Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2012
Thesis Language: Turkish
Student: Sema Karaköse
Supervisor: BAHTİYAR SALAMOV
Abstract:Homogeneous state and conditions in relation to space and time distribution of Ar discharge at high pressures up to atmospheric pressure were experimentally investigated as a function of pressure p, interelectrode distance d and electrode diameter D in the semiconductor gas discharge system (SGDS) with InP photocathode. The stabilization of the discharge current is obtained by uniformity of the distributed resistance of photosensitive semiconductor cathode and the impact of the ionizing component of the discharge plasma on the control of the stable operation mode of a planar gas discharge system considerably changes the current distribution. We studied the processes of various formations and losses in SGDS with microgap width affecting the spatial parameters of plasma in the relatively high electric field. At the same time, the Current-Voltage Characteristics and the Intensity-Voltage Characteristics of the gas discharge system with InP cathode and the Paschen curves of Ar gas under sufficient conditions of space and time development to ignition are evaluated, depending on the pd range and the outputs of experimental breakdown with respect to the calculation of secondary electron emission coefficient. It was observed that the gas discharge light emission (GDLE) increased in Ar and Air medium towards the atmospheric pressure. The nonlinear features and the effect of the voltage amplitude on the dynamics of transient processes in the SGDS with a InP:Fe photocathode are studied to explain the mechanism of the current decay. On the other hand, the oscillatory current with N-shaped and hysteresis peculiarities are related to a nonlinear mechanism of carrier transport in the semiconductor material caused by Fe defect center. Micro-structured dielectric arrays (MSDA) allow large-area uniform glow discharges to be generated over a wide pressure range up to atmospheric pressure. It was determined that breakdown potential in gas discharge gap based on MSDA is decreased with respect to low power handling; however, GDLE and current values are increased, depending on the working pressure. An advantage of the specific discharge configuration of MSDA is that the excitation and ionization efficiency increases due to the parallel plate semiconductor cathode geometry. The emission spectrum measurement of Ar plasma in afterglow mode is performed to characterize the different excitation and ionization states of SGDS dependent on plasma volume and cathode processes and, the 4p-4s atomic and the 4d-4p ionized spectrum peak lines occurring in experiments were discussed with respect to secondary electrons and pressure. Under the experimental conditions, it is shown that the Ar species, especially metastable, will make important contributions to the maintenance of discharge into plasma volume in the right hand of Paschen curve. We believe that, on the basis of the outlined principles, it is possible to build non-thermal and large emitting area plasma light sources with photosensitive semiconductor cathode.