Optimal Detector Thickness

6Li has a higher chance of detecting a neutron if the neutron is lower in energy; this is accomplished by moderating the neutron, good moderators are water, plastic, or anything with a bunch of hydrogen (a neutron can lose all of it's kinetic energy to hydrogen).  We can then increase our detection effiency by moderating the neutron's that come into our detector.  This is the front thickness.  You also want a rear moderator / reflector to reflect neutrons back into the detector; this is the rear thickness.

The data sets are grouped by rear thickness.  The interaction rate will  asymptotically approach some limit for the rear shield thickness, but for practical purposes it needs to be a few (5 cm or so) to have light collection.

Anyway, thought it was very cool.