Posted on 06/29/2003 5:34:59 AM PDT by Wonder Warthog
Researchers Report Record High Temperatures in Compact Fusion Device
Step taken towards environmentally safe, cheap and unlimited energy
May 28, 2002. A team of researchers has announced the achievement for the first time of temperatures above one billion degrees in a dense plasma. The breakthrough, achieved with a compact and inexpensive device called the plasma focus, is a step toward controlled fusion energy using advanced fuels that release little or no radioactivity. "We have achieved a key condition needed to burn hydrogen-boron fuel," said Eric J. Lerner of Lawrenceville Plasma Physics, one of the researchers. "This fuel produces virtually no radioactivity and can potentially generate electric energy without expensive steam generators and turbines."
Mr. Lerner announced the achievement Tuesday, May 28 at the International Conference on Plasma Science, a major scientific conference, in Banff, Alberta, Canada . The other leaders of the research team are Dr. Bruce Freeman of Texas A and M University (College Station, Texas), where the experiments were performed last August, and Dr. Hank Oona of the Los Alamos National Laboratory (Los Alamos, NM). The results have been submitted for publication to Physica Scripta, a widely known physics journal.
The temperatures achieved, up to two billion degrees in some shots of the device, well surpass previous records of 520 million degrees achieved in the much larger and more expensive tokamak device, which has been cornerstone of the US fusion program for 25 years. In addition, the product of the plasma density and the time the plasma lasts, (called the "density-confinement time product") was as much as 8 times more in the new plasma focus results than was achieved by the Princeton Plasma Physics Laboratory's TFTR tokamak. The larger the density and confinement time, the more fusion fuel is burned.
What is particularly important about these results is that temperatures above 1 billion degrees are needed to burn hydrogen-boron fuel. When hydrogen and boron fuse in a plasma focus they will release energy in the form of a beam of charged particle--nuclei of helium atoms. This beam can be converted directly to electricity through a kind of high -tech transformer. This would be much cheaper than producing steam to drive turbines as occurs in fossil fuel and nuclear-electric generator plants. In addition, since the hydrogen boron reaction produces no high-energy neutrons, it does not create radioactive products in the reactor structure or elsewhere.
In contrast, the fuel planned to be used in the tokamak and other fusion reactor concepts , deuterium-tritium, releases its energy in the form of high energy neutrons, which induce radicoativity in the reactors and necessitate the same steam cycle that is in use today.
Additionally, the plasma focus device is much smaller and cheaper to build than the tokamak. While a tokamak fills a gymnasium-sized room and costs several hundred million dollars to build, the Texas AM plasma focus device is contained in a converted service station and cost less than $500,000 to build.
The plasma focus also functions in a fundamentally different way from other fusion devices. Tokamaks and most other fusion devices use powerful magnets to attempt to stabilize the plasma--the extremely hot, electrically conducting gas that the fusion reactions occur in. This task has been likened to lifting gelatin with rubber bands. Instead, the plasma focus uses the natural instabilities of the plasma, so that the plasma's own magnetic fields compress it and heat it.
How the record temperatures and densities were obtained and measured
The plasma focus is not a new device, and some researchers have long suspected that it can produce very high energy electrons and ions.(While we have referred to temperatures, plasma scientists more accurately refer to the average energies of the electrons and ions in a plasma, which are measured in electron volts. An average energy of 100keV is equivalent to a temperature of 1.1 billion degrees.)
Specifically the plasma focus generated high energy x-rays, which indicate high energy electrons colliding with ions. But until the recent Texas experiments, most scientists thought that these x-rays we generated when the electron beam produced in the focus smashes into the electrode, and thus did not indicate a truly "hot" plasmas. Based on theoretical work by Mr. Lerner and other indications, the research team felt that the x-rays did in fact come from the plasmoid and that the plasmoid could be extremely hot. This theoretical work also indicated that higher gas fill densities would help in getting to these high energies.
To find out where the x-rays came from the Texas research team blocked the x-rays from the electrode with a lead brick, so they could not reach a set of x-ray detectors. Only x-ray from the tiny plasmoid could get to the detectors. They then measured the energy of the x-rays by seeing how much they were absorbed by copper filters of various thickness--the less they were absorbed, the higher their energy. From the energy of the x-rays, the team could then cleat the energy of the electrons in the plasmoid.
They found that indeed, typical energies ranged from 80keV to 210 keV(equivalent to 900 million to 2.4 billion degrees )depending on the filling gas used.
The researcher used another technique to measure the energy of the ions. They used deuterium gas in some shots, which produce neutrons through fusion reactions. By measuring the spread in energy of the neutrons coming from the plasmoid, they could calculate the energy of the ions that produced the neutrons. These energies ranged from 45 to 210 keV(500 million degrees to 2.4 billion degrees).
The team was able to measure the confinement time by observing the duration of the x-ray and neutron pulses, which were around 50 billionths of a second.
Finally the researchers were able to calculate the density of the plasmoid. When deuterium fuses with deuterium nuclei, half of the time they produce tritium nuclei. These tritium nuclei are trapped by the powerful magnetic field of the plasmoid and can then fuse again with the deuterium nuclei, producing a very energetic neutron. The denser the plasmoid, the faster this reaction goes. So by measuring the number of high energy neutrons from the DT react (about 70 million in the best shot) and comparing them with the number of low energy neutrons from the DD reaction(about 10 billion in the same shot), the team found that the density of the plasmoid was as high as 1.7x1021 ions/cm3, some 250 times denser than the initial gas that filled the chamber.
The density-confinement time product was thus 9x1013 ions-sec/cm3, compared with 1.25x1013 ions-sec/cm3 for the best tokamak results.
The boranes (basically hydrides of boron) are widely used in the semiconductor industry, so the infrastructure and handling procedures are already well-known.
Well, the posted article "was" written for the web-cruising layman. If you want the hard science stuff, go to the website and look over the actual scientific references and articles posted there.
Chemical energy--not nuclear. Now if you want a really HOT fusion of this sort, try some South Louisiana red beans and rice with a side order of cabbage. I "garontee" that rocket propulsion is possible with such a mixture. And it's hypergolic--no need for external sources of ignition.
Since this does not produce radioactive by-products, I wonder if the cooling system could use sea water -- so the facility would be a power plant and a desalinization plant. How about cheap electricity and fresh water? If the electricity is cheap enough, there are things we could afford to run on electricity instead of fossil fuels. Fresh water could spread agriculture to areas where it currently is not practical, and it would be nice to think that in the 21st century everyone in the world could have access to safe, clean water.
I predict that the "anarchists" (actually, communists) who have rioted in Seattle and elsewhere will commit terrorist acts against this. These are the type of people who want children around the world to starve or die from lack of fresh water -- and these protestors would be horrified if we developed a technology that could raise everyone's living standard without causing pollution.
I also predict that there will be pseudo-scientists who will argue that the universe is running out of hydrogen so we should not try fusion! There will be "environmentalists" who will say that producing fresh water will somehow harm the earth's "balance." The media will parrot whatever these lunatics say -- there will be a concerted effort to make people afraid of fusion. They will try to make people think it is radioactive, and they will tell outlandish lies to scare people like, I don't know, a fusion reactor might explode and turn the earth into a mini-sun. Enough people are ignorant of science that I am afraid the technological battle for fusion might be simple compared to the political battles that will surely come.
But it's fun to watch. (Use one of those long-stem matches.)
Aggie POWER, Wow!
BTW, with all that helium being produced, will we all be talking like Donald Duck!? QUACK! QUACK!
What is particularly important about these results is that temperatures above 1 billion degrees are needed to burn hydrogen-boron fuel. When hydrogen and boron fuse in a plasma focus they will release energy in the form of a beam of charged particle--nuclei of helium atoms. This beam can be converted directly to electricity through a kind of high -tech transformer. This would be much cheaper than producing steam to drive turbines as occurs in fossil fuel and nuclear-electric generator plants. In addition, since the hydrogen boron reaction produces no high-energy neutrons, it does not create radioactive products in the reactor structure or elsewhere.
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