High-intensity Discharge Light Sources Research Articles

Transition Probabilities and Oscillator Strengths for E1 Transitions of Ce III

The lanthanide elements (Z = 57−71) are important in astrophysics in relation to nucleosynthesis and star formation considerations. Spectroscopic investigations of the doubly ionized elements of this group are motivated by astrophysical interest because, in the hot chemically peculiar (CP) stars, there is an overwhelming presence of lines belonging to the third spectrum which corresponds to the dominant ionization stage [1]. The rare-earth element cerium has a particularly rich, even by rare-earth standards, optical emission spectrum from both its neutral and singly ionized stages. This characteristic has made cerium attractive for use in highintensity discharge light sources where it improves both luminous e cacy and colour rendering [2]. The works for energy levels and lifetimes of doubly ionized cerium (Ce III) can be found in, for example, [3 7]. Many strong lines of cerium in the ultraviolet evidently arise from doubly ionized atoms. King and King published a list of these [8]. Triplet and singlet terms of Ce III were reported by Russell et al. [9]. Observations of the third spectrum of cerium from 757 to 11091 A were given by Sugar [10]. The 4f 4f5d lines of Ce III were measured by Johansson and Litzen [11]. Bord and co-workers calculated oscillator strengths for some Ce III lines [12]. Later, the spectroscopic analysis of Ce III was extended. Wyart and Palmeri gave a list of computed oscillator strengths for some selected transitions [6]. Transition probabilities for Ce III were obtained from branching fractions calculated by Cowan code and experimental lifetimes by Li and co-workers [7]. Biemont et al. emphasized the importance of corepolarization e ects on oscillator strength determination in Ce III [1]. The multicon guration Dirac Fock calculation of the transition energies and oscillator strengths for the 6s S0 6s6p P1, P1 transitions in rare earth

LED Lighting for Oil and Gas Facilities

Industrial petrochemical facilities have predominantly used high-intensity discharge light sources and installation practices unchanged for several decades. Today, new light-emitting diode (LED)-based products are being developed, and there appear to be many advantages to this technology; however, caution is advised in its application. This paper examines LED lighting technology, standards, and available products along with design and application considerations. Moreover, presented are case studies of LED luminaire retrofits in existing facilities. This paper discusses the results of the studies as they relate to safety, environment impacts, capital and operating costs, design implications, and installation improvements.

Temperature DIP at the beginning of the photoperiod reduces plant height but not seed yield of maize grown in controlled environments

A semi-dwarf breeding line of maize (Zea mays L., PI 587154) was grown from seed to seed in a growth chamber either at 26.7°C days/18.3°C nights (control treatment) or at 15.6°C for the first 2h of each photoperiod before being returned to standard control temperature for the rest of the photoperiod (DIP treatment). Half of the plants in each 120-day production experiment were grown in 3-L containers and half in 9-L containers, both groupings at equivalent plant-to-plant spacing. Stalks of DIP-treated plants elongated 9–10% less than controls during seed-production cycles in both pot sizes. DIP reduced vegetative dry biomass of stalks 29% relative to controls when using small pots, and 19% for plants grown in medium pots. Root dry weight was reduced 22–25% by DIP in the two container sizes, but stalk/root ratios were not altered significantly by DIP treatment or pot size. Stalk diameter also was reduced 8–9% by DIP for both pot sizes. Neither seed number nor seed weight were affected significantly by temperature treatment or pot size. DIP slowed and prolonged stalk elongation but not differentiation of nodes for both pot sizes. Timing of tassel development and pollen shed were unaffected by temperature or pot size, but timing of silk development was delayed by DIP, slightly more for plants growing in small than in medium pots. Nevertheless, primary ears developed to complete seed fill, suggesting adequate time-window overlap between pollen shed and silk receptivity for effective pollination and fertilization to occur. Controlled-environment production of maize in restricted-height growth facilities or where adequate separation distance is required between the tops of crop stands and overhead high-intensity discharge light sources may be accommodated economically by use of DIP temperature treatments without compromising grain yield. Use of medium-volume containers stabilizes the mature maize stalks bearing grain-filled ears.

LED Streetlight Application Assessment Project

Recent studies have found that LED technology is becoming competitive for streetlight applications compared with commonly employed high-intensity discharge light sources, such as high-pressure sodium (HPS) and metal halide. The expectation is that LED street lighting technology will not only provide more efficient light distribution and increased uniformity but will also save energy and reduce maintenance costs. Seattle City Light (SCL), Washington, has a street lighting system of nearly 84,000 street and area lights that predominantly use HPS light sources. Because of the potential benefits of installing LED luminaires as replacements for these lights, SCL launched the LED Streetlight Application Assessment Project pilot study to evaluate LED luminaires for photometric performance, energy efficiency, economic performance, and other impacts on the SCL streetlight system. The project findings will be used by SCL to create a strategy for the installation of LED streetlights to develop an energy-efficient lighting system. The major elements of this project included LED luminaire selection, simulated photometric performance evaluation of selected LED products, field photometric performance evaluation at selected test sites, and economic performance evaluation in comparison with HPS luminaires. In addition, because combining LED roadway luminaires with new light control systems provides many new options to enhance overall light control, facilitate maintenance, increase luminaire life, and reduce operating costs, a preliminary review of current cutting-edge lighting control systems was conducted.

Chemistry of materials science phenomena in high-intensity discharge light sources

Abstract Continuous development of light sources is required from energy-saving considerations (enhancing luminous efficacy) and an environmental protection point of view (lamps that are easy to recycle or made of environmentally friendly materials). This paper summarizes some of the recent results of materials science research with special attention to chemical aspects. The results will be cited from the field of discharge chemistry, electrodes, ceramics, and other materials.

Mercury-free HID headlamps: glare and colour rendering

This study examined the potential effects of the spectral power distributions of mercury-free high-intensity discharge (HID) headlamps on discomfort glare for oncoming drivers and on colour rendering of retroreflective traffic materials. In both cases, the effects of mercury-free HID light sources were compared to the changes in these properties that occurred when the tungsten-halogen light sources were replaced with traditional (mercury containing) HID light sources. Specifically, the effect on discomfort glare was estimated by comparing the chromaticities of nine mercury-free light sources with the chromaticities of 17 traditional HID light sources. Similarly, the effects on colour rendering were estimated by comparing the chromaticities of seven red retroreflective materials (red being the most important messenger of meaning in traffic control) when illuminated by the mercury-free light sources with the chromaticities of the same materials when illuminated by the traditional HID light sources. The main findings are: (1) The discomfort glare from the mercury-free HIDs is predicted to be comparable to that from the ‘bluest’ of the traditional HIDs. (2) Colour rendering with headlamps using the mercury-free HIDs is likely to be acceptable. (3) The use of mercury-free HIDs is unlikely to have appreciable effects on the relative brightness of coloured retroreflective materials.

LED headlamps: glare and colour rendering

Because of rapid improvements in the light output of light-emitting diodes (LEDs), serious consideration is being given to using LEDs as light sources for headlamps. This analytical study examined the potential effects of LEDs on discomfort glare for oncoming drivers and on colour rendering of retroreflective traffic materials. In both cases, the effects of LED light sources were compared to the changes in these properties that occurred when the traditional tungsten halogen light sources were replaced with high-intensity discharge (HID) light sources. Specifically, the effect on discomfort glare was estimated by comparing the chromaticities of seven LED light sources (considered for use in headlamps) with the chromaticities of the light sources from 17 actual HID headlamps. Analogously, the effects on colour rendering were estimated by comparing the chromaticities of seven red retroreflective materials (red being the most important messenger of meaning in traffic control) when illuminated by the LED light sources with the chromaticities of the same materials when illuminated by the HID light sources. Based on our analyses, headlamps using the currently considered range of LEDs are predicted to result in: 1) more discomfort glare than the current HID headlamps, and substantially more discomfort than tungsten halogen headlamps; 2) acceptable colour rendering; and 3) no appreciable effects on the relative brightness of red retroreflective materials.

A New High-Intensity Discharge Light Source with a High Color Rendition

A New High-Intensity Discharge Light Source with a High Color Rendition

Metal halide lamps

In the last half of the 1960s, new high-intensity discharge light sources based on a halogen cycle have made considerable impact on the lighting market. Such light sources depend on the volatilization of halide compounds to introduce a variety of otherwise nonvolatile metals into a high-pressure arc in a fused silica tube. The excitation of these metal atoms in the arc then produces the characteristic spectrum of the metal; the incorporation of several different metals permits the generation of a number of wavelengths of light, i.e., substantially white light. These lamps combine the high output in a compact size of mercury lamps (to which they are similar in appearance) with the high efficiency and color qualities of cool white fluorescent lamps. Efficiencies as high as 100 Im/W are available in 1000-W lamps. Metal halide lamps are available from a number of manufacturers in this country and abroad and are finding wide application in industrial and commercial lighting, as well as in outdoor lighting installations where color quality is important.