Refraction effect of X-ray laser beam caused by high-density plasmas. Observation of X-ray mirages

This paper introduces the phenomena of mirages in the soft X-ray region discovered at the time of the experiment where soft X-ray laser beams were made incident into plasmas. The mirage phenomena of X-rays were observed accidentally during the measurement of the spatial distribution of intensity of soft X-ray laser composed of laser plasmas as media. This paper firstly describes the plasma soft X-ray laser composed of laser plasmas as media, called a double target system, and the observation of its interference fringes. This plasma soft X-ray laser is composed of two amplification media, called oscillator and amplifier, and the X-ray laser generated by the first plasma (oscillator) is further amplified by the second plasma (amplifier), and thus high coherence can be achieved through this oscillation - amplification process. Then, this paper introduces the theoretical investigation of the refraction effect of soft X-ray laser based on high-density plasma as well as X-ray mirages, and describes the possibility of plasmas as a transient optical element, which can be expected from the theoretical study. (A.O.)