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Vertex detectors

Description: The purpose of a vertex detector is to measure position and angles of charged particle tracks to sufficient precision so as to be able to separate tracks originating from decay vertices from those produced at the interaction vertex. Such measurements are interesting because they permit the detection of weakly decaying particles with lifetimes down to 10{sup {minus}13} s, among them the {tau} lepton and charm and beauty hadrons. These two lectures are intended to introduce the reader to the different techniques for the detection of secondary vertices that have been developed over the past decades. The first lecture includes a brief introduction to the methods used to detect secondary vertices and to estimate particle lifetimes. It describes the traditional technologies, based on photographic recording in emulsions and on film of bubble chambers, and introduces fast electronic registration of signals derived from scintillating fibers, drift chambers and gaseous micro-strip chambers. The second lecture is devoted to solid state detectors. It begins with a brief introduction into semiconductor devices, and then describes the application of large arrays of strip and pixel diodes for charged particle tracking. These lectures can only serve as an introduction the topic of vertex detectors. Time and space do not allow for an in-depth coverage of many of the interesting aspects of vertex detector design and operation.
Date: July 1, 1992
Creator: Lueth, V.
Partner: UNT Libraries Government Documents Department

Lecture notes for criticality safety

Description: These lecture notes for criticality safety are prepared for the training of Department of Energy supervisory, project management, and administrative staff. Technical training and basic mathematics are assumed. The notes are designed for a two-day course, taught by two lecturers. Video tapes may be used at the options of the instructors. The notes provide all the materials that are necessary but outside reading will assist in the fullest understanding. The course begins with a nuclear physics overview. The reader is led from the macroscopic world into the microscopic world of atoms and the elementary particles that constitute atoms. The particles, their masses and sizes and properties associated with radioactive decay and fission are introduced along with Einstein's mass-energy equivalence. Radioactive decay, nuclear reactions, radiation penetration, shielding and health-effects are discussed to understand protection in case of a criticality accident. Fission, the fission products, particles and energy released are presented to appreciate the dangers of criticality. Nuclear cross sections are introduced to understand the effectiveness of slow neutrons to produce fission. Chain reactors are presented as an economy; effective use of the neutrons from fission leads to more fission resulting in a power reactor or a criticality excursion. The six-factor formula is presented for managing the neutron budget. This leads to concepts of material and geometric buckling which are used in simple calculations to assure safety from criticality. Experimental measurements and computer code calculations of criticality are discussed. To emphasize the reality, historical criticality accidents are presented in a table with major ones discussed to provide lessons-learned. Finally, standards, NRC guides and regulations, and DOE orders relating to criticality protection are presented.
Date: March 1, 1992
Creator: Fullwood, R.
Partner: UNT Libraries Government Documents Department

Discrete space-time symmetries

Description: Symmetries have always fascinated human beings; they are found in nature, art, and architecture. Physicists, like other scientists have often used symmetries as a basis of their understanding of nature. When the dynamics is unknown, symmetries serve to delineate and define it. When the dynamics is known, symmetries are used to study structure. These two lectures review the theory and present understanding and status of two discrete space-time symmetries,, namely parity (P) and time reversal (T).
Date: January 1, 1992
Creator: Henley, E.M.
Partner: UNT Libraries Government Documents Department

Aspects of symmetry violation

Description: Violations of symmetries have been used to determine (or test) the theoretical dynamics or to study structure. Recent experiments on parity non-conservation and time reversal symmetry, and that depend on spin properties, are used to illustrate both applications.
Date: January 1, 1992
Creator: Henley, E.M.
Partner: UNT Libraries Government Documents Department

Many-body corrections in XAFS

Description: The importance of many-body effects in the theory of XAFS is reviewed. The dominant effects are inelastic losses: Extrinsic losses refer to inelastic losses in the propagation of the photoelectron and are treated using a complex, energy-dependent self-energy. The real part of the self-energy yields an important energy-dependent shift in the phase of the XAFS oscillations, while the imaginary part contributes to the mean-free-path. Intrinsic losses refer to losses associated with the creation of the core-hole. They give rise to shake-up/shake-off contributions to the absorption spectra. These losses may be calculated in terms of a corehole Green's function. Interference between these processes leads to dynamical corrections, which are important at low energies.
Date: January 1, 1992
Creator: Rehr, J.J.
Partner: UNT Libraries Government Documents Department