High-pressure Discharge Lamps Research Articles

Dynamic weight detector for milligram particles

Starting with a piezoelectric pick-up element for record playing a weight detector was constructed for particles with weights in the 0.1-20 mg range. The detector has a linear response, a sensitivity of at least 10 mu g and can weigh particles at a rate of at least 10 s-1. The detector can be used for weighing and selecting, for instance, metal halide spherules for the fabrication of high-pressure discharge lamps.

Analysis of cathode-spot behavior in high-pressure discharge lamps.

The operation of hot cathodes in high pressure discharge lamps has been investigated in a manner similar to that described by Ecker5). The formalism of Dyke and Dolan8) has been used to calculated emission of electrons from the cathode as a function of temperature and electric field. The electric field at the cathode surface is calculated from ion current and cathode fall, the largest contribution to that field being developed in the free-fall sheath less than one mean free path in thickness at the cathode surface. Two solutions to the coupled system of equations are found: a low-field, diffuse-mode solution in which electron emission is by the Shottky-amplified thermionic process, cathode fall increases with increasing current density, and the cathode spot tends to expand to fill the entire extent of the cathode tip; and a high field, hot-spot mode in which electrons are emitted as a result of the temperature-field mechanism. The lowest cathode fall in the latter mode occurs when the potential drop across the free fall sheath equals the cathode fall required by the cathode energy balance. The operating mode of the discharge in a given lamp depends on which of the two modes has the lowest cathode fall. Examples of each occur in various lamps and can be accounted for with reasonable values of material constants. It is shown that the hot-spot mode is favored over the diffuse mode by high pressures and low cathode work function. The latter surprising result is accounted for by the fact that field emission, varying as exp (-φ3/2), is even more favored by low work function than thermionic emission.

5043. A semi-empirical formula to describe the net emission coefficient of self-absorbed spectral lines for use in modelling high-pressure discharge lamps: B F Jones and D A J Mottram,J Phys D: Appl Phys,14 (7), 1981, 1183–1194

5043. A semi-empirical formula to describe the net emission coefficient of self-absorbed spectral lines for use in modelling high-pressure discharge lamps: B F Jones and D A J Mottram,J Phys D: Appl Phys,14 (7), 1981, 1183–1194

A semi-empirical formula to describe the net emission coefficient of self-absorbed spectral lines for use in modelling high-pressure discharge lamps

The net emission coefficient of a self-absorbed spectral line can be described by a semi-empirical formula which contains terms representing the generation and absorption of radiation. Four empirical constants are determined by applying least-squares fitting to the results of an exact radiation flux density calculation in a cylindrical arc tube. Calculations on the D-lines under conditions which are typical of high-pressure sodium lamps are described. In this case, the empirical formula predicts radiation flux densities which agree to better than 10% with the exact calculation even when the arc tube bore and arc temperature are changed by 15% from their original values. This method allows economical and accurate calculation of energy balances in arcs containing several self-absorbed spectral lines.

Spectroradiometry in research and development on lamps

The importance of spectroradiometry in the research and development on discharge lamps is outlined. The developments in highpressure discharge lamps have stimulated improvements in spectroradiometry, particularly in the area of data-logging where methods applicable to any type of spectrum have been developed. Methods of testing precision are discussed, but assessing accuracy still requires well organised intercomparison experiments.

Mathematical Models for High-Intensity Discharge Lamps

Mathematical models have been determined for mercury and high-pressure sodium electric discharge lamps. The models consist of a set of nonlinear differential equations. They reproduce the electrical characteristics of the lamps from dc to the high audio frequencies with good accuracy. They permit computer simulation of electronic or reactive ballasting circuits. Also, they yield a better qualitative understanding of the properties of a discharge lamp as an electric circuit element. The methods by which these models were determined are described, and the pertinent lamp properties are measured.

Characterization of and constricted high pressure arcs by magnetic balancing

A simple method is proposed to characterize the shape of the temperature profile of the arc in high-pressure discharge lamps. The method is based on the balancing of natural convection by external magnetic forces in the horizontal burning position. Experimental results are given for some well-known lamp systems including the mercury arc, the tin halide arc and the sodium-thallium-indium iodide arc, under various conditions. The results are in accordance with the trends observed in practice. Results are also given for rare-earth iodide arcs. In these systems arc motions occur under certain conditions. The nature of these phenomena is discussed.

Gas evolution and gettering in high pressure discharge lamps

Gas evolution and gettering in high pressure discharge lamps

演色性を改善した高圧ナトリウムランプ

High Pressure Sodium Lamps have the highest efficacy of all high pressure discharge lamps and have been commercially available. However, for their poor color rendition, their uses have been restricted to the places where higher color rendition is not required.This paper describes the new high pressure sodium lamp with high luminous efficacy (120 lm/W, at 360 W) and superior color rendering properties (Ra 60) and moreover, being able to be operated on the conventional ballast for the high pressure mercury lamp.For the development of the new lamp, the effect of Xenon was quite important, that is, Ra value increased with Xenon pressure, the same as luminous efficacy.In addition to it, new sealing glass composition and newly designed electrode had been investigated for th e lamp.The former had superior property that high temperature sodium diffusion layer was estimated to be less than 1. 7 mm thickness at 900°C after 10, 000 hours treatment and the latter had good stability of the arc spot at the lamp starting.

A metal halide high pressure discharge lamp with warm white colour and high efficacy

A Na, Tl, In, Sn high pressure discharge lamp of warm white colour was developed for an efficient energy utilization in indoor illumination. The lamp is characterised by: (1) low colour temperature (CCT = 3300 K) with good colour rendering (Ra = 85). (2) high luminous efficacy of approx. 90 lm/W, corresponding to the 5- to 6-fold of an incandescent lamp, (3) high life time of approx. 4000 h, corresponding to the 4-fold of an incandescent lamp, (4) arbitrary burning position as with an incandescent lamp. These data were achieved through utilization of strongly pressure broadened line radiation (Na, Tl, In) combined with molecular radiation (SnI, SnBr, HgI, HgBr). The main features of the lamp are discussed, in particular a deviation from local thermal equilibrium in the mantle of the discharge.

Gas evolution and gettering in high pressure discharge lamps

The use of getters within the jacket of metal halide lamps is necessary to prevent the deleterious influence of gaseous impurities on their performance. A number of experimental metal halide lamps (400 W) were produced using the St 101 getter alloy (84% Zr-16% Al). Analysis of the jacket atmosphere and the getter gives information about the impurity load and the gas release dynamics. About 35 Pa I of hydrogen and 7 Pa I of CO and lower quantities of CO 2 and CH 4 are evolved. The release seems to be complete within about 1000 h of operation. Practical results confirm that the St 101 alloy, because of its gettering properties and its ability to withstand the contaminating ambient during lamp production, is particularly suited for use in the outer jacket of discharge lamps.

Lighting systems in major New Zealand controlled environment facilities

The lighting systems used in New Zealand in the Department of Scientific and Industrial Research (DSIR) Climate Laboratory controlled environment rooms, the Forest Research Institute (FRI) tree growth rooms, and the DSIR-designed reach-in controlled environment chambers are described. All lighting systems are based on high-pressure discharge lamps which can be used with varying amounts of incandescent light supplementation. The main lighting type used in the Climate Laboratory controlled environment rooms is the high-pressure metal halide lamp, that in the FRI rooms the high-pressure mercury-vapour fluorescent lamp with internal reflector, and that in the reach-in chambers a high-pressure mercury halide lamp. Details of lighting rig design, of irradiance levels obtainable, vertical and horizontal light distribution patterns and spectral quality are presented for each system. The photosynthetic irradiance levels available at 2–3 m below the lighting systems in all of these controlled environment systems are high (180–200 W m −2 PAR). In the Climate Laboratory and FRI growth rooms peak sunlight values of approximately 400 W m −2 PAR (approximately 10,000 ft.c.) have been achieved. A discussion of the performance of these systems is also presented.

A constant DC mercury lamp supply for 125 W lamps

A circuit is described which provides a simple power supply for ionising and running 125 W high-pressure mercury-argon arc discharge lamps (e.g. type MBL/U) on stabilised direct current. An improvement of 10-20 dB, at 300 mu m, in the total noise of an infrared interferometer is reported, relative to AC operation. The reasons for the improvement are examined.

Simulation of the dynamic behaviour of high pressure discharge lamps

A new differential equation representing the time dependence of high-pressure arc conductance for any given lamp parameter is derived. This is useful in order to predict ac characteristics for various operating conditions. A comparison of measured dynamic data of a high-pressure mercury lamp with computations confirms the fair agreement between theory and experiment.

The Development and Application of Metal Halide Lamps for Color Filming and Television

The development of high-pressure discharge lamps over the years has been aimed at improving color rendering, efficiency and life. The compact-source iodide (CSI) lamp was initially developed in 400-W and 1,000-W ratings for projector applications, but it was the new demands of outside broadcast color television in 1969 that led to the introduction of this lamp housed in a PAR-64 sealed-beam globe for floodlighting sports stadia from high corner towers. Sports areas with sidelighting were not so well suited to the use of the symmetrical beam CSI floodlights, so another metal halide lamp was introduced — this one with an unjacketed linear arc tube — in 750-W and 1,600-W ratings. For filming, the 1-kW lamp performs exceptionally well as a fill-in source with daylight. At 90 lm/W, it is five to six times more efficient than tungsten-halogen lamps used with blue filters to correct the daylight; four lamps are approximately equivalent to a 225-A brute arc. Control gear is being made simpler and more versatile, and the problem of “beat,” which is already controllable in filming situations, is expected to be overcome completely with techniques now being developed.

Zirconium-Aluminium Alloy as a Getter for High Intensity Discharge Lamps

Gaseous impurities within lamp envelopes strongly influence their life and performance. High pressure discharge lamps are particularly sensitive to impurities, especially hydrogen which permeates into the burner increasing the striking voltage. A Zr-Al alloy (16% by weight Al) is presented as the most suitable getter for hydrogen, and other noxious gases, in both evacuated and gas filled envelopes. Its behaviour in the simulated operation conditions of various lamp types is described. Sorption performance of the Zr-Al getter when activated or not activated, as a function of operating temperature and other parameters is illustrated.

24] Nanosecond fluorescence spectroscopy of macromolecules

This chapter presents details for constructing a nanosecond fluorimeter, as well as details for analyzing nanosecond fluorescence data. Some aspects of the theory and application of nanosecond fluorometry to the study of the structure and dynamics of macromolecules are also discussed. Advances in the generation and detection of nanosecond light pulses have now made it possible to measure directly the time dependence of fluorescence intensity following excitation by a short pulse of light. The greater wealth of information contained in these time measurements has greatly increased the precision and range of fluorescence techniques. Two types of lamps are presently used in nanosecond fluorescence spectroscopy. One is a high-pressure discharge lamp operated in a self-relaxation circuit. The other is a low- pressure lamp operated with a fast thyratron. The two types of lamps are usually referred to as “free-running” and “gated lamps,” respectively.

Comparison of natural and artificial sources of light

The area of crop plants required to sustain a man in an artificial extra-terrestrial environment is probably about 10 m 2 . If the site is on the Moon, the natural light will alternate with periods of darkness, but will be brighter than any practicable arrangement of artificial lights. The latter can, however, be run continuously. To control plant temperature, an artificial cooling system will be required with either kind of illumination. The energy to be dissipated will be about 700 W m -2 with natural light, or three times this amount with artificial light (high pressure discharge lamps).

Discussion on “New developments in high-pressure discharge lamps”

Discussion on “New developments in high-pressure discharge lamps”

Studies on the Effectiveness of High Pressure Discharge Lamps for Promoting Plant Growth

Studies on the Effectiveness of High Pressure Discharge Lamps for Promoting Plant Growth