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  3. You are going to read a text about the topic of nuclear fusion, followed by a list of explanations(or examples). Choose the best

You are going to read a text about the topic of nuclear fusion, followed by a list of explanations(or examples). Choose the best

admin2013-01-25  14
问题     You are going to read a text about the topic of nuclear fusion, followed by a list of explanations(or examples). Choose the best explanation/example from the list.

    Scientists say they have achieved small-scale nuclear fusion in a tabletop experiment, using tried and true techniques that are expected to generate far less controversy than past such claims.
    This latest experiment relied on a tiny crystal to generate a strong electric field. While the energy created was too small to harness cheap fusion power, the technique could have potential uses in medicine, spacecraft propulsion, the oil drilling industry and homeland security, said Seth Putterman, a physicist at the University of California at Los Angeles.
    Putterman and his colleagues at UCLA, Brian Naranjo and Jim Gimzewski, report their results in Thursday’s issue of the journal Nature.
    (41) Held up to ridicule
    Previous claims of tabletop fusion have been met with skepticism and even derision by physicists.
    (42) Sound theoretical basis
    Fusion experts said the UCLA experiment will face far less skepticism because it conforms to well-known principles of physics.
    (43) Energy in waiting
    Fusion power has been touted as the ultimate energy source and a cleaner alternative to fossil fuels like coal and oil. Fossil fuels are expected to run short in about 50 years.
    (44) Process of fusion
    In the UCLA experiment, scientists placed a tiny crystal that can generate a strong electric field into a vacuum chamber filled with deuterium gas, a form of hydrogen capable of fusion. Then the researchers activated the crystal by heating it.
    (45) Commercial uses
    UCLA’s Putterman said future experiments will focus on refining the technique for potential commercial uses, including designing portable neutron generators that could be used for oil well drilling or scanning luggage and cargo at airports.
    In the Nature report, Putterman and his colleagues said the crystal-based method could be used in "microthrusters for miniature spacecraft." In such an application, the method would not rely on nuclear fusion for power generation, but rather on ion propulsion, Putterman said.
    "As wild as it is, that’s a conservative application," he said.

A. In fusion, light atoms are joined in a high-temperature process that frees large amounts of energy. It is considered environmentally friendly because it produces virtually no air pollution and does not pose the safety and long-term radioactive waste concerns associated with modern nuclear power plants, where heavy uranium atoms are split to create energy in a process known as fission.
B. The resulting electric field created a beam of charged deuterium atoms that struck a nearby target, which was embedded with yet more deuterium. When some of the deuterium atoms in the beam collided with their counterparts in the target, they fused. The reaction gave off an isotope of helium along with subatomic particles known as neutrons, a characteristic of fusion. The experiment did not, however, produce more energy than the amount put in—an achievement that would be a huge breakthrough.
C. Another technique, known as sonoluminescence, generates heat through the collapse of tiny bubbles in a liquid. Some scientists claim that nuclear fusion occurs during the reaction, but those claims have sparked sharp debate.
D. In a Nature commentary, Michael Saltmarsh of the Oak Ridge National Laboratory said the process was in some ways "remarkably low-tech", drawing upon principles that were first recorded by the Greek philosopher Theophrastus in 314 B.C. "This doesn’t have any controversy in it because they’re using a tried and true method," David Ruzic, professor of nuclear and plasma engineering at the University of Illinois at Urbana-Champaign, told The Associated Press. "There’s no mystery in terms of the physics."
E. In one of the most notable cases, Dr. B. Stanley Pons of the University of Utah and Martin Fleischmann of Southampton University in England shocked the world in 1989 when they announced that they had achieved so-called cold fusion at room temperature. Their work was discredited after repeated attempts to reproduce it failed.
F. The technology also could conceivably give rise to implantable radiation sources, which could target cancer cells while minimizing damage to healthy tissue. "You could bring a tiny crystal into the body; place it next to a tumor, turn on the radiation and blast the tumor," Putterman told MSNBC.com.

选项
答案B
解析 副标题(核聚变过程)说明，后续内容应描述具体实验过程，选项B符合要求，故为正确答案。
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