Atomic Spectra Database

A271 TRANSPORT BY INTERMITTENCY IN THE BOUNDARY OF THE DIII-D TOKAMAK. Intermittent plasma objectives (IPOs) featuring higher pressure than the surrounding plasma, are responsible for {approx} 50% of the E x B{sub T} radial transport in the scrape off layer (SOL) of the DIII-D tokamak in L- and H-mode discharges. Conditional averaging reveals that the IPOs are positively charged and feature internal poloidal electric fields of up to 4000 V/m. The IPOs move radially with E x B{sub T}/B{sup 2} velocities of {approx} 2600 m/s near the last closed flux surface (LCFS), and {approx} 330 m/s near the wall. The IPOs slow down as they shrink in radial size from 4 cm at the LCFS to 0.5 cm near the wall. The skewness (i.e. asymmetry of fluctuations from the average) of probe and beam emission spectroscopy (BES) data indicate IPO formation at or near the LCFS and the existence of positive and negative IPOs which move in opposite directions. The particle content of the IPOs at the LCFS is linearly dependent on the local density and decays over {approx} 3 cm into the SOL while their temperature decays much faster ({approx} 1 cm).

/pdf/transport-by-intermittency-in-the-boundary-of-the-diii-d-4unr1kj0ia.pdf

Transport by intermittency in the boundary of the diii-d tokamak

Catalytic combustion is one of the most effective techniques for the removal of volatile organic compounds (VOCs).In this review,the recent developments in catalytic combustion of VOCs with regard to active species such as noble metal catalysts,mixed metal oxides,perovskite and spinel metal oxide phases were examined.The effects of particle sizes of active species,catalyst supports,the water vapor effect and the coking effect on catalytic combustion were evaluated.It is found that the research on noble metal catalysts mainly focuses on developing new supports and bi-elemental noble metal catalysts;while the research on non-noble metal catalysts focuses on developing new mixed metal oxides,perovskites and spinel catalysts,as well as investigating the effects of particle sizes and various supports on the combustion activity.Additionally,as far as practical application is concerned,the effect of water vapor and coking deactivation on the catalytic combustion process are discussed.This review will be helpful in choosing an appropriate technique for the removal of VOCs by catalytic combustion with high activity and high stability.

Recent Progress in the Removal of Volatile Organic Compounds by Catalytic Combustion

http://digital.csic.es/bitstream/10261/191476/1/improving_pollutant_removal_efficiency_packed-bed_plasma_reactors_ferroelectric.pdf

Improving the pollutant removal efficiency of packed-bed plasma reactors incorporating ferroelectric components

Capacitor banks are used to provide a high pulsed power in traditional electromagnetic launch systems, but the large volume of these capacitors greatly limits the movability of the system; meanwhile, more and more applications require a system with significantly higher energy storage density. Rotation machines that can quickly convert rotational kinetic energy into high-current electrical energy have been designed and simulated. These generators are referred to as pulsed alternators. The shape of the high current pulse can be controlled by the triggering time of rectifiers. The direct-quadrature, or Park’s, transformation is used to model a generator for simulation. The pulsed alternator consists of four stator phases, a compensated device, and field winding on the rotor all coupled together electromagnetically, and the theory is based on the standard three-phase Park’s transformation and extends to six-phase systems to make analysis of the four-phase air-core alternator that has a compensation device. After modeling the compensator, we obtain the transformed stator-voltage equations and the flux-linkage current relationship. A method is presented in which the pulsed alternator can be accurately modeled and used to numerically analyze the basic principle of a passive compensator. Finally, we optimize the current using the genetic algorithm. It is shown that this method can simplify the calculation, accurately predict the performance of the system, and provide guidance on the design of the prototype.

The Modeling and Calculation on an Air-Core Passive Compulsator

A Dielectric barrier discharge (DBD) device is set up in Ravenshaw University, Cuttack, India to study the plasma assisted destruction of volatile organic pollutants like nitro - benzene and chloro-benzene etc. Plasma parameters like electron density and temperature for argon plasma is measured using spectroscopic technique. The electron temperature of plasma is found to be ~ 1.81 eV for applied voltage 7 kV, MFC at the rate of 1 lit/min and the plasma current is ~ 0.31 mA. When the applied voltage is increased electron temperature as well as electron density increases so also the plasma current showing enhancement of ionization. Volatile organic compound like nitro-benzene on treatment with argon plasma environment inside DBD reactor increases electron temperature in the system and the electron density also increased twice. On the other hand when chlorobenzene is treated with plasma the electron temperature in the system decreases appreciably so also electron density. This indicates the dissociation of chlorine from benzene to neutralize free electrons of argon plasma acting as electron scavenger.

Effect on plasma parameters in a dielectric barrier discharge reactor with volatile organic compounds

The washer plasma gun is widely used to produce pulsed plasma and has various applications in plasma physics. A washer plasma gun and a Guillemin-E type pulse forming network are designed and fabricated in the laboratory to produce pulsed argon plasma in the Compact Plasma System. The spectroscopic signals of pulsed plasma are taken through toughened float glass at a distance of about 0.3 m from the plasma gun by a USB4000 digital spectrometer. Assuming the gun plasma is in Local Thermodynamic Equilibrium, Boltzmann plot method and the line ratio method are used to measure the excitation/electron temperature of pulsed plasma with different base pressure varying from 0.2 mbar to 1 mbar. The excitation/electron temperature of the plasma increases slightly with increasing base pressure within the range of 0.2 mbar to 0.8 mbar and then decreases slightly at a pressure of 1 mbar. Both methods produce almost similar results in temperature measurement, but the Boltzmann Plot method is most accurate than ...

On the excitation temperature of pulsed plasma produced from washer plasma gun in a compact plasma system

A compact plasma system is set up at Ravenshaw University, India. The plasma system consists of a curved vacuum chamber which is nothing but a part of a toroid (θ=700) having minor radius, r= 0.3 m and major radius, R= 0.5 m, vacuum system, electromagnet, gas injected washer stacked plasma gun to produce plasma blobs/filaments, pulse forming network to energise plasma gun, diagnostic tools like electric probes, magnetic probes, spectrometer, high speed CCD camera, digital pulse/delay generator to synchronise the diagnostic tools. A pair of copper coil is wound over the chamber and capacitive pulse is fed to the coil to produce non-uniform magnetic field inside the chamber. The gas injected washer stacked plasma gun is a mono-anode - multi cathode system having five cathodes made up of brass and an anode made up of copper. The gun impedance is ~ 15 Ω. The pulse forming network (PFN) is Guillemin E type which consists of capacitors having equal capacitance 5.5 μF and inductors having equal inductances 1.5 μH. The pulse width of the PFN is ~ 7.6 μs for a seven stage network, as tested with known resistive circuit. Magnetic probes are designed and calibrated using a Helmholtz coil to map the radial magnetic field profile of the plasma chamber. Electric probes like Langmuir triple probe, velocity probes are designed to measure plasma parameters like blob velocity, density, temperature etc. Emission spectroscopy method is used to identify charged species inside the plasma. High speed CCD camera is used to interpret the structure of the plasma. A digital pulse/trigger generator is used to synchronise the CCD, spectrometer and switching thyristor etc. Preliminary results are also reported.

A Compact Plasma System for Experimental Study

Recent experimental evidence suggests the importance of fast radial plasma transport in the scrape-off-layer (SOL) of tokamaks. The outward transport appears to be convective rather than diffusive, extends into the far SOL, and can produce significant recycling from the main-chamber walls, partially by passing the divertor. A plausible theoretical mechanism to explain this phenomenon is the radial transport of locally dense plasma created by turbulent processes. In our experiment a blob of plasma is produced using a plasma-gun and injected radially to the curved vacuum chamber. In this paper we report the measurement of electron density and temperature of the plasma blob produced by the plasma-gun inside the curved vacuum chamber using cylindrical Langmuir probes. The probes are moved both radially and transversely to flow direction. The electron density and temperature are measured ~ 1016 m-3 and 10-1 eV respectively for radial flow at constant discharging potential, base pressure as well as plasma pulse time.

Density and temperature measurements of pulsed plasma produced inside a curved vacuum chamber

In this paper, we report the measurement of ion density, electron density and electron temperature of the plasma blob produced by plasma gun (PG) inside a curved vacuum chamber using cylindrical double probe. The double probe is placed at different distances from the plasma gun and the profiles of ion density, electron density and electron temperature are obtained. The plasma parameters change continuously as the plasma blob propagates away from the source. As the blob moves away from the source, the dynamics of oppositely charged species are different although the resultant effect contributes towards a coherent structure. The profile of electron temperature is fluctuating in nature which may be due to some sort of perturbation phenomena occurring during the motion of the plasma blob.

G. Sahoo

Papers

Effect on plasma parameters in a dielectric barrier discharge reactor with volatile organic compounds

On the excitation temperature of pulsed plasma produced from washer plasma gun in a compact plasma system

A Compact Plasma System for Experimental Study

Density and temperature measurements of pulsed plasma produced inside a curved vacuum chamber

Study of pulsed plasma across a spatial length inside curved chamber using cylindrical double probe