Jae-Jun Ko

Measurement of Secondary Electron Emission Coefficient (γ) of MgO Protective Layer with Various Crystallinities

The secondary electron emission coefficient γ of a MgO protective layer with various crystallinities has been successfully measured by the γ-focused ion beam system with complete elimination of the charge accumulation problem by scanning-area adjustment techniques. It is found that the (111) surface has the highest γ from 0.14 to 0.26 in comparison with the other films with (200) and (220) crystallinities for operating Ne+ ions, while ranged from 0.03 to 0.24 for Ar+ ions, under operating ion energies from 50 eV to 500 eV throughout this experiment. These observations explain why the (111) crystallinity of the MgO protective layer plays an important role in lowering the firing voltages in AC plasma display panel compared to the films with other crystallinities.

Secondary electron emission coefficient of a MgO single crystal

The secondary electron emission coefficient γ of different MgO single crystal has been measured by γ-focused ion beam system. It is found that the MgO single crystal with (111) orientation has the highest γ from 0.08 up to 0.21, while from 0.06 to 0.19 for (200) and from 0.05 to 0.15 for (220) orientation for operating Ne+ ions ranging from 50 to 300 eV throughout this experiment. It is also found that these observations can be explained by work functions, which are dependent on the crystal orientations of MgO.

Conductivity and ion density of a plasma channel induced by a mildly relativistic electron beam from a gas-filled diode

Conductivity and ion density of a plasma channel induced by a mildly relativistic electron beam (300 kV, ∼2 kA, 10–50 ns) have been experimentally investigated under various gas pressures. Pressures of filling gas (air) in this experiment ranged from 10 mTorr to 100 mTorr. The net currents of the beam-induced plasma channel were measured by four Rogowski coils located along the propagating region, while the electron beam currents were measured by a Faraday cup. The inductive plasma currents observed at the above pressure regimes have been characterized by magnetic decay time. Plasma-channel conductivity and ion density induced by the beam are measured along the propagating axial positions under various gas pressures. The numerical result of the ion density is also obtained at the charge neutralization time when the ion density is just the same as the electron beam density, and the digitizing experimental data of the beam current Ib(t) and voltage Vd(t) have been used. As expected, in both numerical and ex...

Influence of gas mixture ratio on the luminous efficiency in surface discharge alternating current plasma display panels

The improvement of luminosity and luminous efficiency is the one of the most important tasks in alternating current plasma display panels. The influence of gas mixture ratio, Ne–Xe and He–Ne(27%)–Xe(3%), on luminosity and luminous efficiency in surface discharge alternating-current plasma display panels has been investigated. It is found that discharge power does not strongly depend on the gas mixtures, while the luminosity for three species mixture gas, He–Ne(27%)–Xe(3%), is shown to be much higher than those for the two species mixture gas of Ne–Xe. The three species mixture gas, He–Ne(27%)–Xe(3%), can be suggested as the one of the candidates for achieving high luminosity and luminous efficiency for color plasma display panels, based on the experimental observations of luminosity, discharge power, response time, and efficiency.

Ion-Induced Secondary Electron Emission Coefficient(γ)of Bulk-MgO Single Crystals

The ion induced secondary electron emission coefficient ? of bulk-MgO single crystal has been measured by the ?-focused ion beam system. It is found that the bulk-MgO single crystal with (111) orientation has the highest ? from 0.08 up to 0.21, and the ? values are in the order of the crystallinities, (111) > (200) > (220) for operating Ne+ ions ranging from 50 eV to 300 eV in this experiment. These results are consistent with our previous reports for MgO protective layers with respective orientations of (111), (200), and (220).

Influence of Sustaining Pulse-Width on Electro-Luminous Efficiency in AC Plasma Display Panels

The influence of sustaining pulse-width on electro-luminous efficiency has been experimentally investigated for the surface discharge of AC plasma display panels. A square driving voltage pulse with a variable duty ratio and a fixed rise time of 300 ns has been used in this experiment. It is found that the firing voltage decreases as the sustaining pulse-width increases from 2 µs to 8 µs under a given driving frequency, and also decreases as the frequency increases from 10 kHz to 50 kHz. The memory coefficient is found to be significantly increased from 0.16 to 0.71, as the sustaining pulse-width increases from 3 µs to 4 µs, beyond which it maintains a nearly constant value of approximately 0.8 for the driving frequency range from 30 kHz to 50 kHz. The optimal sustaining pulse-width is shown to be in the range of 3 µs and 4 µs for driving frequencies of 30 kHz and 50 kHz, based on the observations of memory coefficient, wall charge, wall voltage and luminous efficiency.

Influence of Driving Frequency on the System Parameters in Surface Discharge of AC Plasma Display Panels

The influence of the driving frequency on the wall charge and voltage is experimentally investigated for the surface discharge of AC plasma display panels. A square pulse with a rising time of 150 ns and a duty ratio of 40% was used in the experiment. It is found that the capacitance C0 of the surface discharge in a gas-filled region is almost constant and is 0.3 pF/cell, whereas the capacitance Cg in the dielectric region is significantly decreased from 7.5 pF/cell to 0.8 pF/cell, as the driving frequency is increased from 10 kHz to 200 kHz. It is also found that both the wall charge and the wall voltage decrease from 34.5 pC/cell to 15.6 pC/cell and from 104.4 V to 76.5 V, respectively, as the driving frequency increases from 10 kHz to 200 kHz.

P-36: LCD Planar Backlight Employing the External Electrode Fluorescent Lamps Driven by Square Pulses from Switching Inverter

The planar luminaries with the external electrode fluorescent lamps arrayed on a flat panel for the LCD-backlight have been improved by driving with the square pulses from a single switching inverter. With the square pulses of the driving frequency about 30 kHz, the high efficiency up to 40–70 lm/W and high brightness up to 30,000 cd/m2 along with the luminance uniformity 90% in the 15-inch, 18-inch, 21-inch diagonal panels, respectively, could be obtained.

Pulsewidth and rising time of relativistic electron beam in gas-filled diode

The pulsewidth and rising time of a mildly relativistic electron beam (300 kV, 1-3 kA) passing through a gas-filled diode region are investigated experimentally under various gas pressures P. The pulsewidth and rising time of a relativistic electron beam (REB) were controlled by adjusting the gas pressures P of the diode region. The pulsewidth and rising time of the relativistic electron beam are experimentally found to scale as P/sup -0.807/spl plusmn/0.054/ and P/sup -0.770/spl plusmn/0.058/, respectively. The REB pulsewidth and rising time are shown to have the same scaling law, within the experimental error range as a function of pressure. In particular, the empirical scaling law of the REB pulsewidth is in remarkably good agreement with the numerical scaling law P/sup -0.809/spl plusmn/0.059/ of the full-space charge neutralization time t/sub n/ at which the ion density n/sub i/ is just equal to the electron beam density n/sub b/ at the diode region under a given gas pressure P. It also is found that ion density n/sub i/ at the full space-charge neutralization time t/sub n/ has quite a similar profile in terms of pressure P to that of the REB peak current detected by a Faraday cup.

Transition of Space Charge to Wall Charge by Control Pulse after Self-Discharge in AC-Plasma Display Panel

The transition of space charge to wall charge after self-discharge has been experimentally tested in an AC-plasma display panel (PDP) with a versatile driving simulator (VDS) system, in which arbitrary driving waveforms and sequences can be used. When the self-discharge occurs immediately after a high voltage reset pulse is applied, a certain amount of space charge is generated in the PDP cell. By applying a suitable control pulse at this time, it is found that these space charges can be converted into sufficient wall charges for maintaining a sustain discharge without any writing pulse. Also, the saturated sustain peak current strongly depended on the control pulse condition in spite of the same sustain waveform. This means that the influence of the initial wall charge which was formed prior to the sustain period is continuously maintained throughout the sustain period.