THE NEUTRON TRANSMISSION THROUGH A CYLINDRICAL GUIDE TUBE

The transmission of neutrons or X-rays through a straight cylindrical channel can be determined for an input beam for which the beam diverge nce has azimuthal symmetry. For polar angles greater than the critical angle, the acceptance of trajectories is restricted and allowable tra jectories are close to the perimeter of the channel. The distribution of available polar angles has been calculated, from which both the tra nsmission and the beam profile as a function of distance from the end of the channel can be calculated as a function of polar angle. Since t he distance between successive reflections can be determined, the numb er of reflections per unit length can be calculated as a function of p olar angle. Hence, the distribution of the beam profile for nonperfect reflectivity can be determined.