A final year undergraduate nuclear experiment is described in which the efficiency of a boron trifluoride (BF3) counter is determined. This involves attaching neutron sensitive activation foils to the surface of the counter, exposing the foils to the neutron flux from an Am-Be neutron source for a given time, and measuring the total number of neutrons entering the sensitive volume of the counter. Several basic principles of nuclear physics are incorporated into one single experiment which has proved instructive and challenging to final year undergraduate students. The student is expected to understand and apply topics such as radioactive half-life, absorption of nuclear radiation, nuclear detection, neutron activation and nuclear decay schemes in a single experiment. The experiment can also be converted into an open ended project where, in addition, the student can study several other aspects of the subject including the kinetics of (alpha,n) reactions. (C) 1996 American Association of Physics Teachers. [References: 8]
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