By Larry Bernard
A new, essentially inexhaustible source of energy for the 21st century may result from experiments under way at Cornell's Laboratory for Plasma Studies.
Fossil fuels? Forget it. They're a limited resource and pollute when burned. Nuclear fission reactors? Not in my backyard. Too dangerously radioactive. How about creating energy from fusion, the way the sun does?
"The problem of nuclear fusion is very important to society," said Cornell's Ravi Sudan, the IBM Professor of Engineering, professor of electrical engineering and of applied and engineering physics and a principal investigator on both the COBRA and FIREX projects. "We must have alternate energy sources. We must have technical options," he said.
There are two approaches to using controlled nuclear fusion for energy production: magnetic fusion and inertial fusion. In the magnetic approach, the hot plasma that generates the fusion reactions is confined by magnetic fields. The mainline approach for achieving magnetic fusion is the Tokamak program. In inertial fusion, tiny fuel capsules or pellets are compressed to 1,000 times liquid deuterium densities and heated to fusion ignition by pulsed, high-powered beams. Because the whole process should take place in only a few nanoseconds, the hot, dense plasma stays together because of its inertia. The mainline approach to inertial fusion uses laser beam drivers.
Cornell's experiments concern alternate approaches to both the mainline magnetic and inertial fusion approaches:
· FIREX, the Field-reversed Ion Ring Experiment, is a Cornell project funded by the U.S. Department of Energy's Fusion Energy Science Program for $2 million over four years. The experiment is designed to create an intense ion ring in a single pulse. The fields of this ring should confine plasma in a new magnetic "bottle."
· COBRA, the Cornell Beam Research Accelerator, is a new 4-megavolt research accelerator, designed and provided to Cornell by DOE's Sandia National Laboratories. The experiments on this accelerator will investigate the advantages of replacing the mainline laser beam drivers in the inertial confinement program with ion beams. Single-pulse, intense ion beams will be focused onto a target to determine if the power density required for pellet ignition can be achieved. This project is funded for $3 million over five years by DOE through Sandia.
Both these projects utilize the technology of intense ion beams generated in diodes that were developed at Cornell. Sudan and Stanley Humphries, former research associate in the Laboratory of Plasma Studies, hold the first patent on this technology.
Bruce R. Kusse, professor of applied and engineering physics and director of the Laboratory of Plasma Studies, said the general public is not very concerned about finding non-fossil fuel energy sources even though the basic research required to come up with them has to be done well in advance.
"The general public interest has waned
because the prices for coal, oil and natural gas are not that bad. But the supplies
of these fossil fuels have finite
lifetimes," Kusse said. "If we wait until they
are exhausted to develop new sources, we will be in trouble."
Early in the next century, scientists anticipate achieving inertial fusion ignition at the National Ignition Facility (NIF). The NIF will focus the energy from an extremely powerful laser to "ignite" small capsules filled with fusion fuel, creating fusion reactions and liberating more energy than was used to start the process. David Crandall, NIF project director, described the program at the meeting here. The NIF will cost $1.1 billion dollars and take seven years to build.
The magnetic fusion program, has focused on the Tokamak approach, with
the next step a $10 billion international program known as the International
Thermo
nuclear Experimental Reactor (ITER). It is in the design phase and may result in
an internationally constructed and operated Tokamak reactor.
The advantages of using fusion energy sources are that the fuel is cheap and plentiful and the reactors will present less of a radiation hazard than the current fission power plants.
"While the fuel for a fusion reactor is cheap, the mainline approaches are leading to large, complicated and, therefore, expensive reactor designs," Kusse said. "This is why it is important to investigate alternative fusion schemes that can result in more compact power plants."
"Our experiments are aimed toward the long term, for the next phase after the NIF is finished," Sudan said. Initial experiments on COBRA will look at the transport and focusing of intense ion beams.