Eun-gi Heo

Test particle simulations for transport in toroidal plasmas

The authors derive the guiding center equations of motion from the phase space Euler–Lagrange formulation for the motion of a charged particle in toroidal magnetic confinement geometry. The guiding center equations are numerically solved together with the Monte Carlo Coulomb collisional pitch angle scattering. The numerically calculated microscopic diffusion coefficients for various values of collisionality ν* in the case of no electrostatic potential agree well with the results of neoclassical theory. The diffusion coefficient is then measured in the presence of a model electrostatic drift wave fluctuation and an equilibrium potential. The diffusion coefficient increases with increasing fluctuation amplitude while the equilibrium potential diminishes the diffusion processes through both the orbit squeezing and the Er×B shear flow of the poloidal velocity.

8.2: New Electrode Structure to Improve Discharge Characteristics in AC PDPs

A new structure including igniter electrode is proposed to achieve a low sustaining voltage and high luminous efficacy. By measuring minimum sustaining voltage(Vsm), discharge current(Ion), displacement current(Ioff) and brightness of the light from a 6-inch AC PDP, performances of the conventional structure and the igniter structure are compared. When compared with the conventional structure, the igniter structure showed 10% Vsm improvement at the Ne-Xe(10%) gas mixture of 600 mbar. Therefore, we could apply the higher partial pressure of Ne-Xe(12%) to the igniter structure, which results in 42% luminous efficacy improvement at the similar sustaining voltage range.

Explanation for Luminance Saturation of PDP Phosphor

Luminance saturation is primary determined by whether the decay time is on the order of microseconds ( μs) or milliseconds (ms), that is, whether or not electric dipole moment transitions are allowable. For prohibited or magnetic transitions, for which electric dipole moment transitions are not allowable (phosphors with ms-order decay times), there is no linear relationship between decay time and luminance saturation. In order to explain the luminance saturation of phosphor with ms-order decay time in plasma display panel we proposed non-radiative transitions as a cause of luminance saturation and derived simulation formulas based on them. The results from the simulation were in good agreement with those from the experiments.

13.4: Three-Dimensional Observations of Reset and Address Discharges of Plasma Display Panel

Three-dimensional infrared emission characteristics of a weak discharge in reset period and two different discharge modes in address period were investigated with 3-D test panel. Based on 3-D infrared emissions measured in reset period, the infrared from the cathode were not observed all during the rising and falling ramp reset period and these characteristics are closely related to the electron energy near the cathode. Based on the front and side images of the weak discharge in reset period, the address discharge mode is estimated and experimentally confirmed with the 3-D test panel. In addition, depending upon various driving conditions, two address discharge modes (single-tail and double-tail modes) were observed and discussed.

28.4: Characterization of Negative Electron Affinity for MgO Film by Ultraviolet Photoelectron Spectroscopy

Many attempts to investigate electronic band structures of various metal oxides such as magnesium oxide (MgO) and calcium oxide (CaO) have been made for a long time, but exact electronic band structures of metal oxides have not been achieved successfully so far due to surface charging during measurement analysis except for ultrathin film. In this study, ultraviolet photoelectron spectroscopy (UPS) is introduced and electronic band structure for MgO film has been obtained by using a unique way of heating the film, which suppresses the surface charging of MgO film through improvement of electrical conductivity during measurement. Negative electron affinity has been characterized for MgO film in the measured UPS spectrum. The characteristics of negative electron affinity can be understood as originating from image-potential states on MgO surface.

15.3: Anti-Electromigration of Lead-Free Ag/Frit Modified Address Electrodes in PDPs

We have studied on the usage reduction and anti-migration properties of newly formulated lead-Free (Bi-based) Ag/Frit modified address electrode (hereinafter VE electrode) systems in PDPs (Plasma Display Panels). It is thought that their high performance such as anti-migration and the cost-competitiveness without any loss of performance in paste, process and luminous efficacy are originated from the optimum controlling of Ag/Frit weight ratio and low specific gravity by low Ag contents, respectively. Currently, lead-free VE electrodes are being applied as main electrode materials of PDP panels fabricated by SDI photo-imageable patterning process including ultra-fine resolution models.

Modified ramp‐reset waveform robust for variable panel temperature and its discharge characteristics

Abstract By the voltage threshold (Vt) close‐curve measurement method, the changes in the discharge characteristics such as a firing voltage and IR emission among the three electrodes were examined relative to the low or high panel temperature ranging from ‐10 to 80°. The variation in the panel temperature was found significantly influence the surface discharge between the MgO surfaces rather than the plate gap discharge between the MgO and phosphor layers. Based on this experimental observation, a modified reset waveform that alleviates the surface discharge during a ramp‐up and ‐down period was deeloped. By adopting the proposed reset waveform, a stable address discharge could be obtained irrespective of the panel temperature variation.

14.4: Plasma Display Panel with Ridged Dielectric Layer between Sustaining Electrodes

This article presents a front panel structure for an alternating current plasma display panel (AC PDP) based on a ridged transparent dielectric layer between the sustaining electrodes. Compared to a conventional AC PDP, the suggested structure can reduce a firing voltage and sustaining voltage due to a strong electric field between the sustaining electrodes. First experiments were conducted to see the effect of ridged dielectric structure in the short electrode gap of 110 μm with various Xe contents from 10% to 50% at a gas pressure of 450 Torr, and the results confirmed that the ridged dielectric structure reduced the firing and sustaining voltages by about 74 and 79 V at 10% Xe content compared to a conventional structure with 10% Xe content, respectively. Also, the proposed structure improved the luminous efficacy and luminance by about 50.9% and 33%, respectively, with 50% Xe content when compared to a conventional structure with 10% Xe content at a similar driving voltage. Second, performances of the conventional structure and the ridged dielectric structure with the electrode gap of 140 μm were compared. Experimental results confirmed that the box shaped ridged dielectric structure could be driven at a lower voltage than conventional AC-PDPs with the same Xe content. Also, the luminous efficacy of box shaped ridged dielectric structure was higher than those of conventional structures.

29.2: Low‐Cost Barrier Rib and Address Electrode Formation for a 42‐in. High‐Definition PDP

The method in which the barrier rib is formed from the glass substrate directly by sandblasting is an effective part of a low cost process, because it can eliminate the baking process and the rib material. Furthermore we developed a new method in which the address electrode is formed without photolithography by using a slurry solution in which the electrode material is dispersed. Finally, we actually produced a 42inch HD-PDP(1366×768).