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Comment by kaycebasques | Hacker News Reader

The article is hinting that there are weapons applications for this. What types of weapons would those be? Bombs? Are there any other countries with research programs similarly far along?

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It’s less that this allows new unprecedented weapons, and more that this allows one to validate material properties in similar conditions to a nuclear bomb detonation without actually testing a full scale device. This lets one verify and refine the otherwise “magic number” constants in computer simulation code that were empirically derived 50-80 years ago.

Of course, if you’re a nascent nuclear power along the lines of NK, you just do full scale tests, treaties be damned.

North Korea hasn't signed any treaties abolishing nuclear weapons tests. In point of fact, the USA itself hasn't ratified[0] any treaties prohibiting the type of underground tests the DPRK has conducted. The US chooses not to do those (and has maintained a voluntary moratorium since 1992), but is under no obligations.

[0] https://en.wikipedia.org/wiki/Comprehensive_Nuclear-Test-Ban...

Notwithstanding the US's deeply hypocritical stance on treaties it hasn't ratified but others must follow, North Korea did in 1985 sign the NPT which forbids them even building nuclear weapons, as well as the 1992 "South-North Joint Declaration on the Denuclearization of the Korean Peninsula" where they explicitly pledge not to test nuclear weapons (which they indeed didn't do until 2006).

https://www.armscontrol.org/factsheets/dprkchron

Sure; though to be fair, North Korea withdrew from the NNPT a full three years before its first nuclear test (2003, 2006).

The US walked away from deals with NK[1].

An agreement was made to suspend the nuclear program in 1994, the US then refused to certify it after 9/11 due to NK's transfers of technology to Iran.

Whatever anyone thinks about that, it's got nothing to do with the 1994 agreement (which is easy to read, it's only a few pages).

NK subsequently withdrew from the NPT, and got a nuclear weapon in 2006.

> South-North Joint Declaration on the Denuclearization of the Korean Peninsula" [...]

I believe that NK's stance on the matter is that SK is hosting military bases for a foreign nuclear armed power (the US).

So it's implicitly threatened by a US nuclear attacks, and that threat became explicit under Trump.

1. https://www.cfr.org/timeline/north-korean-nuclear-negotiatio...

You know, the best part is that US is doing this same thing with the incoming president shitting on the work on the previous president for the sake of domestic politics, and not getting a new deal with the belligerent state!

So instead of Clintons deal Bush tore it up, didn't get anything, and now North Korea has nuclear weapons. And instead of Obamas deal Trump tore it up and got nothing. Now Biden also wants a new deal, so we know how this version of story likely ends (especially with Bibi bombing out of control, the pro-nuke factions in Iran have great fuel for winning the go/no-go argument on building a weapon.)

If I'm not mistaken it's used instead of actual nuclear weapons tests. Wikipedia says the following about the NIF

> It supports nuclear weapon maintenance and design by studying the behavior of matter under the conditions found within nuclear explosions.

The mission of NIF is and has always been to subvert the test ban treaties. It is written down in the original proposal, which are available on the web from the agency. NIF has no civilian energy applications, and will never have any.

> to subvert the test ban treaties

How is this subverting the treaties? The test ban is about not detonating nuclear weapons, and the NIF complies with that.

I suppose it depends on how you interpret the intent of the test ban. If the intent was to stop detonations because they are bad in themselves, then it's not subversive. If the intent was to stop detonations in order to curtail further weapons development, then it is.

It's a test ban treaty, not an agreement to stop development of nuclear weapons.

Detonations are bad in of themselves, they cause various items to become contaminated, causing issues for imaging and science applications. Being able to ignite fusion without using a fission bomb to do it lets you prevent the contamination without sacrificing your negotiating position. Remember, the best lie is the truth, your enemy can't figure out your nuclear weapons don't work if they actually work.

Fission bombs can be tested with subcritical explosions. You have a plutonium core (a sphere the size of a grapefruit) and surround it with high explosives. Not as many as for an actual detonation. You blow them up, create the implosion, and trigger a subcritical fission reaction, or one that is very slightly supercritical. You then take lots of measurements (temperature increase, X and gamma rays, neutrons, etc) and see if they align with your theoretical models. If they do, you have extremely high confidence that the bomb will work as designed.

Now, virtually all nukes in the US arsenal have a fusion bomb stage too. The way that works in practice is this: you first detonate the fission component of the bomb, and that produces a huge amount of X-rays. It's so huge that the wavefront of the X-rays behaves like a solid hammer. That's what produces the compression for the secondary. This design is called the Teller-Ulam design, and it is extremely likely that it was discovered only once (by Ulam and Teller), all other thermonuclear bombs are just the result of successful spying and secret sharing.

This X-ray hammer can't be very easily tested. That's what these guys are doing.

Now, you may wonder if Putin's guys are doing an equally good job at testing their thermonuclear bombs. We don't know, but it doesn't make a difference: the fission part of the bombs is powerful enough to create utter devastation. The fusion part adds some extra punch, but it doesn't change the scale of devastation. And the CIA is highly confident that Russia is properly testing the fission bombs, even undergoing what is called "hydronuclear" tests, which, although not formally banned, other countries don't do.

> This design is called the Teller-Ulam design, and it is extremely likely that it was discovered only once (by Ulam and Teller), all other thermonuclear bombs are just the result of successful spying and secret sharing.

Hans Bethe believed that the Soviets and the British got it by analyzing the fallout from fusion bomb tests. Apparently the high number of heavy elements suggested high rates of compression

Hans Bethe guessed based on the information available to him at the time.

But there was information not available to the West prior to the end of the Cold War.

In December 1991 two US atomic scientists, Danny Stillman and Nerses Krikorian visited the head of the former Soviet nuclear program, Yuliy Khariton [1]. In their discussions, the Americans realized that even Khariton was not aware of the extent of the Soviet spying. In any case, Khariton had a very dubious recollection of who came up with the idea of the radiation implosion (the Teller-Ulam design). This was such an ingenious idea that if it had indeed originated with one of the Soviet scientists, it would have been memorable. By the way, the Soviets did come up with a thermonuclear design, dubbed "layer cake" in the US. But it was an inferior design that resulted in a yield of only 400 kT (the RDS-6 test [2], in August 1953), which was achievable with fission only. In March 54 the US detonated a few hydrogen bombs, and indeed, the Soviets collected radioactive debris. However, Khariton told Stillman that that information was not helpful, aside from the confirmation that higher yields are somehow possible.

Throughout the month of March 1954 the Soviets played with a few ideas, but none was good. Then, miraculously in mid-April 1954, Khariton claims that his deputy Yakov Zeldovich [3] came up with the idea of radiation implosion. But other Soviet nuclear scientists that Stillman and Krikorian interviewed stated that they never heard Zeldovich confirm that story. Moreover, one of these scientists , Lev Feoktistov stated quite candidly "We had neither drawings nor accurate data from the outside, but we were prepared to catch hints and half-hints. I can't shake the feeling that in those times, we were not completely independent"

Stillman put all these things (and quite some more) in a book, The Nuclear Express [4].

[1] https://en.wikipedia.org/wiki/Yulii_Khariton

[2] https://en.wikipedia.org/wiki/Joe_4

[3] https://en.wikipedia.org/wiki/Yakov_Zeldovich

[4] https://www.google.com/books/edition/The_Nuclear_Express/qLT...

Yes, nuclear bombs/warheads

https://lasers.llnl.gov/science/nif-and-stockpile-stewardshi...

H-bombs, the entire thing they do is look at the expansion of plasma that is heated by a thermonuclear reaction. The most prominent application of expansion of a plasma heated by a thermonuclear reaction is the explosion of thermonuclear weapons.

We already have fusion bombs. Making a fusion bomb is a lot easier than creating a fusion reactor that can emit energy in a more controlled manner.

France is building a similar facility called "Laser MégaJoule" (LMJ).

https://en.wikipedia.org/wiki/Laser_M%C3%A9gajoule

Directed high energy weapons, as well as existing nuclear weapons.

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