# How fast is the matter and antimatter reaction compared to nuclear chain reaction?

What I mean is, the nuclear chain reactions take microseconds for every generation and that is the reason that nuclear weapons exist. Because in nuclear reactors the reaction rate is much slower thus it can be controlled and prevent it from exploding. So my question here is about the speed of matter-antimatter reaction. Just imagine we have a kilogram of antimatter, is the annihilation speed enough to make it usable as a weapon ?

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–  raindrop Jan 23 '13 at 8:36
I wonder why this was so heavily downvoted? I think it's quite an interesting question and the answer doesn't seem at all trivial. –  Nathaniel Jan 25 '13 at 8:39
Methinks the same, it's not a silly question at all :-/ –  user17581 Jan 25 '13 at 8:51

There exists an antimatter bomb question on this site so i will only address the "speed of reaction" part of the question.

Strong interactions have a characteristic time of strong interactions take place very fast, of order 10^-24 seconds.

Fission and fusion reactions are due to higher order effects between nuclei and in addition depend on lifetimes of individual nuclear levels. An energy transport equation will also modify times to reach your microsecond claim.

A mass of antimatter meeting a mass of matter, at the interface will react within 10^-24 seconds, but again depending on the shape and masses, a transport equation will determine average speed.The neutron 'lifetime' in nuclear chain reaction of 10^-4 second is the start of timing the build up. As a rough estimate of the complicated transport calculation one can expect a faster annihilation of the bomb by at least 10^4, as there will not be a neutron type delay.

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Thanks for your answer, it has clarified a lot of things. I don't really know how fast the reaction should be to be usable as an explosion, so here is one last question. If we release a kilogram of antimatter to the air, according to what you said, will we get a fast enough reaction for a bomb ? –  Hurricane Jan 25 '13 at 16:38
if it were possible to have a kilogram of antihydrogen gas ( en.wikipedia.org/wiki/Antihydrogen ) then it certainly would react in annihilating with air atoms, but how big/destructive an explosion would be needs a simulation. –  anna v Jan 25 '13 at 18:54
If I am no mistaken, antihydrogen atoms were actually made and contained for a very short time, so it is the most probable form of antimatter if we can produce a larger amount in the future. But why exactly have u chosen antihydrogen gas ? why gas ? –  Hurricane Jan 25 '13 at 20:16
bcause gas is the easiest frm to contain and it will mix by difusion. there has to be mixing, it is not like nuclear fuel.see wiki link or anti h –  anna v Jan 26 '13 at 8:05
@annav It seems like you would gain more insight from researching Protonium. One reason for the (relative) stability is that the orbiting pair needs to lose a large amount of energy before the two come into the range of the strong nuclear force. –  Aron Oct 9 at 3:19