Masaharu Aono

Fundamental Research on Mercuryless Fluorescent Lamps II – External Electrode Operation with Pulsed Dielectric Barrier Discharge –

The characteristics of electrodeless xenon discharge fluorescent lamps using dielectric barrier discharge are described in this paper. All lamps were operated with pulsed discharge. The luminance of phosphor increases as the pressure of xenon increases. As the pressure of xenon increases, the second peak of phosphor emission increases. These increases seem to be caused by the VUV light of xenon excimers. Therefore, in order to obtain high luminance, xenon should be filled at high pressure. In the case of the lamp operated by inner electrodes, if only xenon is contained in the lamp, the cathode is bombarded and is damaged by the large mass of a xenon ion. On the other hand, the external electrode type is never damaged by the ions or electrons. Moreover, the efficacy of the external electrode type is as great as the inner electrode type, and it can be improved by increasing the distance between electrodes.

Fundamental Research on Mercuryless Fluorescent Lamps I – Inner Electrode Operation with Pulsed Discharge –

The characteristics of xenon-neon discharge fluorescent lamps with inner electrodes are described in this paper. All lamps were operated by pulsed discharge. When the partial pressure of neon is high, the ignition voltage and operation voltage are low because of the Penning effect. Thus, a higher mixing ratio of neon is desirable for lower ignition and operation voltages. However, the luminance of phosphor increases as the mixing ratio of xenon increases. As the pressure of xenon increases, the second peak of phosphor emission in afterglow increases. These increases seem to be caused by the VUV light of xenon excimers. Therefore, though there is the problem of ion bombardment of the cathode under a high operation voltage, the pulsed discharge of the xenon-neon mixture at a high xenon mixing ratio is desirable in mercuryless fluorescent lamps because a strong radiation of xenon excimer is obtained.

The study of electronic ballast for fluorescent lamp with an electronic device given two functions

The typical electronic ballast for the fluorescent lamp uses a half-bridge inverter and a boost DC-DC converter. The latter on the input side of the former also works as a power factor correction (PFC) circuit. Since a half-bridge inverter and a boost converter work independently in this ballast, each circuit needs a switching element and a control unit respectively. The electronic ballast proposed in this paper consists of an electronic circuit with two functions. That is, a switching element in the buck-boost converter works as a switching device in the half-bridge inverter too. Then, this combined circuit can be used effectively as the electronic high-frequency ballast for fluorescent lamps.

The afterglow characteristics of xenon pulsed plasma for mercury-free fluorescent lamps

In this study, the spectroscopic characteristics of radiations from xenon pulsed plasma are measured experimentally as a study on a mercury-free fluorescent lamp. Each radiation waveform has two peaks and they vary according to the inner diameter of lamp and the pressure of xenon as follows: (a) As the inner diameter of lamps increases, the afterglow radiation, that is the second peak, decays faster. (b) As the xenon pressure increases the first peak of radiation just after the start of discharge decreases and the afterglow increases. The characteristics of afterglow are explained by the rate equation of metastable xenon atoms Xem, and its coefficients are determined through the experimental results. This equation shows that in order to obtain intense phosphor afterglow, i.e. strong radiation of xenon excimer, high pressure of xenon and large lamp diameter are desirable. Moreover, high pressure of xenon brings fast decay of afterglow. Then the afterglow radiation has no overlap on the first peak of next discharge at a high frequency. Consequently, higher pressure of xenon and large lamp diameter are desirable for high intensity and high efficacy for xenon fluorescent lamps.

ACCELERATION OF RE-IGNITION OF HIGH PRESSURE MERCURY DISCHARGE LAMPS USING PHOTO-PRE-IONIZATION

High Intensity Discharge (HID) lamps are difficult to re-ignite rapidly because of the high pressure of metal vapor at high temperatures. We have succeeded in reducing the re-ignition time of high-pressure mercury lamps by using a pre-ionization step where an excess of electrons are generated by UV laser irradiation into the lamp. The effect of changing the laser focal point of the UV laser in the lamp and the position of an auxiliary electrode were also investigated. The time interval for re-ignition was reduced from 230s to 100s by laser irradiation near to the cathode. The results clearly showed that the effect of accelerating the re-ignition time by the pre-ionization step was determined by the behavior of excess electrons generated during the UV laser irradiation.

Characteristics of positive column contraction of xenon fluorescent lamps with two-pairs of electrodes in pulsed discharge

Summary form only given, as follows. Xenon emits strong radiation in the ultra-violet (UV) region and hence is one of the most promising candidates as an alternative to mercury. Nevertheless, the efficiency with which UV radiation is emitted from a xenon discharge is in general lower than that of mercury. Besides, the positive column of a xenon discharge tends to contract at high current density and the intensity of the phosphor-converted emissions from a contracted discharge is very low. In this study, the relations between the contraction process and the pulse width used in the pulsed discharge are discussed. Moreover, two pairs of electrodes are placed in a xenon fluorescent lamp so that the positive column in a diffused state occupies a larger volume for improving the luminance and the efficiency. The lamps were sustained by pulsed discharge. In the diffused state, as the current was gradually increased, the contraction of the positive column occurred at a specific value. Under all conditions, the luminous intensity of the phosphor-converted emissions reached a maximum prior to the transition of the state of the discharge from diffuse to contraction. When the pulse width was decreased, the luminance and efficiency of the lamps of any electrode type was increased.

Fundamental research on mercuryless rare gas fluorescent lamps at pulsed discharge

The characteristics of xenon-neon discharge fluorescent lamps with inner electrodes, and xenon discharge lamps with external electrodes are described in this paper. All these lamps were operated at pulsed discharge. In the case of inner electrode type, when the partial pressure of neon is high, the ignition voltage is low because of the Penning effect. Then, the high mixing ratio of neon is desirable for the lower ignition voltage. However, the luminance of phosphor increases as the mixing ratio of xenon increases. Therefore, in order to obtain high luminance, xenon should be filled at high mixing ratio. If only xenon is filled in the lamp of inner electrode type, the cathode is bombed and damaged by the large mass xenon ions. Consequently, the most suitable mixing ratio of xenon and neon or some buffer gas should be found experimentally for inner electrode type. On the other hand, when the lamp filled only with xenon is operated by external electrodes, as the pressure of xenon increases, the afterglow peak of phosphor emission increases. These increases seem to be caused by the UV light of xenon excimers. However, the starting voltage becomes high at high xenon pressure. So, the optimization of some conditions such as electrodes, pulse frequency, etc. is required for external electrode type.

A study on color control in gas discharge tube

The electron operation in the gas discharge tube is controlled by the electrical energy as a sinusoidal waveform, a square wave, or a sequence of periodic pulses at a wide range of duty cycle in arbitrary frequency range. The response of the tube depends on the gas composition and on the vessel geometry of the gas discharge tube. In this paper, the color changeable gas discharge tube using pulsed mode is proposed. The operated gas discharge tube of 15.0 mm diameter is filled with mixed gas of Hg-Ar-Ne (1: 9, 60 Torr), by pulsed mode and has variable color from red to blue by modifying frequency and pulse width of the biased signal. As decreasing pulse width and frequency, in the gas discharge tube, the phenomena that the electron temperature in the positive column increases, in turns and the radiation from atoms with higher state energy levels increases.