[HiTech RedNeck]

If they're getting bubbles "the size of a pencil top eraser" by irradiating with neutrons, why doesn't the agitation splash the acetone all over the place. Also why the wimpy shielding if they expect it to produce more neutrons (let alone the original neutrons)... paraffin blocks?!? It ought to be behind some thick lead.

[Rifleman]

Because the container is closed, not open at the top. And because they need to stop neutrons not gamma rays.

[FreeAtlanta]

Typically, you use lead to stop Gamma Rays. Neutrons are better stopped by stuff like water, and paraffin.

[spunkets]

"If they're getting bubbles "the size of a pencil top eraser" by irradiating with neutrons"They're using high energy density ultrasound to produce the cavitation(bubbles). The energy is high enough to produce ionization, but it's still mechanical energy and isn't anywhere near what it takes to enhance a fusion process. The neutron flux added, only serves to produce tritium and more deuterium. Even with this, the probability fusion will occur is still essentially nothing.

The 18 million degrees they mention, really only means some tiny fraction of ions of the light producing plasma are in an excited state, and some others, in the far tail of a velocity distribution, have large velocities. None of this could possibly lead to measurable fusion, because the probability of a deuterium/tritium nucleus having enough energy to overcome the electrostatic repulsion of another nucleus is astronomically small and the cross sections here are similar. All they do is heat the building in an expensive and elaborate way, all using power from the local TN power co.

[e_engineer]

The bubbles are from cavitation, caused by acoustic agitation of the acetone. When they collapse, all of the energy gets focused into a tiny spot at the center of the bubble. In this tiny spot, the pressure momentarily peaks. The temperature peaks with the pressure, since pressure and temperature are proportional. The combination of pressure and temperature are high enough (momentarily)for a few atoms to fuse(according to this paper).

Pariffin is an excellent neutron absorber, it's cheap, easy to get, and you can carve it into dinosaur shapes to play with after the fusion experiment is finished.

[Erasmus]

If they're getting bubbles "the size of a pencil top eraser" by irradiating with neutrons, why doesn't the agitation splash the acetone all over the place. Also why the wimpy shielding if they expect it to produce more neutrons (let alone the original neutrons)... paraffin blocks?!? It ought to be behind some thick lead.

I see that others have done a good job in their replies. Let me just add the following:

The cavitation sites are produced by acoustic standing waves of high frequency. (I haven't heard how high, but it could be up the the megahertz range.) They are very short lived, and they grow and decay symmetrically, therefore there is no net translation, or flow, of the fluid and no 'sloshing.' I'm not sure why neutron irradiation promotes the fusion process, but the cavitation bubble wouldn't be affected by them except perhaps at the very last few picoseconds when the purported fusion would take place.