Nanosecond Pulsed Plasma Actuators

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Electron emission from boundaries is ubiquitous in radio-frequency capacitively coupled plasmas (RF-CCPs) and can exert a significant influence on discharge characteristics. In this work, particle-in-cell Monte-Carlo collisions (PIC-MCC) simulations with an external circuit are performed to investigate a conduction-current-dominated RF-CCP mode, termed the inverted RF-CCP, which is induced by strong boundary electron emission. In this mode, the displacement current becomes negligible, and the conduction cur

Systematic investigations on positive and negative surge waves from upstream have been conducted in a 40 m long channel with a mean bed slope of 1.14? and non-prismatic bank geometries. The channel banks included macro-roughness elements, namely various cavities. In total, 41 different geometrical configurations have been investigated. The surge wave experiments confirmed the applicability of the elementary surge wave theory including secondary waves and wave breaking in the prismatic reference configuratio

In the search of a fusion reactor using magnetic confinement of toroidal plasmas, many important plasma performance parameters directly depend on the shape of the plasma cross-section. The unique shaping capability of the TCV tokamak ("Tokamak à Configuration Variable") has been exploited to study different aspects of tokamak transport and stability, in which the plasma shape may play a role. This presentation will focus on the effects of plasma shape on transport. The TCV tokamak has produced a host of phy

A new understanding of edge localized modes (ELMs) in tokamak discharges is emerging (Snyder P B et al 2002 Phys. Plasmas 9 2037), in which the ELM is an essentially ideal magnetohydrodynamic (MHD) instability and the ELM severity is determined by the radial width of the linearly unstable MHD kink modes. A detailed, comparative study of the penetration into the core of the respective linear instabilities in a standard DIII-D ELMing, high confinement mode (H-mode) discharge, with that for two relatively high

A characterization of the H-mode in Tokamak de Varennes (TdeV) is presented, combining results obtained from spectroscopic measurements with observations of global plasma parameters. Controlled L- and H-modes are obtained by applying an external bias on the divertor plate and/or by varying the plasma triangularity using similar steady-state discharges with electron cyclotron resonance heating (ECRH). A qualitative study of the impurity emission asymmetries is presented and discussed by proposing a simple mo

Microcrystalline hydrogenated silicon films (muc-Si:H) have been deposited by a high current DC plasma in argon-silane-hydrogen mixtures at growth rates up to 10 nm/s and at substrate temperatures below 500 degreesC. Scanning electron microscopy, X-ray diffraction and FTIR analyses show that these films are highly crystallized. The surface morphology depends strongly on the experimental conditions and varies from a cauliflower structure to a prismatic one. The crystalline orientation of the films also chang

An algorithm is proposed for the simulation of unsteady viscous stratified compressible flows. The advantage of the method is its capability to deal with a broad range of subsonic Mach numbers, including nearly incompressible flows, with a single modelling, based on the fully compressible Navier-Stokes equations. The method is second-order accurate both in space and time. To remove the stiffness of the numerical problem due to the large disparity between the flow and the acoustic wave speeds at low Mach num

Within the range of plasma shapes and plasma currents investigated, the electron confinement time, Tau_E increases with density, elongation and negative triangularity (-0.4

Precise control of the shape and position of double-null divertor configurations in the TCV tokamak has been used to trigger reliably the transition from ELM-free to ELMy ohmic H mode and back. Preprogrammed modulation of the magnetic axis height (+/- 1.25 cm), with fixed shaping field, caused the plasma to evolve, during a single discharge, between double-null-upper, double-null and double-null-lower configurations, with the secondary X point remaining close to the separatrix. The transition from ELM-free

The rising part of the current waveform observed when discharging an electrostatically charged person or test generator shows some phenomena which have not been explained satisfactorily. This paper describes an attempt to understand these effects using both experimental and numerical simulation. A special rotating system to simulate a defined, variable closing speed of contact has been built. The length of the arc is also measured and it can be shown that a strong correlation between arc-length and rising s

Nanosecond Pulsed Plasma Actuators

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Exploring the impedance characteristics in an inverted radio-frequency capacitively coupled plasma discharge due to intense boundary emission

Unsteady flow in a channel with large scale bank roughness

Physics Insight from Plasma Shaping of TCV Tokamak Plasmas - focus on Electron Heat Transport

Edge localized modes in DIII-D high performance discharges

Characterization of impurities in L- and H-modes created by divertor biasing and plasma triangularity in TdeV

Rapid deposition of hydrogenated microcrystalline silicon by a high current DC discharge

An algorithm for low Mach number unsteady flows

Preliminary Confinement Studies during ECRH in TCV

Elm Control During Double-Null Ohmic H Modes in Tcv

The correlation of rising slope and speed of approach in ESD tests