Authors: Shanti Thagunna (UAH), Dr. Gary Zank (UAH), Dr. Vladimir Kolobov (UAH)

When the mean free path of electrons in plasma is comparable to the
characteristic plasma dimensions, the electron distribution function (EDF) is
non-local and is controlled by volume averaged processes. A Global kinetic
model calculates the EDF assuming that electrons are trapped in a potential well-formed by the electrostatic potential inside the plasma. Global Kinetic Models
have proven to be very useful to study complex chemistry in plasma-aided
manufacturing and material processing. We are developing a global kinetic
model of hydrogen-based plasmas taking into account electron kinetics, the
kinetics of vibrational states of molecules, and the non-equilibrium chemistry of ion
and neutral species using CFD-ACE software. The key species include the
ground-state hydrogen atoms and molecules, vibrationally excited hydrogen
molecules, electronically excited hydrogen atoms, several positive ions, and
electrons. The key chemical reactions are electron-induced direct ionization and
dissociation of molecules, excitation of vibrationally excited states of molecules
and electronically excited hydrogen atoms, step-wise ionization, and wall
recombination of ions. Simulations help understand the effects of gas pressure,
power deposition in plasma, and plasma density on the electron energy
distribution function and electron-induced reaction rates. The model is applied to
simulations of gas mixtures used for the deposition of superhard materials. The
applications to hydrogen plasma in the Sun photosphere are planned for future
work.