Month: July 2018

This article describes plasma sources, the possible movements of particles created inside the plasma, the origins of these particles, the definitions of thermal/non-thermal plasmas, surface and volume interactions, the processes of electrical breakdown, plasma discharge with boundary relations, 0-D model for density, temperature and electric field, and 1-D model for different pressure levels.

Continue reading “Summary: INTRODUCTION TO GAS DISCHARGES”

The article presents introductory materials for the processes inside atoms and between atoms based on energy levels. Firstly, the particles which have a probability to interact with the other species are described. Among the interacting species, photon and electron are elementary particles. The energy of a photon is calculated depending on its frequency. Electron has only translational kinetic energy calculated by translational speed. For atoms and molecules, their total energy is a summation of translational, vibrational and rotational energies. There are many energy levels representing excited levels. If we consider an atom, the minimum energy above the ground level causes excitation and constitutes a free electron. When energy transmitted to atom exceed the ionization energy (series limit), a free ion is created. After ionization, particles can attain any energy level so they create a continuum. All energy levels correspond to a configuration of possible energy states, which is called as degeneracy. It can be defined as the number of different quantum states with the same energy. For electron, there are only two possible states resulting from electron spin. Atoms can have larger degeneracy values depending on their quantum states.

Continue reading “Summary: PARTIALLY IONIZED GASES”

In this book chapter, particle collisions are examined. Electrons and ions can experience elastic collisions by preserving total momentum and energy. Otherwise, they lose their energy in the form of ionization or excitation and this type is named inelastic collision.  Electrons and fully stripped ions have only kinetic energy but excited and ionized atoms possess internal energy, analogous to potential energy. While their internal energy is constant, kinetic energy is redistributed between the colliding particles in elastic collisions. For the super elastic collisions, an excited atom can be de-excited and the total kinetic energy becomes larger.

Continue reading “Summary: ATOMIC COLLISIONS”

Sanders investigated the Townsend coefficient (α) in the regions with different pressure and distance levels in his two papers. For the former one, the author criticized the early measurements of Townsend, Bradbury and Paavola to give an explanation to the current values for higher X/p (the ratio of electric field strength [V/cm] to the pressure [mm]). Townsend explained the energetic ions cause more ions and introduced value which represents new pairs of ions per centimeter. However, his experiments were conducted in a low pressure, small distance, high electric field environment and the results failed to explain lower X/p values in high pressure conditions. The researchers proposed that at higher pressure level, the number of the created ions increases due to electron impact ionization in the dark current just before the breakdown. The distorted fields with space charge satisfy the Townsend equation with new values.

Continue reading “Summary: MEASUREMENT OF TOWNSEND COEFFICIENT”