Measurement and Simulation of Neutron Leakage Spectrum with Different Sized Polyethylene Samples

The neutron leakage spectra were measured at 60° by using time-of-flight (TOF) method from three different sizes of polyethylene samples. The measured spectra were compared with the calculated ones simulated with MCNP using three different models (simplified point detector model, complex point detector model, complicated ring detector model), respectively. The result shows that for small sized sample（ø13 cm×ø6 cm）, the calculated results from different models all agree well with experimental ones in n-p scattering peak. For large sized samples （30 cm×30 cm×6 cm,ø40 cm×ø40 cm×6 cm）, the calculated results from complicated ring detector model agree better with the experiment. This conclusion is very important for the next step benchmark experiment with large sized sample.