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.