Thesis (M.S.)--University of Michigan, 1966.

Thesis (Ph.D.)--University of California, Berkeley, 1960. / "Physics & Mathematics, UC-34" -t.p. "TID-4500 (15th Ed.)" -t.p. Includes bibliographical references.

Neutron diffusion parameter measurements have been made at 21°C in 20, 50, and 80 percent concentrations of heavy and light water, including pure H20 and D2 0 as moderators. Pulsed neutron techniques were used with a 250-kv Cockcroft-Walton accelerator as the pulsed source. The range of bucklings used was from 0.05 cm⁻² to 0.70 cm⁻². The values for the diffusion coefficient, Dₒ; the diffusion cooling coefficient, C; and the transport mean free path, A_tr, were determined from the expansion of the decay constant to second order using iteration procedure. The values of Dₒ, C, and A_tr are tabulated below for the various concentrations, including pure H₂O and D₂O. <table style="width:100%"> <tr> <th>Percent D₂0</th> <th>Dₒ x 10⁻⁴ (cm²sec⁻¹)</th> <th>C x 10⁻⁵ (cm⁴sec⁻¹)</th> <th>λ_tr (cm)</th> </tr> <tr> <td>0</td> <td>3.634±0.048</td> <td>0.161±0.008</td> <td>0.443</td> </tr> <tr> <td>20</td> <td>3.779±0.017</td> <td>0.170±0.032</td> <td>0.515</td> </tr> <tr> <td>50</td> <td>6.964±0.044</td> <td>0.74±0.12</td> <td>0.915</td> </tr> <tr> <td>80</td> <td>11.75±0.68</td> <td>2.19±0.42</td> <td>1.602</td> </tr> <tr> <td>100</td> <td>19.66±1.37</td> <td>3.56±1.08</td> <td>2.670</td> </tr> </table> / Doctor of Philosophy

The neutron diffusion parameters of water and ice were measured by the pulsed source method at two temperatures; 1.0°C. and -19°C. Neutron pulses were obtained at one millisecond intervals by modulating the beam in a Cockcroft-Walton type accelerator. The ₁H³(d,n)₂He⁴ reaction was used to generate neutrons. The samples were contained in cylindrical aluminum cans covered with cadmium. The experiment was conducted inside a large paraffin block which served as a neutron shield and thermal insulator. The temperature of the samples was maintained constant to within ±1°C. Neutrons leaving one surface of the sample were counted in a BF₃ proportional counter. The time distribution of these neutrons was recorded by an eighteen channel time analyzer. The width of each channel was 20 microseconds. The opening of the first channel was delayed 100 microseconds with respect to the start of the neutron burst to minimize harmonics in the neutron decay. A geometric buckling was calculated for each sized sample from B²=[2.405/(R+∈)]²+[π/(H+∈)]² where B² = geometric buckling 2.405 = first zero of J_o Bessel Functions R = radios of cylinder H = height of cylinder ∈ = extrapolation distance The extrapolation distance ∈ was calculated from ∈ =0.71 λ_tr where λ_tr = mean free path of neutrons in water The extrapolation distance was assumed to vary as T^½ where T is the temperature in degrees Kelvin. The measured decay constants, α, were fitted by the method of least squares to a polynomial in B² of the form α = (∑_av) ÷ D_oB² - CB⁴ where ∑_a = the macroscopic absorption cross-section v = the neutron velocity D_o = diffusion coefficient C = diffusion cooling coefficient The resultant values of (∑_av) and D_o for each temperature are below. The data did not permit a determination of C. 1.0°C. (∑_av) = 4595 ± 365 sec⁻¹ D_o = 29600 ± 840 cm²/sec -19°C. (∑_av) = 4355 ± 263 sec⁻¹ D_o = 27050 ± 630 cm²/sec / Ph. D.

Thermal neutron diffusion parameters of O, 20, 50, 80 and 100 percent D₂O in mixtures of light and heavy water were measured by the pulsed neutron technique at room temperature (21°C), near the freezing point of the mixture in the liquid state, and at -20°C in the solid state (ice). A 250-kv pulsed Cockcroft-Walton accelerator, using neutrons from the ₁H²(d,n)₂He³ reaction, was used to generate fast neutrons bursts. The values of the infinite medium decay constant, λ₀, were computed by a least squares fit of λ versus B² data to the expression: λ = λ + D₀B² - CB⁴ The parameters D₀, C, and λ𝗍ᵣ were determined from the above expression after rearranging: λ-λ₀ = D B² - CB⁴ The resulting values of D₀, C, λ, and λ𝗍ᵣ at several temperatures are tabulated. / Ph. D.

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