hydrogen bomb vs neutron bomb

hydrogen bomb

noun
  • A thermonuclear bomb that derives its destructive power from the fusion of isotopes of hydrogen (deuterium and tritium). 

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. 

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