Radiation source intensity

There are numerous sources of drift. The radiation source intensity may change because of line voltage changes, the source warming up after being recently turned on. 

PMT shot noise induced by dark current, atomizer background emission, sample matrix emission, or scattered radiation source intensity. 

Radiation source intensity fluctuations carried by scatter, contamination fluorescence, or broadband fluorescence from flame and furnace gases or from sample matrix components. 

Induction electron accelerators - betatrons- are widely used as radiation sources in industrial flaw detection of materials and articles of high thickness. However, relatively low radiation intensity has become the barrier for the most wider betatron use in this area. For the efficiencyincrease of radiation control method of articles, as well as for the possibility to control materials and articles of the most thickness the significant increase of betatron radiation intensity has been required. 

Finally, values of sx are directly proportional to transmittance for indeterminate errors due to fluctuations in source intensity and for uncertainty in positioning the sample cell within the spectrometer. The latter is of particular importance since the optical properties of any sample cell are not uniform. As a result, repositioning the sample cell may lead to a change in the intensity of transmitted radiation. As shown by curve C in Figure 10.35, the effect of this source of indeterminate error is only important at low absorbances. This source of indeterminate errors is usually the limiting factor for high-quality UV/Vis spectrophotometers when the absorbance is relatively small. 

Work on EXAFS then progressed very little until the advent of the synchrotron radiation source (storage ring), described in Section 8.1.1.1. This type of source produces X-ray radiation of the order of 10 to 10 times as intense as that of a conventional source and is continuously tunable. These properties led to the establishment of EXAFS as an important structural tool for solid materials. 

Radiation doses required to effect desirable changes in polymers (2-10 Mrad) can be delivered to the product in question in a matter of seconds [39] whereas, it might have taken hours to accomplish the same with 7-radiation sources of reasonable intensity [33]. 

The intensity units for ( ) are related to a primary radiation source, the candela, Cd. The definition of a candela is ... 

No single development has influenced the field of EXAFS spectroscopy more than the development of synchrotron radiation sources, particularly those based on electron (or positron) storage rings. These provide a continuum of photon energies at intensities that can be from 103 to 106 higher than those obtained with X-ray tubes,... 

More and more radiation sources are switching from discontinuous mode to top-up mode. This means that the user is continuously supplied with synchrotron radiation of almost constant intensity. The loss of the electron current is either compensated continuously or in intervals of several hours (at the ESRF 6 h). 

One of the most exciting developments in modem X-ray spectroscopy is the now widespread availability of synchrotron radiation sources. By virtue of its much higher intensity and the tunability of its wavelength over a broad range, synchrotron radiation permits more sophisticated experiments to be performed [43]. 

Optical methods are especially useful for the selective detection of CO and C02 concentrations. In low-priced sensors, a simple miniature light bulb is used as IR-source. The radiation emitted enters an absorption chamber, through which the flue gas is pumped. An added interference filter lets only the absorption spectra of the target gas pass. The IR detector determines the reduction of the light intensity, which is then transformed into an electrical signal. The correlation between the source intensity and the received intensity is given in the Lambert-Beer equation. 

Here, I is the received radiation intensity, I0 is the source intensity, a is the absorption coefficient, c stands for the concentration of the gas to be measured and the length of the radiation pathway filled with gas is called l. Fig. 3.16 shows an optical sensor for detecting C02. 

To make accurate measurements of the integrated absorption associated with such narrow lines requires that the linewidth of the radiation source be appreciably smaller than that of the absorption line. In practice, this could be achieved with a continuum source only if expensive instrumentation of extremely high resolving power were used, and it is doubtful whether conventional photomultiplier detectors would be sufficiently sensitive at the resulting low radiation intensities. An alternative arrangement is to... 

---