Can Antimatter Bombs Cause Explosive Destruction?

[Klystron]

I no longer work designing or operating real weapon systems but fiction and history are another story. My idea of embedding the OP's 'bomb' inside the RF device is a play on WWII proximity fuze.

From 1940 we see a continuous-wave radar system with RF generated by a thyratron embedded in an explosive shell hardened for massive accelerations. Proximity devices were so effective they should have been developed for ground transport back in 20th C. if not for security classifications.

[Edit: added picture from 1940. This gadget looks deadly.]

 

[Rive]

Antimatter annihilation results in high-speed neutrinos and a burst of high-frequency gamma radiation, but not much of an 'explosion' it seems.

That's true only in space, with no matter around. In your case:

...the bomb is intended to go off in an underground base.

All the radiation (of any kind) will be absorbed by the ground, heating it up: so 100% will be converted to a definitely big bang.

By some random source from the web 20kt means ~ 1g matter (antimatter) converted to energy.

 

[newjerseyrunner]

But, from various sources an antimatter bomb is not as destructive as the movies - and novels - suggest. Antimatter annihilation results in high-speed neutrinos and a burst of high-frequency gamma radiation, but not much of an 'explosion' it seems.

What the fuel turns into is not relevant. Nuclear bombs also release their energy largely in gamma rays. The point is all that energy ends up in the surrounding material, heating it up to millions of degrees, which causes it to expand. 99.99999999% of the damage caused by a nuclear weapon is done by the shockwave, not the flash.

 

[member 656954]

[Edit: added picture from 1940. This gadget looks deadly.]

Yes it does (And I'm now on a tangent looking into these, just for fun.)

All the radiation (of any kind) will be absorbed by the ground, heating it up: so 100% will be converted to a definitely big bang.

and

99.99999999% of the damage caused by a nuclear weapon is done by the shockwave, not the flash.

Excellent, that's the missing conceptual piece for me. I need a massive bang - it's a big base! - and this addresses my original concern, thanks @Rive and @newjerseyrunner.

 

[snorkack]

All the radiation (of any kind) will be absorbed by the ground, heating it up: so 100% will be converted to a definitely big bang.

Not any kind. Neutrinos don´ t participate in the bang.

The free path of pions in vacuum before they decay, in the range of 400 MeV energy, is around 10 m. So if you explode antimatter in a room filled with air a few m across, most pions that start off towards the airspace of the room cross the room and are absorbed in the opposite wall or ceiling. Minority of all pions decay in the room and waste part of their energy in neutrinos.

At a minimum, about 1/3 of annihilation energy goes via neutral pions to gammas which are absorbed and 1/6 of the rest goes to electrons/positrons. So absolute minimum 45 % energy into bang. Add energy from pions absorbed in nuclei where annihilation happens, muons that reach condensed matter before decaying... The energy that goes to bang starts from somewhere in 50...60 % if explosion is in midair and goes to maybe over 90 % in an enclosed room.

And even 50 % of 20 kT is a big bang. So is 90 % of 20 kT.

 

[member 656954]

I've participated in a few posts in this forum and wondered what ever happened to the input, so I thought that if you're interested in how your collective feedback translated to my story, the antimatter discussion sequence is below. I've hidden the text in a 'spoiler' so if you're inclined to ever read the novel you don't need to have advance knowledge, though I also don't think it's a big reveal in the scheme of things, but either way, it's your choice...

Spoiler: An excerpt from "Tyranny"

“Tin, if we need to do this up close and personal, then we needed something more substantial than the ten of us with whatever guns we can carry. Let’s cut to the chase, how are we going to win this?”

Tin’s mouth curled down slightly, but he nodded. “Excellent question, Guardian. And I guess it might help you to know the end game. So…” He whistled and raised his eyebrows, then looked over us toward the kitchen. We turned to follow his gaze as a low-slung plonk entered the room. It looked like a millipede carrying an overlarge insulated water bottle tipped on its side.

“As I said before, the base is down deep and not even dropping nuclear bombs would do much damage in the time we’d have for that. So, we sneak in, we lay an egg, then we sneak back out before the egg hatches. It that up close and personal enough, Guardian?”

I shrugged and he gave us a cheeky smile. “Any thoughts on what the egg might be?”

I took it upon myself to talk my way through the options. “The water bottle is obviously the egg, but unless you’ve rewritten the laws of physics, Tin, it’s too small to be a nuclear bomb.”

I did not say it, but there just wasn’t enough fissile material there to set off a chain reaction and a dirty bomb would not damage Colossus, not unless up close and personal meant setting it off right next to Colossus and I wasn’t even sure that was possible.

“I’m not sure you can build a wormhole bomb, but if you’ve managed that the war would be irrelevant. You’d not be waiting here. You’d be opening wormholes all over the place, and nobody would be able to catch you out.”

Tin nodded, “That would indeed be amazing, Guardian, but the resources to open wormholes, no matter the size, is well beyond us.”

“Yeah, I figured. Then there’s only one other thing I can think of, and I am not even sure I want to be right. You’ve created an antimatter bomb, Tin.”

It was half a question, but Tin’s eyes lit up and I knew I was right. The mere thought was triggering informational alarms; even a tiny amount of antimatter was extremely dangerous and while it would pack enough punch to do serious damage to Colossus, it would do even more damage to us. I did not try and hide my concern.

“You don’t look happy, Guardian. Yes, it is antimatter, that was clever of you, but rest assured, it is well contained. Very well contained. I am not inclined to blow myself up any more than you would be, I’d guess.”

The others looked confused, but I ignored them. “Exactly how much antimatter is in that bomb, anyway?”

“Five grams.”

Five grams. About a heaped teaspoon of sugar, yet it would release enough energy to challenge most nukes. It was impressive as such things go, but the details bubbling up into my memories told me there was a problem.

“Tin, antimatter annihilation releases lots of gamma rays but not much in the way of an explosion. That base in New Zealand is extensive, so how is your egg going to do any real damage?”

“You need to brush up on your physics, Guardian. Each gram of antimatter releases about twenty kilotons of energy. It is mostly gamma rays, true, but they heat the surrounding area, creating a shock wave as the very bedrock the base is built into liquefies and then explodes from the pressure. But just in case that is not sufficiently destructive, they also provide the energy to fuse an outer layer of compressed tritium, which is guaranteed to make a bang. You are looking at what I am sure is the very first antimatter atomic bomb, a marvel of technology weighing a mere six kilograms.”

I wasn’t skeptical, not really, but it seemed overly complicated. “And you’ve tested this?”

“Of course. There is nothing casual about this, Guardian, all our lives depend on my device being stable for transport, and then going off as planned. I’ve spent years developing this, the bomb works, let’s just leave it at that,” he said, sounding peeved.

Once again, I was left wondering what he was leaving out. You don’t need a physics degree to know that antimatter is dangerous, so bringing it along as some kind of ultimate hand grenade seemed suicidal. Even a nanosecond glitch in the containment field would turn us all to radioactive waste, and Tin knew it. Something about his too smooth delivery rankled, but I couldn’t put my finger on it, so I merely shrugged.

 

[DEvens]

Small scale anti-matter devices will probably not be doable because the containment has to be perfectly efficient. You can't have even a small amount of leakage because it would produce huge amounts of radiation. We're talking enough radiation that your agents would not want to carry that sucker. An amount of radiation that might set off the car alarm of cars you walked past. So an efficient containment will probably weigh more than a less exotic weapon.

Really big scale, with tech from the far reaches of science fiction, that is interesting. In the Lensman series

https://en.wikipedia.org/wiki/Gray_Lensman
one of the flashier weapons was a 1 km diameter ball of anti-matter. That's a couple 100 million tonnes of anti-matter. It was gathered rather than produced, so that got them a minor advantage. Just dump it onto the planet of the entities you are upset with, and be sure to be far away before it encounters any significant amount of regular matter. The containment was that it was rock.

 

[essenmein]

I'm back to writing the sequel to my first novel and for reasons of maximum destruction, an antimatter bomb is in play.

But, from various sources an antimatter bomb is not as destructive as the movies - and novels - suggest. Antimatter annihilation results in high-speed neutrinos and a burst of high-frequency gamma radiation, but not much of an 'explosion' it seems.

I'm working through whether the gamma radiation will do the damage I need, but can anyone point me in the direction of how to make it physically 'explosive' as well?

If you look at how a nuclear weapon works (fusion or fission) you'll find the output of the reaction is not an explosion either. Splitting a U235 with a neutron, for example, results in ~3 more neutrons, some of the energy in gamma, some in the kinetic energy of the fission products and the neutrons. To make this an explosion of the mushroom cloud type requires these moving fission products or the gamma radiation to interact with some matter, by interact I mean rapidly heat to stupid temperatures, and this now super heated plasma creates a massive over pressure, and that is the "explosion". I don't see why anti matter would be different?

 

[essenmein]

Random curiosity, in my little story also use anti matter extensively. But looking at it, the anti part is only the charged particles, (electrons/positrons and protons/anti protons), there is no "anti neutron", so when say hydrogen and anti hydrogen meet, is it not incorrect to say all the mass is converted to energy? If there are no anti neutrons, is it more correct to say only the mass of electron and proton is converted to energy, leaving a bunch of lonely neutrons?

 

[Rive]

if you're interested in how your collective feedback translated to my story, the antimatter discussion sequence is below.

Just small remarks. Above that 20kt for one gram of matter was not specified as antimatter: thus since that five grams of AM will eat 5 grams of matter too, at the end 10 grams will turn to energy. Maybe you should tell that to your agents in time ...
If you are that wicked type then you can let them notice it later

Also, that 20kt really was some random source on the internet, as 'how many mass turns to energy in an A-bomb'. Maybe you better check it.

 

[newjerseyrunner]

Random curiosity, in my little story also use anti matter extensively. But looking at it, the anti part is only the charged particles, (electrons/positrons and protons/anti protons), there is no "anti neutron", so when say hydrogen and anti hydrogen meet, is it not incorrect to say all the mass is converted to energy? If there are no anti neutrons, is it more correct to say only the mass of electron and proton is converted to energy, leaving a bunch of lonely neutrons?

No, there are antineutrons too. Charge is just the easiest way to describe this stuff heuristically. Neutrons have a baryon number of 1, while antineutrons have a baryon number of -1. They're made of antiquarks. Anti* means that there is some property of the particle that has the same magnitude as it's regular counterpart, but with a negative sign attached to it. Electrical charge is just one of the properties than can do this.

 

[essenmein]

No, there are antineutrons too. Charge is just the easiest way to describe this stuff heuristically. Neutrons have a baryon number of 1, while antineutrons have a baryon number of -1. They're made of antiquarks. Anti* means that there is some property of the particle that has the same magnitude as it's regular counterpart, but with a negative sign attached to it. Electrical charge is just one of the properties than can do this.

Ah interesting, I should perhaps not have taken my friends word for it. lol.

Off down the wiki rabbit hole I go!

 

[essenmein]

Just small remarks. Above that 20kt for one gram of matter was not specified as antimatter: thus since that five grams of AM will eat 5 grams of matter too, at the end 10 grams will turn to energy. Maybe you should tell that to your agents in time ...
If you are that wicked type then you can let them notice it later

Also, that 20kt really was some random source on the internet, as 'how many mass turns to energy in an A-bomb'. Maybe you better check it.

All I know is one mega ton of boom is 46.58g of mass equvalent, which is achieved with a 23g antimatter war head.

 

[newjerseyrunner]

All I know is one mega ton of boom is 46.58g of mass equvalent, which is achieved with a 23g antimatter war head.

Not very useful to try to determine the size of the warhead from the amount of fuel needed. The nagasaki bomb had 6.2 kg of plutonium in it but weighted more than 4000kg.

 

[member 656954]

the Lensman series

I absolutely devoured everything E.E. Doc Smith wrote when I was young and took the whole Lensman "irresistible force meets the immovable object" statement as fact for many years! Science fiction, eh, what a genre

 

[essenmein]

Not very useful to try to determine the size of the warhead from the amount of fuel needed. The nagasaki bomb had 6.2 kg of plutonium in it but weighted more than 4000kg.

Nope it's not, this is just the amount of mass converted to energy to reach a given TNT equivalent yield.

In the case of the Nagasaki bomb, very little of the fuel was consumed, of the 6.2kg of Pu, (from wiki) about 1kg of that underwent fission, converting ~1g of matter to energy yielding 21kt.

In the case of anti matter you don't have that fuel efficiency problem, all of it will get "used", if you want one megaton energy release, you need only 23g of antimatter. The nature and size of the thing holding it is the science fiction part :D

 

[member 656954]

I'm following up on my antimatter bomb for my story, and I wondered whether neutrinos could potentially trigger a detonation? I understand that neutrinos very rarely interact with baryonic matter but does a neutrino interaction trigger annihilation?

If they do, what would be the energy released - my antimatter consists of positrons - and could that trigger annihilation cascade and thus an explosion?

 

[Rive]

...my antimatter consists of positrons...

That'll just kill the show. To keep together few grams (!) of positively charged particles, while they are actively trying to rob electrons from anywhere around - by my humble opinion this is far worse than just isolating that AM.
From this point no amount of technobabble will be able to save it.

 

[member 656954]

Thanks @Rive, as @Vanadium 50 noted in post #28, I already know the whole set up is impossible, I was just wondering whether neutrino interaction would trigger a cascade annihilation. If so, it's a small point for my protagonist to protest upon.

 

[GTOM]

If protons can store positrons in a stabile way, isn't it possible to contain antimatter with non-barionic stuff?
Or rely on light pressure and neutral anti matter, rather than an ion trap?

(I don't think about hand held AM grenades, but the size of spaceship propulsion at least.)

 

[Rive]

Your positrons pushed together more violently and with far more force than protons in a nuclei. No worries: any barrier what can withstand that will keep any neutrino-induced ruckus at bay easily.