Low Pressure Sodium Lamps Research Articles

High Efficacy Low Wattage HPS Lamp for Street Lighting and other Applications

In densely populated residential districts, the illumination level has been continuously increased for crime prevention. Because of the energy crisis, many power companies would like to replace high wattage incandescent, mercury or sodium vapor lamps with a lower wattage light source. However, they would still like to maintain the same illumination level. Here, the results of performance studies, reliability, and the design parameters of low wattage high pressure sodium lamps are presented.

Discharge lamps: some aspects of research and development

A review of discharge lamp developments over recent years shows that a reiterative process takes place between advances in fundamental understanding of discharge phenomena and problems revealed as new lamps find practical application. These two aspects of discharge lamp development govern the evolution of new types of lamps and are considered for low pressure sodium lamps, high pressure sodium lamps, fluorescent lamps, high pressure mercury lamps and metal halide lamps. It is apparent that research is as active on well-established types of discharge lamps as on the newer types.

Oscillations at the Anode of Low Pressure Sodium Lamps

Aanalysis of the anode voltage pulsations for low pressure sodium lamps containing starting rare gases is made with regard to the electron temperature of positive column plasmas. The electron temperature and the anode voltage pulsations of sodium lamps at the wall tempernture 0 to 150°C are related to ionization of rare gases alone, on the contrary the electron temperature at the wall temperature of more than about 150°C is inversely proportional to the vapor pressure of sodium while the anode voltage pulsations are still caused by ionization of rare gas alone from transport phenomena of sodium ions and no pulsations over 250°C. The electron currents in the anode sheaths converge to the hot spots on barium oxide compound layers of double coiled anodes, and consequently cause abrupt ionization around the hot spots of anodes, followed stoppage of the ionization immediatly by quenching of anode sheaths partially with high density charges generated locally. That is followed to recover for the anode drop voltage by ambipolar diffusion of high density local charges and reconbination of them at the walls of tubes. It is shown that the periods (T) of anode voltage pulsations are related to the mean decay time constant (τ) of ambipolar diffusion, T∝τ=γa2/π2Da where γa is radius of anode bulb-wall and Da is ambipolar diffusion constant; and that the electrode life and D lines may be shortened more by anode voltage pulsation of rare gas than by sodium vapor.

A Viewpoint on Lamp Development

Recent progress in electric lamp development has been accelerated by the introduction of new materials and techniques which have brought major improvements in performance. The impact of halogen technology on incandescent lamps continues to broaden as a result of increasing knowledge of design and processing requirements, whilst the introduction of mixed metal iodides, fused alumina envelopes and more sophisticated designs of low-pressure sodium lamps have added to the complexity of discharge lamps. Against this background some problems of design evaluation and application assessment and the conflict between innovation and standardisation are discussed. The viewpoint is expressed that lamp development could benefit at an early stage from a fuller appreciation of the requirements of users, particularly where the direction of a development may be influenced toward specific applications.