CrossTalk

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Geometry

An array of 6 detectors are placed radially at a distance of 1 meter from an uncorrelated 252-CF source. The image below shows a top down view of the simulation geometry. The detector setups have a vertical extent of 30".

Detector physics

Summary

Neutron energy deposition from collisions with hydrogen and carbon are converted to electron equivalent light output by MCNP-POLIMI. Neutron collisions occurring over a pulse collection time window of 10 ns are converted to MeVee and summed. When pulse's total light output exceeds 0.3 MeVee, it is considered a detection. The value 0.03 MeVee was chosen as the detector's light output threshold because it corresponds to a mean neutron energy deposit of 0.2 MeV.

The electron equivalent (MeVee) conversion functions for neutrons were measured for plastic (BC 420) scintillators as a function of neutron energy deposit, [math]E_{n}[/math]. For deposit on hydrogen the measurements fit the following quadratic function:

[math]L=0.036E_{n}^{2}+0.125E_{n}[/math]

and for deposit on carbon:

[math]L=0.02E_{n}[/math]

A light output of 0.03 MeVee corresponded to an average neutron energy deposition of 0.2 MeV in the scintillator.

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