The new sound of fusion

TECHNOBEAT

In the early 20th century, Rube Goldberg and Heath Robinson conceived perpetual-motion machines that worked via ingenious levers and gears.

You'll find prints of their cartoons up on the walls of physics labs; a sign that infinite energy source remains one of the holy grails of modern science.

State-of-the-art science is capable of tapping sources of infinite energy and has been since the 1950s. The problem is, it has so far proved impossible to control this process. The energy is released in titanically destructive bursts.

The most common (and lightest) element is hydrogen. Stars derive their energy from fusing hydrogen atoms to create heavier elements such as helium.

Excess fundamental particles are completely converted to energy during this process of fusion. There is no deadly radioactivity released unlike in the reverse process of "fission". In fission, where heavy elements such as uranium are split into lighter elements, there is accompanying radioactive waste.

There is enough hydrogen to keep billions of stars burning for billions of years. If we could tap this energy in controlled fashion, fuel problems would be solved forever. We could convert that inexhaustible hydrogen into heat, electricity, vehicular power, anything you please.

But in the interior of a star, fusion occurs in big bursts under extreme heat and pressure. The only way to recreate those conditions on Earth is by means of an explosive fission reaction.

In layman's term, an atom bomb is required to create the pre-conditions for a fusion reaction. Fusion also occurs explosively "" again, in lay terms, hydrogen bombs explode.

This was developed during the 1950s when the US, Russia, the UK, France and China successively learnt to use fission explosions to create fusion explosions.

India's official position is that it succeeded in doing this at Pokhran in May 1998, though doubts have been expressed about the success of the fusion device in that five-explosion sequence.

Anyway, nobody has so far given a universally-accepted demonstration of fusion in controlled fashion under less extreme conditions. "Cold fusion", or tabletop fusion, is one subject on which the scientific community is violently divided.

Some scientists maintain that it is impossible; others say it's possible and a chosen few have laid their reputations on the line by claiming to have achieved it.

One of those few is Rusi Talyarkhan, professor of nuclear engineering at Purdue University. In 2002, he led a team of Russo-American researchers who claimed success in a paper published in Science journal.

That initial result met with scepticism. But Talyarkhan's team have done a more refined version of the experiment that, they claim, has reproduced and confirmed the results. The details will be published soon.

In 1989, a Franco-American combination of Stanley Pons and Martin Fleischman claimed to have achieved cold fusion at Utah University. Their results were discredited and, eventually, the two were even accused of deliberate fraud. It was a simple chemical reaction rather than nuclear fusion.

The Purdue team used a radically new method. First, they took a bowl of liquid acetone doped with a hydrogen isotope called deuterium, which has an extra neutron. This liquid was bombarded with fast-moving neutrons (electrically neutral particles). That created cavities, bubbles in lay terms. Then, the acetone was bombarded with ultrasound.

The bubbles trapped the ultrasound energy to go through a process of expansion and contraction, eventually, collapsing with great force. The energy released from the collapse raises the temperature, causing flashes of light.

The technique of sono-luminescence, or creating light through sound, is established and well-known and nobody's disputing this effect.

But the Purdue team claims that fusion occurs and the deuterium changes to tritium (another isotope of hydrogen with more neutrons) with the release of gamma rays. Albeit confined to small spaces, sun-like conditions of temperature and pressure are created within the bubbles.

The techniques used will clarify many questions. It reduces the cost of creating neutrons by orders of magnitude. The high temperature-pressure gradients may be used to produce diamonds and other exotic materials. But did the experiments create fusion? The jury's out.