antimatter weapons

[fire400]

what do you see?

what do you want to see?

 

[lyssword]

black hole ball thing, haven't you played quake 4?

 

[Super Nade]

Originally posted by: lyssword
black hole ball thing, haven't you played quake 4?

lol!!!!

 

[imported_Hamzter]

You realise that they don't exist right? You'll probably never see any kind of weapon in the form of a gun if that's what you're hoping, the only possible use for antimatter is a bomb, and one hell of an unstable bomb at that. They're unlikely to ever be practical though, since the antimatter has to be created whereas nukes you already have the material, you just have to dig it up. The antimatter also has to be contained since it will react with absolutely anything it touches, so you'd need a strong magnetic field which is prone to failure.

What kinda antimatter weapon were you imagining?

 

[fire400]

Originally posted by: Hamzter
You realise that they don't exist right? You'll probably never see any kind of weapon in the form of a gun if that's what you're hoping, the only possible use for antimatter is a bomb, and one hell of an unstable bomb at that. They're unlikely to ever be practical though, since the antimatter has to be created whereas nukes you already have the material, you just have to dig it up. The antimatter also has to be contained since it will react with absolutely anything it touches, so you'd need a strong magnetic field which is prone to failure.

What kinda antimatter weapon were you imagining?

starcraft scout: air-to-air weapon: "anti-matter missiles"

..or a ball of black?

 

[Biftheunderstudy]

Also, unlike fusion and fission, anti-matter/matter reactions do not undergo a chain reaction so ball of antimatter wouldn't explode--per se.

 

[FallenHero]

Originally posted by: Biftheunderstudy
Also, unlike fusion and fission, anti-matter/matter reactions do not undergo a chain reaction so ball of antimatter wouldn't explode--per se.

I thought they reacted and exploded, but it was a 1:1 ratio, where one antimatter atom coming into contact with a matter atom didnt result in more antimatter/matter reactions. They just simply released all their energy and ceased to be.

 

[Biftheunderstudy]

True.
However, in the case of fission, the fissile material breaks into two pieces plus some neutrons. These neutrons radiate out and interact with the next available piece of fissile material. When the density is high enough, the neutrons don't have to go very far before they hit an atom and so a cascade happens--i.e. chain reaction. The amount of energy release is a sort of exponential growth.
In the case of antimatter, like you said its a 1:1 reaction. The energy released by the inital pieces might even serve to keep the rest of the anti-matter from coming in contact with the rest of the normal matter.
Even with a very high constant, exponential still beats linear.

 

[gsellis]

Originally posted by: Biftheunderstudy
True.
However, in the case of fission, the fissile material breaks into two pieces plus some neutrons. These neutrons radiate out and interact with the next available piece of fissile material. When the density is high enough, the neutrons don't have to go very far before they hit an atom and so a cascade happens--i.e. chain reaction. The amount of energy release is a sort of exponential growth.
In the case of antimatter, like you said its a 1:1 reaction. The energy released by the inital pieces might even serve to keep the rest of the anti-matter from coming in contact with the rest of the normal matter.
Even with a very high constant, exponential still beats linear.

If you were techinically advanced enough to make anti-matter, it would be very easy to create an implosion device using a field change in the magnetic container. You just collapse a shell of matter on the anti-matter in a similar fashion as an implosion Plutionium device. The "collapse" would be in the microsecond range. But it would mean that there would be a limit on the amount of anit-matter you can use. You have to increase the available simultaneous contact area. But also remember that you still are going to get reaction will all of the anti-matter as it suddenly has a matter everywhere to react with after the field is gone, even in the explosion. Matter is converted to energy in a fission device and it is a very small amount (they are not that efficient.)

 

[imported_Hamzter]

I doubt the energy release would be linear, as soon as the first bit of antimatter reacted with matter it would release radiation and heat the rest of the antimatter, which would expand at a huge rate, the hotter the antimatter gets the faster it's travelling and the faster the reaction. Granted it probably won't be on the scale of fission, but I doubt it'd matter whether the reaction takes a millisecond or a nanosecond, what counts is the energy released.

What exactly do you mean by it's not an explosion per se? I've always thought of an explosion as an uncontrolled reaction, which this certainly would be!

 

[Biftheunderstudy]

Problem is, to get the antimatter to annihilate it needs to find its anti partice. You would need a pure sample of each. Next(I speculate on this part) when the reaction starts the other pieces are being pushed apart making it much harder to find an antiparticle in the soup that ensues considering the release of proton-antiproton energy scale would make all sorts of virtual elementary particles which might start forming ions and stuff.

In the case of fission, when a neutron is released all it has to do is find a uranium atom and BLAMO you have energy plus a whole bunch more neutrons. Soon you have many more neutrons than uranium atoms--I think this is somewhat akin to a population inversion.

I'm not sure on all of this, I don't know if anyone is since I don't think anyone has attempted to put a bunch of antimatter together to see if it will annihilate spectacularly.

Now, I'm not saying that the energy release wouldn't be large, tremendously large in fact. Its just that the destructive power of the fission bomb comes not solely from the amount of energy release but the reaction rate. The reaction rate and yields of nukes are closely guarded secrets last time I heard. The reaction rate of antimatter is probably not linear, but I think a linear rate is the upper bound since best case scenario is a one to one reaction.

That said, there probably is some critical density where the reaction happens close to the theoretical limit and I'm also sure there are people working on this.

 

[silverpig]

Originally posted by: Biftheunderstudy
Problem is, to get the antimatter to annihilate it needs to find its anti partice. You would need a pure sample of each. Next(I speculate on this part) when the reaction starts the other pieces are being pushed apart making it much harder to find an antiparticle in the soup that ensues considering the release of proton-antiproton energy scale would make all sorts of virtual elementary particles which might start forming ions and stuff.

In the case of fission, when a neutron is released all it has to do is find a uranium atom and BLAMO you have energy plus a whole bunch more neutrons. Soon you have many more neutrons than uranium atoms--I think this is somewhat akin to a population inversion.

I'm not sure on all of this, I don't know if anyone is since I don't think anyone has attempted to put a bunch of antimatter together to see if it will annihilate spectacularly.

Now, I'm not saying that the energy release wouldn't be large, tremendously large in fact. Its just that the destructive power of the fission bomb comes not solely from the amount of energy release but the reaction rate. The reaction rate and yields of nukes are closely guarded secrets last time I heard. The reaction rate of antimatter is probably not linear, but I think a linear rate is the upper bound since best case scenario is a one to one reaction.

That said, there probably is some critical density where the reaction happens close to the theoretical limit and I'm also sure there are people working on this.

It has nothing to do with rate. Simple E = mc**2 is what you want. More m getting annihilated gives more E which makes a bigger boom.

It also wouldn't be hard for a 1kg piece of anti iron (or whatever) to annihilate when brought to atmosphere. The air molecules at room temperature move at something like 700 m/s...

 

[f95toli]

Originally posted by: Biftheunderstudy

In the case of fission, when a neutron is released all it has to do is find a uranium atom and BLAMO you have energy plus a whole bunch more neutrons. Soon you have many more neutrons than uranium atoms--I think this is somewhat akin to a population inversion.

Not quite, the crossection for a neutron to "split" a nuclei is pretty small AND the neutron must have the right speed, if it is too fast or too slow nothing will happen.
The crossectiion for matter-antimatter annhilation is therefore presumably much, much higher than for a fission process.



(btw, "crosssection" is a measure of the probabilty for a reaction to take place in nuclear physics)

 

[Biftheunderstudy]

The yield of the bomb really is a measure of how far the damage is spread. The reaction rate gives rise to the shockwave produced, if the reaction rate is too slow you have no shockwave. And in the case of the nuke, the shockwave does most of the physical damage, that and the vacuum effect.

If I'm not mistaken, U-238 has a relatively high crosssection for fission. When in critical mass quantities the process is run-away, you don't have to even touch the stuff and it'll chain reaction all on its own. Relative to the crosssections for fission for other atoms that is. Remember antimatter annihilation needs the right speed as well or you get funny things like positronium.

P.S.
What I meant by the virtual particles being created was that they would lengthen the time of reaction since the energy would be tied up in mass again for a little while.

 

[gsellis]

Originally posted by: f95toli

Originally posted by: Biftheunderstudy

In the case of fission, when a neutron is released all it has to do is find a uranium atom and BLAMO you have energy plus a whole bunch more neutrons. Soon you have many more neutrons than uranium atoms--I think this is somewhat akin to a population inversion.

Not quite, the crossection for a neutron to "split" a nuclei is pretty small AND the neutron must have the right speed, if it is too fast or too slow nothing will happen.
The crossectiion for matter-antimatter annhilation is therefore presumably much, much higher than for a fission process.



(btw, "crosssection" is a measure of the probabilty for a reaction to take place in nuclear physics)

Yep. My dad used to put it in prospective. The Universe could exist in a wash tub as neutrons with all the space removed. There is a LOT of space between particles in matter.

//Dad worked at Princeton doing biochem analysis on animals exposed to Able and Baker tests. His manager was that guy who formulated E=mc**2.

 

[silverpig]

Originally posted by: Biftheunderstudy
The yield of the bomb really is a measure of how far the damage is spread. The reaction rate gives rise to the shockwave produced, if the reaction rate is too slow you have no shockwave. And in the case of the nuke, the shockwave does most of the physical damage, that and the vacuum effect.

If I'm not mistaken, U-238 has a relatively high crosssection for fission. When in critical mass quantities the process is run-away, you don't have to even touch the stuff and it'll chain reaction all on its own. Relative to the crosssections for fission for other atoms that is. Remember antimatter annihilation needs the right speed as well or you get funny things like positronium.

P.S.
What I meant by the virtual particles being created was that they would lengthen the time of reaction since the energy would be tied up in mass again for a little while.

No it's not. The yield is how much energy is produced. When you talk about a 1 megaton bomb you are equating the energy released in that bomb to the energy released by detonating 1 million tons of TNT. You can probably google for yourself how much energy is released in one kilogram of TNT.

Reaction rate has almost nothing to do with it. All of the times we are talking about here are nanosecond scale.

You're also misusing the term cross section. You talk about the cross section of a reaction given (in general) two particles and two energies. You can talk about the cross section for an electron plus a positron to produce two gamma rays. If you really want to nitpick I guess you could talk about calculating a cross section for U-238 decay using QCD (ie looking at just the strong interactions in the nucleus), but I'm fairly certain that no one in the world would be able to calculate it for you.

Also U-238 isn't used in bombs. It's primarily P-239 or U-235.

Antimatter annihilation doesn't need the right speed at all as far as I know. You can collide electron/positron pairs at pretty much whatever energy you like. There are several such colliders in the world, the old CERN being one of them. LHC will collide protons/anti-protons at various energies as well.

Sure, you might produce positronium in an antimatter reaction, but it'd decay almost instantly as well. All of these virtual particle pairs would re-annihilate or decay themselves in 10^-20 seconds or so.

 

[silverpig]

Oh, and a funny tidbit for those who don't know:

As f95toli already said, a cross section is the probability for a reaction to happen. You basically take two spheres, project along a direction of travel and see how much/if they overlap. Imagine standing in a forest with a bow and arrow. You want to hit a tree x distance away. The probability of you doing so depends on the width (cross section) of the tree.

As a joke, physicists decided to make the official unit of cross section the "barn" (that neutrino couldn't hit the broad side of a barn)...

 

[QuantumPion]

An anti-matter bomb with the same equivalent energy release of a nuclear bomb on earth would look pretty much the same, although the antimatter bomb would create little to no fallout, only a prompt radiation burst. Also, designing the bomb would be trivial if you are able to contain the anti-matter in the first place. Lets say your bomb is composed of a bunch of anti-protons spinning around in an electric field in a vacuum taurus. Simply turn off the field, and the positrons will all smash into the sides of the container. The high energy gamma rays will cause the casing to heat up tremendously and explode. There is no need to contain the bomb for the reaction to complete like a fission weapon, because any anti-protons that get thrown out will inevitably collide with a regular proton and annihilate anyway within a short distance.

 

[Biftheunderstudy]

Interesting to note, although correct that the energy conversion is 100% how this energy is transmitted is important. 50 to 60% of the energy is carried away as neutrinos, these come from the pions which are produced from a long list of decaying particles created by the high energy gammas. The pions are actually the things which do the heating up of the air or whatever is nearest. For this reason the reaction rate although extremely important in nuclear munitions is not so important in AM reactions since the shock wave is an adiabatic expansion of heated plasma.

P.S.
The ground state of positronium has a lifetime in the nanoseconds, the 2S state however lasts milliseconds and the other states are sure to have long lifetimes as well. An excited positronium cascades from the high energy state to the ground state releasing photons as it goes--A fairly lengthy process. This is the main phenomenon happening in PET scanners.

 

[Nathelion]

Originally posted by: QuantumPion
An anti-matter bomb with the same equivalent energy release of a nuclear bomb on earth would look pretty much the same, although the antimatter bomb would create little to no fallout, only a prompt radiation burst. Also, designing the bomb would be trivial if you are able to contain the anti-matter in the first place. Lets say your bomb is composed of a bunch of anti-protons spinning around in an electric field in a vacuum taurus. Simply turn off the field, and the positrons will all smash into the sides of the container. The high energy gamma rays will cause the casing to heat up tremendously and explode. There is no need to contain the bomb for the reaction to complete like a fission weapon, because any anti-protons that get thrown out will inevitably collide with a regular proton and annihilate anyway within a short distance.

An antimatter explosion would generate TONS of fallout, lots of unstable isotopes would be created and surrounding material would be irradiated. This is one good reason why an AM spaceship drive is somewhat... impractical.

 

[QuantumPion]

Originally posted by: Nathelion

Originally posted by: QuantumPion
An anti-matter bomb with the same equivalent energy release of a nuclear bomb on earth would look pretty much the same, although the antimatter bomb would create little to no fallout, only a prompt radiation burst. Also, designing the bomb would be trivial if you are able to contain the anti-matter in the first place. Lets say your bomb is composed of a bunch of anti-protons spinning around in an electric field in a vacuum taurus. Simply turn off the field, and the positrons will all smash into the sides of the container. The high energy gamma rays will cause the casing to heat up tremendously and explode. There is no need to contain the bomb for the reaction to complete like a fission weapon, because any anti-protons that get thrown out will inevitably collide with a regular proton and annihilate anyway within a short distance.

An antimatter explosion would generate TONS of fallout, lots of unstable isotopes would be created and surrounding material would be irradiated. This is one good reason why an AM spaceship drive is somewhat... impractical.

Gamma radiation does not cause radioactivation, only excitation. The only radiation would be from the prompt gammas of annihilation, and secondary x-rays from bremsstrahlung, both of which are short lived. Fallout is composed of fission fragments and their unstable daughter products and material activated by neutrons in the fission process.

 

[QuantumPion]

Originally posted by: Biftheunderstudy
Interesting to note, although correct that the energy conversion is 100% how this energy is transmitted is important. 50 to 60% of the energy is carried away as neutrinos, these come from the pions which are produced from a long list of decaying particles created by the high energy gammas. The pions are actually the things which do the heating up of the air or whatever is nearest. For this reason the reaction rate although extremely important in nuclear munitions is not so important in AM reactions since the shock wave is an adiabatic expansion of heated plasma.

No, antimatter annihilation does not normally involve neutrinos. When a particle and antiparticle of relatively low energy collide, they produce two gamma rays which fly off in opposite directions. You are thinking of beta decay, and even in that case neutrinos only carry away 5% of the energy.

 

[silverpig]

Originally posted by: QuantumPion

Originally posted by: Biftheunderstudy
Interesting to note, although correct that the energy conversion is 100% how this energy is transmitted is important. 50 to 60% of the energy is carried away as neutrinos, these come from the pions which are produced from a long list of decaying particles created by the high energy gammas. The pions are actually the things which do the heating up of the air or whatever is nearest. For this reason the reaction rate although extremely important in nuclear munitions is not so important in AM reactions since the shock wave is an adiabatic expansion of heated plasma.

No, antimatter annihilation does not normally involve neutrinos. When a particle and antiparticle of relatively low energy collide, they produce two gamma rays which fly off in opposite directions. You are thinking of beta decay, and even in that case neutrinos only carry away 5% of the energy.

Actually it does. lepton/anti-lepton reactions give two gamma rays, but nucleons with their quarks quite often involve neutrinos in matter/antimatter reactions. Pions for example (quark/antiquark) decay into a lepton and the associated anti-neutrino.

 

[QuantumPion]

Originally posted by: silverpig

Originally posted by: QuantumPion

Originally posted by: Biftheunderstudy
Interesting to note, although correct that the energy conversion is 100% how this energy is transmitted is important. 50 to 60% of the energy is carried away as neutrinos, these come from the pions which are produced from a long list of decaying particles created by the high energy gammas. The pions are actually the things which do the heating up of the air or whatever is nearest. For this reason the reaction rate although extremely important in nuclear munitions is not so important in AM reactions since the shock wave is an adiabatic expansion of heated plasma.

No, antimatter annihilation does not normally involve neutrinos. When a particle and antiparticle of relatively low energy collide, they produce two gamma rays which fly off in opposite directions. You are thinking of beta decay, and even in that case neutrinos only carry away 5% of the energy.

Actually it does. lepton/anti-lepton reactions give two gamma rays, but nucleons with their quarks quite often involve neutrinos in matter/antimatter reactions. Pions for example (quark/antiquark) decay into a lepton and the associated anti-neutrino.

Oh nevermind, I originally said antiprotons but I was referring to positrons the whole time.

 

[Nathelion]

Originally posted by: QuantumPion

Originally posted by: Nathelion

Originally posted by: QuantumPion
An anti-matter bomb with the same equivalent energy release of a nuclear bomb on earth would look pretty much the same, although the antimatter bomb would create little to no fallout, only a prompt radiation burst. Also, designing the bomb would be trivial if you are able to contain the anti-matter in the first place. Lets say your bomb is composed of a bunch of anti-protons spinning around in an electric field in a vacuum taurus. Simply turn off the field, and the positrons will all smash into the sides of the container. The high energy gamma rays will cause the casing to heat up tremendously and explode. There is no need to contain the bomb for the reaction to complete like a fission weapon, because any anti-protons that get thrown out will inevitably collide with a regular proton and annihilate anyway within a short distance.

An antimatter explosion would generate TONS of fallout, lots of unstable isotopes would be created and surrounding material would be irradiated. This is one good reason why an AM spaceship drive is somewhat... impractical.

Gamma radiation does not cause radioactivation, only excitation. The only radiation would be from the prompt gammas of annihilation, and secondary x-rays from bremsstrahlung, both of which are short lived. Fallout is composed of fission fragments and their unstable daughter products and material activated by neutrons in the fission process.

"High-energy gamma rays can also make the engines radioactive by fragmenting atoms of the engine material. "

Off of Nasa: http://www.nasa.gov/centers/go...imatter_spaceship.html

In general, lepton annihilation does not produce energetic enough radiation to irradiate surroundig materials. Heavier particles, such as protons, do. You are partially right though, "lots of unstable isotopes" would not be created, per se. I was sleepy when I wrote that post