neutron bomb vs physics package

neutron bomb

noun
  • An atomic bomb that produces a greater amount of neutrons, and a lesser amount of blast; the intention being to create equal lethal neutron radiation and blast radii which increases the effectiveness of the weapon against armour while reducing collateral damage. 

physics package

noun
  • The part of any equipment which requires advanced knowledge of physics to design; especially the core nuclear components of a nuclear weapon 

How often have the words neutron bomb and physics package occurred in a corpus of books? (source: Google Ngram Viewer )