Dr.
Hyun-Kyung Chung
AMP Division
Atomic Processes and Spectral Modeling of High
Current-Density Ion Beam-Produced Plasmas
Abstract:
A collisional-radiative (CR) model is applied to understand
highly transient argon plasmas and estimate plasma conditions
in ion beam transport experiments. Atomic processes considered
in our CR model are; collisional excitation, deexcitation, ionization
and recombination, photoexcitation, stimulated and spontaneous
emission, photoionization, stimulated and spontaneous radiative
recombination, and dielectronic recombination. Collisional processes
by ion-beam impact and non-Maxwellian electron impact are included
as well as thermal electron impact. Our results show that ionization
processes are dominated by ion beam impact early in the ion beam
pulse and by electron collisions after electron density is sufficiently
high. Stepwise ionization processes via excited levels are significant
in ionization dynamics. Measured spectra are influenced by non-equilibrium
plasma states and opacity effects. We present a statistical procedure
to estimate opacity broadening from Stark broadening. Electron
density is found to increase from 10^12 cm-3 to a few of 10^17
cm-3 within 30 nanoseconds and temperature is found to be 2 to
3 eV.
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