Yoonho Seo

Vacuum ultraviolet luminous efficiency and plasma ion density in alternating current plasma display panels

The correlation between the vacuum ultraviolet (VUV) luminous efficiency and the plasma ion density has been investigated in terms of the xenon mole fraction in the neon filling gas for alternating current plasma display panels. The VUV luminous efficiency and plasma ion density are found to have strong correlation and to be saturated at xenon mole fractions greater than 7% and gas pressures of 400 Torr.

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.

Plasma propagation speed and electron temperature in surface-discharged alternating-current plasma display panels

The electron temperature and plasma density in coplanar alternating-current plasma display panels (AC-PDPs) have been experimentally investigated by a micro Langmuir probe and the high speed discharge images in this experiment. It is noted in this experiment that the electron temperature obtained from both the micro Langmuir probe and high speed ICCD camera decreases from 1.8 eV to 0.8 eV as the filling Ne gas pressure increases from 150 Torr to 400 Torr. It is noted that these electron temperatures are in good agreement with each other within 5% error limit. The plasma density at the lateral distance of 125 /spl mu/m away from the center of sustaining electrode gap has been found to be decreased from 3.7/spl times/10/sup 11/ cm/sup -3/ to 2.3/spl times/10/sup 11/ cm/sup -3/ at the Ne filling pressures ranged from 150 Torr to 350 Torr.

A diode design study of the virtual cathode oscillator with a ring-type reflector

A numerical simulation study of the high-power microwave generation from the vircator (virtual cathode oscillator) is carried out for coaxial diode structure by using a three-dimensional particle-in-cell (PIC) code called MAGIC. The coaxial vircator has a centered annular cathode body, cathode ring and cylindrical meshed-anode in order to enlarge the active interaction region in the virtual cathode space. In order to enhance a conversion efficiency of the output microwave power, ring-type reflector was installed to coaxial-type diode structure. The simulation results show that the output microwave frequency has a narrow bandwidth and its output microwave power sensitively depends upon the position and width of ring-type reflector. The maximum output microwave power is obtained by adopting a ring-type reflector 10 mm in width and 40 mm in the distance from the intense relativistic electron beam to the ring-type reflector. The output microwave mode without a ring-type reflector is a mixture of TM and TE mode. However, the TM/sub 01/ mode with its resonance frequency of 2.2 GHz is dominant for the ring-type reflector.

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.

A submillimeter Raman free-electron laser in a dense plasma background

Growth characteristics of a Raman free-electron laser in a dense plasma background are investigated. The background plasma is beneficial in the sense that it allows a beam current over the vacuum space-charge limit. It is found, however, that an excessive plasma density reduces the linear growth rate significantly if the radiation mode is not confined well inside the electron beam. The growth rate reduction accompanies a large positive frequency shift of the radiation field. This indicates that the background plasma causes the optical beam to expand outward farther into the plasma.

47.4: The Center Balancing Operation of CCFLs and EEFLs for LCD Backlight

A center balancing operation is proposed for a large area LCD backlight with the multi-lamps driven by a single inverter. This new method minimizes the power leakage due to the parasitic capacitance of the backlight metal housing.

Effects of the Dielectric Layer on a Planar and a Coplanar Discharge Breakdown

There are two influences of a dielectric layer on the breakdown in Paschens law. The potential difference at the dielectric layer itself enhances the minimum value of firing voltage, while the strong field in the discharge space with a large dielectric constant reduces the firing voltage in a high pressure range. Specially in a coplanar geometry like AC-PDP [S. Sato et al. : IEEE Trans. Electron Devices 23 (1976) 328.], the firing voltage is shown to be higher due to the non-uniformity of the electric field along with the thickness of the dielectric layer.

Influence of Vacuum-Annealing Process on the Secondary Electron Emission Coefficient (γ) from a MgO Protective Layer

The secondary electron emission coefficient (γ) of vacuum-annealed MgO films has been investigated using a γ-focused ion beam (γ-FIB) system. The vacuum-annealed MgO films have been found to have higher γ values from 0.05 to 0.12 than those from 0.03 to 0.06 for as-deposited MgO films for operating Ne+ ions whose acceleration voltages ranged from 50 V to 200 V. It is shown that the γ for the as-deposited MgO protective layer is significantly decreased by the influence of holding in air since the hydroxyl OH groups are absorbed onto the MgO surface from the atmospheric air. It is also observed that the secondary electron emission coefficient γ for the vacuum-annealed MgO protective layer is less influenced by holding in air than that for the as-deposited MgO protective layer. Based on these findings, it is concluded that the vacuum-annealed MgO protective layer plays an important role in lowering the firing voltage in alternating current-plasma display panel (AC-PDP) compared with the as-deposited MgO protective layer or the as-deposited MgO protective layer held in air.