Cross section nuclear

One of the most promising appHcations of polyboron hydride chemistry is boron neutron capture therapy (BNCT) for the treatment of cancers (253). Boron-10 is unique among the light elements in that it possesses an unusually high neutron capture nuclear cross section (3.8 x 10 , 0.02—0.05 eV... 

The cross-section curve a(E) gives the dependence of the nuclear cross-section on the projectile energy, E. The measured energy spectra of emitted particles or the excitation curve N(Eq) wiU depend on the depth profile N(x) of the analyzed isotope and on the cross-section curve (t(E(x)), where E(x) gives the energy of the projectiles at a depth x. Evaluation of the depth profile N (x) from measured energy spectra or excitation curves often requires a tedious evaluation procedure if the cross-section curve has a complex structure. It is simplified for two special types of behavior of the cross-section curve ... 

In this framework the different nuclear processes which produce or destroy Li, Be and B must be studied in details and an accurate knowledge of the involved nuclear cross sections are necessary. In particular we will focus our attention on one of the main destruction channels for these elements in stellar environments, the (p, a) reactions. 

The growth of Y will proceed at a rate dependent upon the intensity /of the particle flux, the amount Nx of the target present and the nuclear cross section ax for the reaction (Figure 10.5). After time t, the activity induced due to Y (i.e. AY Y) will be given by... 

Quantitative estimates of the concentration levels of these 16 elements could be obtained by using silver standards containing known amounts of the elements of interest. Two standards were prepared at Brookhaven National Laboratory. Although we have established that the elements in these standards are homogeneously distributed, we have not completed their calibrations. Moreover the standards were not useful for scandium, tin, and iridium. For these elements the concentrations were calculated relative to those of elements for which good standards were available, using nuclear cross-sections and decay constants from the literature (7). 

BARN (b). A unit of nuclear cross section. One bam equals 10 square meter. 

Let us recapitulate what we have said about compound nuclear reactions. We have said that they are basically nuclear reactions with a long-lived reaction intermediate, which is formed by a complicated set of two-body interactions. We can write down a set of equations that describes the overall compound nuclear cross section. We have shown how this general formula simplifies for specific... 

GAR85a] M. A. Gardner, Calculational Tools for the Evaluation of Nuclear Cross-Section and Spectra Data, Lawrence Livermore National Laboratory, Livermore, CA, UCRL-91947 (1985) to be published in Proc. Int. Conf. Nuclear Data for Basic and Applied Science, Santa Fe, NM, May 13-17, 1985. 

The neutron activation production cycle requires only neutron irradiation without chemical separation. The target and the product are the same chemical element but have different nuclide compositions. The specific radioactivity of the product is a function of the nuclide composition of the target, the neutron flux environment, the irradiation time, and the half-life of the product nuclide, along with the nuclear cross-sections of target and product nuclides. 

Carboranes in Boron Neutron Capture Therapy of Cancer (B7YC2). The stable isotope of boron, B (19.8% natural abundance), is very effective as a neutron capture agent with the effective nuclear cross section of 3837 bams, while the "B nucleus is incapable of undergoing a BNC reaction. Therefore, the B-emiched carborane and borane-substituted biomolecules and dmgs are selectively dehvered to the cancer cells in the human body and then the tumor-localized B nucleii are bombarded with either thermal or epithermal neutrons that results in a fission reaction producing the high energy alpha (a) particles as shown in equation (2). 

Ericson, T. (1960). Fluctuations of nuclear cross sections in the continuum region, Phys. Rev. Lett. 5, 430-431. 

Ericson, T. (1963). A theory of fluctuations in nuclear cross sections, Ann. Phys. 23, 390 14. 

For a constant flux of galactic cosmic rays (for further discussion of this point, see LavieUe et al. (1999)), the time dependence vanishes. The parameters, size and depth, remain along with the elemental abundances and nuclear cross-sections in principle, the elemental abundances and nuclear cross-sections can be measured directly. 

The nuclear cross-section for fission of the two kinds of U and/or Pu are shown roughly in Fig. 8.1 where a,is plotted against the log o the incident neutron s energy. 

Inelastic neutron scattering spectroscopy is characterized by completely different intensities because the neutron scattering process is entirely attributable to nuclear interactions [110] Each atom features its nuclear cross section, which is independent of its chemical bonding. Then the intensity for any transition is simply related to the atomic displacements scaled by scattering cross sections. And because the cross section of the proton is about one order of magnitude greater than that for any other atom, the method is able to record details of quantum dynamics of proton transfer. 

The extremely weak interaction of neutrons and matter is dominated by spin-spin interaction with nuclei, whilst interactions with electron-spins are negligible. Nuclear cross-sections for neutron scattering are strictly independent of the electronic structure (ionic or neutral, chemical bonding, etc). There-... 

Table 2. Exponent of the temperature dependence of the Maxwellian averaged nuclear cross section (middle column) for four different nuclear reactions, evaluated at a temperature of 1.5 107 K. The last column gives the Coulomb threshold energy.

We should note that the absolute value of the 170 production factor depends on the still uncertain 17O I p nuclear cross section (cf., Aubert et al. 1996) however, the general trend discussed here is likely to be independent of that. 

Nuclear cross-section or the reaction rates which also depend upon the relative velocity (or equivalently the center of mass energy) therefore need to be averaged over the thermal velocity (energy) distribution. Therefore, the thermally averaged reaction rate per particle pair is ... 

Apart from the input nuclear cross sections, the theory contains only a single parameter, namely the ratio of the number densities of baryons to photons, r. Because both densities scale as their ratio is constant, barring any non-adiabatic processes. The theory then allows one to make predictions (with well-defined uncertainties) of the abundances of the light elements, D, He, He, and Li. 

Nuclear cross section A model used to characterize the probability that a nuclear reaction will occur. Nuclear cross section is measured in units of bams with one bam equal to cm. ... 

Relative measurements are, in most cases, easier than absolute measurements. For this reason, investigators tend to perform the very minimum of absolute measurements and use their results in subsequent relative measurements. One of the most characteristic examples is the determination of the value of nuclear cross sections. Absolute measurements have been performed for very few cross sections. After certain cross sections have been measured, most of the others may be determined relative to the known ones. 

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