Fig. 4-4 Interaction of an ultrahigh peak output laser and a solid thin film Seen in the figure is the interaction of the electric field intensity of the laser light, the interval between the red and blue colors corresponds to the light wavelength (1 micron), and the hatched region shows the solid thin film target. In the case when an ultrahigh peak output laser irradiates a solid thin film, part of the light is transmitted through the thin film, uncommon in the case of a usual laser.

Fig. 4-5 Interaction of an ultrahigh peak output laser and a fine-grained thin film In the case of a fine-grained thin film target (hatched region), the laser light is not reflected as in a solid, but the situation can be clearly seen that at the surface extremely strong absorption (anomalous absorption) is occurring (left figure). Finally when the interaction was completed, we found that all of the laser light is completely absorbed.

When an ultrahigh peak power laser in a short pulse of 100 trillionth of a second, which is the main point of the Advanced Photon Research Center, is focused to the limit and irradiates a solid or something else, an ultrahigh energy, high density plasma is instantaneously generated. In an extremely short time it is said that various phenomena occur which up till now were not expected. We have progressed the understanding these phenomena of large scale plasma particles by optimized calculations with massively parallel computers, we have clarified (in the manner below) results of great interest. In this calculation we used the Kansai Research Establishment massively parallel Paragon XP/S 75MP834 computer which is provided with 2,502 CPUs, having a capability of 125 GFLOPS and 106 GBytes, 100 times greater than that of a regular super computer. When a laser irradiates a solid thin film, the laser light is reflected from the surface. However, in the case of an ultrahigh peak output laser, part is transmitted through the thin film. Furthermore, in a subject of great interest, we have found that this transmitted light is composed of more fine intervals of red and blue stripes, and powerful short wavelength coherent light below 1/10 of the laser wavelength (far ultraviolet or soft x-rays) is emitted (Fig. 4-4). In addition, when shown on thin films made from fine-grained particles of submicron order, the above mentioned phenomena of the solid surface display a completely different aspect. We discovered that the laser is almost completely absorbed, and fine intervals of red and blue stripes of strong x-rays and high energy electrons and ions occur (Fig. 4-5). This kind of condition is considered to be the upper limit of conditions which can be realized on earth and the possible generation of ultrahigh energy particle ensembles which only occur in space. We are expecting early experimental verification.

Reference Y. Ueshima et al., Giga-Particle Simulation of Short Pulse X Ray Generation with Ultra-Shortpulse Relativistic Laser, Inst. Phys. Conf. Ser. No. 159, Proc. of 6th Int. Conf. on X-Ray Lasers, Aug. 31-Sep. 4, Japan, 1998, 325 (1999).

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