March 03, 2004
A. Singh
Senior Science Writer
Rusi Taleyarkhan, Nuclear engineer led the research team at
the Oak Ridge National Laboratory in Tennessee that has proposed
a small table-top sized nuclear fusion device. Taleyarkhan described
the project as true, "tabletop physics, using an apparatus
the size of three coffee cups stacked on top of the other."
The researchers bombarded millimeter-sized bubbles of
deuterated-acetone vapor with sound waves (called acoustic cavitation)
that resulted in a burst of subatomic particles called neutrons
and the production of tritium, an isotope of hydrogen both evidence
of a nuclear fusion reaction. The bubbles reached temperatures
of 10 million degrees Kelvin, as hot as the center of the sun.
Sonoluminescence light flashes were also observed. The experiment
was dubbed "bubble fusion." Richard Lahey Jr. professor
at Rensselaer Polytechnic Institute in Troy, New York, co-authored
the study. The experiments were conducted by Rusi Taleyarkhan,
Colin West, and Jae Seon-Cho. Richard Lahey and Robert Nigmatulin
performed the theoretical analysis of the bubble dynamics and
the shock-induced pressures, temperatures, and densities in
the imploding bubbles. Robert Block, professor emeritus of nuclear
engineering at Rensselaer, helped to set up and calibrate a
neutron and gamma detection system.
Fusion researcher Rusi Taleyarkhan with the sonoluminescence
apparatus at Oak Ridge. (Oak Ridge National Laboratory
A different type of nuclear reaction, called fission, was long
ago harnessed to create the atomic bomb and is used in nuclear
power plants. Fission splits heavy atoms, such as uranium, to
release energy.
Nuclear fusion is a process that joins atoms together.
Inside the Sun, for example, hydrogen is fused to create heavier
elements. In the process, energy is released. Fusion is the
power source of the sun and the stars. The large quantity of
energy released by the sun and the stars is the result of the
conversion of matter into energy. This occurs when the lightest
atom, hydrogen, is heated to very high temperatures forming
a special gas called "plasma". In this plasma, hydrogen
atoms combine, or "fuse", to form a heavier atom,
helium. In the process of fusing, some of the hydrogen involved
is converted directly into large amounts of energy.
There are two primary reasons for pursuing fusion research:
the furthering of our understanding of the behavior of plasmas
that make up most of the known universe, and the creation of
a new energy source. Fusion energy would be a renewable energy
technology that offers a significant mix of potential advantages.
Fusion fuels are abundant and readily available to all nations.
Using fusion energy to generate electricity will neither contribute
to global warming or air pollution nor will it create long-lived
radioactive waste.
The process is known as nuclear fusion, and because it uses
readily available elements like hydrogen – as opposed to
nuclear fission which uses rare, complex, expensive, and dangerous
matter such as uranium and plutonium – scientists have
looked at it as a holy grail for cheap, limitless energy. It
uses the power of sound to create energy comparable to the inside
of stars. In a phenomenon known as isonoluminiscence, a burst
of ultrasound causes a bubble in a liquid to collapse and emit
a flash of light. It is thought that the gases trapped in the
collapsing bubbles could be heated to temperatures hot enough
for fusion to occur.
Scientists have understood fusion since the early 1900s, and
for many decades they have tried unsuccessfully to recreate
this process in labs. Commercial fusion could solve the world's
power woes, some scientists have long claimed, and it would
do so safely, with little or no harmful byproducts like the
radioactive waste that comes from fission.
Many schemes have been developed, from using magnetism to lasers
to create high-speed, high-temperature collisions among atoms.
Other so-called "cold fusion" efforts were widely
reported but never reproduced, and therefore scientists considered
them flawed.
