Point source lamps

Figure 2.21. A, High-intensity point source lamp B, parabolic mirror C, light baffle D, narrow slit E, collimating lens F, Coming filters G, reaction cell or series of cells H, focusing lens I, photomultiplier.

High-pressure mercury lamps operate at pressures about 10 atmospheres and essentially two types are used in industrial applications. The point source lamp focuses on a small-diameter spot, thus delivering an intense radiation to that spot. The capillary lamp is used for narrow webs up to approximately 20 cm (8 in.) wide.4 They are capable of producing a wider spectrum than the medium-pressure lamps and operate with higher power (150-2880 W/cm). Their disadvantage is a relatively short operating life, typically hundreds of hours. 

Fig. 37. The brightness distribution in candles per square mm for a 1000 W Xe-Hg point-source lamp with AC operation. From ref. 9.

High intensity, microwave powered emission sources have recently been developed that are reported to provide substantially higher DUV output than classical electrode discharge mercury lamps 76). These sources suffer from self-absorption of the intense 254 nm emission but have a relatively high output in a band between 240 and 280 nm. They are extended sources of finite size rather than point sources, and they must also be an integral part of a tuned, resonant microwave cavity. Consequently, extensive condenser design work would be required in order to utilize the microwave powered sources in projection printers. 

High-pressure mercury lamps operate at pressures of about 10 atm, and there are essentially two types used in industrial applications. The point source... 

Xenon lamps are available mainly as tubular and point source bulbs. The radiation produced by this type of lamps is not particularly rich at wavelengths below 400 nm, and therefore their applications are somewhat limited. However, it is possible to pulse xenon lamps, which enables them to achieve high peak irradiances. Commercially available pulsed xenon lamps are available with emissions in the UV and visible spectral range. Alternating the gas fill can produce output rich in UV. 

Wastewater, secondary effluent Dose distribution function Fluence rate distribution Modeling of flow and disinfection LP Hg lamps 24 - Point-source summation method Significance of reflection/refraction Steady two-dimensional model of flow and disinfection Coliforms Rummer (1990) Chiu et al. (1999) Bolton (2000) Lyn et al. (1999)... 

Another factor affecting the mapping pattern is the source design. Short-arc (xenon and metal halide) lamps can be considered point sources, which generate bulls-eye patterns whereas long-arc lamps (xenon and fluorescent) will produce oblong patterns. Low-resolution mapping tends to obscure these differences, which are real. How pertinent these results will be to an individual study will depend on a number of factors, one of which will be the samples physical size. 

Determination of safety factors for the required UV dose due to lamp aging and fouling. Determination of UV intensity as a function of the transmittance or absorbance of filtered water samples by the point-source summation method or equivalent. The presence of suspended solids and colors can reduce the intensity of UV light in the waters. 

The advantages of incandescent lamps are their inherent broad spectral range, from blue to the near infra-red and their D.C. operatioa However, they suffer from being point sources that dissipate large amounts of heat. A typical emission... 

At this point, initial cost versus lifetime expenses often comes into play. A cheap answer looks good on the quarterly bottom line, but if it needs constant maintenance, the cost is a ruse. Many plant managers and/or quality control managers decide at this point that spectroscopic measurements are the least labor-intensive of any type on the market. The probe is usually passive, not needing to be renewed or cleaned at frequent intervals, and the most difficult maintenance on the spectrometer normally consists of replacing the source lamp on a yearly basis. 

The surfaces and bubbles may be projected onto a large screen by shadow projection using a strong point source of light such as that produced by a quartz-iodine (halogen) lamp. 

Record the spectrum of a broadband intensity standard. Although white light sources such as halogen or tungsten lamps can be employed, the illumination geometry does not mimic that of the Raman collection well as it does not act as a point source. Thus the use of fluorescent standards (where they exist) such as those provided by the American NIST is recommended, although there are sometimes point to point variations in the signal found from these standards. 

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