For most purposes, a simple PMT, pre-amp, and a good HP electronic counter will do fine. Most such modern counters have a "level" control which will set a trigger threshold for counting. This is a defacto, non-calibrated pulse height discriminator. With this, you can count well.
However, it would be nice to have a good oscilloscope to set this pulse discrimination level and verify counting of narrow pulses. With the preamp output signal looped through the scope to the counter, (be sure to terminate in 50 ohms), set the counter level control to elimenate (not count) the "grass" completely. Next, if possible, hold a fairly hot radioactive source (a, b, y) up to your detector. If this increases your count rate over background, increase the level on the counter even higher and elimenate this as spurious as well. Now you should have only a neutron counter. Checking the waveforms on Scott Little's site will be instructive here too.
While the above is a poor man's system, it is quite serviceable, especially with the BC-720 neutron scintillator by Bicron.
Richard Hull
Created on Tuesday, April 10, 2001 3:15 PM EDT by Richard Hull