High Intensity and Brightness

The flux for 10 keV photons (1.24 A) is equal to 1.5 10 this must be compared with 10 photons produced by a standard molybdenum target X-ray tube operating at 20 kV and 200 mA 

The spectral brillance (or brightness), defined as the number of photons per second within a 0.1 % band pass per mrad and mm, is equal to 3.3 x 10 . 

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Because of the unique features of the x-ray radiation available at synchrotrons, many novel experiments ate being conducted at these sources. Some of these unique features are the very high intensity and the brightness (number of photons per unit area per second), the neatly parallel incident beam, the abihty to choose a narrow band of wavelengths from a broad spectmm, the pulsed nature of the radiation (the electrons or positrons travel in bunches), and the coherence of the beam (the x-ray photons in a pulse are in phase with one another). The appHcations are much more diverse than the appHcations described in this article. The reader may wish to read the articles in the Proceedings of the Materials Research Society Hsted in the bibhography. 

The advances in X-ray spectroscopy are related to the development of X-ray sources, and in this context, electron synchrotron sources play an important role. Notably, they provide a broad continuum of photon energies and generate radiation of high intensity and pronounced brightness also called brilliance. (The brightness... 

Figure 13 FTIR ATR image of the polymer laminate (top left IR spectrum of COPA layer bottom left IR spectrum of EVA layer). The amide I absorption of COPA (top right) and the ester absorption of EVA (bottom right) were integrated (high intensities represented in bright color). An Intermediate region of ca. 5 pm (dimension bar) is assumed to be the LLDPE-MAH layer. Image area 50 pm x 50 pm.

Fig. 25 Schematic of a Mach-Zehnder interferometer (upper) for 2-D recording via two-photon photochromism (beam spiitters are 50 50 at 45°, iaser exposure time) 0.5-3 min, output beam angie 2°. Dark lines in image (lower) resuit from high intensity bright fringe-induced photoisomerization of fuigide 1 in a poiymeric fiim (13 xm line width and 155 p.m line spacing)...

By far the most common lamps used in AAS emit narrow-line spectra of the element of interest. They are the hollow-cathode lamp (HCL) and the electrodeless discharge lamp (EDL). The HCL is a bright and stable line emission source commercially available for most elements. However, for some volatile elements such as As, Hg and Se, where low emission intensity and short lamp lifetimes are commonplace, EDLs are used. Boosted HCLs aimed at increasing the output from the HCL are also commercially available. Emerging alternative sources, such as diode lasers [1] or the combination of a high-intensity source emitting a continuum (a xenon short-arc lamp) and a high-resolution spectrometer with a multichannel detector [2], are also of interest. 

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