Stimulated Gamma Decay Weapons

ExRex writes "New Scientist is reporting on a USDOD project to produce super explosives. 'An exotic kind of nuclear explosive being developed by the US Department of Defense could blur the critical distinction between conventional and nuclear weapons. The work has also raised fears that weapons based on this technology could trigger the next arms race.'"

Comments

Re:Wow...

[saskwach]

Funny, I was just reading "Starship Troopers" last night...but no, there are bans on that:

In the 1950s, the US backed away from developing nuclear mini-weapons such as the "Davy Crockett" nuclear bazooka that delivered an explosive punch of 18 tonnes of TNT. These weapons blurred the divide between the explosive power of nuclear and conventional weapons, and the government feared that military commanders would be more likely to use nuclear weapons that had a similar effect on the battlefield to conventional weapons.

That's what you're thinking of...this is not actually a nuke.

Re:Potential Power Source!

[LinuxParanoid]

You raise a good point, but...

Energy density != Energy efficiency.

You want the former for weapons, the latter for commercial energy production.

(Although in the case of fuel substitutes for cars, both are actually quite important. No matter how much you improve the efficiency and cost of hydrogen or fuel cells, its hard to beat oil's energy density.)

Anyway, based on that article, it appears to me that it takes a heck of a lot of energy to make and "energize" the halfnium with protons (or eventually photons). A lot more than you get out when you eventually shoot the X-Ray in and get that 60-fold increase out. That 60-fold increase is just releasing energy you put in the substance gradually earlier. So it isn't necessarily energy efficient, just energy-dense. Of course, as they make the substance cheaper, that is a sign that they're improving the energy efficiency of the manufacturing process, so who knows how good they'll get at that. Clearly they have a long way to go in any case. Particle accelerators aren't cheap, either dollar-wise or energy-wise.

Re:Potential Power Source!

[Idarubicin]

This interesting technology could potentially lead to some better new-age energy sources.

Well, it's a way to store energy, perhaps, but it can't act as a source in and of itself. Excited-state nuclei aren't just lying around in the ground--they tend to have short half-lives, from decades down to the tiniest fractions of a second. To create these metastable nuclei, you have to put in at least as much energy as you're taking out.

Mind, these metastable isotopes already have nonmilitary uses. Technetium-99m has long been used as a radioactive tracer in medicine. It is produced from the decay of molybdenum-99, and has a half-life of about six hours.

Re:Detection and control.

[Imabug]

It seems a group of scientists at LLNL, Los Alamos and Argonne have data from a couple of years ago that challenges the principles behind this gamma ray weapon.

Read the story here

Excerpts from the story:

Using the Advanced Photon Source at Argonne, which has more than 100,000 times higher X-ray intensity than the dental X-ray machine used in the original experiment, and a sample of isomeric Hf-178 fabricated at Los Alamos, the team of physicists expected to see an enormous signal indicating a controlled release of energy stored in the long lived nuclear excited state. However, the scientists observed no such signal and established an upper limit consistent with nuclear science and orders of magnitude below previous reports.

...

The team set out to verify previous findings that stated a nuclear isomer, (hafnium) Hf-178, which has a half life of 31 years, is able to release a controlled amount of energy (decay quicker) when tickled with dental machine X-rays. However, when the team turned the APS X-ray beam onto the sample of 31-yr. Hf-178, no detectable increase of the isomer decay occurred. In other words, the X-ray irradiation did not decrease the time it takes for hafnium to decay; a result that Becker and the team claim is consistent with nuclear physics.

Re:Other than useful mass

[Phanatic1a]

You could produce a small yield neutron bomb and do the same thing and be less dirty with the radioactive material.


Huh? A small-yield neutron bomb?

A neutron bomb is a fusion warhead. As such, it requires a fission warhead to set it off. A 'small yield' fission warhead is, at the very least, going to be equivalent to anywhere from a few hundred to a few thousand tons of TNT, and the second stage fusion warhead, which releases the neutrons, is going to add to that. "Small-yield fusion bomb" is something of an oxymoron.

And neutron bombs are rather dirty, indeed. In addition to the fallout from the fission primary, the intense neutron flux transmutes many substances, notably metals, in the surrounding area into radioisotopes. Some of those will have rather long half-lives.

Re:Wow...

[jafiwam]

The "Davy Crockett" is more accurately described as a portable recoilless rifle launched nuke. It's about the same size as a more modern TOW setup, can go on a tripod. It probably took 4 or 5 guys to carry all the stuff on foot, so it's not really a bazooka (an anti-tank weapon).

It had a "dial a yield" warhead from 10 to 250(1) Tons of TNT. The higher settings would cause almost certain death to the launch crew as the lethal radiation kill zone was much farther than the maximum range of even the biggest launcher (2 miles or so).

One of the new thingies or an old Davy Crockett might be a good device to wipe out a bunch of tanks out in a desert, but it's still a friggin huge weapon compared to the precision stuff used nowdays. (I doubt any army will be dumb enough to go head-to-head against the US Army in desert tank battle for a looonngg time. Even the Iraqis didn't try it a second time.)

Here's some links with pictures:
http://www.wikipedia.org/wiki/Davy_Crockett_(nucle ar_device)

http://www.guntruck.com/DavyCrockett.html

not very plausible

[bcrowell]

I did my thesis research on isomers like these, and this doesn't sound plausible to me at all. Here is some data on the isomer they're talking about. The reason this isomer is cool from a basic research point of view is that it has 16 units of spin, which is a huge amount for a long-lived state; most high-spin states decay rapidly (within nanoseconds) by emitting gamma-rays, which means there's no way to store them in bulk, not even in theory. The reason this particular state has such an unusually long half-life is that there aren't any lower-energy states with similar spins, and it's hard to get a gamma ray to carry off more than one or two units of spin.

The article says they're planning to make this isomer in gram quantities by shooting gamma rays into a sample of ground-state 178Hf, which is the reverse of the decay process. The problem is that the cross-section is going to be very low, for exactly the same reason: it's hard to get a photon to carry many units of angular momentum into or out of a nucleus. People have discussed making small (microgram) quantities of it for use as a high-spin target in reactor experiments, but nobody could figure out any reasonable way to do it.

You also have to realize that although the half-life of 31 years is long compared to most isomeric states, it's still relatively short compared to, say, 235U, which lives for gazillions of years. The relatively short half-life means that even if you could get a gram of this stuff, it'd be virtually impossible to handle safely. It would be much more radioactive than a subcritical mass of weapons-grade fissionables.

There's a long history of impractical ideas like this, going back to the Reagan-era idea of a gamma-ray laser. Luckily we're still only faced with the same basic bomb threats that've been around since the Kennedy administration, but that's bad enough. The real thing to worry about, IMO, is the nuclear cauldron that's shaping up in Asia: Iran, Afghanistan, India, and North Korea.

OT: Are other people finding Slashdot extremely slow and unresonsive recently? I can hardle even access it anymore.

Timeline

[Oestergaard]

The article claims that the AF supplier, SRS Technologies, said that technology to provide the materials needed in "gram quantities" would be about five years away (he say they "would exist within five years").

Certainly, for a project such as this, it is completely unbelievable that one of the key entities in the weapon development would give anyone and everyone a remotely precise estimate as to when larger scale production (and real weapon production) could possibly begin.

The true timeline must be years away from that. In one of the two directions possible... Which poses an interesting question: are real weapons based on this technology available today already, and did they agree to participate in the story simply to "prepare" the general public for real-world testing which will happen in the following year or two? Or do they know that others are working on this technology as well, and therefore need to tell their nation that "they're right on it", when some other country launches their tests within the next year or two?

That's speculation. Time will show.

What will be interesting to see, too, is how the real testing will commence. Currently they are working on three possibly viable materials. Most likely they will have different characteristics, and their exact effects in a real-world scenario will be impossible to simulate.

In 1945, there were two materials available for fission weapons - uranium and plutonium. One bomb was made with each, and the two bombs were dropped on each their civilian target. Hiroshima got Uranium, Nagasaki got Plutonium.

Which three cities will this new weapon be tested on? And to raise the bar, which city will get Hafnium, which one will get Thorium, and which one will get Niobium?

Oh, and don't tell me war has gone soft and that the weapon would not be tested on civilian targets this time... A gamma discharge weapon has many of the properties of a neutron weapon - it is extremely useful mostly against people (and electronics - it will kill you *and* your Aibo, oh the wonders of modern civilization ;).

On a second note... Did anyone notice how there is no longer anything called a "neutron bomb"? It is, today, called a "low yield" bomb. In the media at least. Because it's blast and heat isn't as great as "real" fusion weapons. Neutron weapons are now almost politically correct - at least, the public wouldn't raise an eye if they were told a low-yield bomb was dropped to stop riots in some third-world city.

Now, to go find lead coating for my tinfoil hat.