zero weight coherent scattering chains in Single_crystal

[erkn]

If incoherent scattering is set to 0, Single crystal may end up in nonending scattering chains with neutron weight set to 0. The particular cause is the probability for tunneling may be <1.

Thus the neutron may end up in the scattering branch, but if no coherent peaks are in the vicinity the weight is simply set to zero (unchecked for). There's a mixing of monte carlo/real scattering models here