Talk:Boosted fission weapon

Use in Implosion Weapons

As I understand it, the usual configuration of a tritium boosted weapon is that deuterium (D) and tritium (T) are placed in the centre of the pit (ie the core of plutonium or highly enriched unranium) of an implosion-type weapon. The shockwave of the implosion passes into the pit and produces a very high temperature in the centre sufficient to ignite thermonuclear fusion in the DT mix. The fusion reactions give off a burst of neutrons which initiate the fission chain reaction more quickly than would spontaneous fission alone. This increases the amount of fission that can occur in the brief time before the pit blows itself apart. The thermonuclear yield is insignificant, but the yield of the fission reaction is greatly increased.Man with two legs 14:12, 11 October 2005 (UTC)

I believe it takes not just the implosion energy from conventional explosives, but fission energy from the early stages of the fission chain reaction, to start fusion. After this, both fission and fusion proceed, the fission assisting the fusion by continuing heating and compression, and the fusion assisting the fission by radiating fast neutrons. As the fission fuel depletes and also explodes outward, it falls below the density needed to stay critical by itself, but the fusion neutrons keep fission going for longer than it would otherwise.

Besides increased yield (for the same amount of fission fuel with vs. without boosting) and the possibility of variable yield (by varying the amount of fusion fuel), possibly even more important advantages are allowing the weapon (or primary of a weapon) to have a smaller amount of fission fuel (reducing the risk of predetonation) and more relaxed requirements for implosion.

Also, I believe all boosting of primaries is done with gas, not 6LiD, probably because the latter is not a net producer of neutrons, and would not provide the quick neutron boost that DT fusion does. --JWB (talk) 07:19, 22 November 2007 (UTC)

Both have been used. See Operation Grapple#Grapple Z. I'll expand on this when I have time.Man with two legs (talk) 09:21, 22 November 2007 (UTC)

It's been used in tests, but did it ever make it to production weapons?--JWB (talk) 04:26, 24 November 2007 (UTC)

Dunno. But if you look here: [1] you will see a diagram of the American mk28 H-bomb which crops up on the internet from time to time. It is not at all certain that the details are right, but you can see it uses both kinds of fusion boosting. Why this design also uses an external neutron generator is something I have not made sense of (though remember this drawing is not reliable).

My guess is that tritium gas is used to initiate the explosion by giving a burst of neutrons when the imploding shock wave reaches the centre, and Li-6/D is used to improve immunity because it is a neutron absorber when cold and a way of turning neutrons into high energy neutrons when hot. I have never seen a source for this, which is why I did not put that in the article. It occurs to me that tritium gas could work in both modes.

Rather frustratingly, I cannot find my source for the bit about shock waves. I remember that it pointed out that a converging shockwave produces a theoretically infinite temperature. In practice, you merely get a very high temperature but because at any time some atoms have more than the average energy, a small proportion (a few million) can fuse. Of course, that source might have been wrong. I also remember seeing a description of this reaction: T+T -- > He-4 + 2n suggesting that pure tritium can be used and not a DT mix.

In Britain and the H-bomb around p.189 there is mention of tritium and no mention of deuterium use in the Burgee shot. In Dark Sun p.501-3 it describes putting tritium (it loudly does not say D-T) in the sparkplug of Ivy Mike. These two support the use of pure tritium. The use of 'a very small amount' in Mike (where an awful lot of other fusion was about to happen and weight was not an issue) suggest to me that the shockwave bit is correct because the neutron contribution from the tritium would be insignificant by the time the sparkplug had become hot enough to cause fusion.

Man with two legs (talk) 12:01, 24 November 2007 (UTC)

Boosting is explained quantitatively on page 563 of A Technical History of America's Nuclear Weapons by Dr Peter Goetz. His example uses 12 grams of a 3:2 D+T mixture biased in favor of Tritium, which kindles after 0.1 kT to 0.3 kT of fission yield.

The boost gas cannot kindle from chemical implosion alone, which typically compresses the gas to "50 to 100 times the density of solid DT", or roughly 11 to 22 g/cm3. The example in the book has the DT gas starting in a high-pressure canister at 5000 bar, which is a density of roughly 1 g/cm3, so that's maybe 20:1 compression. Or even if the gas expands 5:1 during injection, it's still only 100:1 compression. This is a large compression ratio compared to the, at most, 2.5:1 compression of the Plutonium, but is orders of magnitude insufficient to reach the 20,000,000K needed to kindle rapid fusion. Adiabatic compression puts the DT gas in the ballpark of only 1000K; the initial temp may be higher, and there may be shock heating and other effects, but none of these could plausibly close such a large gap. Another argument is that were it possible for chemical explosives alone to trigger fusion, then pure-fusion bombs would be possible, and being desirable, would certainly have been developed, yet despite the best efforts of many weapons labs, none have ever achieved fusion w/o the aid of fission (or building-sized banks of lasers). In fact, avoiding early heating of the DT gas is actually desirable, as it allows for a higher final density. Final density is limited by implosive pressure, which is on the order of 50 GPa (500,000 bar).

The boost gas compresses faster than Rayleigh-taylor instability can mix the DT gas with the Plutonium. On page 564, the boost estimates that R-T instability takes ~100 nanoseconds, versus only a few nanoseconds for kindling fusion, although this estimate seems to exclude the fractional microsecond taken for implosive compression.

Once the boost gas kindles, the fusion rate accelerates catastrophically, and the entire burn finishes within "a few nanoseconds", which is less than one neutron generation. One intuition for this is that the DT gas was already being heated to fusion temperature by the fission process, which is only accelerating, and thus, any additional heating provided from the fusion reactions would tend to further elevate the temperature, vastly increasing the reaction rate (temperature dependence is highly non-linear). The book provides an example of 12 grams of DT gas, producing enough 14.1 MeV neutrons to fission 576 grams of Pu239 (~10 kT). Then, due to the higher speed of the fusion neutrons, the number of neutrons released per fission event jumps from 2.9 to 4.6, providing enough neutrons to fission 2649 grams of Plutonium in the next generation. It further states that real-world yields of 80% to 90% efficiency are possible from a boosted ~3 kg Plutonium pit. The fusion reaction takes "a few nanoseconds", the fast neutron generation takes <10 ns, and the subsequent generation takes ~10 ns, so this suggests that boosting can drive the fission reaction from <0.5% (<0.3 kT) to >80% (>48 kT) in barely more than 20 ns. For comparison, neutron doubling in even an infinitely supercritical compressed mass of Pu239 could only grow by 2.9X per ~10 ns neutron generation, requiring ~50ns for 200:1 scaling. The book cites "40 to 50 nanoseconds" as the interval between the onset of expansion and the core becoming subcritical. In an unboosted core, the maximum efficiency is limited by the exhaustion of fissile material and the creation of neutron absorbing fission products, both of which reduce criticality, slowing reaction growth, and also by the expansion of the core outpacing the slower reaction growth. The book cites 35% as typical yield for a well-designed unboosted core, and 50% as the ceiling available for heroic efforts such as the Ivy King shot. Versus 80% to 90% for a smaller 3kg core with less compression, but with boosting. Such a core might only produce 0.3 to 1 kT w/o boost-gas insertion, as is demonstrated by many dial-a-yield designs, implying an unboosted yield of only a few percent efficiency. In such a precisely engineered "barely sufficient" design, insertion of the boost gas is an order-of-magnitude yield increase. Alternatively, boosting provided roughly 2X yield increases over contemporary unboosted designs that were intended to be as efficient as feasible.

The book I am citing provides good insights, but must be taken with a grain of salt as it clearly contains a few unit conversion errors, and possibly other more serious inaccuracies. For example, on pg 564, the book implausibly quotes the DT gas as being compressed to 7 kg/m3, which is only 0.007 g/cm3, substantially less than its original density at 5000 bar! I believe this to be a mistake of using the wrong units (perhaps 7 g/cm3 was intended?) as the following sentence says "50 to 100 times the density of solid DT", and solid DT has a density of 0.21 g/cm3. A similar mistake of units happens on page 28, where the book says that implosion reaches "500,000 kilobars, or 500,000 times the pressure at [E]arth's surface". Clearly, the book meant 500 kilobars, not 500,000, as that's 50 GPa, which is comparable to both explosive pressures and the bulk modulus of Plutonium; the larger figure is vastly too optimistic. My confidence in the rough accuracy of the figures that I'm quoting comes from extensively comparing figures from different chapters with each other, and sanity checking them in the equations.

[User: DDopson] — Preceding unsigned comment added by Ddopson (talk • contribs) 18:56, 8 November 2023 (UTC)

The Nuclear Weapons Archive you gave discusses fusion via chemical explosive implosion farther down the page and says it's not practical.

You haven't got it: the amount of fusion I am talking about from the dead centre of the shock wave is tiny and is for initiating the fission reaction. Not at all the same thing as the hypothetical fission free bomb. Man with two legs (talk) 10:59, 25 November 2007 (UTC)

The external neutron generator is the initiator.

I know. The thing that puzzles me is the need for one of those and tritium gas at the same time because I have reason to believe that the gas itself can be used as the initiator, which is the main point that needs nailing down here. Man with two legs (talk) 10:59, 25 November 2007 (UTC)

The presence of an external initiator strongly suggests that the boosting gas at the center is not acting as the initiator. I've seen somewhere saying that it doesn't work, but don't have the reference handy at the moment. --JWB (talk) 16:56, 25 November 2007 (UTC)

I agree that is evidence against the shockwave thing. I finally found a reference for it at nuclearweaponarchive.org (in a section which is puzzlingly hard to find on Google) where it says:

“ A somewhat similar approach is to use the implosion to initiate a neutron generating fusion reactions with tritium and deuterium (described in Section 2.2 below). It may seem surprising that this can be made to work, given the well known fact that fission explosions are required to produce the temperatures that fusion reactions normally need. Three considerations overcome this obstacle. First, an exceedingly low rate of fusion is actually required. One neutron (and thus one fusion) every 10 nanoseconds is sufficient, a rate that is only some 10^-24 as fast as an actual fusion explosion would need. Second, implosions focus energy and can reach very high temperatures near the center. Theoretically the temperature at the center is infinitely high, but lack of perfect symmetry reduces this. Even so, a high precision implosion can reach temperatures of several hundred thousand degrees C. Third, the velocity of atoms in a gas or plasma is a statistical (Maxwellian) distribution. A very small portion of the atoms can greatly exceed the average energy. Thus enough atoms in the D-T mixture near the center can reach fusion energies to produce the required rate of neutron production. This type of implosion initiator is even more difficult to engineer than the Be/Po-210 type since the very high precision implosion is required to achieve the required symmetry. The major advantage is that the short half-life Po-210 is not needed. ”

However, that seems to contradict other things in the same (reasonably reliable) site. Also, Georgewilliamherbert says below that he has not heard of this working, and the signs are that he has looked into this quite a lot. By the way, according to Dark Sun only about six neutrons were produced by the urchin in the primary of Ivy Mike so a tiny number of fusions really would be enough: 3g of tritium is 6E23 atoms so a 1 in 1E23 rate of fusion would be enough to match the urchin.

Most telling is that every modern weapon design we have component details on includes some sort of neutron generator, in all the recent ones an external pulse neutron generator tube array. Georgewilliamherbert (talk) 00:56, 29 November 2007 (UTC)

With the implosion fusion method, initiation would be very sensitive to the schedule (is peak energy in the boost gas at exactly the same time as maximum density of the fissile material?) and symmetry of the implosion, and it would be difficult to control timing precisely and reliably. The pulse tube seems to offer precise timing control. Also, the NWA quote doesn't actually say implosion fusion initiation was used in any bomb tests. And, even if it were used in a test, it might be hard to tell if it worked or not, given that Pu-240 has a high spontaneous fission rate. --JWB (talk) 08:38, 29 November 2007 (UTC)

T-T fusion is listed at Nuclear fusion#Criteria and candidates for terrestrial reactions. It produces less total energy (11.3 MeV) than D-T fusion (17.6 MeV), and the energy is split between one alpha particle and two neutrons. D-T fusion has only two products, and conservation of momentum forces the neutron to exit at 4 times the speed that the alpha does, I think 17% of speed of light, which makes the neutron carry 4/5 of the fusion energy. These extremely fast and energetic neutrons spread the fission chain reaction faster, and produce fissions that themselves release larger number of neutrons. T-T fusion will produce less energetic neutrons. The initiation temperature or temperature-reaction curve for T-T is not given but may be higher than D-T. Given that deuterium is much cheaper, and can be handled in the same way as tritium, there is little reason not to include deuterium with tritium.

Thanks for that detail of the reaction.

My point was that both sources strongly suggest tritium was being used alone. Man with two legs (talk) 10:59, 25 November 2007 (UTC)

I have a hard time believing tritium would be used alone in any actual weapon (as opposed to physics measurements in a test device) and hope you will include the actual quotes for readers to evaluate. In a discussion of tritium vs. lithium boosting, it's possible the deuterium was not mentioned because it's present in both boosting methods and therefore not an issue worth mentioning each time. --JWB (talk) 16:56, 25 November 2007 (UTC)

Ivy Mike's secondary was mostly deuterium, so there was certainly deuterium present. It is hard to say what the tritium was intended for with out more information. The tritium would reach higher thermal velocities than uranium or fission products because it is lighter, so some may have been ejected into the surrounding deuterium at high speed, where it might fuse and supply heat and neutrons. Or, since the test was an experiment, it may have been included simply to facilitate some measurements. Anyway, a secondary is a very different case than a primary, and is not what is meant by "boosted fission weapon".

The tritium was a "quite a small amount" (Dark Sun, p. 501) inside the spark plug (the fission component in the centre of the deuterium container) where its only possible purpose would have been to boost the fission therein. There is no chance it could have got near the deuterium (if they had wanted them to mix, they would simply have put them in the same place). It was certainly some kind of fusion boosting of fission in the spark plug, but we are back to the same question: was it the high temperature of the fission reaction or the high temperature in the centre of the converging shockwave that initiated fusion in that tritium? In short, we need a source. Man with two legs (talk) 10:59, 25 November 2007 (UTC)

Was it in a separate compartment inside the sparkplug, or diffused in as hydride? I'm not sure how much this has to do with the boosted fission weapon (the title of this article) case. Implosion of a primary fission pit is carefully engineered to make the most of the relatively weak chemical implosion, while radiation implosion is much more powerful. And in the secondary case, there are already lots of neutrons floating around from the primary explosion, so initiation is not a question. --JWB (talk) 16:56, 25 November 2007 (UTC)

It was in a cavity in the sparkplug. "To make things more certain, push them further in a favorable direction" so it looks likely that the bomb would have worked without it. Just why the zillions of thermalised neutrons from the primary were not considered enough is not clear. But it is also true that making an H-bomb work is very hard to do, presumably for reasons that are not publicly known. Man with two legs (talk) 23:14, 28 November 2007 (UTC)

This was the very first thermonuclear test, so they were not even sure what was needed to make an H-bomb work! If the tritium was contributing anything in particular, its contribution was more likely to be adding to the sparkplug's heating at the right time, than initiation neutrons. --JWB (talk) 08:45, 29 November 2007 (UTC)

Also, the radiation implosion of the secondary is supposed to avoid heating the fusion fuel too much, because that would interfere with the goal of maximum compression. Once maximum compression is reached, then you want to quickly raise the temperature to initiate fusion.

Not clear what point you are making. BTW, I did know that. Man with two legs (talk) 10:59, 25 November 2007 (UTC)

Too much neutron-absorbing 6Li in the center of a primary would raise the critical mass of plutonium needed for criticality, which would detract from boosting's reduction of the plutonium requirement to reduce predetonation insensitivity. --JWB (talk) 04:13, 25 November 2007 (UTC)

Reducing plutonium is not a way to create radiological immunity, although it does seem to help. Immunity was a problem with the British 1/2 megaton atom bombs which seem to have used no plutonium at all. I am certain that fusion boosting was the cure for this problem because that is specifially stated in Britain and the H-Bomb p. 177 on, but I have no source for the mechanism (that book is reliable but it concentrates on the tests rather than technical details). Man with two legs (talk) 10:59, 25 November 2007 (UTC)

Sorry, I meant reducing the weight of fissile material in the pit, whether that is Pu or enriched uranium. The huge fission bomb had something like 4 critical masses, so reducing the fissile material below 1 critical mass by boosting was not an option. And looking at p. 177 on Google Books, I see no mention of the huge fission bomb; it only says that plutonium cores are more susceptible, and at the bottom of the page, that reducing the quantity of fissile is the way that boosting helps. Could you give a more specific reference for boosting of the 1/2 megaton bomb itself? --JWB (talk) 16:56, 25 November 2007 (UTC)

If you re-read it you will see it doesn't quite say those things. That is a problem with that book: you have to read it like a lawyer to extract the technical information from the story.

The big A-bombs (later estimated at only 0.4MT) were not boosted and not immune. They just used large amounts of uranium and nobody told the Russians they were vulnerable. They were also staggeringly unsafe. Man with two legs (talk) 23:14, 28 November 2007 (UTC)

This discussion is wandering around too much. Here some facts I have nailed down with 99%-100% certainty:

1. Both tritium gas and solid LiD fusion boosting have been demonstrated
2. Fusion boosting is essential for radiological immunity in efficient fission bombs
3. Tritium (not D-T) fusion boosting was used in the secondary of Ivy Mike separately from the large scale fusion of deuterium
4. The amounts of tritium used in fusion boosting are of the order a few grams

One that is taken seriously but may be wrong:

1. The mk28 H-bomb used both kinds of boosting

And here is one I did not make up but which needs sourcing or rebutting:

1. The converging shockwave of an implosion device creates a high enough temperature in the exact centre to cause a very small amount of fusion in pure tritium

An example of converging waves producing remarkably high temperatures appears in Sonoluminescence.

Man with two legs (talk) 10:59, 25 November 2007 (UTC)

I have posted a question on this at User_talk:Georgewilliamherbert. He knows something about this and may be able to shed light on it. Man with two legs (talk) 16:09, 25 November 2007 (UTC)

I would like the article not just to try to document all techniques that have ever been used, but to state which are used in modern weapon designs. Designs like Ivy Mike were only used a couple of times, were obsolete within the same month, and are nothing like the tens of thousands of weapons that have been in service starting in the '60s. They are of purely historical interest. --JWB (talk) 16:56, 25 November 2007 (UTC)

I suggest putting in details about the mk28 with a caveat that the drawing is not necessarily correct. It might be worth saying something to the effect "both have been tested" and that "gas boosting appears to be more common" though that statement would need a citation or three. Man with two legs (talk) 23:14, 28 November 2007 (UTC)

I will post some more intelligent replies later, but...

Solid Li-D fission stage boosting has been demonstrated - it's known as "pill boosting". It's described as "much harder" than gas boosting and modern warhead designs generally include features which are presumed to be part of gas boosting systems. How prevalent it was in any generation of deployed weapons is currently hard to guess based on purely public information.

Fusion boosting is more important to avoid predetonation than to make weapons immune to high radiation environments, though both are advantages.

Don't take the warhead diagrams and Mark-28 internal details too literally. The drawings are oversimplified and slightly wrong.

In terms of whether you'd boost a secondary's sparkplug with pure T or D-T mix, it's the same logic that applies to primaries. Modern weapons probably use D-T for both.

As far as I know, nobody has used shockwave imploding the gas to start any useful fusion reaction in a test or deployed nuclear weapon. Under ideal conditions it may be possible; the inside of a realistic bomb is likely not ideal enough.

Anyways, just a few comments off the top of my head. Back to the grindstone. Georgewilliamherbert (talk) 00:31, 27 November 2007 (UTC)

Thanks! Man with two legs (talk) 23:14, 28 November 2007 (UTC)

Rewrite

I have rewritten most of it. Positive criticism welcome. Man with two legs 22:43, 25 May 2007 (UTC)

Alarm clock/layer cake doesn't belong here

Apparently inclusion in this article was motivated by a final comment at the FAS site:

"This design should probably be considered distinct from other classes of nuclear weapons. This design is something of a hybrid and could be considered either a type of boosted fission device, or a one-stage type of fission-fusion-fission bomb."

In actual usage "boosted fission weapon" always refers to a normal fission bomb with a small amount of fusion boosting at the center.

Boosting is used in all modern nuclear weapons, while Alarm Clock/Sloika designs are only of historical interest and were deployed briefly if at all.

The "one-state fission-fusion-fission bomb" is somewhat more accurate. The secondary of a radiation implosion weapon uses the same arrangement.

On the other hand if Alarm Clock can be considered a boosted fission device, so can staged thermonuclear weapons, which usually also derive most of their yield from fission.

I am going to remove the section from the article. --JWB (talk) 01:30, 1 January 2008 (UTC)

That is wrong, it certainly was not derived from the FAS site. I rewrote the article from my own knowledge. If you look up Boosting in the index of Lorna Arnold's book, you get references to both Alarm clock and Joe 4 so the term is used in both contexts. Man with two legs (talk) 12:02, 6 January 2008 (UTC)

On p.86-87 she uses the terms "core boosting" and "tamper boosting" to distinguish the two, and that is something that is worth putting in the article. Man with two legs (talk) 12:58, 6 January 2008 (UTC)

I also think there is a fundamental difference between a bomb that uses the Li-6 D / U-238 cycle with little compression, and one that achieves D-D fusion by colossal compression. Man with two legs (talk) 12:10, 6 January 2008 (UTC)

Li-D requires similar compression to D-D; in fact according to NWFAQ 4.4.5.3.2.1 Li-D relies on D-D for its initial neutrons (so requires the same temperature and compression) and fission neutrons do not play a significant role. So there is little difference.

That is not correct: Joe-4 was a single stage weapon and could not possibly have had a high level of compression. The comment in the nuclear weapons archive is presumably correct when the fission spark-plug in the secondary is small and D-D fusion is able to happen for other reasons (ie high compression). Both Joe-4 and the early British H-bombs were certainly using fision neutrons to create tritium from Li-6. At that stage, they had not realised that D-D fusion was possible at a fast enough rate. Man with two legs (talk) 13:56, 6 January 2008 (UTC)

That is true of Joe-4 (when you said Li-6 D / U-238 cycle it sounded like you meant radiation implosion weapons), however NWFAQ [2] never refers to the Alarm Clock/Sloika design as "boosted" or "boost"ing, and neither have any other sources I have seen except for that one book on the British program. --JWB (talk) 16:38, 6 January 2008 (UTC)

In fact the top of NWFAQ 4.3 specifically contrasts fusion boosting (small amount of gas in core) with Alarm Clock/Layer Cake as two different kinds of designs, making clear it is not applying the term boosting to the latter. This is normal usage and there is no reason to suppress it in the article. --JWB (talk) 16:58, 6 January 2008 (UTC)

Arnold pp. 86-87 is quoting British scientist Keith Roberts speculating in 1955 without full knowledge of the American program. As Arnold notes on p. xiii, the British at the time were confused and inconsistent in their use of nuclear weapon terminology. And on p. 223 she defines boosted bombs in a way that would include most later thermonuclear weapons.

Correction: it is page 233. That definition fits both core and tamper boosting, but would not fit any bomb with a high fusion yield. Man with two legs (talk) 14:07, 6 January 2008 (UTC)

Most later weapons derived a majority of yield from the final fission stage. The Mk-21 is the only deployed weapon I've confirmed to not have the final fission stage. --JWB (talk) 14:31, 6 January 2008 (UTC)

There is clearly a fundamental difference between a weapon that could have a high fusion yield if the designers felt like it, and one that could not. And there is a clear difference in the reactions going on. Man with two legs (talk) 15:03, 6 January 2008 (UTC)

The fundamental difference is staging and radiation implosion. Other than that, the secondary of a Teller-Ulam weapon is similar to the Alarm Clock/Sloika design. There is no difference in the reactions going on, unless you are thinking of Ivy Mike, which was apparently the only non-lithium thermonuclear bomb ever tested. --JWB (talk) 16:22, 6 January 2008 (UTC)

You could not be more wrong. You do not get significant D-D fusion in single stage thermonuclear weapons and you do get it in two-stage weapons. Man with two legs (talk) 17:19, 6 January 2008 (UTC)

In the weapons designs the US standardized on by the 1960s and deployed in the tens of thousands to the exclusion of anything else, "boosted fission weapon" always refers to small amounts of fusion fuel inside the primary's pit. In contrast the British experiments were a short-lived dead end, abandoned after the US agreed to share its technology.

I think it is fair to say that while "boosting" may have been used early on to refer to various uses of fusion to supply neutrons for fission, "boosted (fission) weapon" and "boosting" have more specific connotations in the context of the actual US nuclear arsenal and program, as it stabilized after the experiments of the first few years. --JWB (talk) 13:30, 6 January 2008 (UTC)

As I see it, the fact that the term "boosting" has been used in both contexts is reason to include both in the article. It is entirely appropriate that the fact that tamper boosting is obsolete and that boosting now almost always means core boosting should be clearly stated, and that is not far off the current state of the article. Man with two legs (talk) 14:03, 6 January 2008 (UTC)

US centric view not appropriate

Incidentally, there is no case for making this article US-centric. The Russians and British certainly developed successful h-bombs before it was known how the US did it, and I guess the French and the Chinese did the same. Man with two legs (talk) 14:14, 6 January 2008 (UTC)

I don't know of any evidence that the Russians used the word "boosted" or equivalent, or categorized the Sloika design as similar to fission bombs with tiny amounts of gas boosting rather than similar to Teller-Ulam designs. The French, Chinese and later nuclear powers went straight to Teller-Ulam designs as by then this was known to be the way to go, and again we don't have any evidence on their usage of "boost" or equivalent words. The point is not that Alarm Clock/Sloika designs should not be documented, but that they primarily belong in the articles on the history of nuclear weapons in general or at least thermonuclear weapons, not in a much more specific article answering the question of what "boosted fission weapon" normally means. --JWB (talk) 14:31, 6 January 2008 (UTC)

The fact that the term "boosting" has been officially used in both contexts is all the reason needed to include both in this article. Man with two legs (talk)

Officially by who? There is even less case for making the article UK-centric. --JWB (talk) 16:18, 6 January 2008 (UTC)

By the Ministry of Defence (United Kingdom) who own the copyright on Arnold's book. And I am not suggesting making the article anything but English-language-centric. Now stop wasting my time. Man with two legs (talk) 17:07, 6 January 2008 (UTC)

Now that we know where and when "boosting" was used to describe one-stage layer cake weapons, those specifics can be added to the article. --JWB (talk) 01:24, 7 January 2008 (UTC)

BTW, what other countries have Teller-Ulam weapons? Man with two legs (talk) 14:46, 6 January 2008 (UTC)

Teller-Ulam design says right at the top that France and China have them. --JWB (talk) 16:18, 6 January 2008 (UTC)

I was referring to the "later nuclear powers" you alluded to above. Man with two legs (talk) 17:07, 6 January 2008 (UTC)

Israel is suggested in the Teller-Ulam article. Many sources say Israel has thermonuclear weapons including neutron bombs, which can only be done as a radiation implosion design. [3] states that all later nations have used the Teller-Ulam design. --JWB (talk) 01:24, 7 January 2008 (UTC)

Questioning the need for this article

1. This article has been rated Start-Class and has a warning about lack of sources.

2. The bulk of this information has been incorporated into Nuclear weapon design where the reader can see it in a useful broader context.

3. Instead of fixing it and bringing it up to acceptable quality, should it be simply eliminated?

HowardMorland (talk) 12:28, 8 May 2008 (UTC)

1. Sources have in fact been added since the lack of sources tag, which is now incorrect. The Start-Class tag also dates back some time.
2. I think this article does in fact have more detail and can be considered a subarticle. Nuclear weapon design is already longer than policy suggests; when you edit it, you get a warning This page is 84 kilobytes long. It may be appropriate to split this article into smaller, more specific articles. See Wikipedia:Article size. Given this, it will have to summarize and send more detailed coverage to subarticles soon, if not already.
3. What fixes do you think are necessary?

Teller-Ulam design, on the other hand, is closer to a duplicate article on the whole topic, though it still has some difference in emphasis.

One split that has occurred to me as reasonable is an article on History of nuclear weapons vs. a Nuclear weapon design that concentrates on modern designs. --18:01, 8 May 2008 (UTC)

Last section still problematic

Early thermonuclear weapon designs such as the Joe-4, the Soviet "Layer Cake", used large amounts of fusion to induce fission in the uranium-238 atoms that make up depleted uranium.

What is a "large amount"? It is not large compared with the amount of fusion in a Teller-Ulam (two-stage) design.

Also, why only list depleted uranium and exclude natural and enriched uranium?

These weapons had a fissile core surrounded by a layer of lithium-6 deuteride, in turn surrounded by a layer of depleted uranium. Some designs (including the layer cake) had several alternate layers of these materials.

Why not just say they had multiple layers then? Alarm Clock also had multiple layers.[4]

The Soviet Layer Cake was similar to the American Alarm Clock, which was never built, and the British Green Bamboo, which was built but never tested.

When this type of bomb explodes, the fission of the highly enriched uranium or plutonium core creates neutrons, some of which escape and strike atoms of lithium-6, creating tritium.

Fissile should not be described as "core" if much of the fusion fuel is inside some fissile layers.

At the temperature created by fission in the core, tritium and deuterium can undergo thermonuclear fusion without a high level of compression. The fusion of tritium and deuterium produces a neutron with an energy of 14 MeV—a much higher energy than the 1 MeV of the neutron that began the reaction. This creation of high-energy neutrons, rather than energy yield, is the main purpose of fusion in this kind of weapon.

It is the main purpose of fusion in almost all staged thermonuclear weapons too, so this sentence is misleading.

This 14 MeV neutron then strikes an atom of uranium-238, causing fission: without this fusion stage, the original 1 MeV neutron hitting an atom of uranium-238 would probably have just been absorbed. This fission then releases energy and also neutrons, which then create more tritium from the remaining lithium-6, and so on, in a continuous cycle. Energy from fission of uranium-238 is useful in weapons: both because depleted uranium is very much cheaper than highly enriched uranium and because it cannot go critical and is therefore less likely to be involved in a catastrophic accident.

Decreased criticality is true not only of depleted and natural uranium, but also low-enriched uranium and even uranium with U-235 content slightly greater than 20%, the definition of HEU.

This kind of thermonuclear weapon can produce up to 20% of its yield from fusion, with the rest coming from fission and is limited in yield to less than one megaton of TNT (4 PJ) equivalent. Joe-4 yielded 400 kilotons of TNT (1.7 PJ). In comparison, a true hydrogen bomb produces typically 50% of its yield from fusion, with 97% having been achieved, and there is no upper limit to its explosive yield.

Estimates of 75% or more are what I've been hearing.

4 grams per warhead needed?

There is a source and some usable content at Tritium#Boosting that could be moved or copied here. The source by Hisham Zerriffi says "the estimated quantity needed is 4 grams per warhead." -- Petri Krohn (talk) 13:52, 21 November 2010 (UTC)

That photo

This article is not about multi-stage weapons, and yet it has a photo of one being tested (Ivy Mike). 180.200.183.94 (talk) 11:19, 27 February 2015 (UTC)

External links modified

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Link to German Wikipedia Article

There is no link to a German article, and I do not know how to edit links, so maybe somebody can help? Deutsch ---- https://de.wikipedia.org/wiki/Kernwaffentechnik#Geboostete_Spaltbomben

The German article is organized in a different manner. Boosted weapons is a section of "nuclear weapon technology". The link I'm giving is to the appropriate section.

76.254.31.171 (talk) 06:33, 17 January 2017 (UTC)

Bad section

Some of this article is very misguided. The problems seem so consistently wrong in the following quote that it is hard to imagine it is not intentionally wrong: . '....Deuterium-tritium fusion neutrons are extremely energetic, seven times more energetic than an average fission neutron, which makes them much more likely to be captured in the fissile material and lead to fission. This is due to several reasons: Their high velocity creates the opposite of time absorption: time magnification. When these energetic neutrons strike a fissile nucleus, a much larger number of secondary neutrons are released by the fission (e.g. 4.6 vs 2.9 for Pu-239). The fission cross section is larger both in absolute terms, and in proportion to the scattering and capture cross section...' . Not one of those supposed reasons is without serious problems.

The first reason, 'time magnification' is a made-up techno-sounding term. Note there is no link to any such buzz word in wikipedia. Note there is no footnote number for a supporting link for this or any of the claims in this section. Perhaps the author was dreaming about the relativistic effect known as 'time dilation'. If that was it, correcting the name won't help. Time dilation would delay the beta decay of free neutrons, but the halflife of that is many orders of magnitude higher than the processes discussed here and does not have any meaningful effect for nuclear weapons. . The second supposed reason fails because it is not related causally to the question it is supposed to answer, namely, why the more energetic d-t fusions neutrons might be more likely to be captured in fissile matetial and result in fission. The additional fission neutrons produced by d-t fusion neutrons is a result and not a cause of absorption. . The third supposed reason is just flat wrong. With the possible exception of u238 over very specific ranges, the absorption and fission crosssections are smaller at higher energies over an range of significance. . . Please review and delete this section. You can try to find support for those claims in question, but you will be looking a long time, so better to take out the offending inaccuracies in the interim. . 98.183.55.219 (talk) 18:19, 17 March 2017 (UTC)BGriffin

So... This came from: Carey Sublette's NW FAQ sec 4.3.1 and the original source says:

4.3.1 Fusion Boosted Fission Weapons

Fusion boosting is a technique for increasing the efficiency of a small light weight fission bomb by introducing a modest amount of deuterium- tritium mixture (typically containing 2-3 g of tritium) inside the fission core. As the fission chain reaction proceeds and the core temperature rises at some point the fusion reaction begins to occur at a significant rate. This reaction injects fusion neutrons into the core, causing the neutron population to rise faster than it would from fission alone (that is, the effective value of alpha increases).

The fusion neutrons are extremely energetic, seven times more energetic than an average fission neutron, which causes them to boost the overall alpha far out of proportion to their numbers. Is this due to several reasons:

1. Their high velocity creates the opposite of time absorption - time magnification.

2. When these energetic neutrons strike a fissile nucleus a much larger number of secondary neutrons are released (e.g. 4.6 vs 2.9 for Pu-239).

3. The fission cross section is larger in both absolute terms, and in proportion to scattering and capture cross sections.

Taking these factors into account, the maximum alpha value for plutonium (density 19.8) is some 8 times higher than for an average fission neutron (2.5x10^9 vs 3x10^8).

Obviously someone has subsequently attempted to simplify and mangled some of the technical details. Losing the "boost the alpha" bit is a key tech detail whoever edited it lost / did not understand. Obviously not a bomb designer there, but no Wikipedia expectations that editors are experts.

It's not a good idea to yank it all out. Fixing the goofs in "improvements" would be a good idea. And it should be a cited quote as it's lifted from an external source (I expect / hope Carey wouldn't mind but it needs to credit it appropriately, and despite knowing him I can't speak for him or his intellectual property rights). Georgewilliamherbert (talk) 00:48, 18 March 2017 (UTC)

Literature

I believe this is the technique used in the Tom Clancy book, The Sum Of All Fears. In the book, they discuss recovering a plutonium ingot from a Mark 12 bomb "lost" in the Yom Kippur war. The bulk of the story is about a former Soviet nuclear scientist and his protege that use metallurgical methods to reshape the ingot to produce a high yield weapon for some terrorists. At one point, they obtain some boosting fuel (it's been a while, could have been Lithium) that adds significant neutrons in order to make the explosion go from a 10Kt yield to a 400Kt yield. I read the Sum Of All Fears Wikipedia article just now, and it omits these details. Anyway, my point is, you might consider adding an "in the literature" section to call out to this. Maybe someone with more recent knowledge of the book can shore up my description. — Preceding unsigned comment added by 96.255.18.130 (talk) 11:18, 3 April 2017 (UTC)

Fusion? Not.

Lithium7, Deuterium, and Tritium participate in (n,2n) neutron doubling reactions. Deuterium splits circa 2MeV into proton and neutron. Beryllium9 generates neutrons from high MeV alpha emission in Polonium210/Beryllium neutron sources. Nazi Germany sought to enhance natural Uranium by adding “light metals” to increase Uranium neutron flux. Shjacks45 (talk) 00:03, 16 November 2019 (UTC)