In a fusion, or H Bomb, the tritium (which is just hydrogen with an extra two neutrons) is that which produces the boom -- the main fuel, as it were. Its a "neutron source" only in the weakest possible sense -- the same way dynamite might be considered to need nitroglycerine as a "neutron source". (I'm not sure that people outside of the bomb building industry really know *for sure* what the geometries used in the atomic weapon that sets off the fusion reaction.)
This also depends on the type of bomb. In a two-stage fusion bomb, you are quite correct - the tritium-deuterium/tritium fusion reaction gives the boom. However, in a three-stage bomb, there is an additional fission reaction, this due to the fact that the neutrons produced by the fusion reaction have the precise energy required to fission U-238. Since U-238 is vastly easier to obtain than enriched U-235, there is no great problem with sticking in half a tonne of it. Around that you can add cobalt jackets, etc, for more interesting effects. -- * * Mikolaj J. Habryn dichro@tartarus.uwa.edu.au * "I'm just another sniper on the information super-highway." PGP Public key available by finger * #include <standard-disclaimer.h>