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Wall effects
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  • The size of a BF3 tube is not infinite, the effects occur within the tube and are seen in the produced spectrum. If either particle (alpha or lithium) strikes the chamber wall a smaller pulse is produced.
  • Due to the incoming neutron carrying no appreciable momentum, the two reaction products must be oppositely directed. Therefore if the alpha hits the wall the 7Li recoil is likely to deposit its full energy within the gas, and vice versa. These procedures can be seen in the inset and compared with points in the graph.
  • The gas pressure and neutron detector material play a large part in the extent of the wall effects. The diameter of the tube being increased also reduces the wall effects.

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