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Transient plasma in atmospheric pressure fuel-air mixtures, that is, plasma during a formative, short time period prior to equilibration of the plasma electron energy distribution, is studied for applications to the fundamental improvement of fuel-burning engine efficiency. Transient plasma has been demonstrated to substantially reduce ignition delay, and shows promise for improving engine efficiency...
Breakdown threshold voltage of an electrode less toroidal discharge has been studied using H- type solenoid coil excited by a 13.56 MHz radio frequency power in absence and in presence of a pre ionizing condition with different pressures, aspect ratio and axial magnetic field for dry air, molecular and rare gases. The breakdown threshold depends on various filling parameters, Pre-ionising condition,...
Plasma-discharges using nanosecond repetitive high voltage pulses has been very effective for the stabilization of lean flame1. To explain the chemical mechanisms of active species production by pulsed discharges, a two-step mechanism was proposed to explain the production of high densities of atomic oxygen. This mechanism first creates excited electronic states of nitrogen, which then dissociate...
A two-dimensional particle-in-cell simulation has been developed to study density enhancement of capacitively coupled rf discharges with multi-slit electrodes. The observed density increase is shown to result from a hollow cathode effect that takes place within the multi-slit electrode configuration, which forms as a result of secondary electron emission due to ion bombardment. By investigating the...
This study focuses on the generation and loss of reactive oxygen species (ROS) in low-temperature atmospheric-pressure rf (13.56MHz) He+O2+H2O plasmas, which are of interest for many biomedical applications.
Over the past years cold atmospheric pressure plasma jets (CAPPJ) have received considerable attention due to their unique capabilities and considerable application potentials in various industrial and scientific applications. It has been demonstrated by several research groups that CAPPJs are not continuous jets but discrete fast-moving plasma bullets with supersonic velocities in the order of104...
Atmospheric pressure weakly ionized plasma (APWIP) is utilized at Washington State University to explore plasma-polymerized film deposition. Gas composition greatly affects the streamer properties. Here we present research into the correlation between needle streamers for an argon acetylene environment.
Nonthermal atmospheric pressure plasmas have attracted much attention for their convenient applications on surface modifications, thin film deposition, biological sterilization and inactivation et al. Most atmospheric pressure glow discharges (APGDs) are generated by sinusoidal excitation with repetition frequency from kilo hertz to mega hertz. Recently, high voltage pulses with duration less than...
In the interaction of high power laser beams with solid density plasma, there are a number of magnetic field generating mechanisms that result in very strong fields that can inhibit energy transport. Here, we present 2D numerical modeling of near critical density plasma using a fully implicit Vlasov-Fokker-Planck code, IMPACTA, which includes self-consistent magnetic fields as well as anisotropic...
Warm dense iron is of great interest from the perspective of planetary physics and geophysics. Understanding the microscopic structure would help make great advances in understanding the thermodynamics and mechanics of planetary structure and formation. To this end, x-ray scattering from warm dense matter can make a significant contribution. We have created warm dense samples of Fe by laser-drive...
The physics of the transport of large currents of fast (relativistic) electrons in dense matter underpins many topics in high intensity laser-solid interactions, including warm dense matter, ion acceleration and the fast ignition approach to inertial confinement fusion. The propagation of fast electrons within the target is subject to transport instabilities (e.g. resistive instabilities) which give...
Terahertz radiations, which have a frequency range between 100 GHz and 30 THz, have applications in many fields, including nanotechnology, and photonics1. The use of femto-second laser pulses and a gallium arsenide photoconductive switch (PCSS) to generate THz radiations is well known. THz radiation waves occur when the signal generated in the substrate moves along the PCSS material (which acts as...
Development of new biomaterials takes a very time before of long certification processes and government approval. Therefore, it is normally more efficient to use existing biomaterials and then selectively enhance the pertinent properties to expedite the acceptance of biomaterials and biomedical implants. This is because the surface of biomaterials plays the major role in determining the effects and...
The vehicle exhaust gas is one of the major causing environmental pollution. It contains a mass of VOC and NOx, which is very harmful to human body. In order to remove pollutants from automotive exhaust, many studies about plasma-driven catalysis for VOC or NOx gas purification have been done. However, heir studies were based on simulated gases( mixed gases or single gas), which were quite different...
The development of periodic structures for use as oscillators and amplifiers in the millimetre and sub-millimetre region has been an important topic in science in recent years [1–4]. The 2D periodic structure used in this instance to form the interaction region has a potential for application in sources of high power microwave and THz radiation [5]. Such a structure can be observed using a hollow,...
The axis of symmetry of the magnetic field is not always ideally aligned to the mechanical axis of the gyrotron, mainly for two reasons: (i) misalignment of the coils in the magnet and (ii) mechanical inaccuracies on the gun and cavity position. In this work, the effects of the magnetic field misalignment are numerically studied for the coaxial cavity EU gyrotron1 for ITER. First, the degradation...
Use of low-loss magnetic materials in high-power microwave devices can improve significantly their performance. We have demonstrated1 that the electromagnetic losses in the composite structure can be reduced by up to two orders of magnitude, compared to those of the uniform magnetic sample made of the same lossy magnetic material. Importantly, the dramatic absorption reduction is not a resonance effect...
The start-oscillation-current of a gyro-TWT determines the stable operating current level of the device. The amplifier is susceptible for oscillations when the operating current level is higher than the start-oscillation current. There are several ways of calculating the start-oscillation current, including using the linear theory of a gyro-TWT. In this paper, we present a simple way of determining...
In high-power gyrotrons sweeping systems are used in order to distribute the energy of the spent beam in a larger area of the collector1. Currently, there are two common types of sweeping systems, the axial and transversal sweeping system2. In the first case, the sweeping coils surround the collector creating a harmonically varying magnetic field that is coaxial to the externally applied one. In the...
Cyclotron masers1 are fast wave devices which typically operate in the centimetre to submillimetre region of the electromagnetic spectrum. They find application in numerous fields such as radar, plasma science and materials processing. Two amplifer devices have been studied to establish their potential for efficiency enhancement. By tapering either the magnetic field or the physical dimensions of...
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