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LIFE, short for Laser Inertial Fusion Energy, was a fusion energy effort run at Lawrence Livermore National Laboratory (LLNL) between 2008 and 2013. LIFE aimed to develop the technologies necessary to convert the laser-driven inertial confinement fusion (ICF) concept being developed in the National Ignition Facility (NIF) into a practical commercial power plant, a concept known generally as inertial fusion energy (IFE). LIFE used the same basic concepts as NIF, but aimed to lower costs using mass-produced fuel elements, simplified maintenance, and diode lasers with higher electrical efficiency. The failure of NIF to achieve ignition in 2012 led to the LIFE project being cancelled in 2013. ==Background== LLNL has been a leader in laser-driven ICF since the initial concept was developed by LLNL employee John Nuckols in the late 1950s. The basic idea was to use a ''driver'' to compress a small pellet known as the ''target'' that contains the fusion fuel, a mix of deuterium (D) and tritium (T). If the compression reaches high enough values, fusion reactions begin to take place, releasing alpha particles and neutrons. The alphas may impact atoms in the surrounding fuel, heating them to the point where they undergo fusion as well. The result is a chain reaction known as ignition, which burns a significant amount of the fuel.〔(【引用サイトリンク】title=How NIF works )〕 Comparing the driver energy input to the fusion energy output produces a number known as fusion energy gain factor, labelled ''Q''. A ''Q'' value of at least 1 is required for the system to produce net energy. Since some energy is needed to run the reactor, in order for there to be net electrical output, ''Q'' has to be at least 3. For commercial operation, ''Q'' values much higher than this are needed. For ICF, ''Q''s on the order of 25 to 50 are needed to recoup both the electrical generation losses and the large amount of power used to power the driver. In the fall of 1960, theoretical work carried out at LLNL suggested that gains of the required order would be possible with drivers on the order of 1 MJ. At the time, a number of different drivers were considered, but the introduction of the laser a few years later provided the first obvious solution with the right combination of features. The desired energies were well beyond the state of the art in laser design, so LLNL began a laser development program in the mid-1960s to reach these levels. Each increase in energy led to new and unexpected optical phenomena that had to be overcome, but these were largely solved by the mid-1970s. Working in parallel with the laser teams, physicists studying the expected reaction using computer simulations adapted from thermonuclear bomb work developed a program known as LASNEX that suggested ''Q'' of 1 could be produced at much lower energy levels, in the kilojoule range, levels that the laser team were now able to deliver. From the late-1970s, LLNL developed a series of machines to reach the conditions being predicted by LASNEX and other simulations. With each iteration, the experimental results demonstrated that the simulations were incorrect. The first machine, the Shiva laser of the late 1970s, produced compression on the order of 50 to 100 times, but did not produce fusion reactions anywhere near the expected levels. The problem was traced to the issue of the infrared laser light heating electrons and mixing them in the fuel, and it was suggested that using ultraviolet light would solve the problem. This was addressed on the Nova laser of the 1980s, which was designed with the specific intent of producing ignition. Nova did produce large quantities of fusion, with ''shots'' producing as much as neutrons, but failed to reach ignition. This was traced to the growth of Rayleigh-Taylor instabilities, which greatly increased the required driver power. Ultimately all of these problems were considered to be well understood, and a much larger design emerged, NIF. NIF was designed to provide about twice the required power, allowing some margin of error. NIF's design was finalized in 1994, with construction to be completed by 2002. Construction began in 1997 but took over a decade to complete, with major construction being declared complete in 2009. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Laser Inertial Fusion Energy」の詳細全文を読む スポンサード リンク
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