Shlomo Wald

A high-power pulsed corona source for pollution control applications

The system comprises an all solid-state compact nanosecond pulser and a plasma reactor. The pulser makes use of magnetic compression techniques. Owing to a fast switching at the feed of the HV transformer provided by an ABB GCT switch, one compression stage suffices for the forming of 45-kV, 100-ns pulses across a 120-/spl Omega/ resistive load at a PRF of up to 1 kHz; the risetime is 15 ns. Plasma reactor is capable of handling both gases and liquids by adding small amounts of atomized water to the gas discharge, in the case of gas, or atomizing polluted liquid itself. In both cases, the treatment is conducted in heterogeneous media. Circuit analysis of compressor and charging system accounting for nonlinear processes in magnetic switches and numerous parasitic parameters is presented. Mechanical and electrical designs are detailed. Typical voltage and current waveforms, volt-ampere characteristics, corona discharge appearance, and light emission characteristics are presented. At operation on a resistive load, the compressor efficiency was found to be approximately 80%, which allowed for air cooling. The experimental results obtained with a resistive load are in fair agreement with the circuit simulation. A novel magnetic compressor circuit improving the coupling to PC discharge is proposed and evaluated.

A 1 KW pulsed corona system for pollution control applications

The system comprises an all-solid state compact nanosecond pulser and a plasma reactor. The pulser makes use of magnetic compression techniques. Owing to a fast switching at the feed of the HV transformer provided by an ABB A-Z switch, one compression stage suffices for the forming of 45 kV, 100 ns pulses across a 120 /spl Omega/ load; the risetime is 20 ns. Plasma reactor is capable of handling both gases and liquids by adding small amounts of atomized water to the gas discharge, in the case of gas, or atomizing polluted liquid itself. In both cases, treatment is conducted in heterogeneous media, which proved high removal efficiency. Circuit analysis of compressor and charging system accounting for nonlinear processes in magnetic switches and numerous parasitic parameters is presented. Mechanical and electrical designs are detailed. Typical voltage and current waveforms and the corona discharge appearance are presented. The compressor efficiency was found to be approximately 65%, which allowed for air cooling. The experimental results obtained with a dummy resistive load are in fair agreement with the circuit simulation.

Hazardous waste treatment and recovery of valuable products with a thermal pulsed-plasma technology

Material decomposition is an essential process in chemical industries. A new, efficient and environmentally friendly technique that can be used in a closed-loop process for the treatment and recovery of materials is described. The idea is to decompose a material using a high-energy pulsed-plasma jet. The plasma specific features enable an efficient radiative heat transfer to the treated material bed. Therefore, enhanced energy transfer to selected chemical bonds is achieved. The process can be defined as a highly efficient photolysis. Proof-of-concept tests were carried out on 1,2-dichloroethane (DCE) fed in batches of a few grams each. A total decomposition of the DCE was achieved with less than 60% of the energy consumption required in a conventional treatment. In the current project, a modular transportable laboratory has been constructed. It comprises a 30 kW pulsed power supply featuring an all-solid state power switching system, confined plasma injector, reactor and gas handling and monitoring systems. The expected treatment capacity is 10 kg/h of fluid waste with expected lifetime of the plasma injector of 10/sup 5/ pulses. Simulations and experimental characterization of major components are presented. It is expected that the proposed method will be the Best Available Technology (BAT-as defined by the European Union regulations) for many fluid wastes.

Plasma-propellant interaction at low plasma energies in ETC guns

The ignition of solid propellants by plasma jets with high temperature and density has been suggested as an improvement over conventional primers. Plasma ignition may enable the ignition of propellant charges with high loading density and/or low sensitivity, which is difficult using conventional primers. In addition, plasma ignition can provide a better control of the ballistic process, improving repeatability and enabling compensation for the propellant temperature effect. Due to the typically large volume and weight of electrical energy storage devices and pulsed power systems, which increase with the required energy, it is important to reduce the amount of plasma energy needed for ignition. In this paper, we present and analyze experiments performed in a gun simulator as well as a series of 105-mm gun firings. The aim is to improve the understanding of the plasma-propellant interaction at low plasma energies, in order to reduce the energy needed for a proper propellant ignition and smooth ballistic process.

Electrothermal-chemical research at Soreq Nuclear Research Center, Israel

An overview of the electro-thermal-chemical launcher (ETC) research program at the Propulsion Physics Laboratory, Soreq NRC, Israel is presented. The main avenue explored is a detailed study of solid propellant ETC (SPETC) performance and optimization. A better knowledge of the physical phenomena taking place inside the device and in parallel efforts to tackle the engineering aspects of specific weapon systems based on the SPETC concept. Theoretical and experimental tools have been developed. Permanent efforts toward developing optimal and efficient components for such systems are invested. A second avenue is the design and the construction of a small-caliber ETC demonstrator, as an answer for present military demands for urban combat conditions. All system options are dealt with including a novel inductive pulse power supply.

Hazardous waste treatment and valuable products recovery with a thermal pulsed-plasma technology

Material cracking, or decomposition, is a basic and essential process in chemical industries. This process is a major energy consumer and a cause of environmental pollution. A new, efficient and environmentally friendly technique and equipment that can be used in a closed-loop process for the treatment and recovery of materials is proposed. The idea is to decompose a material using a high-energy pulsed-plasma jet. The plasma specific features enable a most efficient radiative heat transfer to the treated material bed. Therefore, enhanced energy transfer to selected chemical bonds is achieved. The process can be defined as a highly efficient photolysis. Proof-of-concept tests were carried out on 1,2-Dichloroethane (DCE). The material was fed in batches of a few grams each. A total decomposition of the DCE was achieved with less than 60% of the energy consumption required in a conventional treatment. A modular transportable laboratory has been constructed in the framework of 4 European Brite Euram R and D program. It comprises a 30 kW pulsed power supply featuring an all-solid state switching system, confined plasma discharge injector, reactor and gas handling and monitoring systems. The expected treatment capacity is 5-10 kg/hour of fluid waste. The plasma injector is designed to operate in repetitive mode with expected lifetime of 10/sup 5/ pulses. Simulations and experimental characterization of major components are presented. It is expected that the proposed method will be the best available technology for many fluid wastes.

Experimental demonstration and simulation of a dual-stage solid propellant gun concept

A novel method for the acceleration of projectiles to hypervelocity is presented. The method utilizes two solid grain propellant charges which are operated in tandem in a dual-stage mode. The second charge is encapsulated into a massive case which is placed adjacent to the projectile. This stage is ignited at a time delay, after the first charge. Experiments done on a 13-mm barrel demonstrate the feasibility of this acceleration scheme. Zerodimensional simulations predict significant improvement over single-stage gun, using the same maximal pressure as imposed by conventional barrels. A specific calculation of a 0.48-kg projectile accelerated in a 4.4-m-long, 60-nim barrel predicts velocities over 2500 m/s. Nomenclature A = barrel cross-sectional area C,, C2 = mass of main charge and moving charge I = y2 ~ y.i, the distance between ra2 and ra, m{, m2 = masses of the dynamic breech and the projectile, respectively Pair = air pressure in front of the projectile PI-PI = measured pressures in successive locations along the barrel, PI = at the breech P,, P2 = average pressures in the two gas media, 1 = main, 2 = moving charge PII>-> ?2b behind the dynamic breech and at the

Visualization of plasma-fluid mixing through X-ray shadowgraphy

Changes induced by the impact of a hot plasma jet on a fluid have been recorded using X-ray shadowgraphy. The process is of particular importance in the operation of electrothermal acceleration devices. Sets of frames taken every 40 mu s reveal details of the interaction. Fluid erosion is observed to occur only at the fluid extremity directly hit by the plasma. The erosion rate has been evaluated for the initial collision stages when the volume accessible to the fluid remains constant; the measured values range between 100 m/s and 200 m/s. >