Dongjun Jin

An Experiment and Analysis for Standardize Measurement on CCFL

A method of measuring the current and voltage is suggested in the circuit of cold cathode fluorescent lamps (CCFLs) which are driven at a high frequency of and a high voltage of several kV. It is difficult to measure the current and voltage in the lamp circuit, because the impedance of the probe at high voltage side causes the leakage current and the variation of luminance. According to the analysis of equivalence circuit with the probe impedance and leakage current, the proper measuring method is to adjust the input DC voltage and to keep the specific luminance when the probe is installed at a high voltage circuit. The lamp current is detected with a current probe or a high frequency current meter at the ground side and the voltage is measured with a high voltage probe at the high voltage side of lamp. The lamp voltage() is measured between the ballast capacitor and the lamp electrode, and the output voltage() of inverter is measured between inverter output and ballast capacitor. As the phases of lamp voltage() and current () are nearly the same values, the real power of lamp is the product of the lamp voltage() by the lamp current(). The measured value of the phase difference between inverter output voltage() and lamp current() is appreciably deviated from the calculated value at

Longitudinal and transverse discharges with mercury-rare and xenon gases

cos{\theta}

Electron collision ionized plasma waves in the positive column of a fine discharge tube

The properties of longitudinal and transverse discharges are investigated with the use of external electrode tubular lamps, with respect to the characteristics of current and voltage, luminance and spectral radiation. With the mercury-rare gases, a high luminance of over 10 000 cd m−2 is readily obtained in the longitudinal discharge with a long positive column where the spectral radiations from Hg are dominant. However, the luminance is extremely low, a few hundred cd m−2, in the transverse discharge with a short gap where all kinds of atom species are ionized and the intensity of the spectral lines from Ne and Ar is rather high. With pure Xe and a mixture of Xe, the transverse discharge is superior to the longitudinal discharge in that the breakdown voltage is low and the luminance for a high pressure above 200 Torr is relatively high.

Plasma diffusion in the atmospheric pressure plasma jets

In fluorescent lamp tubes, a few millimetres in radius, operating at several tens of kilohertz, the initiation of light radiation is characterized by the propagation of an electron plasma wave, accompanied by ionization caused by electron collision. Due to the effects of the ionization collision of electrons on the dispersion behaviour of the plasma waves, the electron plasma waves generated by the pulses of operation voltage, propagate along the positive column plasma without experiencing damping. The propagation velocity of radiated light, which represents the propagation of the electron plasma wave, can be higher than the electron thermal velocity.

Electric field solution of cylindrical hollow cathode

The plasma diffusion has been investigated with respect to the atmospheric-pressure plasma jets (APPJ). The ambi-polar diffusion equation is solved in the radial and axial directions. To explain the plasma diffusion process, the plasma diffusion equation is derived with the charged particle motion and the plasma fluid continuity equation¹. Supposing the initial plasma density n(t=0, r, z), the plasma flux Γ<inf>D</inf>=−D<inf>a</inf>∇n and the diffusion velocity u<inf>D</inf>=−D<inf>a</inf>(∇n)/n are calculated.

P-79: Luminous Mechanism in a Fine Tube of Fluorescent Lamp

Hollow cathode is widely used in a gas discharge experiment because the electrode structure is good at the high current discharge with a high efficiency. However, the analytic solution of electric field has not been reported elsewhere to our knowledge. In this study, Laplace solution of cylindrical hollow electrode is analyzed. The profiles of potential and electric field are represented according to the hole-diameter and the depth of hollow cavity. Using the breakdown criteria, the discharge characteristics are analyzed such as the breakdown voltage, the current, and the main discharge path at the hollow cavity. The structure of hollow cathode can be discussed through this analysis.

P-82: Super-Length External-Electrode Fluorescent Lamps

The origin of optical emission in a fine-tube fluorescent lamp is verified. The diffusion of plasma generated at a high voltage electrode, causes a radiation before Townsend discharge. At the normal glow, the propagation of electron plasma wave causes the light emission.

Plasma description with optical signal propagation along the fine tube of positive column discharge

The lamp length 0.6∼2.0 m of external electrode fluorescent lamps for the backlight of LCD-TVs has been investigated with respect to the lamp property, such as the current and voltage, the luminance and efficiency, and the luminance uniformity along the tube.

P‐116: Minimum Mercury Quantity Required in the Discharge Plasma of CCFLs and EEFLs

When the optical signals are observed along the fine tubes of cold cathode and external electrode fluorescent lamps for the light sources of LCD-TVs, the light signal is measured and found to be propagated from the high voltage to the ground sided. The phenomenon of the light propagation has been explained with the electron drift along the tube in Cho et al. (2007). In Cho et al. (2008), this has been analyzed as the propagation of electron plasma wave along the tube. In both cases, the plasma parameters of electron temperature and density have been verified as kTe~1 eV and ne~1017 m-3. However, they leave room for doubt. In the analysis of electron drift, the electron drift velocity has been measured as ~105 m/s which is unreasonably higher than the conventional glow discharge plasma of ~104 m/s. In the electron plasma wave propagation, it has still some doubt that the propagation distance along the positive column plasma can be as far as ~10 centimeter or ~1 meter since the electron plasma wave damping coefficient is too high for the electron wave to propagate such a long distance. Further more, it might be impossible that the electron energy can be transferred to the positive column plasma through the propagation of electron plasma wave. In this study the effects of plasma diffusion as well as the influence of electron plasma propagation on the optical signal propagation are investigated. However, the analysis of optical observation results provides the verification of plasma generation mechanism as well as the plasma properties in a positive column of a fine tube fluorescent lamp.

Mercury Quantity in a Fluorescent Lamp for a Backlight of LCD-TVs

Using the ionization rates of each atom species in a mixture gas of Ne(95%) + Ar(5%) + Hg(∼mg), the minimum quantity of mercury in the glow plasma discharge of CCFLs and EEFLs for a large area LCD backlight, is calculated to be 0.05 ∼ 0.36 mg without considering the mercury consumption.