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Solid state physics program. Final report

Description: During the 17 year period of this research, experimental and theoretical investigations were completed in many aspects of cohesive properties of metals and alloys and dielectric properties of various crystals and glasses together with the temperature and pressure derivatives of both properties. Studies of the magnetization and magnetic anisotropy indicate superparamagnetism is common in oligatomic condensed films and any decreased magnetic moment must be associated with surface atoms. Large intrinsic stresses are associated with growth morphology and impurities at grain boundaries. Transport properties in normal metals have been investigated theoretically. A number of basic theorems for disordered systems were derived. (204 references) (auth)
Date: June 1, 1975
Partner: UNT Libraries Government Documents Department

Progress report No. 51, July 1, 1974--June 30, 1975. Technical summary

Description: Research work in the following areas is briefly reviewed: applied mathematics and mechanics (computational fluid dynamics, controlled thermonuclear research, numerical analysis); computational physics, chemistry, and biology; computer science research (computer netting; programing languages and compilers; operating systems, micro-processor networks, and modular systems); and systems programing, user services, and hardware support. A list of publications is also given. (RWR)
Date: November 1, 1975
Partner: UNT Libraries Government Documents Department

Self-diffusion of Co$sup 60$ in crystals of Co$nu$sub 1-x/O

Description: Tracer self-diffusion coefficients were measured as functions of temperature and deviations from stoichiometry. The arc-transfer technique of crystal growth was found to produce crystal of Co/sub 1-x/O of essentially the same purity as the starting Co rod, and the quality was comparable to commercially available crystals grown by Verneuil process. Measurements at x = 0.005 in Co/sub 1-x/O showed the Co tracer self-diffusion coefficient to be D = 3.88 x 10$sup -4$ exp (--31600 +- 2400/RT) cm$sup 2$/s between 1037 and 1350$sup 0$C. This activation energy is in agreement with measurements made in air, if proper compensation is made for the effect of variation in stoichiometry. Measurements on crystals having deviations between 0.002 and 0.008 at 1150$sup 0$C showed the diffusion coefficient to depend on p/sub O$sub 2$/ as D = 9.74 x 10$sup -9$ p/sub O$sub 2$//sup 1/(3.59)/ cm$sup 2$/s, where p/sub O$sub 2$/ varied between 10$sup -2$.$sup 5$ and 10$sup -0$.$sup 25$ atm. Comparison with thermogravimetric and electrical conductivity measurements confirms that the defects responsible for Co diffusion in the range of temperature and p/sub O$sub 2$/ of this investigation are singly ionized cobalt vacancies. The Co tracer self-diffusion coefficients in single crystals are nearly identical to those in polycrystalline Co/sub 1-x/O. 53 references, 29 fig, 6 tables (DLC)
Date: January 1, 1976
Creator: Rahman, S. F.
Partner: UNT Libraries Government Documents Department

Some effects of parallel energy propagation on the structure of dissipative trapped electron modes

Description: The limitation of ballooning by parallel energy propagation is investigated for the dissipative trapped electron mode, wherein the local energy influx is proportional to the poloidally dependent trapped particle fraction. For small energetic asymmetries [mg less than 2.5 ($Omega$/sub i/a/c/sub s/) (a/R/ sup $sup 3$/$sub 4$/] the structure along the field line is predominantly a phase shift, dictated by the condition that the asymmetric energy input be compensated by parallel energy flow. For large asymmetry, mode number, and parallel arc length, the phase and amplitude variations necessitate an integral equation treatment. (auth)
Date: January 1, 1976
Creator: Sauthoff, N. R.
Partner: UNT Libraries Government Documents Department

Optical properties of Nb--Mo and other alloys of Nb with its nearest neighbors in the periodic table

Description: Optical properties of Nb alloys were investigated. Calorimetric measurements of absorptivity between 0.2 and 5.5 eV were taken for Nb samples with 20, 50, and 80 percent Mo and for Nb samples containing 10 percent Zr, 20 percent V, and 20 percent Ta. Reflectivity data for two of these samples in the ultraviolet region and known reflectivities for the pure metals to 35 eV provided the basis for extrapolation to high energies. The data were Kramers--Kronig analyzed to determine the dielectric function. The structure is discussed in terms of interband transitions as predicted by a rigid band model for the NbMo alloys. (auth)
Date: October 1, 1975
Creator: Black, E. S.
Partner: UNT Libraries Government Documents Department

Application of soft x-ray appearance potential spectroscopy to light lanthanides, 4d transition metals, and insulators

Description: Evaporated films of La, Ce, Yb, Y, Ag--Mn(5 percent), KCl, MnF$sub 2$, CsCl and LaF$sub 3$ were studied using the soft x-ray appearance potential spectroscopy (SXAPS) technique. Studies were also made of bulk polycrystalline samples of Y, Zr, Nb, and Mo. The results are discussed in terms of existing SXAPS theories. Several similarities between soft x-ray absorption (SXA) data and the SXAPS results are discussed, and it is shown that the SXA data can aid in the interpretation of SXAPS spectra when using the well-known self-convolution model. In this approximation the absorption coefficient, $alpha$(E), is substituted for the density of states, N(E-E/sub c/) $Yields$ $alpha$(E). For more localized excitations, a convolution of $alpha$(E) with bremsstrahlung isochromat data, based on Wendin's two density of states formalism is used to predict SNAPS results. (auth)
Date: October 1, 1975
Creator: Smith, R. J.
Partner: UNT Libraries Government Documents Department

Quasilinear theory of ion-cyclotron resonance heating of plasmas and associated longitudinal cooling

Description: It is shown from quasilinear theory that an initially isotropic magnetized plasma will be forced into an anisotropic state in ion-cyclotron resonance heating. Strong heating of perpendicular ion temperature and strong cooling of longitudinal temperature should occur simultaneously. The maximum temperature ratio predicted by quasilinear theory is in exact agreement with that predicted from basic thermodynamic arguments by Busnardo--Neto, Dawson, Kamimura and Lin. Heating by fast hydromagnetic wave is also examined. (auth)
Date: February 1, 1976
Creator: Arunasalam, V.
Partner: UNT Libraries Government Documents Department

Research in nuclear chemistry. Annual progress report, September 15, 1974- -September 14, 1975

Description: The nuclear chemistry research program at Carnegie-Mellon University includes studies of nuclear reactions induced by heavy ions, nuclear properties, nuclear transitions and decay, and the hyperfine interactions of nuclear moments with extranuclear environments. Gamma-ray angular correlation measurements in the decay of $sup 75$Se have been carried out, and the data indicate absence of appreciable perturbation in the $sup 5$/$sub 2$$sup -$ intermediate nuclear state in $sup 75$As. Integral and time-differential perturbed-angular-correlation experiments in $sup 181$Ta have elucidated strong quadrupolar interaction effects in several compounds. The origins of the observed electric field gradients are traceable to chemical bonding effects. Studies have been made of the evaporation residues from complete fusion reactions induced by heavy ion beams in several target nuclei, using a new experimental technique. Measurements of energy spectra, angular distributions, and total cross-sections for these processes have been carried out for $sup 16$O + $sup 27$Al, $sup 20$Ne + Cu, and $sup 20$Ne + In. Proton evaporation spectra in coincidence with evaporation residues were determined in one case. In other studies, light fragments from the reaction of $sup 12$C with $sup 65$Cu were identified in a counter telescope, and cross sections for production of boron isotopes were determined by integration of the measured angular distributions of the several species. The cross-section for the process $sup 12$C + $sup 65$Cu $Yields$ $sup 12$B is found to be very much smaller than radioactivity measurements of $sup 65$Zn from the same reaction, and hence $sup 12$B and $sup 65$Zn are probably not correlated fragments in a two- body break-up. (auth)
Date: July 1, 1975
Creator: Kaplan, Morton
Partner: UNT Libraries Government Documents Department

Environmental {sup 129}I Measurements

Description: Environmental levels of {sup 129}I and natural {sup 127}I have been measured by neutron activation analysis .on samples from throughout the United States at locations near and remote from release points . Highest {sup 129}I concentrations were observed near nuclear fuel reprocessing facilities. Levels of {sup 129}I above natural iodine background were observed at all locations studied. The sample data establishes baseline levels of environmental {sup 129}I for the expanding nuclear industry.
Date: July 29, 1974
Creator: Brauer, F. P.
Partner: UNT Libraries Government Documents Department

Hydrogen Isotope Separation System for the Tokamak Experimental Power Reactor

Description: An isotopic separation system for processing the fuel in the Tokamak Experimental Power Reactor is described. Two cryogenic distillation columns are used in sequence to recover 80% of the hydrogen from a fuel mixture originally containing equal parts of deuterium and tritium with a 1% hydrogen impurity. The hydrogen thus removed contains less than 1/2% tritium, which may be recovered in a separate system designed for that purpose. It is assumed that separation of the deuterium and the tritium is not required. A total tritium inventory of approximately 38,000 Ci (3.8 g) is projected.
Date: March 1, 1976
Creator: Wilkes, W. R.
Partner: UNT Libraries Government Documents Department