Metal halide lamp

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. 

Lighting equipment Fluorescent lamps, metal halide lamps... 

More recently, metal halide lamps have been introduced that give a reasonable simulation of sunlight and offer very high irradiance with modest heat generation. They have mostly been employed in large solar simulation systems. 

Yorio, N. C., Mackowiak, C. L., Wheeler, R. M., Sager, J. C. (1995b). Vegetative growth of potato under high-pressure sodium, high-pressure sodium SON-AGRO, and metal halide lamps. HortScL, 30, 374-376. 

Spectral outputs of some typical metal halide lamps compared to that of the standard mercury lamp mercury barrier discharge lamp (a) mercury barrier discharge lamp, (b) iron additive lamp, and (c) gallium additive lamp. (Courtesy of American Ultraviolet Company.)... 

Spectral outputs of some metal halide lamps compared with that of a standard mercury lamp Spectral output of commercial micro-wave-driven lamps The process of generation of reactive species. 

A solution of perfluoroalkyl iodide (0.4 mmol), a-chlorostyrene (1.2 mmol) and Bu3SnSnBu3 (0.44 mmol) in benzene (3 ml) was irradiated using a metal halide lamp (National Sky-beam MT-70) in Pyrex tube under 02 atmosphere for 5 h. After removal of the solvent, ethanol and hydrazine acetate were added. The resultant solution was stirred under refluxing conditions for 2 h. After removal of the solvent, the residue was chromatographed on silica gel using a mixture of hexane and dichloromethane as an eluent, to give perfluoroalkylated pyrazole in 59% yield [117]. 

Based on the results obtained, a testing protocol was developed, encompassing as many of the practices as possible. Fluorescent, xenon and metal-halide lamps were all deemed to be equivalent for photostability testing. The protocol developed was used for a collaborative study by 49 member companies of 175 items described in the Japanese Pharmacopoeia as being "unstable to light." Based on the results obtained, a proposed monograph General Test was sent to the Japanese Pharmacopoeia. 

Option 1 specifications remained the same, except that references to any particular lamp were removed. The original Options 1 and 2 were now combined and Option 1 became a two-part specification. Part 1 for the VIS range and 2 for the UV range. Option 2 now became a specification for "Use (of, authors insert) a xenon lamp fitted with a window glass filter to eliminate radiation below 310nm." A new Option 3 was introduced. Option 3 covered the "Use (of, authors insert) a metal halide lamp fitted with a window glass filter to eliminate radiation below 310nm." The particular metal-halide lamp (s) that were acceptable were not specified. 

Option 1 can be achieved by use of a fluorescent lamp combining UV and VIS outputs or by use of a xenon or metal halide lamp. In actuality. Option 1 offers a choice between three different types of sources. A window-glass filter should be used in combination with sources producing significant radiation below 320 nm (e.g., xenon- and metal halide lamps, near-UV fluorescent tubes). It has also been questioned whether filters should be recommended for fluorescent lamps (Option 2) (2). 

Because the confirmatory study also represents "worst-case" conditions, there should be few chances that an unstable product is not discovered. Examples of sources currently used by the pharmaceutical industry are xenon- and metal halide lamps (Option 1), artificial- and full spectrum daylight fluorescent tubes (Option 1), white fluorescent- and near UV-fluorescent tubes (Option 2). In (Northern) Europe (e.g., Scandinavia, England, and Germany), it seems that Option 1 with the xenon lamp is the preferred source. 

In Figure 6, we can see just how much radiation is not measured by this instrument when it is used with a xenon or metal-halide lamp. Upwards of 60% of the incident radiation is not measured. This leads to the "overexposure" of samples and less than accurate correlations between potentially similar/equivalent sources and significantly increases analysis times. 

Option 1. Artificial daylight fluorescent lamp, or Xenon arc lamp, or metal halide lamp. 

For metal halide lamps, mercury is used to initiate and maintain conduction through the lamp. Its arc provides the heat for vaporizing the metal halide, ionizing it and raising the bulb temperature to aid in the revaporization of any deposited metal on its surface. 

The warming up process of a metal halide lamp is easily visible in the mercury and sodium vapor lamps used for street lighting. Their shift in coloration during warm-up is easily seen. 

Figure 1 Comparison of the spectral power distributions of a metal halide lamp during its aging process. Source Courtesy of Atlas Electric Devices, Inc.

There are many varieties of metal halide lamps, the most familiar being the tungsten-halide lamps found in many homes, or the sodium and mercury vapor lamps found on streets and in auditoriums, convention centers and large space commercial buildings. Many have seen the change in color given off as these lamps warm up to their operating temperature. 

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