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Scientists take step toward usable fusion energy

Scientists take step toward usable fusion energy
Sci­en­tists have tak­en a key step to­ward us­ing fu­sion, the pro­cess that pow­ers the Sun, to pro­duce en­er­gy, ac­cord­ing to a re­port to ap­pear Feb. 13 in the re­search jour­nal Na­ture.

Fu­sion en­er­gy is en­vi­sioned as a way to pro­duce vir­tu­ally un­lim­it­ed pow­er to supply the Earth's needs, but no one has suc­ceeded in de­vis­ing a fu­sion pro­cess that gives out more en­er­gy than it takes in.

Phys­i­cists at Law­rence Liv­er­more Na­t­ional Lab­o­r­a­to­ry in Cal­i­for­nia said they suc­ceeded in at least re­leas­ing more en­er­gy through a fu­sion re­ac­tion than is ab­sorbed by the fu­el that trig­gers the re­ac­tion.

But that en­er­gy is still only about a hun­dredth of the to­tal en­er­gy needed to set up the pro­cess in the first place, they said, most of which goes in­to com­press­ing a fu­el pel­let where fu­sion takes place.

“The next nec­es­sary step would be to achieve a to­tal gain, where en­er­gy en­ter­ing the whole sys­tem is ex­ceeded by the en­er­gy pro­duced,” the re­search­ers said in a state­ment. None­the­less, “we are clos­er than an­y­one has ev­er got­ten” to ob­tain­ing fu­sion as a vi­a­ble en­er­gy source, said Omar Hur­ri­cane, a re­searcher at the lab­o­r­a­to­ry and one of the au­thors of the re­port.


The whole pro­cess took place in a space less wide than a hu­man hair and in only the ti­ni­est frac­tion of a sec­ond-150 pi­cosec­onds, to be ex­act.

Their pro­cess used in­er­tial con­fine­ment fu­sion, which ini­ti­ates nu­clear fu­sion re­ac­tions by heat­ing fu­el pel­lets un­til they im­plode, com­press­ing the fu­el. The fu­el con­sists of deu­ter­i­um and tri­tium-iso­topes, or var­i­ant forms, of hy­dro­gen. When squeezed to­geth­er, they merge cre­at­ing a he­li­um nu­cle­us, and re­leas­ing en­er­gy along with a neu­tron, or sub­a­tom­ic par­t­i­cle.

The con­fine­ment squeezes the atoms of fu­el “to get them run­ning to­ward each oth­er at high ve­lo­city, which over­comes their mu­tu­al elec­tri­cal re­pul­sion,” said Hur­ri­cane.

The sci­en­tists said they used 192 lasers to heat and com­press a small pel­let of fu­el to the point where the fu­sion re­ac­tions take place.

What made the pro­cess suc­cess­ful was that the sci­en­tists man­aged to in­i­ti­ate a pro­cess called “boot­strap­ping,” a sort of vi­cious cy­cle, Hur­ri­cane said. In this, “the al­pha par­t­i­cles [he­li­um nu­cle­i] that come out of that re­ac­tion start leav­ing en­er­gy be­hind and caus­ing the tem­per­a­ture to go up” with­in the ti­ny cham­ber. “When the tem­per­a­ture goes up, the re­ac­tion rate goes up, and when the re­ac­tion rate goes up, you make more al­pha par­t­i­cles.”





Source : http://www.world-science.net

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