity surface-emitting laser (VCSEL) under large signal operation is presented, using devices with K-factors ranging from 0.1 to 0.4 ns. Time-domain measurements of turn-on transients are used to quantify damping dependent rise times, overshoots, and signal amplitudes. Optical eye diagrams together with timing jitter and bit error rate measurements reveal a tradeoff between the rise time and the duration of the relaxation oscillations. To produce a high-quality eye at a specific data rate, a proper amount of damping is needed to simultaneously obtain sufficiently high bandwidth and low timing jitter. We found that for error-free transmission, a VCSEL with a 0.3 ns K-factor achieved the best receiver sensitivity at 10 and 25 Gb/s, whereas a less damped VCSEL with a 0.2 ns K-factor achieved the best sensitivity at 40 Gb/s.

Superior electro-optic response in multiferroic bismuth ferrite nanoparticle doped nematic liquid crystal device

Abstract: A superior electro-optic (E-O) response has been achieved when multiferroic bismuth ferrite (BiFeO3/BFO) nanoparticles (NPs) were doped in nematic liquid crystal (NLC) host E7 and the LC device was addressed in the large signal regime by an amplitude modulated square wave signal at the frequency of 100 Hz. The optimized concentration of BFO is 0.15 wt%, and the corresponding total optical response time (rise time + decay time) for a 5 μm-thick cell is 2.5 ms for ~7 V(rms). This might be exploited for the construction of adaptive lenses, modulators, displays, and other E-O devices. The possible reason behind the fast response time could be the visco-elastic constant and restoring force imparted by the locally ordered LCs induced by the multiferroic nanoparticles (MNPs). Polarized optical microscopic textural observation shows that the macroscopic dislocation-free excellent contrast have significant impact on improving the image quality and performance of the devices.

Double closed-loop resonant micro optic gyro using hybrid digital phase modulation.

Abstract: It is well-known that the closed-loop operation in optical gyros offers wider dynamic range and better linearity. By adding a stair-like digital serrodyne wave to a phase modulator can be used as a frequency shifter. The width of one stair in this stair-like digital serrodyne wave should be set equal to the optical transmission time in the resonator, which is relaxed in the hybrid digital phase modulation (HDPM) scheme. The physical mechanism for this relaxation is firstly indicated in this paper. Detailed theoretical and experimental investigations are presented for the HDPM. Simulation and experimental results show that the width of one stair is not restricted by the optical transmission time, however, it should be optimized according to the rise time of the output of the digital-to-analogue converter. Based on the optimum parameters of the HDPM, a bias stability of 0.05°/s for the integration time of 400 seconds in 1 h has been carried out in an RMOG with a waveguide ring resonator with a length of 7.9 cm and a diameter of 2.5 cm.

Electric to Mechanical Energy Conversion of Linear Ultrafast Electromechanical Actuators Based on Stroke Requirements

Abstract: The operational efficiency of ultrafast actuators used as drives in high-voltage direct-current breakers is at best 5%. To boost their efficiency, the design of the energizing circuit is crucial. A multiphysics finite-element method model coupled with a SPICE circuit model that is able to predict the performance of the actuator with an accuracy of at least 95% has been developed and verified experimentally. Several variants of prototypes and models have been simulated, built, and tested. It was shown that one of the main problems leading to low efficiencies is the stroke of the drive. However, there is a possibility to increase the efficiency of the electric to mechanical energy conversion process of the studied Thomson coil (TC) and double-sided coil (DSC) to a maximum of 54% and 88%, respectively, if their stroke is minimized. These efficiencies are idealistic, and these were obtained with clamped armature studies. The efficiency of the actuator can be increased at the expense of increasing the complexity and the cost of the contact system by designing a switch with several series-connected contacts that is encapsulated in a medium with a high dielectric strength. Another proposed solution is to design a current pulse with a rise time that is considerably shorter than the mechanical response time of the system. Parametric variations of capacitances and charging voltages show that the TC and the DSC can achieve efficiencies up to 15% and 23%, respectively. Regardless of the chosen method, the DSC has a superior efficiency compared to a TC.

The influence of the voltage rise rate on the breakdown of an atmospheric pressure helium nanosecond parallel-plate discharge

Abstract: The influence of the voltage rise rate on a nanosecond discharge in atmospheric pressure helium is investigated. The experiment is performed with a parallel-plate discharge configuration. The voltage rise rate is varied between 0.17?kV?ns?1 and 0.42?kV?ns?1. It is found that the rise rate of both the discharge current and the emission intensity increases drastically with the voltage rise rate. This demonstrates the remarkable capability of generating high energy electrons in the discharges with a high voltage rise rate. These arguments are supported by the increase in the measured effective electron temperature during the breakdown processes, namely ~18?eV when dV/dt is ~0.17?kV?ns?1 and ~33?eV when dV/dt is ~0.42?kV?ns?1. Furthermore, a higher voltage rise rate results in a shorter rise time of both the discharge current and the emission intensity. Since the breakdown process evolves in the form of a cathode directed ionization wave, a shorter rise time indicates faster propagation of the ionization wave. In addition, a simple fluid model is proposed and its predicted results agree reasonably well with the important discharge parameters measured in the experiment, such as the breakdown voltage, the rise rate and rise time of the discharge current.

Sensorless speed measurement for brushed DC motors

Abstract: This study describes two new methods of sensing the speed of a pulse-width modulation-driven brushed DC motor based on measuring the inductive spikes generated when the motor is turned off. The research has studied the relationship between the rise time or duration of the inductive spike, and the motor current and speed. Computationally inexpensive algorithms have been developed that use either rise time or duration to estimate speed. The algorithms have been implemented on an inexpensive microprocessor and show a speed error of approximately 10% over most of the motor's range of operation. The spike rise time implementation requires an analog-to-digital converter (ADC) as found in many microprocessors, while the spike duration implementation requires only a single digital input thus reducing the cost of the controlling microprocessor. This work has shown that sensorless speed measurement can be based on the inductive spike and has also raised future research questions, such as to the best way to optimise the speed measurement in dynamic situations, and measurement errors to be expected in a mass production environment.

Effects of discharge voltage waveform on the discharge characteristics in a helium atmospheric plasma jet

Abstract: We present here an analysis of the discharge characteristics of a He plasma jet operating under three different types of applied voltage waveform: (a) a μs-pulse voltage waveform with a slow voltage rise time, (b) ns-pulse, and (c) rectangular voltage waveforms with fast voltage rise time. Optical emission measurements show that the application of a voltage with a fast voltage rise time induces rapid discharge growth and, consequently, produces an abundance of energetic electrons, which in turn leads to high optical emission from the O atoms. We also estimate the optical emission efficiency of the O atom (ηo), which corresponds roughly to the production efficiency of the reactive O species. ηo increases with increasing applied voltage, and the highest value of ηo is obtained in the shortest pulse discharge, which was ignited by a ns-pulse voltage waveform with a fast voltage rise time and short pulse width.

Anode initiated impulse breakdown in water: the dependence on pulse rise time for nanosecond and sub-nanosecond pulses and initiation mechanism based on electrostriction

Abstract: The effect of the voltage rise time on nanosecond and sub-nanosecond impulse breakdown of distilled water is studied. The dependence of anode initiated streamer inception on this parameter is shown to be more intricate than previously reported, particularly as it relates to mechanisms directly in the liquid phase. Dynamics of the emission phase for sub-nanosecond pulses with 600 ps rise time are presented to enable comparison with previous work on nanosecond initiation features. Schlieren imaging is also used to show the development of optical density perturbations and rarefactions as a result of electrostriction in the liquid which were previously found for nanosecond pulses as well. The mechanism of nanopore generation in the liquid due to fast impulses proposed by Shneider, Pekker and Fridman is used to explain the results.

Michelson Interferometer Thermo-Optic Switch on SOI With a 50- $\mu \text{W}$ Power Consumption

Abstract: We demonstrate photonic ultra-efficient thermo-optic switches on a 220-nm silicon-on-insulator platform We used several approaches to increase the tuning efficiency of the switches We used folded waveguides in a Michelson interferometer configuration to increase the optical interaction length of the light with the heated region, and used a suspended structure to improve thermal isolation An ultra-low switching power of 50 $\mu \text{W}$ is realized with an extinction ratio of over 26 dB for the transverse electric mode at 1550 nm The 10%–90% response time of the switch is 128 ms, including a 780 $\mu \text{s}$ rise time and a 500 $\mu \text{s}$ fall time Compared with the best thermo-optic switch in the literature, our device shows approximately an order of magnitude reduction in power consumption

Embedded sensor fusion and moving-average filter for Inertial Measurement Unit (IMU) on the microcontroller-based stabilized platform

Abstract: Sensor Fusion (Complementary and Kalman filters) and Moving Average filter are implemented on an Arduino microcontroller based data acquisition of rotation degree from Inertial Measurement Unit (IMU) sensor for stabilized platform application. Stable platform prototype is designed to have two degrees of freedom, roll and pitch rotation. Output data from gyro and accelerometer were combined to take the advantage of each sensor. Digital filter algorithm was embedded into microcontroller programming. This paper analyzes overshoot percentage, rise time, and data series smoothness of Sensor Fusion (Complementary and Kalman filter) and Moving Average filter response in IMU data acquisition from step input of 20-degreerotation. Moving-average filter resulted in the smallest overshoot percentage of 0% but produce theslowest responsewith 0.42 second rise time. Overall best results are obtained using Complementary filter (alpha value 0.95) by overshoot percentage of 14.17%, 0.24 second rise time, and 0.18 data series smoothness.

A novel on-line cable pd localisation method based on cable transfer function and detected pd pulse rise-time

Abstract: This paper presents a novel Partial Discharge (PD) localisation method, based on PD pulse Rise-Time and Transfer Function (RTTF), for use in on-line cable PD monitoring systems. This is based on the change in rise time as a function of cable length along which a PD pulse has propagated. A comparison with four other well-known location techniques, i.e. Time-Domain Reflectometry (TDR), Phase difference, Arrival Time Analysis (ATA) and Amplitude-Frequency (AF) mapping has been made and presented. Analysis shows that the TDR and Phase difference methods, although requiring a single measurement point, are only applicable to short length cable systems as both incident pulse and reflected pulse should be observable when it reaches the detection point. On the other hand, the ATA and AF mapping, which can be applied to longer cable systems, need to install detectors at multiple points and detect synchronously. In comparison, PD localisation by the proposed RTTF method, which requires detection of the incident pulse at only one measurement point, can be used to localise a PD source which is further away from the PD detection point than other methods and can be used in on-line PD monitoring systems. As on-line PD monitoring sensors commonly comprise of a high frequency current transformer (HFCT) and a high-pass filter, the rise time of detected PD pulses depends on the attenuation of the cable, the HFCT used and the filter applied. Simulations of pulse propagation in a cable and PD monitoring system are performed, based on analyses in the frequency domain using the concept of transfer functions. Results of RTTF from the simulations have been verified by laboratory experiments and on-site PD measurements, which provide evidence that the RTTF method is a very valuable and useful PD localisation technique.

Anode initiated impulse breakdown in water: the dependence on pulse rise time for nanosecond and sub-nanosecond pulses and initiation mechanism based on electrostriction

Abstract: The effect of the voltage rise time on nanosecond and sub-nanosecond impulse breakdown of distilled water is studied. The dependence of anode initiated streamer inception on this parameter is shown to be more intricate than previously reported, particularly as it relates to mechanisms directly in the liquid phase. Dynamics of the emission phase for sub-nanosecond pulses with 600ps rise time are presented to enable comparison with previous work on nanosecond initiation features. Schlieren imaging is also used to show the development of optical density perturbations and rarefactions as a result of electrostriction in the liquid which were previously found for nanosecond pulses as well. The mechanism of nanopore generation in the liquid due to fast impulses proposed by Shneider, Pekker and Fridman is used to explain the results.

The effect of impulsive voltage rise time on insulation endurance of inverter-fed motors

Abstract: Endurance tests under repetitive impulse voltages should be performed on inverter-fed motor insulation to evaluate its insulation performance according to the technical specification (TS) released by the International Electrical Commission (IEC), i.e. IEC TS 60034-18-42. To simplify testing procedures in the application, the TS allows life tests to be performed under sinusoidal waveform, as it assumes that sinusoidal and impulsive voltages will provide comparable results if they have same peak-to-peak voltage and frequency. However, we have found that voltage rise time can have significant effect on PD features in both time and frequency domains, so that if PD are deemed the cause of accelerated aging, rise time must be taken into account and sinusoidal waveform may be not the best choice for accelerated aging procedures which resemble the real stress experienced in service by insulation systems of rotating machines controlled by Pulse Width Modulation (PWM). This study aims at summarize the effect of impulsive voltage rise time on insulation life based on endurance tests on crossed enameled wires used for type I motors and turn/turn insulation for Type II motors. Repetitive voltages of 6 rise times (i.e. 50 ns, 200 ns, 1 µs, 16 µs, 200 µs and 500 µs, sinusoidal voltage with same peak-to-peak voltage and frequency) and 3 rise times (i.e. 150 ns, 2 µs and sinusoidal voltage with same peak-to-peak voltage and frequency) are used in the endurance tests on Type I and Type II motor insulation, respectively. Statistical analysis indicate that, due to the different PD features caused by the impulsive voltage rise time, impulsive voltage rise time can have significant effect on insulation lifetime. Accordingly, when performing endurance tests on high-voltage inverter-fed motor insulation, the rise time influence on final life of inverter-fed motor insulation should be carefully considered.

Time to failure of medium-voltage form-wound machine turn insulation stressed by unipolar square waves

Abstract: The lifespans of enamelled turn insulation samples are studied when stressed with square waves characterized by different rise times, duty cycles, switching frequencies, and applied voltages. Partial discharge activities under these test conditions have also been recorded using an RF antenna in an effort to correlate the time to breakdown with material degradation under fast repetitive pulse aging. The aging and PD features were independent of rise time for a 50 % duty cycle; however, slightly faster times to failure were observed at a 15 % duty cycle for the faster rise times, for the considered range. The higher duty cycle and the higher number of applied cycles accelerated the aging.

A thyristor switch with a subnanosecond switching time

Abstract: The possibility of triggering thyristors by an overvoltage pulse with a short rise time was investigated. Low-frequency thyristors of pellet design with diameters of semiconductor structures of 32 and 40 mm and an operating voltage of 2 kV were used in the experiments. An external overvoltage pulse that increased from 2 to 5–8 kV within a time of 0.8–1 ns was applied to the thyristors. Under such conditions, the time of switching a thyristor into a conducting state was no longer than 200 ps. An assembly of six thyristors connected in series switched a capacitor with a capacitance of 2 μF, which was charged to a voltage of 13 kV, to a resistive load of 0.25 Ω. The following results were obtained: a discharge-current amplitude of 27 kA, an initial current-rise rate of 110 kA/μs, a FWHM pulse duration of 1 μs, and a peak power in the load of 190 MW. The circuit diagram of the experiment and the obtained results are described.

Small-signal theory of subterahertz overmoded surface wave oscillator with distributed wall loss

Abstract: A small-signal theory of the overmoded surface wave oscillator (SWO) with distributed wall loss is presented in this letter. The wall loss considered here includes the surface resistance and surface roughness. The cold and hot characteristics of 0.14 THz SWO are studied by the small-signal theory. Numerical results show that as the increase of wall loss, the working frequency decreases slightly, the rise time and startup time of oscillation increase significantly, and the output power decreases dramatically. Particle-in-cell (PIC) simulation confirms the prediction by the small-signal theory.

Improving Control Dynamics of PMSM Drive by Estimating Zero-Delay Current Value

Abstract: Dynamic performance of current control loop still remains crucial for position-, speed-, and torque-controlled drives. In the study, a current loop solution has been designed for field oriented control of permanent magnet synchronous motors (PMSM). It enhances typical PI controller with an estimator of zero-delay current (ZDC) value. The ZDC estimation allows for selecting substantially higher controller gain. It reduces control loop step response rise time to a single control cycle, which is the shortest technically possible value, while avoiding overshoot. The method does not require any hardware changes and it needs only negligible processing overhead. Both simulations made and experimental results obtained in the study have proved the effectiveness of the proposed solution. DOI: http://dx.doi.org/10.5755/j01.eee.21.2.11507

Simulation of Nanosecond Pulsed DBD Plasma Actuation with Different Rise Times

Abstract: NPDBD plasma actuation is a novel method for active flow control. In Benard's paper, compression waves induced by NPDBD plasma actuation with shorter rise time are stronger. But the mechanism is still not clear yet. In this paper, NPDBD plasma actuation with different rise times are simulated using a two-dimensional plasma-fluid coupled model. Along with the decrease of rise time from 150 ns to 50 ns, discharge current, peak power, and input energy increase with constant voltage amplitude. The whole ultrafast heating energy and heating efficiency also increase, while the ratio of quenching heating and ion-neutral collision heating remains almost unchanged. Due to higher heating energy, the strength of the induced compression wave also increases with the shorter rise time. The variation law of discharge current and compression wave strength is consistent with the trends observed in Benard's paper. The main mechanism for higher ultrafast heating energy and efficiency with shorter rise time is that both maximum reduced electric field and electron density are higher. Evolution of reduced electric field, electron density, heating distribution, and induced compression wave are also presented.

Optimization of PID Controller Parameters on Flow Rate Control System Using Multiple Effect Evaporator Particle Swarm Optimization

Abstract: This study aims to improve the performance of Proportional+Integral+Differential (PID) control to reduce the speed of the steam flow rate and search optimal points in the evaporation process of Multiple Effect Evaporator (MEE). Optimization of PID control tuning parameters using Particle Swarm Optimization (PSO) by adding a weighting factor of inertia is expected to handle nonlinear systems with evaporator undershoot response characteristics that are difficult to treat and improve response of the system with large overshoot, and long rise time. The results showed PSO is able to provide improved performance tuning PID control system to improve system response in MEE control system with a rise time of 0.01 seconds, 3.35% overshoot, settling time of 6.10 seconds and able respond plant undershoot MEE of 28.11%.The results show that, PSO with inertia weight w provides additional tuning better than PID control by ZN method of max criteria over shoot, rise time and settling time of 5.38%, 3.05 seconds, 10.1 seconds, compared to tuning PID control method with PSO (3.35%, 0.01 seconds, 6.10 seconds).

A nanosecond-pulse generator with an optimized diode switch

Abstract: A diode-transistor generator of high-voltage nanosecond pulses, which is based on an inductive energy storage and an opening switch in the form of an assembly of drift step-recovery diodes (DSRDs) connected in series, is considered. It allows switching of a voltage pulse with an amplitude of 12 kV and a rise time of 4 ns into a load of 75 Ω at a frequency of 10 kHz. The results of investigations of the process of disabling DSRDs with different thicknesses of the base regions and different diffusion-layer profiles are presented. The design of optimized DSRDs with reduced energy losses during disabling is described. It is shown that the use of an assembly of optimized DSRDs in the developed generator provides a twofold increase in the limiting switched energy.

Experimental considerations on the step shear strain in polymer melts: sources of error and windows of confidence

Abstract: Shear step strain experiments with various strain amplitudes have been performed on poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) melts using both stress-controlled and strain-controlled rheometers. Firstly, the onset of the rheological nonlinearity, i.e., nonlinear stress damping behavior, occurring after a large step strain is found to be a phenomenological consequence of an abrupt stress decline within the transient period of strain actuation. Such a feature, analogous to the stress overshoot in a fast startup shear with sufficiently high rates, is interpreted based on theoretical frameworks concerning chain disentanglement/re-entanglement arising from chain retraction. Furthermore, this work infers that full technical considerations in step strain experiments are indispensable for acquisition of accurate stress relaxation data, as some common but easily overlooked technical problems are influential, probably introducing errors. For instance, a too long finite rise time and a stress overload enable to hinder the nonlinearity onset in the transient period, resulting in inaccurate experimental data. In this sense, the stress-controlled rheometer is advantageous relative to the strain-controlled one, although the inertia in the stress-controlled mode incurs a strain overshoot effect. Nevertheless, the amplitude-dependent strain overshoot offers a very subtle effect on the stress damping behavior. Moreover, transducer compliance problems need to be taken into account, especially for high stiffness polymers. Overall, the effects of such technical factors are dictated by their ability to influence the chain stretching/retraction and the disentanglement. A well-considered experimental methodology is necessary to achieve confidence windows in step strain experiments for analysis accuracy.

Study of fast rise time pulse power generator using SiC-MOSFET and FRD

Abstract: There are various methods of pulsed power generation using semiconductor switch. Semiconductor switching device is indispensable to realize a high repetitive operation of the pulsed power modulator. High repetitive operation of the modulator have contributed to industrial application of pulsed power, but the semiconductor switching device wasn't able to generate fast rising pulse and high voltage directly. In this study, we have tried to use fast recovery diode for pulse compression system. Primary switching device were using Silicon-Carbide based Metal Oxide Semiconductor Field Effect Transistor (SiC-MOSFET), the pulse compression circuit was using Saturable Transformer (ST) and a Fast Recovery Diode (FRD). The switching loss has decreased by using SiC-MOSFET. We have adjusted the saturation timing of the ST for applied reverse current to FRD. We have realized generating a fast rising high voltage pulse using fast recovery characteristics of the diode. The development modulator can be obtained an output voltage of 77kV with 18.7ns voltage rise time.

Effects of Optical Pulse Parameters on a Pulsed UV-Illuminated Switch and Their Adjusting Methods

Abstract: Ultraviolet (UV) illumination can effectively shorten the statistical lag and jitter in gas breakdown processes. The spark gap discharge can produce abundant spectrum including UV waveband. In this paper, a simple but reliable spark gap operating with $N_{2}$ at atmospheric pressure is used to test optical radiation characteristics, such as spectrum intensity, rise time, fall time, and duration of optical pulse, which are adjusted by changing the circuit or configuration parameters. Three UV-illuminated switches with different UV spark gap configurations have been tested. The experimental results approve our assumption. With a uniform electric field UV spark gap, the breakdown voltage standard deviation percentage of the switch is 0.74%.

Study on Graphite-Electrode Gas Switch Applied for Pulsed Power Supply With a 700-kA Peak Current

Abstract: A 700-kA gas switch with graphite electrodes for pulsed power supply module has been developed This paper describes the design, construction, and testing of the high-current gas switch and its trigger system The two-electrode gas switch is selected, which suffers high peak and fast rise time currents The trigger generator based on resonant charging of a pulse transformer is constructed to trigger the gas spark An electrodynamic force model of switch electrodes is established The electrodynamic force of connecting wires is also calculated By comparison of the mechanical strengths of polyformaldehyde, epoxy, and fiber-reinforced plastic (FRP) rods, where FRP rods are selected as switch rods, the experimental results show that the mechanical strength of the switch increases by 200% Extensive electric testing has proven the operating parameters of the switch and its trigger system The experimental results show that the measured discharge current waveform is demonstrated to be over a 700-kA peak current and a 500- $\mu \text{s}$ pulsewidth The transfer charge per shot is more than 500 C

Plasma density temporal evolution in a high-power microwave pulse compressor switch

Abstract: Time-resolved optical-emission spectroscopy measurements are used to evaluate plasma density in an interference switch during the extraction of a nanosecond output pulse from a high-power microwave compressor. The compressor represents a resonant cavity connected to an H-plane waveguide tee with a shorted side arm filled with helium at a pressure of ; the plasma discharge in the tee side arm is triggered by a Surelite laser. A nanosecond-scale dynamics of the plasma density is obtained by analyzing the shape of the helium spectral lines. The analysis of the experimental data evidences a correlation between the rise time of the plasma density and the peak power of the microwave output pulse. Numerical simulations of the microwave energy release from the cavity with the appearance of the plasma yield results in good agreement with the measured output pulse peak power and waveform.

High-Voltage Pulsed-Power Supply Operating at Repetitive Discharge Mode for Driving Very Small Plasma Focus Devices

Abstract: The technology of switched-mode power supplies (SMPSs) has been employed to design and build a much simpler and portable high-voltage pulsed-power supply (HVPPS) as an efficient pulse drive unit for very small plasma focus devices (PFDs). The HVPPS is designed in such a way that it is able to charge a low-energy capacitor bank (84 nF, 7 kV, 2.1 J), from 4 to 7 kV at a repetitive discharge mode of 5 Hz. All control processes are carried out via a laptop through a graphical interface, written in C# language. The experimental runs were carried out in argon at 4-mbar gas pressure and the 7-kV maximum charging voltage level of the HVPPS. The results of diagnostics at a repetitive discharge mode of 5 Hz successfully confirmed the accurate performance of the SMPS and the spark gap switch for driving a very small PFD. The rise time of 10%–90% of the charging voltage, at each single-shot trace was obtained to be 110 ms. This consequence demonstrated that the control and sampling circuits were being implemented as well. After discharging, the pinching evidence was genuinely observed in the capacitor bank voltage trace. The quarter period of the discharge traces was observed to be 100 ns, which leads to a total system inductance of about 48 nH. The measured inductance was low enough to be compatible with successful performance of the very low energy PFD, leading to fast and high magnitude discharge pulses to assist the pinching evidence. This HVPPS could emerge as one of the very low cost, compact, light weight, and highly efficient power supplies used for driving the very small PFDs so far.