Nuclear Physics (1986) / Chapter Skim
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6 Scientific and Societal Benefits
6 Scientific and Societal Benefits
Pages 120-136
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From page 120... ...
This is all the more puzzling in light of the profound impact that nuclear physics has had on the development of the other sciences as well as on countless areas of modern technology. From solid-state physics to molecular genetics, from food technology to forensic medicine, from mineral prospecting to cancer therapy, the principles and techniques of nuclear physics are applied in ways far too numerous to survey comprehensively in a book of this size.
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From page 121... ...
One can also study aspects of the crystal structure, such as the locations and mobilities of impurities, as well as the radiation damage caused by the implanted ions, the healing of this damage through heat treatment,.and the eject of the ions on the crystal's electrical conductivity. Information obtained by the ion-implantation technique and by other techniques derived from nuclear-physics research, such as perturbed angular correlations, is of great value in developing new materialsmagnetic compounds and alloys, for example with properties that are tailor-made for specific purposes.
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From page 122... ...
Here the energetic projectiles bombarding the surface of the crystal are found to be channeled through the tunnels formed by adjacent rows of atoms in the lattice structure (see Figure 6.11. Studies of the behavior of charged particles as they are channeled-or sometimes blocked inside crystals have yielded much information on surface conditions and the locations of impurities, for example.
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From page 123... ...
Relativistic effects associated with extremely high velocities are being exploited in order to measure ultrashort time intervals, in an effort to determine the lifetimes down to perhaps 10-20 second or even less-of some elementary particles. An intriguing offshoot of these experiments was the discovery that by bending the crystal, even the most highly relativistic particles at energies of hundreds of GeV-can be made to follow curved paths; to bend such particle beams through equivalent deflection angles in an accelerator would require immensely powerful superconducting magnets.
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From page 124... ...
For many years, much information about nuclear properties has been deduced from analyses of atomic spectra. Now, however, with nuclear accelerators that can produce ion beams of precisely controllable energy and ionization state, it is possible to create exotic atomic species unlike any that exist under ordinary conditions, and thus to use nuclear beams to study novel aspects of atomic physics.
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From page 125... ...
The study of x rays resulting from such collisions is expected to provide a better understanding of the processes that are critical for the production of superheavy atoms and to enable further tests to be made of the attendant QED phenomena in very heavy atomic species. The experiments described above illustrate only a few of the ways in which the techniques of nuclear physics have expanded the boundaries of atomic physics, thereby both broadening and deepening our understanding of this vital subject.
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From page 126... ...
Thus the technique of accelerator mass spectrometry, still in its infancy but developing rapidly, has vastly enlarged our scientific window on the past. Among the growing list of subjects being investigated with this powerful new tool are atmospheric methane, polar ice, lake and ocean sediments, manganese nodules, tektites, meteorites, and long-lived radionuclides produced by cosmic rays.
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From page 127... ...
In addition, nuclear physics serves medical science through the development of exotic materials for use in prosthetic implants. In a typical nuclear-medicine examination, of which many millions are performed annually, a radiopharmaceutical agent is administered intravenously, and gamma rays emitted by the tracer nuclide are recorded with an array of radiation detectors positioned about the patient; this technique is called emission tomography.
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From page 128... ...
by gamma rays resulting from annihilation of the positrons with electrons in the surrounding tissue. The technique of positron-emission tomography has become a powerful tool of nuclear medicine.
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From page 129... ...
Improved dose localization can be achieved by using accelerated beams of charged particles such as electrons, protons, heavy ions, and negative pions. Biological electiveness depends in part on the stopping power of the tissue for the particle in question and can be increased by using the particle in its characteristic stopping region.
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From page 130... ...
Most semiconducting devices require the selective doping of silicon or germanium crystals with impurity atoms, and ion implantation has rapidly become the dominant doping technique in the semiconductor industry. Among its many advantages is that it permits extreme miniaturization; consequently, most semiconductor devices and integrated circuits for watches, calculators, computer chips, and other electronic porducts requiring small components are fabricated by this method.
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From page 131... ...
Passive forms of nuclear well-logging employ gamma-ray detectors to distinguish regions containing clean sands and carbonates (low natural radioactivity) from the less productive but more radioactive regions containing clays or shale rock.
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From page 132... ...
The conservation occurs not only through corrosion reduction but also because nuclear accelerators permit the implantation of these scarce elements selectively into the surface of the materialprecisely where they are needed for corrosion resistance. Intimately intertwined with these ongoing studies are efforts by metallurgists and other materials scientists to understand the ejects of intense radiation on the properties of structural materials and to design new materials for service in advanced fission and fusion reactors.
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From page 133... ...
SCIENTIFIC AND SOCIETAL BENEFITS 133 A: :] FIGURE 6.3 Saint Rosalie interceding for the Plague-Stricken of Palermo, by Anthony Van Dyck.
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From page 134... ...
THE FINE ARTS Nuclear techniques based on the use of neutron-induced radioactivity in art objects have been used for many years as tools for determining the elemental composition and thus, often, the origin of these objects. Recently, however, the complete neutron irradiation of paintings, followed by autoradiography, has proved to be a valuable technique for studying the underlying paint layers, which record the evolution of paintings by the great (and lesser)
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From page 135... ...
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