Y-ray spectroscopy

At the end of the irradiation, the samples are withdrawn from the reactor and y-ray spectroscopy is carried out. Most often the laboratory performing the y-ray spectroscopy is located in a different city, in which case the samples are shipped and the reactor serves as a neutron source only. Many reactors also have y-ray spectroscopy capability so that measurements can be made at the reactor site as well. 

Chemical bonding and dynamic properties of Au clusters are obtained by recoilless y-ray spectroscopy and- P NMR investigations - . ... 

HI, xny) reactions Further details concerning y-ray spectroscopy with MT reactions can be found elsewhere [HAE82]. ... 

Since the early days of diffraction y-ray spectroscopy [DUM47], online applications have been considered. The success in neutron capture work is obvious [K0C80]. Application to the study of (LI,xny) reactions has met with considerable difficulties [JET74]. The main problems to be solved are to obtain ... 

Our knowledge of the geochemistry and mineralogy of Venus surface primarily comes from six types of information (i) elemental analyses of several major elements by X-ray fluorescence (XRF) spectroscopy (ii) analyses of potassium, uranium, and thorium by y-ray spectroscopy ... 

More details about these detectors are presented in Chap. 12 in connection with y-ray spectroscopy. 

Conventional fast mass separation with y-ray spectroscopy. The combination of online mass separation (of fission products stopped in the target, volatilized, ionized, and separated) with y-ray spectroscopy would be an ideal tool to determine both independent and cumulative yields, because mass separation of nuclides diffusing out of a target under irradiation can be performed within seconds. The selection of a single mass chain would simplify the y-ray spectra dramatically, so that even short-lived nuclides could be measured. Unfortunately, problems arise with the volatilization fi-om the targets and ionization in the ion source that show different yield and time characteristics for different elements ( chemical selectivity ). Therefore, yields obtained with this technique have frequently been considered unreliable. 

Most of the y rays emitted in the decay chains are emitted following P decay. Most of the Q values for a decay are considerably larger than those for P decay, but P decay is much more likely to populate states that are just barely accessible energetically. Therefore, the use of y-ray spectroscopy to measure the amounts of various components in a mixture emphasizes the P decays. O Figure 13.7 shows the y-ray spectrum (Helmer et al. 1999) of a sample of thorium ore, i.e., a sample that has been undisturbed for long enough time that the chain is in secular equilibrium. O Table 13.4 lists the energies and intensities of the most intense y rays emitted by components of the chain. 

All of the details involved in obtaining precision results from y-ray spectroscopy with Ge detectors apply to Nal(Tl). If fact, the methods were developed with Nal(Tl) and later applied to Ge. Nal(Tl) is superior to Ge in effective atomic number (total energy absorption), operation at room temperature, and size (up to 25 cm linear dimensions for the scintillator). But the vastly superior resolution of Ge dominates aU other characteristics for most users. At about 1,000 keV, the energy resolution of a Ge detector is about 1.5 keV, and that of Nal(Tl) is about 60 keV O Fig. 48.15. Whereas Ge spectra can be analyzed in terms of individual peaks and their areas, Nal(Tl) spectra are usually analyzed in terms of the overall, somewhat indistinct pattern each nuclide produces under the conditions of the measurement. When conditions change and effects such as summing and pileup change, the patterns change. 

While Ge(Li) detectors are primarily used for y-ray spectroscopy in the energy range of 50 keV to 10 MeV, the Planar pure Ge detectors have inherently good response down to very low energies (2-200 keV). 

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