From: Sunil C. (email@example.com)
Date: Fri Feb 02 2007 - 05:46:56 CET
Thanks Mario for the references. The link pointing to CERN ref is is in
French. IS there an English version?
Regarding the isotropocity I have seen some calculation that predict symmetric
behavior around 90 degree in the CM frame for any compound nucleus systems.
Since GDR is the predominant component in the photo nuclear reactions even at
2 GeV, the photo neutrons would be from a compound nucleus like system. For
Photons, CM and lab would not be much different and probably this behaviour.
As for Nisy's question, The forward direction is always 10 radiation lengths
while the lateral dimensions are 5 cm height and 5 cm width
for all target elements.Even for Cu these lateral dimensions would be almost 4
radiation lenghts. But for say W, whose
radiation length is 0.35 cm (IAEA 188) these lateral dimensions are almost 10
radiation lengths which is what my forward thickness is. W shows a dip at 90
degree instead of peak. So does U. Pb shows a mild peak at 90 degree.
I have attached an input for the case of Cu and plots of angular distribution
of photoneutrons in n/sr divided by the incident electron energy.
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