Measurements of the angular distribution and total reaction rate in neutron-proton scattering are described. The emphasis of this work has been to obtain an accurate normalization of the distribution, which is difficult to achieve with neutral beams. Nearly monoenergetic neutrons from the d(p,n)pp reaction were scattered from a liquid hydrogen target. The neutron beam energy was determined from the time of flight with respect to the radio frequency signal of the TRIUMF cyclotron. The differential cross section was measured at 319 and 493 MeV from 10 to 180 degrees in the centre of mass (CM.). Calibrated neutron beam monitors upstream of the scattering target provided an absolute normalization over the whole angular range. Between 10 and 100 degrees CM. a neutron detector consisting of a charged particle veto, a carbon convertor and two trigger scintillators sandwiching 7 multiwire proportional chambers was used to select elastic neutrons by time of flight techniques. The neutron angular distribution was measured with an average precision of 5% and an uncertainty on the normalization of 1.3%. An associated particle experiment (neutrons and recoil protons detected in coincidence) determined the efficiency of the neutron detector and the monitors were calibrated by measuring the incident neutron flux with the neutron detector in the beam, i.e. at zero degrees. The recoil protons were detected in the angular range between 60 and 180 degrees CM. with a precision of 1% to 2% and an error on the normalization of 2.8% at 319 MeV and 3.7% at 493 MeV. Elastic events were selected by time of flight and by either a measurement of magnetic rigidity (momentum) or total energy. The absolute normalization of the two experimental techniques is verified by the overlap of the two measurements and by comparing the integrated differential cross section with the measured total cross section. The neutron-proton total cross section was measured at six energies between 200 and 500 MeV by a transmission type experiment to a precision of 1% to 3%. The systematic corrections were small, of the order of 1%, and the statistical errors were increased to include monitor and beam instabilities. The measurements show a smooth quadratic energy dependence. The data was included in a phase shift analysis and a dispersion relation analysis along with the previous world data. Agreement between the real part of the forward scattering amplitude predicted by the phase shift analysis and by the dispersion relation analysis is improved. The errors on the 1=0 (isoscalar) phase shifts are decreased and to a lesser extent on the 1=1 phase shifts. There is a marked improvement in the smooth variation with energy of the 1=0 phase shifts and a better agreement of the higher partial waves with the theoretical predictions of the Paris potential. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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<p> The dispersion relations in Platinum have been measured at 90°K by the inelastic scattering of thermal neutrons. Born-von Karman models of the force system have been calculated by a process of linear least squares fitting to the dispersion curves. Fourth neighbour forces with weaker interactions extending to at least sixth neighbours are required to fit the data. A frequency distribution has been computed using the force constants of the most realistic model.</p> <p> Some interesting anomalous behaviour in the [035]T1 branches of both Platinum and Palladium has been investigated in detail at temperatures of 90,296 and 473°K. A qualitative analysis indicates that the behaviour is caused by the Kohn effect though its manifestation is rather unusual.</p> / Thesis / Master of Science (MSc)

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A single crystal neutron spectrometer using a copper crystal has been designed and constructed for the purpose of studying the low energy (<1 ev) neutron spectrum from the V.P.I. reactor. The basic theory necessary for the design, the details of the spectrometer, calibration data and method of operation are presented in this thesis. A relation between angle of diffraction and neutron energy is obtained from the known lattice spacing of the copper crystal. A measure of the total cross section of cadmium from 0.01 to 1.0 ev has been obtained from transmission data for a thin cadmium sheet. The position of the low energy resonance peak confirms the computed calibration. The resolution of the instrument and the intensity of the diffracted beam as a function of energy were studied in order to ascertain the usable range of the spectrometer. / Master of Science

The objects of this research to construct the necessary equipment for use with the solid stets surface-barrier detectors employed neutron detectors. This research also had the ultimate aim of showing the possibility of producing a neutron spectrometer using the proton recoil telescope with the surface-barrier detector. These objects were fulfilled. From the results with the protein recoil telescope, there is a possibility of producing a neutron spectrometer using the proton recoil telescope and surface-barrier detectors. However, if s thinner radiator were employed, the energy spread of the recoiling protons would be less end ultimately improve the resolution. The radiator in this trial had a large -dE/dx for protons and caused considerably straggling in the proton energy. Besides the straggling produced by the radiator there was some effect on energy spread by the collimator. A collimator with essentially an infinite number of baffles was used, since it consisted of a hole drilled through the collimator material. If the number of baffles were decreased, the possibility of protons being scattered from the collimator walls and benign detected, but at a lower energy, would be eliminated. With this batter collimation there will be a smaller solid angle and ultimately better resolution. Evacuating the chamber should also improve the resolution. Thus with some improvements, the present equipment could be changed into a neutron spectrometer with good energy resolution. / Master of Science