Resonant Charging Research Articles

Triggered Spark Gap Command Charger for High Repetition Rate Applications

A normal dc resonant charger was transformed into a command-mode charger by connecting a spark gap at its output terminal, prior to the load circuit. This charging spark gap was triggered by a transformer connected in series, pulsed by a fast spark gap circuit. Noise suppression schemes were implemented throughout the command charger, in particular around the charging spark gap to order prevent misfiring. The ringing noise and spikes from the capacitor discharge and those of the stray capacitance of coaxial cable were strongly suppressed by a simple LCR circuit so that these would not induce self-breakdown in the charging spark gap. This triggered spark gap command charger was tested to 2 kHz and < 10 kV with a resistive load. A transversely excited atmospheric CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser was operated up to 300 Hz and (10-15) kV that was limited only by the flow rate of the laser gas mixture

Magnetotunneling spectroscopy of ring-shaped (InGa)As quantum dots: Evidence of excited states with 2 p z character

We study the effect of a high magnetic field ( B) on the current–voltage characteristics, I( V), of a GaAs/(AlGa)As resonant tunneling diode incorporating a layer of ring-shaped quantum dots (QDs) in the quantum well (QW). The dots give rise to a series of four unusual resonances in I( V) which show a high degree of reproducibility across the epitaxial wafer. By combining data for B parallel and perpendicular to the growth axis z, we identify that the unusual resonances arise from resonant tunneling into QD excited states with 2 p z -like symmetry. The two series of magneto-oscillations in I for B∥ z allow us to determine the resonant charging and discharging of the QW with varying bias.

Resonant charging

Abstract. It has been shown (Athas et al., 1994) that adiabatic switching can significantly reduce the dynamic power dissipation in an integrated circuit. Due to the overhead in the realization of adiabatic logic blocks (Saas et al., 2000) the best results are achieved when it is used only for charging dominant loads in an integrated circuit (Voss and Glessner, 2001). It has been demonstrated (Saas et al., 2001) that a multi stage driver is needed for minimal power dissipation. In this article a complete three stage driver including the generation of oscillating supply is described. To obtain a minimal power dissipation during synchronization the resonant frequency has to be constant. Therefore the waveforms for the logic states of the signal and the realization of a single stage differ from those presented in (Saas et al., 2001). In the H-SPICE simulations losses of the inductor are taken into account. This allows to estimate the power reduction that is achievable in a real system.

A high-voltage pulse generator for corona plasma generation

This paper discusses a high-voltage pulse generator for producing corona plasma. The generator consists of three resonant charging circuits, a transmission line transformer, and a triggered spark-gap switch. Voltage pulses in the order of 30-100 kV with a rise time of 10-20 ns, a pulse duration of 100-200 ns, a pulse repetition rate of 1-900 pps, an energy per pulse of 0.5-12 J, and the average power of up to 10 kW have been achieved with total energy conversion efficiency of 80%-90%. Moreover, the system has been used in four industrial demonstrations on volatile organic compounds removal, odor emission control, and biogas conditioning.

Diode-less operation of a resonantly charged repetitive high voltage pulser circuit

We report here that the unique geometry of the rotating dielectric spark gap allows the diode-less operation of a command resonant charging pulser network. An average power of about 3.5 kW with a peak value of 75 MW was switched at a repetition rate of 600 Hz into a dummy load resembling a typical TEA CO2 laser.

A 10 kW high-voltage pulse generator for corona plasma generation

In this article we discuss a 10 kW high-voltage pulse generator for producing corona-induced plasma. The generator mainly consists of a three-step resonant charging circuit switched by thyristors, a transmission line transformer, and a triggered spark-gap switch. Voltage pulses of 30–100 kV with a rise time of about 20 ns, a pulse duration of 50–250 ns, pulse repetition rate of 1–900 pulses per second, energy of up to 12 J/pulse, and an average power of up to 10 kW have been achieved with a total energy transfer efficiency of about 80%–90%. At each frequency, the deviation of the energy per pulse is around 1.0%. Moreover, the generator has been tested for more than 100 h for both industrial demonstrations and laboratory investigations at an average output power of 1–10 kW.

On the recovery of a spark gap in a fast discharge circuit

We have shown theoretically that the maximum repetition rate attainable with a switch for both resistive and resonant charging is independent of the value of energy transferred through the switch in case of a very fast discharge. Experimental confirmation of this has been achieved with a resistively charged 20 kV pulse generator (C was varied from ≅5 to 35 nF) switched by a spark gap into a load whose resistance varied from few ohms to a kΩ.

High efficiency discharge-pumped XeCl laser

An X-ray preionized 0: 7l active volume discharge- pumped XeCl laser is described. A simple CLC resonant charging pumping scheme has been used. A specific laser en- ergy of about 5J = lat the efficiency of > 5:5% with respect to the electrical energy stored in the driving capacitors has been reached. A standard deviation< 0: 2% was obtained for 3J output energy.

A Compact High-Voltage Pulse Generator for Plasma Applications

The design and construction of a compact high-voltage pulse generator for providing input electron beam power for the LAP/INPE 32 GHz gyrotron and for treatment of metal and polymer materials by plasma immersion ion implantation (PIII) are described. The generator was built on a circuit category of Pulse Forming Network (PFN), consisting of nine LC sections with L = 270 μH and C = 2.5 nF. The instrument was designed to produce a flat 30 kV, several Amps pulse in 15 μs pulse length with pulse repetition frequency (PRF) of 8 to 100 Hz. By means of a resonant charging inductance it is possible to gain an output voltage with a factor of 1.8 higher than the voltage supplied by the pulse generator. The generator is fed with sine-wave, constant current source, and a 60 kV, 15 mA switching power supply.

Latch proof operation of a switch of a high repetition rate laser with dc resonant charging

We report on the operation of a high voltage high current switch in which command resonant charging capability is built in. Elimination of switch latch up problems do not require any extraneous and complex circuitry. The indigenously developed switch delivers power in excess of 3 kW into a dummy load typical of a TE laser at a pulse repetition rate of 200 Hz. The test on a real TEA CO2 laser load was, however, limited up to 50 Hz repetition rate beyond which the accumulation of dissociation products within the active volume led to arcing.

Resonant tunneling and charging effects in semiconductor quantum dots

The current in the stationary state through an interacting island coupled to several reservoirs is investigated. Recent discussions about the occurence of Pauli-blocking factors are clarified and a generalization of the linear-response theory of Coulomb-oscillations and cotunneling is presented for many-level quantum dots at low temperatures. A strong influence of repeated cotunneling processes on the resonant line shape is obtained.

Practical method for heat treating large toroids for pulse compression applications

Using DC current heating during the winding of toroidal pulse transformers, the authors have demonstrated that it is possible to achieve a pulse response using Co-based metallic glass, which closely matches the best which has been achieved by conventional heat treatments. This development overcomes some of the problems experienced in making large toroids using this material. The results under resonant charging or step magnetization are very close to the best achieved on test cores using a conventional thermal cycle in a furnace. IT is thus demonstrated that there is a viable method producing pulse compression cores of any size from Co-based metallic glass. It is not believed that any of the parameters or details of the production process are critical apart from the current.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An induction linac developed for FEL application

Abstract An induction linac is being studied and built at CESTA for FEL application. At first we studied the induction technology and namely the high-voltage (HV) generators and the induction cells. A HV generator designed to feed the cells with calibrated pulses ( 150 kV , 50 ns , δV/V ) has been built using a resonant charging system and magnetic switches. This generator is planned for kHz repetition-rate operation. A prototype induction cell has also been built and tested with a cable generator. An electron injector (1.5 MeV, 1.5kA) has been designed and is now under test: it uses ten induction cells and a thermionic dispenser cathode. Numerical codes have been developed and simulations have been compared with experimental results for HV generators, induction cells, and the injector. An induction accelerating module has been studied and we plan to have the accelerator working at 3 MeV in 1992.

Design and initial operation of LELIA induction accelerator

The objective of the LELIA program is to produce a high-brightness and high-average-power electron beam for FEL applications. Therefore a linear induction accelerator is under development at CESTA. As a first step, a prototype induction cell has been constructed and tested in order to check its mechanical design feasibility and experimental electrical response, gap geometry and vacuum technology. Moreover, by the end of 1990, an injector will operate with the following parameters: 1.5 MeV beam energy; 1/5 kA beam current; 60 ns flat-top pulse with a few Hz repetition rate capability. An osmium dispenser cathode will produce the high-current-density electron beam. Numerical simulations have also been processed in order to study the beam cavity coupling, minimize the beam breakup (BBU) instability, and optimize the injector electrode configuration. To drive the induction cells a high-power pulse generator has been developed. It consists of two parts: (i) a command resonant charging system (CRCS), (ii) a pulse-forming and magnetic compression device (MAG). Initially the CRCS was tested with a resistive load and the MAG with a spark-gap driver. These preliminary experiments have been successful and the high-voltage flat top has been further improved by charging the MAG-forming line in the middle. A new generator including a cooling system, designed for high-repetition operation, is now under construction.

High-efficiency operation of a gas discharge XeCl laser using a magnetically induced resonant voltage overshoot circuit

An electrical to optical efficiency of 5% has been demonstrated in an x-ray preionized XeCl discharge laser using an improved prepulse-mainpulse circuit, based on resonant charging of the peaking capacitor. In contrast to known prepulse-mainpulse circuits, the new scheme has no time delay between prepulse and mainpulse nor a voltage reversal on the electrodes. We present three possible configurations of the scheme and one of them has been realized for demonstrating its high-efficiency capabilities.

The ringer: an efficient, high repetition rate circuit for electromagnetic launchers

The Meatgrinder is an efficient, current-multiplying circuit which can be used to optimize the energy transfer to various electromagnetic gun configurations. The authors present a simple variant of the Meatgrinder circuit which permits a first-order current profiling into the gun and recovery of the inductive energy in the barrel at a high repetition rate. The circuit is basically a one-stage Meatgrinder which utilizes the ringing of the energy storage capacitor (less than 40% reversal) to perform the opening switch function and a solid-state diode as the crowbar switch between the two mutually coupled inductors. With resonant charging, this results in a completely passive, high-repetition-rate electromagnetic-gun power supply. Since most of the barrel energy is recovered, a railgun with negligible muzzle flash can be realized.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simple capacitor charging power supply for a 100-pps laser pulser

A very simple, compact, and inexpensive capacitor charging power supply for a 100-pps laser pulser is described. Unlike dc resonant charging, this power supply does not use a high-voltage filter capacitor, charging choke, and diode.

Charging Large Capacitor Banks for Fusion Research Using HVDC Conversion Equipment

Fundamental considerations in the choice of a continuous duty capacitor bank charging system using HVDC conversion equipment are presented. Large systems of the type used in fusion related research pose significant system related problems if they are to be supplied from a conventional power grid. Schemes for conditioning the required power in order to overcome such problems are presented and evaluated. A resonant charging system is examined in detail and shown to be superilor in a number of ways to constant current charging. Results of digital computer simulation studies are used to demonstrate the feasibility of the system. It is shown that the resonant charging system reduces rectifier capacity, simplifies control and reduces reactive power fluctuations. Sequential bank charging and use of a motor-generator set are presented as techniques for compensation of real power fluctuations and a comparison on the basis of initial cost is presented.

Resonant transformer command charging system for high repetition rate rare-gas halide lasers

A resonant transformer pulse generator for the pumping of high repetition rate rare-gas halide discharge lasers is described. Since with this design a low-voltage dc power supply is needed, command charging can easily be achieved by using a thyristor as the switching element. The pulse generator has been tested driving a thyratron-switched laser operating up to 100 pps free running and up to 200 pps in the burst mode.

A Practical SCR Model for Computer Aided Analysis of AC Resonant Charging Circuits

The SPICE2 SCR MODEL by C. Hu and W. Ki [1] is modified to better simulate the SCR turnoff transient while maintaining the practicality of using only data sheet specifications to determine model parameters. The modified SCR model is used to do SPICE2 simulation of ac resonant charging circuits for pulse power applications.