激光在不同环境下烧蚀铝靶冲量耦合系数研究 .doc

摘 要

高能聚焦激光和固体金属铝靶作用，通过烧蚀固体靶材产生等离子体，会使靶材料

获得一定动量。在不同的环境条件下，通过实验研究激光能量密度和靶材料的冲量耦合

系数关系，可以分析环境条件对激光烧蚀靶材冲量耦合系数的影响。在气体环境和液体

环境中，激光烧蚀靶材料会呈现不同规律。

本文先从理论上研究了不同环境下激光和靶材作用，对空气和液体中冲击波行为进

行模型分析。接着实验测量不同条件下的激光烧蚀铝靶冲量耦合系数。实验测量方法为

响；（6）变换不同液体介质，研究液体介质性质对铝靶冲量耦合系数影响。

实验结果表明：气体环境中激光烧蚀铝靶，在改变激光能量密度时，铝靶冲量耦合

系数大小会受到激光烧蚀铝靶的速率及等离子冲击波压强的影响，并且存在烧蚀阈值时

也会影响冲量耦合系数的数值。液体环境中激光烧蚀铝靶，铝靶冲量耦合系数随激光能

量密度变化趋势和空气中近似，但是液体环境中冲量耦合系数要明显高于空气中。实验

发现在液体水柱中，聚焦位置距离靶面越远，铝靶冲量耦合系数越小，同时靶前靶后聚

焦效果不同。最后实验还发现，在一定条件下，密度大的液体介质冲量耦合系数大，并

且冲量耦合系数还和电离程度的难易有关。

关键词：环境条件；激光烧蚀；激光能量密度；铝靶冲量耦合系数

Laser ablation of target can present differently in gas and liquid.

Firstly, the interaction between laser and target under different conditions was theoretically

studied in this paper, and then the shock wave model in gas and liquid was analyzed. Then the impulse

coupling coefficient of aluminum target was measured. The measurement of this experiment is by using

piezoelectric sensor which was designed dependently with the material of aluminum. Experiments were

undertook separately in both gas and liquid. In a gas environment, the research content are as follows:

(1)Under the standard air pressure, the relationship between laser energy density and the impulse coupling

coefficient of aluminum target was researched; (2) Changing air pressure, the impulse coupling coefficient

of aluminum target was measured under the same energy density, then the effect of air pressure on the

aluminum target’s ablation was studied;(3)When the laser energy density was changed, the effects on the

condition of gas, the ablation rate and the laser plasma shock wave pressure may have influence on the

impulse coupling coefficient of aluminum target in different laser energy density, at the same time, the

ablation threshold would affect the value of the impulse coupling coefficient. When ablation of aluminum

is in liquid, the trend of laser ablation variation under different energy density is closed to the trend in gas,

but the value of the impulse coupling coefficient in liquid is greatly higher than in the air. It was found that

the farther focus distance from target surface, the smaller value of the impulse coupling coefficient in liquid,

and the result may vary differently before target and behind target. At last the experiment also found that

the density and the ionization degree of liquid may influence the result. When the density and the ionization

degree of liquid is big, the value of the impulse coupling coefficient is big.

准直性好等优点在激光应用中得到推广。其中，激光在航天烧蚀推进

烧蚀材料

激光在烧蚀方面的应用，主要利用聚焦产生高能量密度的激光来使靶材料受热、气

化、蒸发，达到烧蚀材料目的。对于烧蚀推进，主要利用激光烧蚀靶材料产生等离子体

冲击压来使靶获得动量。一般人们用烧蚀材料比冲和冲量耦合系数等参数来衡量烧蚀效

率。比冲为消耗单位质量工质产生的推力，冲量耦合系数为消耗单位能量所产生的动量。

激光和传统的燃料推进相比优点是具有较高的比冲，同时具有较大的冲量耦合系数，并

且能量造价低

；其缺点是可提供的激光器能量有限，无法满足长距离推进需要，一些

度进行测试研究。2000 年，美国用高功率 CO

激光器驱动光帆在 Wright-Patterson 空军

基地进行实验测量，在同一年，Bohn，Willy L 研究了测试了一激光飞行器

。2002 年

Yabe, Takashi 也进行了激光推进实验

，主要分析了激光从大气层到外太空可能遇到的

各种状况。在太空中，激光推进效果演示如图 1-1，其底部为高能量激光器，空中为类

似于光帆的航天器。