Neutronic Performance on a Mixed Cold Moderator of Polyethylene Particles and Liquid Hydrogen.

摘要

We measured the neutronic performance of a mixed moderator of polyethylene particles plus liquid hydrogen as the first test of a mixed type moderator. The energy spectrum from the mixed moderator looks like a linear combination of each spectrum from the polyethylene particles and from liquid hydrogen. We obtained 1.2~1.4 times higher cold neutron intensity, but with a longer pulse width than a decoupled liquid hydrogen moderator in the cold neutron region. In the slowing-down region it gave much higher intensity with almost the same pulse width. We found that this type of moderator exhibits better characteristics as a narrow pulse thermal neutron source.