H-bomb vs neutron bomb

H-bomb

noun
  • A hydrogen bomb. 

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 H-bomb and neutron bomb occurred in a corpus of books? (source: Google Ngram Viewer )