Laser plasma generation method and structure thereof

#This application claims priority to prior application JP 2002-109587, the disclosure of which is incorporated herein by reference.

#The present invention relates to a laser-plasma generation method and its structure in which a target material that is fluid at least in one of liquid and solid states is ejected from a nozzle to form a column-like jet flow and then irradiated by focused pulsed lasers composed of at least single beam to generate a high-temperature high-density plasma that emits high-average power x-ray which is useful for x-ray material processing, x-ray lithography, and material analysis. In particular, the present invention relates to a laser-plasma generation method and its structure which provides a method that can supply with target continuously at a small gas emission rate, and which can enhance the x-ray conversion efficiency.

#The effort has been made to realize a practical laser-plasma x-ray source in order to use x-rays from a high-temperature plasma that is produced from a target and heated by irradiating a high peak power laser. It is desirable to obtain an x-ray conversion efficiency as high as possible in the focus spot area of the heating laser beam in order to achieve a high-brightness x-ray source. On the other hand, a higher plasma density is favorable to obtain a higher x-ray conversion efficiency. For this purpose a method has been developed as a mean supplying the target that prepares the target material in a fluid state of a gas phase or a liquid phase which is ejected as a jet flow through a nozzle into a vacuum chamber and then heated by a focused laser beam With this method, a continuous supply of the target material is relatively easy, thus a high average power x-ray source will be achieved by using a high repetition rate pulsed laser.

#FIG. 1 is a view describing one embodiment of conventional x-ray generation structure using a liquid target;

#FIG. 2 is a sectional view for describing one embodiment on the structures relating to the present invention;

#FIG. 3 is a sectional view for describing one embodiment in which a part of FIG. 2 is modified and improved;

#Now, embodiments of the present invention will be described referring to figures. The figures used are only for illustration to explain the present invention so that the dimensions including sizes of components and configurations are partially exaggerated, thus not accurate.

#And the jet tube target with a hollow shell may be a flow of solid state material which has been solidified immediately after it was ejected from the nozzle opening. But, for convenience we assume that the jet tube target is in a cylindrical column which is of a most effective shape in the embodiments described hereunder.

#FIG. 2 is a block diagram of function for describing one embodiment according to the present invention.