Sonofusion

Normally in this column, I profile new, emerging technologies that can be applied to musical endeavors. This month, however, I am profiling something
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Normally in this column, I profile new, emerging technologies that can be applied to musical endeavors. This month, however, I am profiling something a bit different: a process whereby sound waves might one day be used to generate energy — potentially so much energy that the world could finally be freed from its dependence on oil and other fossil fuels.

Controlled fusion is the process by which the sun shines, and if we could harness it on Earth, our energy worries would be over forever. In the sun, hydrogen atoms are ripped apart into separate protons and electrons, and the protons are forced together — despite their mutual electromagnetic repulsion — by the incredible temperature and pressure in the sun's interior. As the protons fuse together, they release an astounding amount of energy, which is emitted as heat, light, and many other types of radiation.

The most successful fusion reactions created on Earth are those from hydrogen bombs — effective for destroying vast areas and killing millions of people, but not very useful for generating sustained energy. During the past 50 years, billions of dollars have been spent on attempts to generate controlled fusion reactions, but so far the resulting reactions have required far more energy than they have yielded.

You may recall the furor over the announcement in 1989 that two scientists had chemically induced a fusion reaction without extreme temperatures and pressures. This so-called cold fusion was later discredited, mainly because their results couldn't be duplicated in other labs.

Now, another approach could hold more promise. As in 1989, the initial experiments are being conducted using small containers of liquid; however, there's nothing cold about the results this time. The new approach is based on a process called cavitation, in which bubbles in the liquid rapidly implode, momentarily increasing the temperature and pressure within the bubbles, perhaps to the levels required to initiate fusion.

Cavitation can be induced by bombarding certain liquids (specifically hydrocarbons such as acetone) with neutrons, which generates nanometer-scale bubbles. At the same time, sound waves are directed into the container at one or more of its resonant frequencies, causing standing waves to form. Bubbles at the antinodes (regions of maximum pressure variation) expand and collapse at the same rate as the acoustic frequency, and as they collapse, they emit flashes of light; this is called sonoluminescence.

Scientists at Oak Ridge National Laboratory in Tennessee realized that sonoluminescence might indicate fusion-friendly conditions within the cavitating bubbles, especially if the acetone is laced with deuterium, a heavy isotope of hydrogen that fuses more easily than conventional hydrogen. According to a recent peer-reviewed paper, their preliminary findings seem to support this hypothesis. For example, they detected neutrons emerging from the liquid that were clearly not coming from the initial bombardment — one telltale sign that fusion was occurring. They also detected traces of tritium, another heavy isotope of hydrogen and a byproduct of fusion.

This process is technically known as acoustic inertial confinement fusion (ICF), but some refer to it informally as sonofusion. Among those now working on acoustic ICF are D. Felipe Gaitan and Ross Tessien at Impulse Devices (www.impulsedevices.com). They intend to develop commercial applications within the next decade. Their system uses piezocrystals as the acoustic source, generating sound waves in the 10- to 100 kHz range. At any one of the resonant frequencies, their reaction chamber amplifies the sound waves by a factor of 300 to 1,000.

If they're right, the sound waves we all use to make music could be the key to complete energy independence for the entire world. Who knows, maybe your studio could provide the sound waves that allow a sonofusion reactor to power your studio. Now that's what I call a beneficial feedback loop!