Can Antimatter Bombs Cause Explosive Destruction?

[member 656954]

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?

 

[some bloke]

You would be looking for something which reacts violently to gamma radiation, proportionally to its intensity. I don't know whether the gamma burst from annihilation would be able to create a fission reaction from a lump of uranium, simultaneously on all it's atoms due to the intensity & penetrating power of gamma rays. Alternatively, use the "unobtanium" approach and have a fictional material which reacts violently to gamma. It could be a key ingredient in solar sails, or some such.

 

[member 656954]

Love unobtanium. Actually writing another story based on that premise, but anyway, thanks @some bloke, that works for me

 

[Vanadium 50]

I haven't thought hard about this, but since the energy of individual particles produced in antimatter interactions is larger, they go farther. That probably causes the energy density to fall, even as the energy rises. Makes it harder to have an explosion.

As suggested before, you could make up some material with magical properties to keep this from happening. Or you could just make up a new explosive material. The "rhenium bomb". Or of that's too mundane., the "dilithium bomb". Since one has to invent new science and technology to even make and store enough antimatter to make a bomb, why not go all out?

 

[snorkack]

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.

Quite a lot of explosion, actually.

Largest source of gamma rays is the neutral pions that escape and decay to photons.

Most energy initially goes to charged pions. And the about 300...400 MeV charged pions have a few dm range in condensed matter.
If pions escape to air and decay, most energy does go to neutrinos, but even then 1/6 goes to electron.
So the yield is always a lot to begin with. And you can limit those modest losses: the losses are maximum if the bomb is small (up to a few cm in condensed matter) and beyond that the pions will escape in some dam of air. The losses are minimized if the bomb is surrounded by a few dm of condensed matter in all directions, where pions are absorbed before they can decay.

 

[member 656954]

Thanks @snorkack, I've now had a look into pion decay, but when you refer to "condensed matter", do you essentially mean anything but air?

 

[Klystron]

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?

Use Hydrogen. Instead of a fissile core you can trigger a hydrogen bomb either with your matter/antimatter annihilation or by directing gamma radiation.

You can make the H-bomb as large as needed and/or distribute tubs of the hydrogen isotope of your choice at strategic points. Blam! Refer Bikini Atoll for details.

 

[member 656954]

What about Hydrogen?

An atomic bomb triggered by antimatter could definitely work. I do try and use current physics where possible, so is a bomb of this kind likely to be small enough for a person to carry?

 

[member 656954]

Or you could just make up a new explosive material.

Don't know why that hadn't occurred to me, @Vanadium 50. Guess I just got stuck on antimatter as the best 'compact' bomb type, good reminder to get back to the big picture of the plot and not stuck in the weeds of any particular detail.

 

[phinds]

An atomic bomb triggered by antimatter could definitely work. I do try and use current physics where possible, so is a bomb of this kind likely to be small enough for a person to carry?

Using current physics, it pretty much can't be done. Reread post #4. I don't mean that it's not theoretically possible, just not using today's technology.

 

[member 656954]

Sorry, @phinds, I'm not following. I know that making / storing antimatter is currently beyond our technology, so that's pretty much handwavium in the story because it's set downstream of our timeline and everything we'd think is miraculous or impossible is 'Egan tech', which is to say, developed in the late 2030's and early 2040's.

But which aspect of current physics do I need to ignore - or bend? - for an AM triggered H-bomb?

 

[phinds]

But which aspect of current physics do I need to ignore - or bend?

As we both have said, neither. It's the engineering that is pretty much beyond us (obtaining / storing any significant amount of antimatter for any significant amount of time). AGAIN, reread post #4

 

[member 656954]

Thanks @phinds, but it was your 'Using current physics, it pretty much can't be done' comment in Post #10 that confused me.

I think of physics as the theory, I get that the engineering / technology aspect is not currently feasible.

 

[phinds]

Thanks @phinds, but it was your 'Using current physics, it pretty much can't be done' comment in Post #10 that confused me.

I think of physics as the theory, I get that the engineering / technology aspect is not currently feasible.

You are correct and my statement in post #10 was poorly worded. Sorry about that.

 

[BWV]

H-bombs and A- Bombs fail safe- i.e. they don't accidentally explode, while an antimatter bomb would detonate on any failure (i.e. it comes into contact with matter). If a culture has the tech to make an antimatter bomb, presumably they could also make a fusion bomb with same yield, it would just be bigger and consume more fuel. The question is then what would justify the risk of the antimatter weapon

 

[snorkack]

A fission bomb has a minimum size due to critical mass.
Smallest bomb designed as explosive is W54. While Wikipedia does not disclose the mass of the nuclear core, the whole bomb - core, high explosive and containment - weighs 23 kg. 40 cm long, 28 cm diametre.
The yield of W54 goes up to 1 kT.
Demon Core was 6,2 kg, 89 mm diametre. It went critical twice, aided by reflectors both time. It did not explode either time... but I´ ve seen estimates of yield as much as 70 g, gone to just warming the core and not enough to disassemble the 6 kg.

The possible size of an annihilation bomb depends on the unknown confinement mechanism.
Full efficiency is 42 MT/kg. At that efficiency, a 1 kT bomb needs 24 mg antimatter.

For comparison, weight of safety match head is about 20 mg (without the underlying stick).
How small can you make the trigger mechanism?

If you can hide a bomb the size of a match head and yield of 800 T, it would be effective. Even if you cannot bury it under several cm of Earth and some pions escape to air upwards, those that start down into ground would still be effective, so a bomb whose yield is lessened to just 500...600 T would still be effective.

 

[member 656954]

H-bombs and A- Bombs fail safe- i.e. they don't accidentally explode, while an antimatter bomb would detonate on any failure

Yeah, I'm thinking that's potential suspense in the story, @BWV. And regarding a more traditional atomic bomb, the plot requires a person-portable, highly-destructive explosive device, essentially something that a mobile infiltration team could carry. Hence the antimatter concept, but I may need to tweak it, depends on how realistic sounding I can make it.

 

[member 656954]

How small can you make the trigger mechanism?

If you are referring to the antimatter bomb, @snorkack, I was thinking that just turning off the magnetic containment is the 'trigger'. If you're referring to a conventional atomic bomb, then I'm out of my depth, so would revert to handwavium and keep on trucking.

If you can hide a bomb the size of a match head and yield of 800 T, it would be effective.

My novel being a sequel, it's not much of a spoiler to note that the bomb is intended to go off in an underground base. So, it's kind of buried, but that's probably not quite what you mean

 

[Nik_2213]

IMHO, there are two problems:
First, generate enough anti-matter. It does not come cheap, or in sufficient quantity.
( IIRC, even StarTrek had to hand-wave manufacture via an early version of 'Transporter' technology that re-assembled atoms as their opposites... )
Second, portably contain sufficient quantity to do extensive damage.

Which are why I found Dan Brown's 'Angels & Demons' totally, irredeemably silly...

Due care, please ??

 

[member 656954]

No comment regarding Brown's novels, but I'm trying hard not to be silly, @Nik_2213, because I find careless sci-fi very annoying myself when I read it.

In terms of manufacture, I am thinking the laser beam / gold foil method to generate positrons is viable. I thought about using a particle accelerator of some kind to create antiprotons, antineutrons, or antihelium, but that's a bit too same-same with regard another aspect of the story, so I decided against it. Though partially ionized antihydrogen, along the lines of ATRAP, might work as well.

The containment is basically an advanced Penning trap and the 'extensive damage' aspect is what this thread is helping me work out. I am imagining, courtesy of @Klystron in Post #7, the inner core being the AM, with an outer shell of compressed tritium so the intensive gamma ray burst of the annihilation fuses the tritium and thus provides the more explosive aspect of the bomb.

 

[Vanadium 50]

You're not going to be able to store grams of antimatter in an ion trap for the same reason you can't store grams of matter in an ion trap.

 

[Klystron]

No mention of plot yet. So, a character designs large magnetrons at Varian in her spare time and equips model Mx9n's with a secondary raceway or magnetic pocket that can contain a few grams of anti-hydrogen/-protons (or positrons possibly cycling in the opposite direction?). Our heroes commandeer a working model, attach the anti-widget and inject anti-matter conatined by the B-fields but only for some limited time frame ostensibly to satisfy some science but also to increase tension. Tick, tick, tick... Run, girl, RUN!

The tritium shells can be hidden in the standard radiation shields, then a resonant cavity depending on the magnetron application, and for the big blast, presuming multiple bangs, the walls of the structure. Better run far...

 

[jackwhirl]

You would be looking for something which reacts violently to gamma radiation, proportionally to its intensity.

Doesn't everything?

That was fun to type, but now I'm curious. Are there forms of matter that don't react violently to excessive amounts of gamma radiation? Thank you.

 

[snorkack]

If you are referring to the antimatter bomb, @snorkack, I was thinking that just turning off the magnetic containment is the 'trigger'. If you're referring to a conventional atomic bomb, then I'm out of my depth, so would revert to handwavium and keep on trucking.

My novel being a sequel, it's not much of a spoiler to note that the bomb is intended to go off in an underground base. So, it's kind of buried, but that's probably not quite what you mean

You don´ t need to turn off magnetic containment.
You might have magnetic containment on until it is destroyed by explosion. And the explosion triggered by failure of vacuum containment.
The said vacuum containment being designed to fail on incineration or mechanical mishandling.

How would you like an antimatter bomb whose warhead, magnetic and vacuum containment are designed to fit in fraction of a gram, and a few grams of the rest are camouflage designed to make it look like legitimate trash?

Like a bomb in a pen that looks and functions like an ordinary spent pen, but is designed to explode when burnt or crushed?

Sure, you could pack a pen with chemical explosives, too - only a few grams. In a trash incinerator, it is a minor mischief. In a waste paper basket, it could set the basket on fire or break a few fingers.

But how about a pen designed to explode with yield of many kT?

 

[Klystron]

Pardon, I did not see all the posts before posting about using a magnetron.

1) Can we read the first novel somehow, without violating privacy? Based on reading your posts, I like your writing style. FTR I have never been able to finish a Brown novel.

2) Magnetic containment for your antimatter need not resemble that needed for fusion devices. A large magnetron or gyratron made with the benefit of future materials science could believably suffice, especially since you can overload the magnetron since it is going to be destroyed in the blast.

3) You can hide your device inside AND power it from the RF installation using the gaffed magnetron or gyratron. Maybe your story has a collider or just a big RADAR installation underground or sterlizes produce for surrounding habitats.

4) The trigger can be highly scientific and dramatic if your bomb is pre-hidden in an underground installation. A special signal code can be sent to the Antenna of a radar or a special code inserted at the control console of a collider or food sterilizer or whatever fits your world plan.

If your plot requires that characters carry something in, it could be a replacement circuit board a/o chip that sends a coded signal to detonate. As in 3) above, your anti-matter widget can already be installed, waiting for a coded signal to produce anti-matter contained by the powerful magnetic field. Then your device can either detonate when overloaded or when commanded to.

 

[member 656954]

If your plot requires that characters carry something in

It does, but they are literally like SWAT, carefully entering a hostile building, so the AM bomb looks like a bomb, I don't need to disguise it. So to the protagonist it looks like "an overlarge insulated water bottle tipped on its side" which already contains the AM.

 

[member 656954]

You're not going to be able to store grams of antimatter in an ion trap for the same reason you can't store grams of matter in an ion trap.

This I don't get, @Vanadium 50. Apparently a Penning trap is used to store AM at CERN, so I'm clearly missing something (which is entirely likely, I'm way outside my knowledge zone!). How would you store AM for periods of months to a few years?

 

[Vanadium 50]

Let's focus on matter for the moment. If I use an ion trap to store a gram of ionized hydrogen in the size of a water bottle (say a sphere 20cm on a side?) that works out to a charge of 100,000 C, a potential of 5 trillion volts, and a stored energy of 60 kilotons.

This is impossible: 5 trillion volts is enough - way, way more than you need - to turn the Penning trap itself into a puff of plasma.

You can store a few atoms in a trap. Not anything macroscopic.

 

[Vanadium 50]

Phinds, you think that's informative? Ask yourself how much more destructive it would be if I swapped antimatter for matter?

About 50% more. That's right - antimatter ions (in this hypothetical configuration) are more dangerous because they are ions than they are because they're antimatter.

 

[member 656954]

that works out to a charge of 100,000 C, a potential of 5 trillion volts, and a stored energy of 60 kilotons.

Ah, yeah, that's not practical. Let me think this through because discussing the whole concept here has triggered a wicked plot idea that could solve the physics / tech issues, meaning I would not have to violate anything but the protagonists trust!

 

[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.