Engineering topics

Nonnast, J. H.

Publications and source records attributed to Nonnast, J. H..

6 records

NASA NTRS1983

Numerical simulation of a disk-shaped electron accelerating electrostatic probe

This paper presents a method utilizing the numerical plasma simulation particle-in-cell technique for studying electron accelerating probe characteristics. A probe configuration other than the commonly used plane, cylindrical, or spherical case will be studied; the probe configuration used is that of a disk. Cylindrical geometry is used in the simulation model. One of the advantages of a numerical simulation is the ease with which the details of the system can be examined. Therefore, in addition to the current-voltage characteristics of the static probe, other results are presented such as the time evolution of the plasma properties and studies of the sheath region surrounding the probe.

Nonnast, J. H.↗

NASA NTRS1982

Numerical simulation of a conducting disk partially covered by an insulator interacting with a plasma

A numerical simulation has been made of the 'pinhole effect' which produces the characteristic 'S-shaped' current-voltage curve. A disk-shaped conducting probe immersed in a plasma is modeled using a particle-in-cell (PIC) code. A probe partially covered by a very thin insulating layer is considered, as well as a probe mounted on an insulating disk. The simulation uses a cylindrical particle mover and allows for a variable number of particles in the system. The simulation space grid uses three different mesh sizes, the coarsest being away from the probe and the finest near the probe, in order to accurately calculate the trajectories of the simulation particles contributing the current to the probe and to the surface charge density on the dielectric. The calculation of the electrostatic potential is done self-consistently using successive over-relaxation (SOR). Backscattering and secondary electron emission are included for the case of positive probe voltage.

Chaky, R. C.↗

NASA NTRS1982

A study of solar flare soft X rays and their relation to particle events observed with IMP 8

Data from the Johns Hopkins University Applied Physics Laboratory charged particle measurement experiment aboard IMP 8 was used to study solar flare events and find correlations between soft X rays (4-17 A) and particle events. The results show that a greater probability exists of observing a proton event if the observed soft X ray flare has a relatively large decay time. It is also found that the H-alpha brightening area is a good indicator of the strength of the soft X ray burst. Results also show that the strength of the soft X ray burst can be used to estimate a probability that a proton event will occur, along with the strength of that particle event.

Nonnast, J. H.↗

NASA NTRS1981

Numerical simulation of sheath structure and current-voltage characteristics of a conductor-dielectric disk in a plasma

A computer program is being developed to simulate the interaction of a plasma with a conducting disk. Two configurations are examined: (1) the conductor is a 'button' in the center of a larger dielectric disk, and (2) the conducting disk is covered by a dielectric disk to the same size with a circular hole in the center of the dielectric, exposing a region of conductor. Results of the electrostatic plasma simulation are presented both with and without secondary electron emission from the dielectric; characteristic curves and voltage profiles are included.

Chaky, R. C.↗

NASA NTRS1980

Numerical simulation of plasma insulator interactions in space. Part 1: The self consistent calculation

A computer program is being developed to simulate the interaction of a plasma with a conducting disk partially covered by an insulator. Initial runs consider only charge sticking to the dielectric. Results indicate that the current density drawn by the hole in the dielectric increases approximately linearly with voltage for conductor voltages between 5 volts and 250 volts.

Nonnast, J. H.↗

NASA NTRS1980

Numerical simulation of plasma insulator interactions in space. Part 2: Dielectric effects

Any process which may be modeled statistically for a simple plasma particle may be modeled by the particle in cell technique. The success of the calculation is then dependent on having a large enough number of particles that the statistical treatment is meaningful. Thus it is possible to include the effects of secondary emission, backscattering, charge sticking and possibly dielectric breakdown, photoemission, and spallation. The first plasma dielectric interaction included in the computer code for simulating plasma insulator interactions is secondary electron emission. A calculated current density vs. voltage curve is presented and compared to an experimental curve.

Chaky, R. C.↗