Sodium lamps, types

Lamp types (a) incandescent and tungsten-halogen lamp shapes (b) fluorescent and compact fluorescent lamp shapes (c) typical high-pressure sodium lamp (d) typical metal halide lamp. 

We wish to test a new type of ceramic tube to the AljOg tube normally used to fabricate high-pressure sodium lamps in order to eompare lamp qualities and life-time operation. Select a method which would produce the desired results and describe how this would be accomplished. Note that the ceramic tube requires both strength and a high melting point. 

Low-Pressure Sodium Lamp - A type of lamp that produces light from sodium gas contained in a bulb operating at a partial pressure of 0.13 to 1.3 Pascal. The yellow light and large size make them applicable to lighting streets and parking lots. 

The high-pressure sodium discharge takes place in a sintered aluminium oxide arc tube contained within a hard glass outer bulb. Until recently no suitable material was available which would withstand the extreme chemical activity of sodium at high pressure. The construction and characteristics of the high-pressure sodium lamp classified as type SON are given in Fig. 3.52. 

Almost all emission that we usually encounter, such as that from a sodium vapour or tungsten filament lamp, is of the spontaneous type. 

Sulfur eontent must be eontrolled in units with exhaust reeovery systems. If sulfur eondenses in the exhaust staek, eorrosion ean result. In units without exhaust reeovery there is no problem, sinee staek temperatures are eonsiderably higher than the dew point. Sulfur ean, however, promote hot-seetion eorrosion in eombustion with eertain alkali metals sueh as sodium or potasium. This type of eorrosion is sulfidation or hot eorrosion and is eontrolled by limiting the intake of sulfur and alkali metals. Contaminants found in a gas depend on the partieular gas. Common eontaminants inelude tar, lamp blaek, eoke, sand, and lube oil. 

This type, made by the General Electric Co., is resistant to sodium vapour and is used in sodiiun vapour discharge lamps. It has a very high boric oxide content, a low softening temperature, and a low electrical resistance. It is used as an internal layer in soda glass tubing X.8. ... 

Abbe-Type Refractometer Use an instrument with fourth decimal place accuracy that can be placed in a nearly horizontal position for measurement of the refractive index of solids. An Amici-type compensating prism for achromatiza-tion is necessary unless a sodium vapor lamp is used as a light source. 

Lamps containing free metallic sodium (e.g. low-pressure sodium vapour lamps) are not permissible. This is valid in general, i.e. not only a requirement for increased safety - e -, but for all types of protection. 

Flameproof luminaires open a wide range of applications, based upon the fact that all types of lamps - with the exception of sodium vapour low pressure lamps - can be used (see Table 6.23, Section 6.7.4), especially those with ... 

Table I. Types of Commercial Discharge Lamps Containing Sodium...

The addition of electrodes and possibly an easily volatilized and ionized metal to the most basic lamp design creates an arc pathway through an ionizable gas. This produces a single element arc lamp like those of mercury, sodium, and xenon. Their emission spectra primarily is that of the pure element. Because of the intense heat generated by the arc, electrodes and impurities vaporized and ionized, all of which contribute to the overall spectral power distribution (SPD) of the lamp. This effect is more probable for short-arc (less than 5 mm distance between electrode tips) than the long-arc types. 

So far in this discussion of diffraction, we have assumed that the periodic object is illuminated by coherent light, such as that produced by a small laser of the type used in the Porter experiments. However, the light produced by a thermal source (e.g., a sodium vapor lamp or a heated filament coupled with a narrow bandpass filter) is never strictly monochromatic even the sharpest spectral line has a finite width. Moreover, such a source has finite extent, and the light is emitted by many independent radiators (atoms). These two characteristics of thermal sources are directly related to what are usually referred to as temporal and spatial coherence, respectively. 

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