薄膜钯靶烧蚀特性的实验研究

EXPERIMENTAL STUDY OF ABLATION CHARACTERISTICS OF Pd THIN FILM TARGET

薄膜靶是ｘ射线激光研究中常用靶型之一，了解它在强激光作用下的烧蚀过程是非常重要的。本文介绍了把薄膜靶烧穿时间的测量，井通过时所测数据拟合给出薄膜靶质量烧蚀速率与吸收功率密度的定标关系。

thin film target is one of the target types usually used in x-ray laser in vestigation;Under-standing ablation proeesses of the thin film target irradiated by high-intensity laser and its lawis very important for designing targets of the x-ray laser study.A method investigating theablation processes of the thin film target by means of measuring the burn-through time of it ispresented in this paper.The burn-through time of the thin film target is measured by the timedifference between the incident laser and the transmission light pulse.The experiments was carried out at“Xing guang”facility.The wavelength of theincident laser is 0.53μm,its FWHM is 350～500ps, the output energy of the laser pulse is1～10J.The thin film target was made by coating a formvar film(its thickness is 300nm)with70nm thick pure palladium,The arrangement of the experimental setup is shownin Fig.1.At thedifferent laser intensity, the pulse pictures of the incident laser and the transmission light pulsewere recorded with a visible streak camera,The temporal evolutions of the incident laser and thetransmission light pulse were gained by translating the recorded pictures into the data files andprocessing it with a computer, the results are plotted in Fig.2 ang Fig.3. Therefore,theburn-through time of the thinfilm targets was obtained and listed in Table 1.By fitting the data of the burn-through time, we find that the scaling law between massablation rate of Pd thin film and the absorbed irradiation intensity is M=4.15 × l0￣(-5)·.Usingthe obtained parameters, the mass ablation thicks of the thin film for all shots were calculatedwith the scaling law(eqs 9 and l0 ).The results are shown in Table 2.Comparing the data inTable 2 with the thicks of the Pd thin film used in the experiments,one can see that the calculatedvalues are in good agreement with the ones used in the experiments.Under the same conditionsas used in the experiments, the burn-through time ofthe thin film targets was theoretically calcu-lated. These results are shown in Table.3.Theoretically calculated results are fundamentlyin accordance with the experimental ones.