Talk-Polywell.org

A PMT is a Photo Multiplier Tube.

http://www.eetasia.com/STATIC/PDF/20090 ... S=DOWNLOAD

If that link doesn't work you can get to it through this link:

http://www.eetasia.com/ART_8800565064_4 ... ICLE_ALERT

To count neutrons, you generally use an inorganic scintillator in front of the PMT. Every student of nuclear physics needs to memorize that reference you link, though.