Source of Be-7 (was job coverage...)

[welch@CEBAF.GOV (welch)]

>>What is the source of these filters?  Might they be high volume air 
     filters with sample volumes somewhere in the Mega-cfm range?  I am 
     interested in how this filter is used and what you credit as to the 
     source of the Be-7.

The source is a high energy electron beam.  Although there is Be-7 in
atmospheric air, we have airborne concentrations well above background.  The
mechanism for production is photon and neutron spallation of O-16 and N-14.
Maybe we can claim that there is just more naturally occuring Be-7 here ......
KW