Do Heavy or Light Elements Better Stop Slow Neutrons?

[kylemadigan]

Hey guys,
I was wondering if light or heavy elements would be better at stopping slow moving neutrons? And how come? By heavy and light, i mean mass.

I always thought a heavy element would have a better chance of stopping particles because they have a high probability of smacking the heavy elements' nucleus, but does this apply to neutrons flying through other heavy elements? Kinda like Rutherford's experiment eh?

Thanks guys.

 

[arcnets]

kylemadigan,
since the neutron has zero charge, it does not feel any electromagnetic repulsion from the nucleus (the force that governs Rutherford's experiment of elastic scattering). Instead, the neutron goes right through, thus probing the inner structure of the target nucleus. If it is absorbed (an inelastic process), then this happens via resonance.
Yes I agree, the heavier a nucleus is, the more resonance peaks will be there. However, experiment has found that the cross-section for absorption can vary by a factor of ~100, depending on neutron energy. Here's a quote from Paul A. Tipler's 'Physics': "Some isotopes, like e.g. ¹¹³Cd, reach a cross-section of more than 50000 barns and thus are very useful in shielding low-energy neutrons."

 

[kylemadigan]

ahh very interesting information arcnets. thanks for the all the insightful info m8. thanks to you and hallsofivy.