Study on pulse power supply by using pulse forming network modules toward intense X-ray source

A model of pulsed inductive plasma thrusters consisting of a set of coupled circuit equations and a 1-D momentum equation has been used to study the effects of adding a second parallel capacitor into the system. The equations were nondimensionalized, permitting the recovery of several already known scaling parameters and leading to the identification of a parameter that is unique to the particular topology studied. The current rise rate through the inductive acceleration coil was used as a proxy measurement of the effectiveness of inductive propellant ionization since higher rise rates produce stronger, potentially better ionizing electric fields at the coil face. Contour plots representing thruster performance (exhaust velocity and efficiency) and current rise rate in the coil were generated numerically as a function of the scaling parameters. The analysis reveals that, when the value of the second capacitor is much less than that of the first capacitor, the performance of the two-capacitor system approaches that of the single-capacitor system. In addition, as the second capacitor is decreased in value, the current rise rate can grow to be twice as great as the rise rate attained in the single-capacitor case.

Ion current-adapted control of the arc current in a pulsed cathodic arc process

The influence of charging current rise rate on the maximum operating current was determined for a 42-layer Nb–Zr solenoid 15.24 cm long with an i.d. of 3.05 cm and an o.d. of 5.74 cm which generated a magnetic field of 1.4 kG/A. A rise rate of 10.7 A/sec (15 kG/sec) was found to lower the maximum operating current of this solenoid by ∼30%. In addition, the rise-rate dependence of the transition current was determined with various configurations of built-in electrical shorts. In all cases, the presence of a short greatly increased the rise rate dependence, and in several cases led to depression of the transition current by more than 50% for rise rates as small as 0.2 A/sec (0.28 kG/sec). These results indicate that the strong rise-rate dependence of the transition current observed in some superconducting solenoids arises from the presence of shorts, and is influenced more strongly by the rate of change of field than by the current rise rate. Several relations have been derived which accurately predict the rise-rate dependence of the critical current of a shorted superconducting solenoid.

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.

An extensive grid of high-resolution seismic data, hundreds of sediment cores, and a robust radiocarbon-age data set acquired over nearly four decades allows detailed analysis of Holocene coastal evolution of western Louisiana and Texas, USA. Results from this study provide a framework for assessing the response of a myriad of coastal environments to climate change and variable sea-level rise. Climate varies across the region today, spanning four climate zones from humid to semi-arid, and has fluctuated during the Holocene. The most notable changes were alterations between cool/wet and warm/dry conditions. Sea-level records for the northwestern Gulf of Mexico indicate an average rate of rise during the early Holocene of 4.2 mm/yr, punctuated by rates exceeding 10.0 mm/yr. After ca. 7.0 ka, the rate of rise slowed, and by ca. 4.0 ka, the average rate decreased from 0.6 mm/yr to 0.3 mm/yr. The current rate of sea-level rise in the region is 3.0 mm/yr, marking a return to early Holocene conditions. Despite its incomplete stratigraphic record of coastal evolution during the middle and early Holocene, it is still the most complete record for the Gulf Coast. Bay evolution, as recorded within the offshore Trinity and Sabine incised valleys, was characterized by periods of bayhead delta and tidal delta expansion, followed by episodes of dramatic landward shifts in these environments. The ancestral Brazos, Colorado, and Rio Grande river deltas and coastal barriers also experienced landward stepping during the early Holocene. The widespread nature of these flooding events and their impact on multiple coastal environments suggests that they were caused by episodes of rapid sea-level rise. Similar methods were used to study modern bays, including the acquisition of seismic lines and drill cores along the axes of the bays to examine the magnitudes and timing of transgressive events. Results from Lake Calcasieu, Sabine Lake, Galveston Bay, Matagorda Bay, Copano Bay, Corpus Christi Bay, and Baffin Bay reveal that landward shifts in bayhead deltas, on the order of kilometers per century, occurred between 9.8 ka and 9.5 ka, 8.9–8.5 ka, 8.4–8.0 ka, and 7.9–7.5 ka. These results are consistent with those from offshore studies and indicate that punctuated sea-level rise dominated coastal evolution during the early Holocene. By ca. 7.0 ka, the average rate of sea-level rise in the northern Gulf of Mexico decreased to 1.4 mm/yr, and there was considerable sinuosity of the coastline and variability in the timing of bay and coastal barrier evolution. The diachronous nature of coastal environment migration across the region indicates that sea-level rise played a secondary role to climate-controlled oscillations in river sediment discharge to the coast. At ca. 4.0 ka, the average rate of sea-level rise decreased to 0.5 mm/yr. During this period of slow sea-level rise, coastal bays began to take on their current form, with the exception of changes in the sizes and locations of bayhead deltas caused by changes in sediment supply from rivers. There were also significant changes in the size and configuration of tidal inlets and deltas as a result of barrier growth. The late Holocene was also a time when coastal barriers experienced progradation and transgression on the order of several kilometers. The timing of these changes varied across the region, which is another indication that sea-level rise played a minor role in coastal change during the late Holocene. Instead, barrier evolution during this time was controlled by fluctuations in sand supply to the coast from rivers and offshore sources. Historical records indicate a dramatic reversal in coastal evolution marked by increased landward shoreline migration of chenier plains and coastal barriers across the region. The main cause of this change is accelerated sea-level rise during this century and diminished sediment supply to the coast. Wetlands are also experiencing rapid change due to their inability to keep pace with sea-level rise, especially in areas where subsidence rates are high. Although direct human influence is a factor in these changes, these impacts are more localized. Coastal change is expected to increase over the next several decades as the rate of sea-level rise increases, the climate in Texas becomes more arid, and more severe storms impact the coast.

High current operation of the BLT switch is described. This paper includes a description of the switch structure and several optical triggering methods. Result of experimental observations of high current operation are reported including measurements of peak currents >80kA and rates of current rise >1011A/sec. Observations of the discharge plasma using a streak camera and electrode surface analysis by electron microscope are used to describe the dense glow discharge and the self heated cathode of this switch. Two phases of the discharge are identified, a hollow cathode phase responsible for the fast buildup of the discharge plasma and a dense glow discharge phase with self heated thermionic cathode responsible for the high peak currents obtained.KeywordsGlow DischargeDischarge PlasmaThermionic EmissionCathode SurfaceHollow CathodeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Summary form only given. A design study was conducted on the Mega Ampere Generator for Plasma Implosion Experiments (MAGPIE), a project currently under construction to study radiative collapse of a dense Z-pinch plasma created from a 20-mm-diameter cryogenic hydrogen fiber. Detailed simulation of the generator performance when coupled to the fiber pinch has been carried out with both a 0-D and 1-D plasma code including radiation transport. Machine tolerances have been studied in the context of the ultimate achievable density. The rate of rise of current prior to the onset of the radiative collapse is found to be important, and a double bounce technique has been employed in the design of the transfer line to enhance the rate of current rise at late time, 1-D numerical simulations suggest that the shapes of radial profiles of the pinch column change significantly during radiative collapse. The high radiation emission region on axis becomes increasingly separated from the region of maximum ohmic heating near the surface, preventing the fall in current from terminating the collapse. Radiation transport and high density equation of state models show that the collapse is eventually terminated by a combination of opacity and electron degeneracy effects. Utilization of the double bounce voltage serves to increase the maximum current and the reservoir of vacuum magnetic pressure which does work on the plasma during collapse. Therefore, the temperature is kept high during collapse, delaying the onset of the termination processes and achieving higher density compression

Multigap gas spark switches are commonly utilized in linear transformer drivers (LTDs) because of their outstanding static and triggering performance. The number of discharge channels in the switch gap has an effect on the inductance and dissipated energy of the switches. To explore the multichannel discharge characteristics of the switch gaps, a two-gap gas switch (TGGS) with one trigger gap and one self-breakdown gap is designed. The trigger experiments are conducted on the TGGS under various switch working coefficients and nanosecond trigger pulses with different rise rates. The number of discharge channels in the switch gap is recorded by a intensified charge-coupled device (ICCD) camera. The frequency distribution of the number of discharge channels in the trigger gap and the self-breakdown gap is shown under different operating conditions. The experimental results indicate that the number of discharge channels in the self-breakdown gap is significantly more than that in the trigger gap. The preionization obviously increases the number of discharge channels in the trigger gap. The influence of the number of discharge channels in the switch ON the discharge loop current is discussed, and the inductance and dissipated energy of spark channels in the switch gap under different trigger settings are calculated. Increasing the trigger voltage rise rate, the working coefficient, or introducing preionization can correspondingly promote the number of discharge channels in the switch gap, which reduces the inductance and dissipated energy of the switch and thus improves the rise rate and amplitude of the brick current.

The emitter turn-off (ETO) thyristor is a new MOS-controlled thyristor that is suitable for use in high-power converters due to its improved switching performance and easy control. This paper analyzes the uniform turn-on process of the ETO for the first time. To achieve uniform turn-on, the required gate current amplitude and rise rate are characterized for different ETO prototypes. Experimental results show that the ETOs can be uniformly turned on. Correspondingly, the maximum anode current rise rate is improved and the minimum on-time is reduced.

Risk estimates for lightning faults make use of log-normal distributions for lightning characteristics such as peak current. Simplifications for highly correlated parameters, notably peak current and rate of current rise, justify use of equivalent front time of 2 µs in backflashover calculations for first negative return strokes. The transmission line backflashover rate is also affected by uncorrelated and broad statistical variations in soil resistivity, tower footing impedance Z f and resistance R f . Statistical properties of R f from transmission lines in Tennessee USA and Portugal are compared. Modeling of R f variation using a ten-step distribution from the IEEE Standard 1243 FLASH program is compared with estimates using finer probability step intervals, log-normal and log-logistic models.

Solid-State Circuit Breakers (SSCBs) are being considered for several of the new Navy ships' power distribution platforms. This is because SSCBs offer many advantages to electrical systems that conventional Electro-Mechanical Circuit Breakers (EMCBs) cannot. These advantages include much faster interruption of overcurrents, based on lower current thresholds and/or di/dt rate of current rise; reduced energy flowing into the electrical system during faults; and reduced system ringing during fault interruptions. Additional advantages of SSCBs are the elimination of electrical arcing, which is particularly useful for DC and higher voltage distribution systems and systems in environments with volatile gases or explosives; reduced acoustic noise and Electro-Magnetic Interference (EMI) levels during circuit breaker switching; and reduced maintenance and lifecycle costs during the typical 40-year lifetime of the ship [1, 2]. This paper describes the advantages and disadvantages of SSCBs using IGCTs, SSCBs using IGBTs and conventional EMCBs. It will also describe the differences between IGCTs and IGBTs and will consider the design of the bus voltage snubber. This paper will also show how redesigning the ship's electrical system, while considering these important issues, can result in a more reliable, cost-effective power distribution system for the ship.

Short-pulse high-current discharges in vacuum were investigated with the goal to maximize the ion charge state number. In a direct extension of previous work [G. Y. Yushkov and A. Anders, Appl. Phys. Lett. 92, 041502 (2008)], the role of pulse length, rate of current rise, and current amplitude was studied. For all experimental conditions, the usable (extractable) mean ion charge state could not be pushed beyond 7+. Instead, a maximum of the mean ion charge state (about 6+ to 7+ for most cathode materials) was found for a power of 2–3 MW dissipated in the discharge gap. The maximum is the result of two opposing processes that occur when the power is increased: (i) the formation of higher ion charge states and (ii) a greater production of neutrals (both metal and nonmetal), which reduces the charge state via charge exchange collisions.

This paper details the experimental evaluation and simulation of a 4-kV n-type gate turn-OFF thyristor (GTO) designed for pulsed power applications. The primary criteria of evaluation are rate of current rise (dI/dt), turn-ON delay time (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> ), and resistance of the device during turn-ON transients [R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> (t)]. The device under test (DuT) is an n-type asymmetric-blocking GTO manufactured by Silicon Power (Part No. 14N40A10) with a rated dc blocking voltage of 4 kV. A test circuit was specifically designed to minimize stray inductance in order to capitalize on the dI/dt capabilities of the DuT. Experimental data collected from resistance measurements are used to develop a single-switch approximate model for use in simulation. The results of dI/dt experiments provide a profile of DuT dI/dt operation beyond rated values; specifically dI/dt values >70 kA/μs were readily achieved. The turn-ON delay time of the DuT is also characterized and determined to be ~225 ns on average.

Linoleic acid (LA) had two effects on human Kv1.5 and Kv2.1 channels expressed in Chinese hamster ovary cells: an increase in the speed of current activation process (EC(50) = 2.4 and 2.7 microM for Kv1.5 and Kv2.1, respectively) and current inhibition (IC(50) = 6.6 and 7.4 for Kv1.5 and Kv2.1, respectively). LA affected the activation kinetics via two processes: a leftward shift in the instantaneous activation curves and an increase in the rate of current rise. Current inhibition by LA was time dependent but voltage independent. Hill slopes for plots of current inhibition (3.5 and 3.9 for Kv1.5 and Kv2.1, respectively) vs. dose of LA suggested that cooperativity was involved in the mechanism of current inhibition. A similar analysis of the effects of LA on current activation did not reveal cooperative interactions. The effects of LA were mediated from the external side of the channels, since addition of 10 microM LA to the patch pipette solution was without effect. Additionally, the methyl ester of LA was effective at enhancing peak current and promoting channel activation for Kv1.5 and Kv2.1 without inducing significant current inhibition.

We have studied the temporal development of the electrical breakdown in water by means of electrical and optical diagnostic methods. Distilled water with a resistivity of 200 k/spl Omega/cm was placed between a 1.7 mm diameter sphere steel electrode and a plane stainless steel electrode. The gap distance was varied from 50 /spl mu/m to 400 /spl mu/m. Up to 50 kV high voltage pulses with duration of 200 ns, provided by a 50 /spl Omega/ Blumlein generator, were applied to the electrodes. The temporal development of voltage current in the prebreakdown and the breakdown phase was recorded. Laser Schlieren diagnostics and Mach-Zehnder interferometry with a temporal resolution of 1 ns was used to observe the temporal development of plasma formation and changes in the index of refraction before and during breakdown. The electrical breakdown, with highest values of almost 1.2 MV/cm between a sphere and a plane with a gap distance of 50 /spl mu/m, is preceded by a phase of slightly increased current, indicating streamer development. The rate of current rise during breakdown was measured as 2.5/spl times/10/sup 11/ A/s. According to the time resolved observation, the discharges are initiated by streamer development between the electrodes. The streamer development in quasi-homogeneous fields is compared to that in inhomogeneous fields or large gap distance electrode configurations.