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Absolute measurement of the critical scattering cross section in cobalt

Description: Small-angle neutron scattering techniques have been used to study the angular distribution of the critical scattering from cobalt above T/sub c/. These measurements have been put on an absolute scale by calibrating the critical scattering directly against the nuclear incoherent scattering from cobalt. In this way the interaction range r$sub 1$, which appears in the classical and modified Ornstein--Zernike expressions for the asymptotic form of the spin pair correlation function and is related to the strength of the spin correlations, has been determined. We obtain r$sub 1$/a = 0.46 +- 0.03 for the ratio of the interaction range to the nearest-neighbor distance in cobalt. This result is in good agreement with theoretical predictions. Lack of agreement among previous determinations of the ratio r$sub 1$/a made in iron failed to provide a definitive comparison with theory. (auth)
Date: January 1, 1975
Creator: Glinka, C. J.; Minkiewicz, V. J. & Passell, L.
Partner: UNT Libraries Government Documents Department

Measured and evaluated fast neutron cross sections of elemental nickel

Description: Fast neutron total and scattering cross sections of elemental nickel are measured. Differential elastic scattering cross sections are determined from incident energies of 0.3 to 4.0 MeV. The cross sections for the inelastic neutron excitation of states at: 1.156 +- 0.015, 1.324 +- 0.015, 1.443 +- 0.015, 2.136 +- 0.013, 2.255 +- 0.030, 2.449 +- 0.030, 2.614 +- 0.020 and 2.791 +- 0.025 MeV are measured to incident neutron energies of 4.0 MeV. The total neutron cross sections are determined from 0.25 to 5.0 MeV. The experimental results are discussed in the context of optical and statistical models. It is shown that resonance width-fluctuation and correlation effects are significant. The present experimental and theoretical results, together with previously reported values, are used to construct a comprehensive evaluated elemental data file in the ENDF format. Some comparisons are made with previously reported evaluated files. In addition, some selected reactions which are widely used in dosimetry and other applications are presented as supplemental evaluated isotopic-data files. The numerical quantities are presented in tabular form. (3 tables, 29 figures) (auth)
Date: July 1, 1975
Creator: Guenther, P.; Smith, A.; Smith, D.; Whalen, J. & Howerton, R.
Partner: UNT Libraries Government Documents Department

Cu(n,x$gamma$) reaction cross section for incident neutron energies between 0.2 and 20.0 MeV

Description: Differential cross sections for the neutron-induced gamma-ray production from copper have been measured for incident neutron energies between 0.2 and 20.0 MeV. The Oak Ridge Linear Accelerator (ORELA) was used to provide the neutrons and a NaI spectrometer to detect the gamma rays at 125$sup 0$. The data presented are the doubly differential cross section, d$sup 2$sigma/d$Omega$dE, for gamma-ray energies between 0.3 and 10.6 MeV for coarse intervals in incident neutron energy. The integrated yield of gamma rays of energies greater than 300 keV with higher resolution in the neutron energy is also presented. The experimental results are compared with previous measurements made at ORELA and with the Evaluated Neutron Data File (ENDF/B-IV, MAT 1295). 41 figures, cross section tables. (auth)
Date: February 1, 1976
Creator: Chapman, G.T.
Partner: UNT Libraries Government Documents Department

$sup 63$Cu and $sup 65$Cu neutron elastic and inelastic scattering cross sections from 5.50 to 8.50 MeV

Description: Measured neutron elastic and inelastic scattering cross sections for / sup 63/Cu and /sup 65/Cu between 5.50 and 8.50 MeV are presented and compared with elastic data of Holmqvist and Wiedling and with ENDF/B III MAT 1085 and 1086. The elastic differential cross sections are in fair agreement with those of Holmqvist and Wiedling in shape. The angle-integrated differential elastic cross sections are systematically higher by as much as 28% than those of Holmqvist and Wiedling above 5 MeV, a situation similar to that found in comparing the two sets of data for other elements. ENDF/B III MAT 1085 and 1086 angular distributions underestimate the elastic forward peak below 20 deg. when compared with experimental results and display unphysical fluctuations due to the use of a Legendre series of order 20 where order 9 is the highest required by the data. An evaporation model with temperature ranging from 0.8 to 1.05 MeV reasonably describes inelastic scattering to levels in the residual copper nuclei of excitation energy above 3.2 MeV. (auth)
Date: February 1, 1974
Creator: Kinney, W.E. & Perey, F.G.
Partner: UNT Libraries Government Documents Department

Natural nickel and $sup 60$Ni neutron elastic and inelastic scattering cross sections from 4.07 to 8.56 MeV

Description: Measured neutron elastic and inelastic scattering cross sections for natural nickel between 4.07 and 8.56 MeV are presented and compared with the elastic differertial cross sections of Holmqvist and Wiedling and with ENDF/B III MAT 1123. The elastic differential cross sections are in general agreemert with those of Holmqvist and Wiedling but our angle-integrated differertial elastic cross sections are systemati cally higher by about 10% than those of Holmqvist and Wiedling above 4.6 MeV, a situation found in comparing the two sets of data for other elements. The ENDF/B II1 MAT 1123 elastic angular distributions are found to be in poor agreement with experimertal results from 4 to 8.5 MeV, though the ENDF/B III MAT 1123 angle-integrated differertial elasti c cross sections agree generally within experimertal uncertairties with our results over this energy range. Additional measurements of /sup 60/Ni neutron elastic and inelastic scattering cross sections at 4.34 and 4.92 MeV are given and compared with previous results from 6 to 8.5 MeV and with natural nickel results. Agreement is shown to be excellent. Inelastic scattering cross sections to the 1.450 MeV level in sup 58/Ni are computed from the natural nickel and /sup 60/Ni data. An evaporation model of inelastic scattering to levels of excitation energy in the residual nucleus below 6 MeV is found to be of questionable validity. (auth)
Date: January 1, 1974
Creator: Kinney, W.E. & Perey, F.G.
Partner: UNT Libraries Government Documents Department

Effect of free-particle collisions in high energy proton and pion-induced nuclear reactions

Description: The effect of free-particle collisions in simple ''knockout'' reactions of the form (a,aN) and in more complex nuclear reactions of the form (a,X) was investigated by using protons and pions. Cross sections for the $sup 48$Ti(p,2p)$sup 47$Sc and the $sup 74$Ge(p,2p)$sup 73$Ga reactions were measured from 0.3 to 4.6 GeV incident energy. The results indicate a rise in (p,2p) cross section for each reaction of about (25 +- 3) percent between the energies 0.3 and 1.0 GeV, and are correlated to a large increase in the total free-particle pp scattering cross sections over the same energy region. Results are compared to previous (p,2p) excitation functions in the GeV energy region and to (p,2p) cross section calculations based on a Monte Carlo intranuclear cascade-evaporation model. Cross section measurements for ($pi$/sup +-/, $pi$N) and other more complex pion-induced spallation reactions were measured for the light target nuclei $sup 14$N, $sup 16$O, and $sup 19$F from 45 to 550 MeV incident pion energy. These measurements indicate a broad peak in the excitation functions for both ($pi$,$pi$N) and ($pi$,X) reactions near 180 MeV incident energy. This corresponds to the large resonances observed in the free-particle $pi$$sup +$p and $pi$$sup -$p cross sections at the same energy. Striking differences in ($pi$,$pi$N) cross section magnitudes are observed among the light nuclei targets. The experimental cross section ratio sigma($pi$$sup -$,$pi$$sup -$n)/ sigma($pi$$sup +$,$pi$N) at 180 MeV is 1.7 +- 0.2 for all three targets. The experimental results are compared to previous pion and analogous proton-induced reactions, to Monte Carlo intranuclear cascade-evaporation calculations, and to a semi-classical nucleon charge exchange model. (108 references) (auth)
Date: July 1, 1975
Creator: Jacob, N.P. Jr.
Partner: UNT Libraries Government Documents Department

High resolution neutron total cross section measurements with the (A) ORNL linac and (B) the Columbia University's Nevis Synchrocyclotron and (C) with B.N.L. HFBR. Progress report, April 1, 1975--March 31, 1976

Description: The research involved the measurement, analysis and interpretation of high resolution neutron total and partial cross sections in the neutron energy range of few eV to few hundred keV in the following nuclei: Bi, Ta, Natural Copper, Natural Zinc, separated isotopes of copper, iron and zinc, e.g., $sup 54$Fe, $sup 56$Fe, $sup 58$Fe, $sup 63$Cu, $sup 65$Cu, $sup 64$Zn, $sup 66$Zn, $sup 67$Zn, $sup 68$Zn, $sup 70$Zn and Mn, Co, V. Some of these measurements were performed with the Columbia University's neutron velocity selector and the measurements on separated isotopes of iron, copper and zinc were performed with the Oak Ridge electron linear accelerator. By using area and shape analysis of resonances, the data were analyzed to extract the values of resonance parameters such as resonance energies (E/sub o/), neutron widths ($lambda$/sub n/), capture widths ($lambda$/sub $gamma$/) etc. The systematics of these results were investigated in detail. The results of these investigations have been submitted for publication in professional journals. (auth)
Date: December 1, 1975
Creator: Garg, J.B.
Partner: UNT Libraries Government Documents Department