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Geometrical Effects on the Resonance Absorption of Neutrons


Ludewig, Hans (1966) Geometrical Effects on the Resonance Absorption of Neutrons. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/DDW9-CY15.


An investigation was conducted to estimate the error when the flat-flux approximation is used to compute the resonance integral for a single absorber element embedded in a neutron source.

The investigation was initiated by assuming a parabolic flux distribution in computing the flux-averaged escape probability which occurs in the collision density equation. Furthermore, also assumed were both wide resonance and narrow resonance expressions for the resonance integral. The fact that this simple model demonstrated a decrease in the resonance integral motivated the more detailed investigation of the thesis.

An integral equation describing the collision density as a function of energy, position and angle is constructed and is subsequently specialized to the case of energy and spatial dependence. This equation is further simplified by expanding the spatial dependence in a series of Legendre polynomials (since a one-dimensional case is considered). In this form, the effects of slowing-down and flux depression may be accounted for to any degree of accuracy desired. The resulting integral equation for the energy dependence is thus solved numerically, considering the slowing down model and the infinite mass model as separate cases.

From the solution obtained by the above method, the error ascribable to the flat-flux approximation is obtained. In addition to this, the error introduced in the resonance integral in assuming no slowing down in the absorber is deduced. Results by Chernick for bismuth rods, and by Corngold for uranium slabs, are compared to the latter case, and these agree to within the approximations made.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Applied Mechanics and Physics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Mechanics
Minor Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Lurie, Harold
Thesis Committee:
  • Unknown, Unknown
Defense Date:11 November 1965
Funding AgencyGrant Number
Union ScholarshipUNSPECIFIED
Record Number:CaltechTHESIS:09242015-135757893
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9174
Deposited On:24 Sep 2015 21:29
Last Modified:05 Mar 2024 22:13

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