Comparison of thermonuclear and antimatter explosions of equal yield

  • #1
FtlIsAwesome
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Main Question or Discussion Point

Hi
This is my first post, and I have a lot of ideas to talk about

I'll start with this one:
What would the difference be between a thermonuclear explosion and an antimatter explosion, of equal yield (say 2 megatons each), and similar location and weather?

I think that the each would have a "mushroom cloud" and a similar shockwave. As mathman pointed out, the antimatter explosion would be only photons.
From a distance, the explosions would look similar. Would they have different types of radiation, due to the lack of neutrons in the antimatter explosion, and would the antimatter explosion have higher energy EM radiation?
 
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Answers and Replies

  • #2
mathman
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Antimatter explosion would end up essentially as all photons, while thermonuclear explosion includes neutrons and atomic debris as well.
 
  • #3
Astronuc
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Ostensibly, one would be using matter-antimatter reaction, e.g., hydrogen-antihydrogen. The positrons and electrons would annihilate producing gamma radiation, but the proton-antiprotons produce pions, which decay to muons, which decay to electrons (with various neutrinos and anti-neutrinos produced). The neutral pions do decay to photons.

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/hadron.html#c2

Antiprotons could annihilate protons in more complex nuclei, which could produce spallation reactions.

With regards to thermonuclear, one could use aneutronic reactions (Li-6 + d -> 2 alphas), but d+t fusion is typical. The result is high energy neutrons and alpha particles.
 
  • #4
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First, the comparison depends on whether the explosion is ground level, atmospheric, or above the atmosphere. The differences are most pronounced above the atmosphere. This discussion implies atmospheric.

The antimatter-matter annihilation bomb initially will generate mostly a flux of energetic pions (1/3 each +, -, and zero charge), about 4 to 7 pions per annihilation. There are no high-Z elements. The pi zeroes will decay to two 67-MeV gammas (+ Lorentz shift). The 67-MeV gammas eventually create electromagnetic cascades in the atmosphere. The charged pions will decay to muons (which are very penetrating, ionizing, charged particles with 2.2 microsecond lifetime) and neutrinos (carry off missing energy). Muons decay to electrons or positrons (max energy about 52 MeV), which create electromagnetic cascades (plus 511 keV annihilation photons). The physical size of the fireball is probably determined by the electromagnetic cascade, which would be physically larger than the electromagnetic cascade from the thermonuclear device. Muons will carry off about 1/6 of the total energy, and decay in maybe 1 km.

The main difference compared to thermonuclear is the lack of 14 MeV D-T (or equivalent) fusion neutrons, higher energy (multi-MeV) gamma rays, and fewer x-rays from heavy elements.

There will be no fission byproducts (e.g., iodine, strontium, cesium, cobalt-60 etc.). Actvation of air leads primarily to short half-life ( 2 to 10 minute) positron emitters.

[added] (gamma,n) reaction in air will produce giant-resonance neutrons.

[Astronuc beat me]

Bob S
 
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  • #5
FtlIsAwesome
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The physical size of the fireball is probably determined by the electromagnetic cascade, which would be physically larger than the electromagnetic cascade from the thermonuclear device. Muons will carry off about 1/6 of the total energy, and decay in maybe 1 km.

The main difference compared to thermonuclear is the lack of 14 MeV D-T (or equivalent) fusion neutrons, higher energy (multi-MeV) gamma rays, and fewer x-rays from heavy elements.

There will be no fission byproducts (e.g., iodine, strontium, cesium, cobalt-60 etc.). Actvation of air leads primarily to short half-life ( 2 to 10 minute) positron emitters.

[added] (gamma,n) reaction in air will produce giant-resonance neutrons.
So far, I understand these points:

The antimatter explosion has a larger fireball.
The fusion explosion will emit neutrons, while the antimatter one will not.
The fusion explosion will emit more x-rays.
And the antimatter explosion will emit more gamma radiation.

First, the comparison depends on whether the explosion is ground level, atmospheric, or above the atmosphere. The differences are most pronounced above the atmosphere. This discussion implies atmospheric.
We could examine each scenario: ground level, atmospheric, and space vacuum explosions.
 
  • #6
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Ground level tests are very dirty. Towers supporting the device are evaporated. All the material in the crater is sucked up into the mushroom cloud and radioactivated. Probably not much difference between an antimatter and thermo bomb except the 14 MeV neutron yield from the D-T reaction. (n,2n) and (n,alpha) reactions create a lot of radioactivation.

In theory, there is only a small amount of material in an antimatter bomb. 4.7 MJ = 1 kg of TNT. So 4.7 x 1015 Joules = 1 MT. 1 antimatter annihilation yields 2 x 109 eV = 3.2 x 10-10 joules, so 1 MT is about 1.4 x 1025 annihilations. This is about 12 gram-atomic-masses of antimatter (antiprotons), and 12 grams of matter (protons). This would be two 170 cc containers of liquid (anti) hydrogen (at 21 kelvin) or two 12 gram (anti) hydrogen ice balls (at 14 kelvin). For comparison, Fermilab has created and stored about 1015 antiprotons since 1985.

So an above-atmosphere antimatter bomb would yield a few Avagadro numbers of 67-MeV gamma rays, and a few Avagadro's of positrons and electrons. No baryons or antibarions left. Not much fireball (??). Can an equal number of positrons and electrons create an EMP (electromagnetic pulse)?

An above atmosphere thermo device is loaded with a lot of high-Z materials in the fission ignitor, plus a lot of D-T, leading to a lot of fission byproducts, x-rays from same, 800 million kelvin fireball, EMP (electromagnetic pulse), 14.1 MeV neutrons, and 3.5 MeV alpha particles. See
http://en.wikipedia.org/wiki/High-altitude_nuclear_explosion

Not much else, in my opinion.

Bob S
 
  • #7
FtlIsAwesome
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Would the radiation effects on people be stronger for the antimatter bomb?

Not much fireball (??)
What? You're kidding!
 
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  • #8
QuantumPion
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A conventional nuclear bomb has a mushroom cloud and shockwave due to almost all of the energy being absorbed by the the casing and surrounding air, creating extremely high temperatures and densities. The question is, what is the range of 67 MeV gammas in air? If half of the gammas make it out 100+ meters, than you might just end up with a bright but comparatively tame conventional fireball.
 
  • #9
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Would the radiation effects on people be stronger for the antimatter bomb?
Probably a lot more high energy neutrons from the thermo (D-T) device, a lot more electromagnetic radiation from the matter-antimatter device.
[from Bob S] [antimatter bomb in space] .......... Not much fireball (??).
What? Not much fireball?? You're kidding!
What do you think the composition of the matter-antimatter fireball is? Do 67 MeV gammas or 10 to 50 MeV electrons/positrons create a fireball in space? I have worked with liters of liquid hydrogen targets at 21 kelvin in thin mylar containers, so the antimatter casing would be minimal in a perfect vacuum.

Bob S
 
  • #10
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A conventional nuclear bomb has a mushroom cloud and shockwave due to almost all of the energy being absorbed by the the casing and surrounding air, creating extremely high temperatures and densities. The question is, what is the range of 67 MeV gammas in air? If half of the gammas make it out 100+ meters, than you might just end up with a bright but comparatively tame conventional fireball.
The air is heated by the burn temperature of the D-T fusion plasma. The 3.5 MeV alphas heat the plasma. Hot x-rays from plasma heat the surrounding air by deep core photoejection and Compton scattering. See plot of burn temperatures in

http://en.wikipedia.org/wiki/Nuclear_fusion

I think a desirable minumum temperature is about 20 KeV (guess).

The 67-MeV gammas transfer energy to the atmosphere in about 3 radiation lengths (100 grams per cm2) (standard electromagnetic cascade). See column labeled "radiation length" for dry air in

http://pdg.lbl.gov/2010/reviews/rpp2010-rev-atomic-nuclear-prop.pdf

See photos of mushroom cloud (???) for 1.4 MT Starfish Prime in

http://en.wikipedia.org/wiki/Starfish_Prime

Much of the light came from interaction of primary radiation with the atmosphere including auroras. What would it look like in deep space?

Bob S
 
  • #11
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.......For comparison, Fermilab has created and stored about 10[STRIKE]15[/STRIKE] 16 antiprotons since 1985.
Note this change.

Bob S
 
  • #12
FtlIsAwesome
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When detonating any explosive in space far from any atmosphere, I don't expect much except a brief flash.
Rather I am wondering as to the appearance of the explosions in an atmosphere.
If someone was exposed to the radiation from one of the bombs, how would it be different from someone exposed to the other bomb?
How would the different types of radiation affect metals and other materials?
 
  • #13
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Most of the effects of a nuclear detonation are the result of the released energy being absorbed and re-radiated by the surrounding air as thermal heat (Planck spectrum) and as x-rays. In addition, there are high energy neutrons (14.1 MeV) from the D-T reaction in a thermonuclear device. Neutrons are very damaging to hydrocarbons (e.g., tissue) because of proton recoil). Here is a reference of weapons effects with some quantitative numbers:

http://www.princeton.edu/~aglaser/lecture2007_weaponeffects.pdf

Metals generally are very rad hard, much more so than other materials (glass, rubber, semiconductors, batteries, etc.). Radiation will turn glass opaque (F-center dislocation), but usually the rad damage can be annealed out. Most materials rad hardness literature unfortunately is specifically for nuclear reactor applications (e.g., pressure vessel steel). See

http://www.nature.com/nature/journal/v308/n5954/abs/308051a0.html

and references therein.

Bob S
 
  • #14
I don't know about the rules of resurrecting old threads.
Sorry guys I'm new here.

Out of curiosity, is it possible to harness the explosion of matter and anti matter in similar ways of fusion energy?

Where can we find anti matter in large amounts on Earth?
 
  • #15
Astronuc
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I don't know about the rules of resurrecting old threads.
Sorry guys I'm new here.

Out of curiosity, is it possible to harness the explosion of matter and anti matter in similar ways of fusion energy?
Like fusion, the products of antimatter-matter annhilation are nuclear (or subatomic) particles which have kinetic energy, or in the case of electron-positron annihilation, 2 gamma rays. The nucleons would annhilate to form pions, which rapidly decay to muons, which in turn rapidly decay to electrons.

Where can we find anti matter in large amounts on Earth?
How does one define large? If > a picogram, then there is isn't such a source.
 
  • #16
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Out of curiosity, is it possible to harness the explosion of matter and anti matter in similar ways of fusion energy?
In theory yes.

Where can we find anti matter in large amounts on Earth?
Nowhere.

They have managed to create and annihilate a few particles of anti hydrogen. It's not so much the creation that is difficult, although that's no mean feat, its the storage of such material that becomes problematic too. It tends to become annihilated by anything it comes into contact with matter wise.

Theoretically anti matter-matter reactions should convert 100% of the matter to energy in the form of photons, of course in practice that wouldn't happen. Thermo-nuclear devices are only a few percent efficient though so in theory an anti matter device that held the same amount of matter antimatter as a modern ICBM does plutonium would probably take out the planet smashing it to pieces. I dread to think what the tectonic stresses would be, probably a good deal greater by several orders of magnitude than the cometary strike on Earth at 65ma on the Richter scale.

Nice thought eh.

*Retreats back into his lair to plot world domination.
 
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  • #17
Drakkith
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*Retreats back into his lair to plot world domination.
Gee Calrid, what are we going to do tonight??

The same thing we do every night Drakk...TRY TO TAKE OVER THE WORLD!!!

*Que Pinky and the Brain Theme*
 
  • #18
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Gee Calrid, what are we going to do tonight??

The same thing we do every night Drakk...TRY TO TAKE OVER THE WORLD!!!

*Que Pinky and the Brain Theme*
:smile:

I loved that series it was superb, shame its not still around. I suppose there's always Stewie in Family Guy.
 
  • #19
FtlIsAwesome
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Out of curiosity, is it possible to harness the explosion of matter and anti matter in similar ways of fusion energy?
Yes. An antimatter propeled spacecraft would be an example, but first you have to obtain the antimatter.
Where can we find anti matter in large amounts on Earth?
The only natural sources I've heard of is high energy rays striking Earth's atmosphere, and the radiation belt around Jupiter. And I'm not sure how much antimatter these produce, or how to extract any from them.

Scientists have been making it in particle accelerators at high inefficiency. An analogy I heard is that they used up enough energy to power a city, and the usuable antimatter they produced could only power a low watt bulb.

Generally, antimatter won't be good as a stationary power plant, but it would be good for a propulsion mechanism.
Some guesstimate numbers I've seen: a fusion drive could get a spacecraft up to 0.1 c, while a antimatter engine could potentially reach 0.9 c.

So if a civilization wanted to build these kind of ships, they'd probably build a http://en.wikipedia.org/wiki/Dyson_sphere" [Broken] so they have enough energy to produce the antimatter.
 
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  • #20
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