Filters, for radiation

There are three accessories used to produce monochromatic radiation metal foil filters, crystal monochromators, and focusing mirrors. An element with atomic number Z can be used as a selective filter for radiation produced by an element of atomic number Z+ 1. For example, a nickel (Z=28) absorption filter, may be used to cut out the Cu KjS (Z=29 for Cu) radiation, leaving only Cu Ka radiation.Not all white radiation, however, is eliminated by this method. Alternatively a single-crystal monochromator may be used. An intense Bragg reflection from the monochromator crystal is used as the incident beam for X-ray diffraction studies. Focusing mirrors, designed to produce a beam that is not only monochromatic but also convergent, may be used. In this case the incident beam is doubly deflected by two perpendicular mirrors. 

Initially, DADC polymers were used in military aircraft for windows of fuel and deicer-fluid gauges and in glass-fiber laminates for wing reinforcements of B-17 bombers. Usage in impact-resistant, lightweight eyewear lenses has grown rapidly and is now the principal appHcation. Other uses include safety shields, filters for photographic and electronic equipment, transparent enclosures, equipment for office, laboratory, and hospital use, and for detection of nuclear radiation. 

The SU5 beamline [89] at the Super-ACO synchrotron (LURE, Paris ) employed an electromagnetic undulator to produce fully variable polarization in the VUV region [83, 90, 91]. This beamline was equipped with a gas filter for the suppression of unwanted higher order radiation [92] and had a VUV polarimeter [93] permanently installed just before the experimental chamber that could be rapidly lowered into the beam for polarization determinations. Full polarization analyses had been performed in commissioning, with 53 values ranging from 0.9 to 0.96 for rep and from 0.9 to 0.99 for Icp [93]. The remainder was determined... 

X-ray diffraction has been applied to certain AB cements. For example. Crisp et al. (1979), in a study of silicate mineral-poly(acrylic acid) cements, used the technique both to assess the purity of the powdered minerals employed and to monitor mineral decomposition in mixtures with poly(acrylic acid), in order to indicate whether or not cement formation had taken place. They employed Cu radiation passed through a nickel filter for most of the samples, a seven-hour exposure time was found to be adequate for the development of a discernible diffraction pattern. Samples were identified by reference to published powder diffraction data. 

The IR probe radiation, provided by a liquid N2-cooled line-tunable CO laser, is passed through the cell collinearly or almost collinearly with the uv photolysis radiation. The probe beam is then directed onto an IR detector using a filter for either selectively blocking the photolysis beam or... 

Following variant II, after treating by the modifier, the solid phase was separated by filtration and additionally washed off with 0.2 liters of water under vacuum of the water-jet pump. Further, as in variant I, one part of the product was dried at 105°C for two hours (product C), while the other was dried at 20°C until a sample mass became constant (product D). The products were investigated by the powder X-ray phase analysis (PXRD) using nickel-filtered CoKa radiation. 

Photochemical activation of [ESE, TNM] complexes. Colored solutions of the ESE derived from the relatively unreactive cycloalkanones and acyclic ketones in Table 2 and TNM persist for prolonged periods, and they can thus be separately subjected to filtered actinic radiation with /exc > 420 nm. (Note that under these conditions, neither TNM nor ESE alone is excited since they absorb only below 400 nm.) The photonitrations of ESE with TNM are carried out at low temperatures (—40°C) at which the thermal reactions are too slow to... 

As with prisms, there are other devices that have been historically used for dispersing or filtering electromagnetic radiation. These include interference filters and absorption filters. Both of these are used for monochromatic instruments or experiments and find little use compared to more versatile instruments. The interested reader is referred to earlier versions of instrumental analysis texts. 

Accelerated exposure equipment may also be used to test for weatherfastness in plastic materials [106], The natural destructive agents inherent in weather are approximated by filtering the radiation emitted by the xenon arc lamp and by spraying the sample with water under standardized conditions [106], Test programs are designed to relate to actual outdoor exposure to rain and humidity. In a standard program, a 3 minute wet cycle typically alternates with a 17 minute dry period. Weatherfastness tests are carried out and evaluated like lightfastness tests the black panel temperature and other parameters are the same in both procedures. 

In research laboratories, different types of light sources are used instead of solar radiation. In most cases the simulated spectrums have considerable deviation from the solar spectrum. Based on equation (3.6.9) Murphy et al [109] analyzed the maximum possible efficiencies for different materials according to their band gap in the case of solar global AM 1.5 illumination and xenon arc lamp, see Fig. 3.21. For example, anatase titania with a bandgap of 3.2 eV has a maximum possible efficiency of 1.3% under AM 1.5 illumination, and 1.7% using Xe lamp without any filter. For rutile titania these values are 2.2% and 2.3% respectively. 

X-Ray Powder Patterns. Samples for x-ray pattern determinations were sealed in 0.2-mm. glass capillary tubes under an atmosphere of argon. The samples were then exposed to nickel-filtered, CuKa radiation in an 11.459-cm. Debye-Scherrer camera for 18 to 20 hours. 

X-Ray Diffraction Analysis. X-ray powder diffraction data for indexing were obtained with a General Electric XRD-6 diffractometer. Samples were sealed in glass capillaries (0.5 mm o.d.) and exposed to nickel-filtered CuKa radiation. KCl or iridium was used as an internal standard. X-ray powder diffraction intensity data were obtained with a General Electric XRD-5 unit. Here,... 

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