In reply to Eric Walker's message of Sun, 24 Mar 2013 12:39:44 -0700: Hi, [snip] >Lou, > >I wish it was great work. Unfortunately, there was an important flaw once >again. From Robin's Web site I obtained the total cross sections, and from >your Web site I obtained the neutron capture cross sections. It is the >total cross section, only one component of which is the neutron capture >cross section, that should be used in the attenuation calculation.
...maybe, however neutrons that bounce around without being absorbed, still contribute to the total. IOW if you are trying to calculate how many escape from the material, then only the neutrons that are actually absorbed/captured won't make it. The rest are free to continue trying to get out. ...however, that having been said, the path that the "bouncing" neutrons follow would be longer because of a "random-walk". Since the path is longer, their chances of being captured increases...but maybe this is already included in the concept of cross-section? BTW I also think you should be using the thermal cross-section, i.e. the cross-section at the temperature of the experiment. That should be at an energy of roughly 0.025 eV, which is a commonly used value, for just that reason. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
