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Kodama R Sentoku Y Chen ZL Kumar GR Hatchett SP Toyama Y Cowan TE Freeman RR Fuchs J Izawa Y Key MH Kitagawa Y Kondo K Matsuoka T Nakamura H Nakatsutsumi M Norreys PA Norimatsu T Snavely RA Stephens RB Tampo M Tanaka KA Yabuuchi T 《Nature》2004,432(7020):1005-1008
The development of ultra-intense lasers has facilitated new studies in laboratory astrophysics and high-density nuclear science, including laser fusion. Such research relies on the efficient generation of enormous numbers of high-energy charged particles. For example, laser-matter interactions at petawatt (10(15) W) power levels can create pulses of MeV electrons with current densities as large as 10(12) A cm(-2). However, the divergence of these particle beams usually reduces the current density to a few times 10(6) A cm(-2) at distances of the order of centimetres from the source. The invention of devices that can direct such intense, pulsed energetic beams will revolutionize their applications. Here we report high-conductivity devices consisting of transient plasmas that increase the energy density of MeV electrons generated in laser-matter interactions by more than one order of magnitude. A plasma fibre created on a hollow-cone target guides and collimates electrons in a manner akin to the control of light by an optical fibre and collimator. Such plasma devices hold promise for applications using high energy-density particles and should trigger growth in charged particle optics. 相似文献
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<正>对采自气候为非限制性因子地区的柳杉树轮稳定碳同位素比 δ13 C进行气候响应分析。用排除法消除大气二氧化碳中δ13C的变化对柳杉树轮δ13C变化的影响后,建立残差年序列RE,并结合西天目山气象站的气象记录,分析了树轮δ13C年序列对气候要素的响应。结果表明:西天目山地区树轮 δ13C的高频振荡与 11、12月最高气温的平均值,1、2、3月降水总和以及6、7月降水总和显著相关,在一定程度上反映了东亚季风对该区的影响大小。可见气候非限制性因子地区树轮稳定碳同位素组成年序列同样可以作为气候变化指针。 相似文献
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