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Sodium Vapor Lamps: A Comprehensive Overview

Low-pressure Sodium Lamps

Low-pressure sodium lamps (LPS lamps) are designed with a cylindrical or U-shaped glass tube that operates at low pressures, typically below 1 Pa. These lamps emit orange light primarily at 589 nm, known as the D-line of sodium atoms. The light emitted is monochromatic with narrow spectral lines. LPS lamps require a small amount of starter gas, such as neon or argon, to initiate the electric discharge. They are energy-efficient, have a long lifespan exceeding 10,000 hours, and are commonly used for street lighting due to their distinctive orange glow.

High-pressure Sodium Lamps

High-pressure sodium vapor lamps (HPS lamps) operate at higher pressures, ranging from 10 kPa to 100 kPa. These lamps contain mercury and produce a broad spectrum of light, including red, orange, yellow, green, blue, and violet emissions. The arc tube in HPS lamps is typically made of alumina ceramics to withstand high temperatures and chemical reactivity. While HPS lamps offer high luminous efficacy, around 150 lm/W, they have a poor color rendering index compared to other light sources. Xenon is commonly used as the starter gas in HPS lamps, and they can have lifetimes exceeding 20,000 hours.

Advantages and Disadvantages

Sodium vapor lamps, both low-pressure and high-pressure variants, offer energy efficiency, long lifespans, and high luminous efficacy. They are suitable for applications where color rendering is not critical, such as street lighting. However, high-pressure sodium lamps contain mercury, which poses environmental challenges and health risks. As a result, there is a shift towards alternative lighting solutions, such as metal halide lamps, which offer better color rendering and are mercury-free.

In conclusion, sodium vapor lamps have been widely used for outdoor lighting due to their efficiency and longevity. However, advancements in lighting technology are driving the adoption of alternative solutions with improved color rendering and environmental sustainability.

Source: Hiten Techno Products Corporation
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