Cold-cathode Lamps Research Articles

An efficient photo reactor design and its application in photo-oxidation of acetone

The rate of CO2 production obtained from the photodecomposition of acetone with different loadings of TiO2 as a photocatalyst is remarkable. This study aims to develop a flow-type photo reactor with excellent contact between all the reacting species. To achieve total mineralization with minimal waste, the flow rate of gases was controlled. During this investigation, the acetone was fed at the rate of 2.8 mmol h-1 and the air flow rate was maintained at 4.3 Lh-1. The reaction was carried out at near room temperature as the cold cathode lamps increased temperature very slowly to 63 ᵒC. No CO2 was produced either without light or catalyst indicating a photocatalytic reaction. There was a proportional increase in the production of CO2 with an increase in TiO2 loading. A maximum rate of 5.75 ± 0.07 mMh-1 for CO2 production was achieved with a catalyst loading of 5 mg/gbeads. Increasing the catalyst loading above 5 mg/g showed a decrease in CO2 production rate which can be attributed to reduced contact between light and catalyst. This technique used here can be adopted for the decomposition of various Volatile Organic Compounds (VOCs).

RECYCLING OF LIQUID CRYSTALS FROM E-WASTE

For several decades, Liquid Crystal Displays (LCDs) have been widely used in televisions, laptops, mobile phones, and other devices. Nowadays, liquid crystals (LCs) represent an important economic value of the recycling system of LCDs. The reuse of these organic molecules could become a profitable basis since it permits to preserve the value of these materials. In this context, the general objective of this work focuses on the recovery of LCs as well as on other valuable materials present in end-of-life LCDs. An orderly, manual LCD dismantling line is put into operation for differentiated recycling of electronic boards, cold cathode lamps that may contain mercury, polymers, metals, and other valuable materials. There is also an extraction line where LCD panels are opened and exposed to an ultrasonically activated organic solvent bath to recover LCs. The resulting solution contains LCs, solvent, organic and inorganic impurities. The LCs mixtures were purified and then characterized mainly by spectroscopic, chromatographic, and thermal techniques. A study of the influence of adding diamond nanoparticles at 0.05, 0.1 and 0.2 wt% to recycled LCs was also performed using dielectric spectroscopy. Dielectric properties of LCs were measured at room temperature, using an impedance analyzer in the frequency range from 0.1 to 106 Hz.

Efficacy of 265-nm ultraviolet light in inactivating infectious SARS-CoV-2

Although, Low-pressure (LP) mercury lamps that emit wavelengths of around 254 nm have been widely applied as ultraviolet (UV) light devices for decontamination of microorganisms, they have raised environmental concerns due to their mercury content. Therefore, UV-LED lamps have high potential for practical use as a replacement for LP mercury lamps. In this study, we evaluated the efficacy of 265-nm UV irradiation in comparison to 254-nm and 280-nm UV irradiation for inactivating infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Irradiation from a 265-nm deep UV light-emitting diode (DUV-LED) lamp efficiently inactivated SARS-CoV-2 at a similar level as a 254-nm UV cold cathode lamp, and at a higher level than a 280-nm DUV-LED lamp.

Experimental validation of plasma tomography algorithms at ISTTOK

Plasma tomography is an ill-conditioned inversion problem. Algorithms based on Tikhonov regularization and minimum Fisher information try to overcome this issue by introducing regularization parameters that require empirical tuning. In general, to validate the implementation of these algorithms, either artificial phantoms are used, or one must rely on information provided by other diagnostics. In this work, an experimental setup was developed that allows the use of physical phantoms to tune and validate the reconstruction algorithms. The setup was assembled in a replica of the ISTTOK tokamak with a cylindrical cold cathode lamp placed perpendicular to the poloidal plane at multiple radial and angular positions. It is assumed that this physical phantom acts approximately as a point source in the emissivity profile. Knowing these profiles a priori, it is possible to compare them with the reconstructions produced by the algorithms, in order to tune and optimize the reconstruction parameters. After validation with these physical phantoms, several reconstructions were successfully computed for some tokamak discharges.

Effect of Excitation Frequency on Breakdown Voltage in Narrow Cold Cathode Tube under Ne Discharge

We investigated the discharge characteristics in a cold cathode lamp of 4 mm inner diameter used for backlighting liquid crystal displays. The electrode on one side of the lamp was made of nickel, and that on other side was platinum. The Ne gas pressure filling the lamp was 53 hPa. The cathode voltages of a lamp with the electrodes made of different materials were simultaneously measured with a high voltage probe connected to a digital oscilloscope when the lamp was operated by a sine wave power supply under the same discharge condition. The breakdown and maintained voltages in the case of the nickel electrode were lower than those of the platinum electrode. The measured reignition voltages were almost constant breakdown voltages in the frequency region of 0.1 to 100 Hz. In frequencies above 100 Hz, the reignition voltages decreased sharply, a becoming close to the maintained voltages. The accurate breakdown voltage was estimated to be less than a 100 Hz sine wave.

Growth of the green algae Chlamydomonas reinhardtii under red and blue lasers

Red and blue lasers, holding promise as an electric light source for photosynthetic systems on account of being true monochromatic, high-power, and having high electrical-conversion efficiency, were employed in growing a green alga, Chlamydomonas reinhardtii. The laser treatments tested included: 655-nm Red; 680-nm Red; 655-nm Red+474-nm Blue and 680-nm Red+474-nm Blue. A white cold cathode lamp with spectral output similar to that of white fluorescent lamp served as control. C. reinhardtii successfully grew and divided under the 655 and 680-nm red lasers as well as under the white-light control. Supplementing either red with blue laser, however, resulted in increased algae cell count that significantly exceeded those under both red lasers and the white-light control on average by 241%.

Effect of Filled Gases and Electrode Material on Electrical Characteristics of Cold Cathode Lamps

A low-pressure mercury (Hg) cold cathode lamp (CCL) was filled with neon at a few kilopascals and mercury (Hg). It was important to grasp the difference in electrode characteristics between normal lighting condition (Hg-vapor exists in the CCL) and end-of-life lighting condition (Hg-vapor is used up in the CCL) when we developed the CCL electrode. Then we investigated the variation of the electrode characteristics in some electrode materials with the CCL (Hg plus) filled with Hg and neon (Ne) and the CCL (Hg less) filled with only Ne. It is clear that when the CCL was filled with Hg, the cathode fall voltage (CFV) was higher and the negative glow of the CCL (Hg plus) spread larger (the current density on the electrode was lower). The former result is due to the fact that the value of γ (Hg2+) was lower than that of γ (Ne+), and the later result is due to the fact that the Hg ion's mobility was higher than the Ne ion's one. By observing the CFV waveform, it is clear that the CCL (Hg less) was in abnormal glow discharge, whereas the CCL (Hg plus) was in normal glow discharge. According to these results, the electrode consumption increased rapidly when the Hg was used up in the CCL.

Influence of Mercury on the Characteristics of Hot Cathode Lamps and Cold Cathode Lamps

Discharge lamps that have electrodes are classified into two categories, hot cathode lamps (HCLs) and cold cathode lamps (CCLs). We investigated the relationship between the presence of Hg, the kinds of rare gases present, and the cathode fall voltage (CFV) of both CCLs and HCLs. The results show mainly two points. One is the difference in the CFV characteristics, that is, CCLs’ CFV is positive, while HCLs’ is negative. This is because the emission mechanism of CCLs, due to the gamma effect, differs from that of HCLs due to the Schottky effect. The other main point is the influence of Hg on the CFV. The CFV of CCLs increases when Hg is present because of the difference between γ-coefficients for Ne+ and Hg2+ due to the energy potentials. The CFV of HCL also increases when Hg is present because of the difference between the cathode temperatures in an Ar discharge and an Ar-Hg discharge.

The Study on the Relation between the Cathode Fall Voltage and the Electrode Material of the CCL

To improve the efficiency of the cold cathode lamp (CCL), it is important to select the optimum electrode material to reducing the cathode fall voltage (CFV). Furthermore, it is necessary to understand the relationship between the electrode material and the CFV. Considering the above, we measured the CCL’s CFV with an indirect CFV measurement method using a hot cathode fluorescent lamp. By observing the negative glow of the electrode, we investigated the relationship between the CFV and the negative glow condition. The results showed that there is a relationship between the CCL’s CFV and the γ coefficient of the electrode. Moreover, they make it clear that there is a relation between the CFV and the negative glow condition of each electrode material. We conclude that the CFV measurement method is useful for estimating the performance of a CCL’s electrode.

Glow discharge in the external electrode fluorescent lamp

From the characteristics of current and voltage, the capacitive coupled external electrode fluorescent lamps are found to be similar to cold cathode fluorescent lamps having the ballast capacitors at both ends of the lamps. From the current-voltage characteristic for two types of lamps, the discharge mechanism is similar with respect to discharge process: initially a dark current, Townsend discharge with a firing voltage, followed by a normal glow. The slope and magnitude of the dark current have the same values since the gas species in the lamps are identical. At the Townsend discharge, the lamp current increases abruptly with a firing voltage of about 1 kV. In the normal glow region, the cathode fall voltage is sustained at about 600 V in the cold cathode discharge tube after Townsend breakdown at about 1 kV, while the voltage increases linearly as the current increases without negative resistance in both the external electrode lamp and the cold cathode lamp including the ballast capacitors.

Controlling field-emission patterns of isolated single-walled carbon nanotube rope

We report a method of controlling field-emission patterns from an isolated single-walled carbon nanotube (SWCNT) rope. By positioning two soda-lime glass flakes on both sides of a SWCNT rope, we found an anomalous current jump, enlarging the field emission current above the threshold bias voltage. The electron trajectories were systematically controlled with different configurations of glass flakes. This was explained by the induced charges on the surface of the dielectric that modified the electric field distribution near the cathode and anode, and hence, the electron trajectories and the field emission patterns as well. This opens a possibility of tuning electron beam trajectories in field emission that can be applied to various electron sources such as field emission displays and cold cathode lamps. (c) 2005 American Institute of Physics.

Ar concentration characteristics of electron temperature in narrow cold cathode lamp

Ar concentration characteristics of electron temperature in narrow cold cathode lamp

Development of Yttrium-Dihydride Film for Use in Cold Cathode Lamps

In this paper, we examine the research and discovery of a highly efficient electrode material which we called yttrium-dihydride. This material is effective in a cold cathode lamp which is illuminant. The composition of crystal yttrium-dihydride (YHx) film was compared from the optical reflectivity. A cold cathode lamp with a tube of 63 mm length and an outside diameter of 2.6 mm was fabricated for the experiment, and the glow-discharge voltage was measured to evaluate the performance of the electrode using the YHx film. The lamp current was set at 5 mA for the measurement. The lamp voltage in the nickel electrode for the reference lamp was 220 V. The lamp voltage in the YHx electrode was 169 V. The yttrium-dihydride is revealed to be a more highly emission efficient material. In addition, the lamp voltage remained constant for more than 7,500 h, thus demonstrating that this material is extremely stable.

矩形波点灯における冷陰極放電管の効率改善

矩形波点灯における冷陰極放電管の効率改善

Thyratron control of discharge lamps

The general principles of thyratron control are discussed, the various points of difference between circuits being mentioned, together with some recently introduced improvements.Two valves are connected in reverse parallel, in series with the load. The brightness is controlled by varying the period of conduction of the valves, the ignition angle being varied by grid phase control. Hotcathode lamp filaments must be continuously heated from a separate current supply. Each lamp requires a separate ballast. Cold-cathode lamps require normal leakage-flux transformers only. Reduction of light to 1% or 2% of its maximum value is obtained with simple circuits, but improved stability can be obtained with special ballast arrangements which give a further reduction of light by an approximate factor of 10. Power factor can be corrected on the load side of the dimmer, with improvement in dimmer load rating and increased flexibility of use. Waveforms illustrating proper circuit conditions and various modes of malfunctioning are included.

Comparisons of wave-length standards emitted by mercury-198 lamps

The reproducibility of high-quality wave-length standards emitted from water-cooled mercury-198 discharge lamps of the electrodeless and cold-cathode (Geissler) types has been investigated by means of a Fabry-Perot interferometer. These lamps, now produced commercially in this country, contain a small quantity of the isotope 198 80 Hg with argon, as carrier gas, at a nominal pressure of 3 or 5 mm, in electrodeless and 10 mm. in cold-cathode lamps; electrodeless lamps containing only the isotope and its vapour are also available. Employing for excitation a 100 Mc./sec. oscillator with electrodeless lamps and a transformer delivering 750 V at 25 mA and 50 c./sec. with cold-cathode lamps, the wave-lengths of six 198 80 Hg lines between 4046 and 5791 Å, emitted from a sample of each kind of argon-filled lamp, have been measured in terms of the cadmium red line at retardations of 5 to 25 cm. These measurements, supplemented by intercomparisons of argon-filled and argon-free slectrodeless lamps at a retardation of 20cm., reveal that 198 80 Hg lines are probably subject to an asymmetrical pressure broadening effect, producing a red shift of about 0.0001Å (— 0.0004 cm. -1 ) per mm. of argon. Wave-length reproducibility among different samples of the same kind of lamp with the same filling is of the order of ± 0.000 05 Å, or ± 1 part in 10 8 , for electrodeless lamps and ± 0-0001Å for cold-cathode lamps.