Something I've been wondering about, here. We all know that the primary effects of an antimatter weapon would be similar but better than a nuclear weapon. But what about the secondary effects? The secondary effects of fission and fission-fusion bombs are pretty well-understood, but what about antimatter? It seems to be often assumed that an antimatter weapon would be clean, compared to nuclear weapons, since its reactants would perforce be annihilated very soon, especially within an atmosphere. However, I have some specific questions about secondary effects: Could a sufficiently large antimatter explosion on a planetary surface or in the atmosphere heat the sphere of expanding plasma quickly enough that would form around ground zero to undergo fusion? If so, would neutron flux and subsequent capture produce significant quantities of radioactive material? Likewise, would gamma ray photodisintegration of matter nuclei contribute any significant radioactive byproducts?