Volume 91, Issue 2, 15 January 2002
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
Influences on ionization fraction in an inductively coupled ionized physical vapor deposition device plasma91(2002); http://dx.doi.org/10.1063/1.1425447View Description Hide Description
A computer simulation was created to model the transport of sputtered atoms through an ionized physical vapor deposition (IPVD) system. The simulation combines Monte Carlo and fluid methods to track the metal atoms that are emitted from the target, interact with the IPVD plasma, and are eventually deposited somewhere in the system. Ground-state neutral, excited, and ionized metal atoms are tracked. The simulation requires plasma conditions to be specified by the user. Langmuir probe measurements were used to determine these parameters in an experimental system in order to compare simulation results with experiment. The primary product of the simulation is a prediction of the ionization fraction of the sputtered atom flux at the substrate under various conditions. This quantity was experimentally measured and the results compared to the simulation. Experiment and simulation differ significantly. It is hypothesized that heating of the background gas due to the intense sputtered atom flux at the target is primarily responsible for this difference. Heating of the background gas is not accounted for in the simulation. Difficulties in accurately measuring plasma parameters, especially electron temperature, are also significant.
Direct measurement of electron density and temperature distributions in a micro-discharge plasma for a plasma display panel91(2002); http://dx.doi.org/10.1063/1.1419264View Description Hide Description
Spatial distributions of electron density and electron temperature of a micro-discharge plasma for an alternating currentplasma display panel cell were directly measured using the laser Thomson scattering method. The use of a triple-grating spectrometer was very successful in suppressing the strong stray laser light and allowed us to perform measurements at 0.1 mm above the surface of the electrode substrate. Values of and were and (1.6–3.4) eV, respectively, depending on the time from the beginning of the pulsed discharge and the observation position. The structure of the micro-discharge is discussed in terms of the obtained distributions of and
91(2002); http://dx.doi.org/10.1063/1.1426239View Description Hide Description
High currentdischarge channels can neutralize both current and space charge of very intense ion beams. Therefore, they are considered an interesting solution for final focus and beam transport in a heavy ion beamfusion reactor. At the Gesellschaft fuer Schwerionenforschung accelerator facility, 50 cm long, free-standing discharge channels were created in a 60 cm diameter metallic chamber. Discharges with currents of 45 kA in 2 to 25 mbar ammonia gas are initiated by a laser pulse along the channel axis before the capacitor bank is triggered. Resonant absorption of the laser, tuned to the vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. The influence of an electric prepulse on the high currentdischarge was investigated. This article describes the laser–gas interaction and the discharge initiation mechanism. We found that channels are magnetohydrodynamic stable up to currents of 45 kA, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a one-dimensional Lagrangian fluid code (CYCLOPS) and is identified as the dominant initiation mechanism of the discharge.