黑腔靶中超热电子特性研究

近几年来,在“神光”装置上进行了1.053μm激光与平面靶及一系列柱形黑腔靶相互作用实验。用一台多道滤波—荧光X光能谱仪(FFS)测得各种靶发射的超热X射线谱,由谱推导超热电子温度T_h和超热电子总能量E_h当照射靶单束激光能量E_(tar)为400～670J、脉宽τ=650～1150ps时,发现黑腔内明显存在两群服从Maxwell分布高能电子(T_h=35～45keV;T_(hh)=150～350kev),而且E_(he)占E_(tar)的份额为10％～12％。实验还表明:腔内的E_(he)与非线性过程特征量(SRS)有较好的线性关系,因此推断出腔内超热电子产生的主要机制是受激Raman散射。在相同照射条件下,黑腔靶产生的超热电子比平面靶严重。

STUDIES OF SUPRATHERMAL ELECTRONS IN HOHLRAUM TARGETS

Experiments of planar and cylindrical hohlraum targets have been conducted on " Shenguang" laser Facility in recent years. A multichannel filter-flourescer spectrometer was used to obtain the hard X -ray spectrum. The temperature and energy of suprathermal electrons were induced from the hard X-ray spectrum. When the energy of a single beam of incident laser is in the range of 400 - 670J, and the pulse duration in the range of 650 -1150ps, it is found that two groups of suprathermal electrons obey Maxwellian distribution (Th = 35 - 45keV, Thh= 150 - 350keV) in hohlraums, and total energy of suprathermal electrons Eke is about 10%-12% of incident laser energy. Experiments also show that Ehe is fairly concordant with the amount of stimulated Raman scattered (SRS) light, so we can conclude that SRS is the primary mechanism for producing suprathermal electrons in hohlraum targets. Fraction of suprathermal electrons in hohlraum is bigger than that of planar. The results are analysed and discussed.