Probing nuclear fusion at high powers.At sufficiently high temperatures, nuclei of the two hydrogen isotopes deuterium deuterium (d  tēr`ēəm), isotope of hydrogen with mass no. 2. The deuterium nucleus, called a deuteron, contains one proton and one neutron. and tritium tritium (trĭt`ēəm), radioactive isotope of hydrogen with mass number 3. The tritium nucleus, called a triton, contains one proton and two neutrons. It has a half-life of 12.5 years and decays by beta-particle emission. fuse to create neutrons and alpha particles (helium nuclei). This nuclear reaction also releases copious quantities of energy. But it hasn't been clear to researchers what happens to the energetic alpha particles generated in the fusion reaction. Do they remain largely confined to the hot, ionized i·on·ize tr. & intr.v. i·on·ized, i·on·iz·ing, i·on·iz·es To convert or be converted totally or partially into ions. i gas (or plasma) within the reactor, or does a significant fraction escape befoe the alpha particles can deposit their energy in the plasma? last December, using a magnetically confined mixture or equal parts deuterium and tritium, researchers at the Princeton University Plasma Physics laboratory and their collaborators achieve record outputs of fusion power at the Tokamak Fusion Test Reactor The Tokamak Fusion Test Reactor (TFTR) was an experimental tokamak fusion test reactor built at Princeton Plasma Physics Laboratory (in Princeton, New Jersey) circa 1980. (TFTR TFTR Tokamak Fusion Test Reactor TFTR Toroidal Fusion Test Reactor TFTR Thanks for the Report TFTR Thanks for the Reminder ) (SN: 1/1/94, p.12). Subsequent experiments and measurements suggest that no unexpected losses of alpha particles occurred. Such a result is encouraging for the design of future fusion reactors. Alpha particle losses of more than 15 percent would present difficulties in sustaining the temperature of about 250 million kelvins needed for initiating fusion. In addition, large numbers of vagrant VAGRANT. Generally by the word vagrant is understood a person who lives idly without any settled home; but this definition is much enlarged by some statutes, and it includes those who refuse to work, or go about begging. See 1 Wils. R. 331; 5 East, R. 339: 8 T. R. 26. particles could deposit enough heat in the reaction vessel's walls to cause damage. The measured rate of loss of alpha particles is approximately 5 percent, the physicists report. They see no evidence of unexpected wave activity or disruptive magnetic forces that could destabilize the plasma. The researchers also note that the tritium-deuterium plasma used in the experiments stores about 20 percent more energy in its electrons and ions than a pure deuterium plasma. Such an increase indicates that the presence of tritium improves particle confinement and that alpha particles may be directly heating electrons in the plasma. In producting a record power output of 6.2 megawatts, the researchers pushed the plasma's ion temperature to 430 million kelvins and its electron temperature to 120 million kelvins. Now the TFTR team is aiming for a power output of 10 megawatts. The researchers describe these preliminary results in two papers to be published in the May 30 PHYSICAL REVIEW LETTERS Physical Review Letters is one of the most prestigious journals in physics.[1] Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. . |
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