Instrumentation – Silver activation detector installed

Per Eric Lerner:

We now have a silver activation neutron detector working.  This instrument, constructed by Dr. Haboub based on a design that has been calibrated by others, uses a standard method for counting neutrons and is much more sensitive than the solid-state commercial neutron dosimeters we already have.

Neutrons from the device are moderated down to lower energies by layers of plastic and then collide with two thin silver foils.  Some of the silver absorbs the neutrons to form radioactive isotopes that decay very rapidly—one half-life in 24 seconds.  The particles emitted by the decaying silver nuclei go through several layers of scintillator plastic, creating flashes of light that are amplified by a photomultiplier tube.  The pulses from this tube go to electron circuitry which counts them.  The number of counts is then proportional to the number of neutrons emitted.  We are currently using this device on each shot, but are still calibrating it and it is not yet as reliable as the Far Time-of-Flight detectors in measuring neutrons.  Soon it will be a cross-check on the FTF.