Small-scale fusion back in the news!

[Lumpy]

Evidence Bubbles Over To Support Tabletop Nuclear Fusion Device

We can only hope. Maybe that would finally end the “Peak Oil” worries.

[Rabid_Squirrel]

It’s not looking very likely. New Scientist link.

The article says that it’s using sonoluminescence to detect fusion. I’m not familar with the technique - is it likely that the light flashes came from another source or is due to another phenomena?

Can’t find any follow up papers in Science since 2002 (did full text search on ’
Taleyarkhan’) - which is a bit suspicious.

[wolf_meister]

The last 2 paragraphs are very important. They state that the process has not yet reached the break-even point.

[Q.E.D]

I find this part to be relatively telling:

Within nanoseconds these large bubbles contract with tremendous force, returning to roughly their original size, and release flashes of light in a well-known phenomenon known as sonoluminescence. Because the bubbles grow to such a relatively large size before they implode, their contraction causes extreme temperatures and pressures comparable to those found in the interiors of stars.

According to various gas laws, one such expansion-contaction cycle should return the contained gasses to their starting temperature. And why would the pressure be any different than when the bubble first formed, if it goes back to the same size it started from? It wouldn’t. My conclusion is that this is complete BS, like the original cold fusion claims.

[bibliophage]

What exactly is the factual question here?

[bonzer]

No, I don’t quite see the factual question in the OP either, but FWIW I discussed the controversy around Taleyarkhan’s earlier paper in this previous GQ thread.

The new paper doesn’t seem to be available yet and any comment prior to that would be indulging science by press release.

[Omphaloskeptic]

@Q.E.D.

According to various gas laws, one such expansion-contaction cycle should return the contained gasses to their starting temperature. And why would the pressure be any different than when the bubble first formed, if it goes back to the same size it started from? It wouldn’t. My conclusion is that this is complete BS, like the original cold fusion claims.

This is true if the bubble is adiabatic, but that’s not the case here. The liquid may boil or recondense at the interface, for example, changing the pressure inside the bubble. The expansion-recontraction cycle is fast enough that the interface may not be in equilibrium, so there’s an asymmetry between the expansion and collapse.

I think that the temperature and pressure inside collapsing bubbles have been measured (by multiple experiments) to be surprisingly high, so this in itself is not in doubt. What’s questionable is whether the temperatures are high enough for fusion.

[Erroneous]

Looks like the article’s online now

The abstract:

Time spectra of neutron and sonoluminescence emissions were measured in cavitation experiments with chilled deuterated acetone. Statistically significant neutron and gamma ray emissions were measured with a calibrated liquid-scintillation detector, and sonoluminescence emissions were measured with a photomultiplier tube. The neutron and sonoluminescence emissions were found to be time correlated over the time of significant bubble cluster dynamics. The neutron emission energy was less than 2.5 MeV and the neutron emission rate was up to ~4×105 n/s. Measurements of tritium production were also performed and these data implied a neutron emission rate due to D-D fusion which agreed with what was measured. In contrast, control experiments using normal acetone did not result in statistically significant tritium activity, or neutron or gamma ray emissions.

I was going to say it’s too bad that my insititutional access has lapsed since I’m not a student any more, but having read the abstract, I doubt that I would have understood the article anyway.

[Wikkit]

@Erroneous

I was going to say it’s too bad that my insititutional access has lapsed since I’m not a student any more, but having read the abstract, I doubt that I would have understood the article anyway.

Buzzword heavy, but fairly low tech. I don’t see the difference between this and the last time they claimed to accomplish this, but I haven’t read very deep. Please don’t think I’m taking down, just being thorough.

Time spectra of neutron and sonoluminescence emissions were measured in cavitation experiments with chilled deuterated acetone.

Cavitation is forming and collapsing bubbles, sonoluminescence is just light that gets emitted when bubbles collapse. Neutron emission would be an indication of fusion. Acetone is a solvent, CH[sub]3[/sub]COCH[sub]3[/sub]. Deuterated acetone is acetone in which the hydrogen atoms have a proton and a neutron, unlike normal hydrogen that just has a proton. It was cold.

Statistically significant neutron and gamma ray emissions were measured with a calibrated liquid-scintillation detector, and sonoluminescence emissions were measured with a photomultiplier tube.

If there is fusion, you have to be able to measure it, and it should be putting out neutrons and gamma rays. The “calibrated liquid-scintillation detector” is just a bit of some chemical that glows under gamma radiation. By measuring the glow, you can measure the amount of radiation. They’re very sensitive, so they’re not measuring much. A photomultiplier tube is a vacuum tube that can measure tiny amounts of light, like really good night vision.

The neutron and sonoluminescence emissions were found to be time correlated over the time of significant bubble cluster dynamics.

There, they’re just being deliberately obtuse. “The radiation came out when the bubbles happened.”

The neutron emission energy was less than 2.5 MeV and the neutron emission rate was up to ~4×105 n/s.

Here, they make efficiency claims. MeV is a measure of energy, 2.5 MeV means the neutrons are coming out at about fifty million degrees F, and they’re getting about 400000 of them per second.

Measurements of tritium production were also performed and these data implied a neutron emission rate due to D-D fusion which agreed with what was measured.

The hydrogen with the one proton and one neutron is called deuterium. With one proton and two neutrons, it’s called tritium. D-D fusion is deuterium-deuterium, which makes either an atom of helium and a neutron, or an atom of tritium and a proton. Half of the D-D fusion events should be making tritium, so you can figure out how much fusion you did by measuring how much tritium is produced. Deuterium is relatively stable, whereas tritium is radioactive, used for cool glow-in-the-dark green exit signs that last for 10 years.

In contrast, control experiments using normal acetone did not result in statistically significant tritium activity, or neutron or gamma ray emissions.

Not getting anything out of a similar setup with normal acetone is important, because it means you’re not just seeing what you want to see. Not that they still might be making this up.

I think this is why we have science writers.

Small scale fusion isn’t difficult, anyone can build or buy a Farnsworth Fusor, and have hydrogen making nookie on their kitchen table. The heavy acetone approach is interesting, but not likely to be the precursor to a Mr. Fusion that you can mount in your DeLorean.