Talk:Teller-Ulam design

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[edit] "Expiration" of Hydrogen-warheads??

Tritium has a half life of just 12 years, so to maintain a viable warhead, doesn't this mean that the tritium in hydrogen weaponry must be continually replenished with new tritium every 6 months or so? Wouldn't this require the existence of processing facilities to manufacture additional tritium near the warhead's holding areas?


[edit] Wow

I can't believe this article is new. It's gorgeous. Scary topic, of course, but v. nicely done. jengod 02:58, July 25, 2005 (UTC)

Thanks, it's just something I've studied for awhile, so I had all of the references handy. --Fastfission 10:51, 25 July 2005 (UTC)

[edit] X-rays

The article describes "X-rays ... which reflect along the inside of the casing" and the diagram gives the impression that X-rays ricochet around the inside of the casing. It is pretty hard to make X-rays reflect: they either pass through or are absorbed by the reflecting medium. Astronomical X-ray telescopes (Chandra, XMM, ASCA) are forced to resort to grazing incidence and nested nearly-cylindrial mirrors.

There is a much better description in radiation implosion:

The term reflector is misleading, since it gives the reader an idea that the device works like a mirror. Some of the X-rays are diffused or scattered, but the majority of the energy transport happens by a two-step process: the X-ray reflector is heated to a high temperature by the flux from the primary, and then it emits X-rays which travel to the secondary. Various classified methods are used to improve the performance of the reflection process.

This seems to imply that the casing is irradiated such that it fluoresces in the X-ray. -- ALoan (Talk) 08:31, 25 July 2005 (UTC)

Hmm, that's interesting. I'd appreciate it if anyone with technical insights could help smooth out that section of the article — I am not a physicist, and am likely to make mistakes (I thought they were "reflected" like a mirror, I must admit, but I have no idea about such things except what I have read, none of which is what I'd call "technical literature"). My only fear in such things, of course, is that I don't want the article to have too much confidence in things which are not securely known (i.e., the secret things), but with a little care that can be avoided. --Fastfission 10:55, 25 July 2005 (UTC)
Also, about the diagram: I've never seen it drawn any other way than "reflecting" like that. I can't think of a better way of drawing it though. --Fastfission 17:15, 25 July 2005 (UTC)
Just as a note: I updated the text to reflect this better. --Fastfission 17:20, 6 August 2005 (UTC)

[edit] Suggestions

  1. That the sentence about Ivy Mike's impracticability be reenforced, from "The "Ivy Mike" device was far too large to be dropped" to "The elaborate refrigeration plant necessary to keep its fuel liquid meant Ivy Mike was too heavy and too complex to be of practical use." or something similar.
  2. That a bit of explanation be added to W-88 revelations. The article says its primary is oblong (IMO "oblate" is a better word for this than "oblong", as "oblong" means "rectangular" to most people) and that W-88 is intended for MIRVs. I think we should add why it's oblate, and why this is such a big deal. My understanding of this is that the diameter of the MIRV is limited by the diameter of the primary - if you can make an oblate primary work properly, then you can get the same bang from a smaller diameter MIRV or missile, which gives you nicer characteristics for that missle (faster, better gas milage, etc.). The reason an established nuclear power might be thought to want to steal info on W-88 (it's not like China doesn't know how to make A bombs already) is that the calculations needed to get a nonspherical primary to explode efficiently are orders of magnitude harder than those for a spherical primary.
  3. The article isn't entirely clear about this: should it mention that the US had already exploded a boosted device (Greenhouse George) before Ivy Mike, so that no-one had lingering doubts that the secondary wouldn't light? The article does mention boosting, but for the US program it's not clear that boosting came before the super (the wording for the Soviet program is clear in that respect).

-- Finlay McWalter | Talk 13:37, August 4, 2005 (UTC)

Good suggestions -- I'll try to incorporate these in and clarify what is not clear. --Fastfission 12:46, 5 August 2005 (UTC)
I think I've implemented all of these suggestions. --Fastfission 17:20, 6 August 2005 (UTC)


[edit] The Foam Plasma Pressure Fallacy

Aaaaarrrrggghhhhhh, not the foam plasma pressure fallacy again! Doesn't anyone read the FAQ anymore? Nuclear Weapon FAQ Sect 4.4.4.2.2, Radiation Channel. The implosion pressure does not come from the filler foam. It's possible to build and fire a Teller-Ulam device with a completely empty radiation channel in the radiation case. The foam is there to retard initial liner and pusher ablation long enough for the energy distribution to even out smoothly. The pressures generated are trivial compared to those required to implode the secondary. What generates the implosion pressure is the ablation (effectively as if it were an in-turned rocket motor) of the fusion pusher layer of the tamper/pusher assembly. A large portion of the tamper/pusher ablates away in this process, leaving a thinner tamper layer up against the now-compressed fuel layer.

I know Moorland's article said that the foam plasma pressure was significant, but Morland wasn't a bomb physicist, and we know a lot more now than we did then. These inaccurate descriptions have got to stop, they're grossly misleading everyone.

I can rewrite the article's implosion description sometime this week, but for now, it flunks peer review on that basis. Sorry. It's not your fault for believing the Morland article, but Morland got that detail (and several others) wrong... Gotta get it right here. Georgewilliamherbert 09:12, 8 August 2005 (UTC)

Per discussion here and on the Peer Review page, I intend to redo the implosion physics section and correct the foam plasma issue probably Wednesday night, Aug 10. Georgewilliamherbert 02:59, 10 August 2005 (UTC)

[edit] Split the article

In my humble opinion... The history stuff should be split into a separate article, with this article containing a shorter summary and link. This article has just gotten too big. Georgewilliamherbert 06:41, 14 August 2005 (UTC)

[edit] Neutron Bombardment, Aluminium?

Neutron Bombardment of the lithium deutride - Wouldn't that require something to slow down the neutrons to assist the deutrium to become tritrium? Something like aluminium casing on the inside of the lead / uranium secondary casing? or does the lead casing on the outside of the secondary do a good enough job of slowing down the neutrons? Or is it the Li that does the job? or a combination?

  • You should sign your notes (typing four ~ characters in a row gives the name/date signature you see a lot). To answer your question, it's not neutrons being absorbed by the deuterium to make tritium, it's neutrons fissioning the lithium, into tritium, helium-4, and with the Li-7 isotope of Lithium, another free (lower energy) neutron. The original neutron is captured in the lithium nucleus but only briefly. The reactions are described in detail in the Nuclear Weapons FAQ. Georgewilliamherbert 21:14, 30 October 2005 (UTC)

[edit] Two small issues

Both in the "Basic principle" section:

  • "When fired, the plutonium and/or uranium-235 core would be compressed" Is it really possible to build a uranium implosion bomb? Is there any reason to suppose anyone has ever built a teller-ulam fusion bomb with a U235 primary?
  • "unenriched uranium-238" seems redundant, and confusing (there's really no such think as "enriched U238", so surely there can't be such a thing as "unenriched U238". Shouldn't this just read either "uranium-238" or "depleted uranium"?

-- Finlay McWalter | Talk 02:47, 14 January 2006 (UTC)

First question: Yes, Uranium implosion has been widely discussed. It's a lot easier to do that Plutonium implosion, since U-235 has so much fewer random neutrons generated and the risk of predetonation goes way down. Including the metalurgical issues with Plutonium, it's considered a much better long-term stable bomb design approach, in fact... U metal stays that way, in its standard phase, as far as we know essentially forever without suffering physical degradation or phase changes, as long as you protect it from oxidization.
Second question: I think I agree that the phrasing has gotten bad. Natural, unenriched Uranium is a valid choice there, as is "U-238", or "Depleted Uranium". Unenriched + U-238 is a nonsequitur. Georgewilliamherbert 03:06, 14 January 2006 (UTC)
  • And on point 1 -- I believe that it is thought that most modern cores are composite u-235/pu cores. More bang for the buck or something like that. --Fastfission 02:41, 10 March 2006 (UTC)

[edit] Recent edits

While I appreciate User:Bockspur's enthusiasm, I'm not so hot on all of the edits he/she recently made.[1] I feel they have simply made things more confusing, dressed them up in more complicated (but in the end, not meaningful) language, and much of it is unsourced. The only source added is a paper which nobody outside the classified community has seen, which doesn't help anybody very much, and I suspect Bockspur has not seen it either. But before reverting I thought I'd solicit a second opinion. --Fastfission 02:41, 10 March 2006 (UTC)


[edit] Bockspur replies10th of mar 06:outside of the classified community?

the paper is not that restricted, merely it's not currently availible on the internet or in most libraries. there is nothing ground shaking in the paper, in fact if you were going to use it as a reciepe to make a fusion device you would definetely fail. The paper outlines two key elements for compressing the secondary: the use of soft x-ray radiation proposed by teller as opposed to particle compression by ulam and the concept of ablation. unfortunately teller makes the mistake of assuming that he can bounce the soft x-rays of the interior of the casing like ping pongs. Later someone else would correct this with the hohlraum concept. Also, the use of a second fission source inside of the the secondary to act as a neutron source and to ignite the compressed but relatively cool dueterium liquid is completely missing in the paper. This too would come later.

The paper use to be availible at the library of the university that use to manage LL, take a wild guess where that was. I think some undergrad must have stolen it; technically the paper is classified but for all purposes next to useless other than to point how brillant teller was.

Just because you haven't seen something doesn't make it imaginary.If you would like to get a copy make a fia request, i personally see no reason to reject one for such an aged document. but , as i said earlier you'll be a little disappointed when it doesn't turn out to contain much that can't be done with pencil a piece paper calculation. kid i have a Phd in physics, and a masters in applied math and am working on a phd in math; which is an order of magnitude harder than physics. I've never written a NPDE code for a nuclear device but i have used very similar integrator schemes to run icf simulations in grad school. And yes we read everything in the library hoping for a break that would make the lab projects easier. But , I'm sure that i'm not alone in that boat and others have probably had access to more pertinint information, but , until those people show up to edit my work, you'll just have to be content with my chicken scratchings, ok kiddo.

  • Please see our Verifiability policy. No references can be given that cannot be verified or confirmed. Hard-and-fast rule, and you can make up all sorts of noise about how you have a PhD or secret access or whatever (every crackpot suddenly becomes a PhD on here, it seems) but it doesn't go into the article, simple as that. --Fastfission 00:46, 13 March 2006 (UTC)

[edit] DOE statements

One thing I don't understand from reading the article is, why does the DOE keep declassifying these pointless little statements? What's the point? Who benefits? --220.111.92.12 15:38, 23 April 2006 (UTC)

Several reasons.
  • Much of the technology and information ends up being dual-use, and eventually the other, unclassified use ends up needing to have some sort of reference back in to the nuclear weapons usage.
  • Much of the information accidentally or informally leaks out. Once it's been revealed, non-DOE experts can confirm its accuracy by analysis, and eventually it becomes so well known that continuing to classify it is hard.
  • Some of the information is disclosed due to its relevance to other issues, such as explosives safety, health of nuclear weapons workers, etc.
  • Some information becomes so old and obsolete that classification is pointless.
  • Finally, a lot of the info that's covered under Restricted Data is pretty silly to have classified in the first place, and is eventually just released.
Georgewilliamherbert 23:48, 24 April 2006 (UTC)

[edit] Tamper-Pusher ablation, does the tamper fission?

After ~3/4 of the tamper is ablated off, the rest being forced inwards with the fusion fuel/spark plug, does that 1/4 of the tamper also undergo fission? --Fxer 19:35, 1 June 2006 (UTC)

Depends on the design. Thermonuclear bombs can be "clean" or "dirty". "Dirty" designs us a fissionable tamper/pusher (or at least tamper), such as U-238, the fission of which typically doubles yield. "Clean" designs use a non-fissionable tamper/pusher (lead, tungsten, in some cases perhaps gold) at lower yield and no fission, but much reduced fallout.
Figuring out what modern weapons are clean and dirty is somewhat difficult, since governments tend not to discuss design details, and since underground testing became standard the fallout isn't available for analysis. Yield to weight analysis suggests the modern compact ones tend to be dirty, though. Georgewilliamherbert 20:40, 1 June 2006 (UTC)
I think what he's asking specifically is that does ablation reduce the amount of material remaining to fission, in the end? I never thought about that aspect of it, myself. --Fastfission 20:51, 1 June 2006 (UTC)
Oh, yeah. The ablation material (for example, 3/4, though it may be more or less) moves outwards and is effectively not part of the tamper fissioning.
Basic H-bombs use a single material for the ablation pusher and tamper. Really creative designs from advanced nuclear weapons nations might use different materials, with one material (say, cheap/safe lead) as the ablation pusher, and another (DU, or even HEU) as the tamper. But to know for sure where the boundary is, you almost certainly have to do an H-bomb test program... Georgewilliamherbert 21:47, 1 June 2006 (UTC)

[edit] "Dark Sun" description of Mike device

The description of the Ivy Mike device within this article does not quite agree with that given in "Dark Sun". Within Chapter 24 there is a series of five figures showing the sequence of events within the device. The caption accompanying the second figure states that "X rays from the primary vaporize polyethylene lining of Mike casing and heat it to a plasma. Plasma reradiates longer wavelength X rays that ablate surface of secondary pusher, causing rocket effect that implodes secondary, compressing and heating deuterium to fusion temperature and imploding fission sparkplug". This quite clearly states the presence of polyethylene and not polystyrene, as claimed in the article. The polyethylene is a source of plasma although compression of the secondary is by ablation of the pusher, not radiation from the primary. RegIP 16:51, 16 August 2006 (UTC)

I would have to check again but I'm pretty sure that Rhodes actually includes two slightly different descriptions of how it works in the book, something of a contradiction in any case. --Fastfission 13:11, 1 February 2007 (UTC)


[edit] Could it destroy the Whole world?

my gosh...

After reading this article, Can't you see your "Gosh" does not exist? And if he/she/[fsm] does exist then it should be obvious to you that he/she/it/fsm doesn't care at all? - Eshywiki

It can destroy the whole world within a few seconds.
and then that 'w' would be gone and a big hole would be all that is and isn't.
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