Laser plasma interaction in copper nano-particle targets

In this paper, we present the results of studies on ion emission characteristics of a laser plasma produced from a copper nano-particle layer of 1–3 µm thickness coated over polished surface of a solid copper target. Laser intensity of 1013–1014 W/cm2 was produced on the targets by a 2 J Nd:glass laser having a variable pulse duration of 300–800 ps. Nano-particle size was in the range of 15–25 nm. Ion emission from the nano-particle plasma was compared with plasma generated from a polished copper target. Ion emission from the nano-structured target was observed to depend on the polarization of the incident laser beam. This effect was stronger for a shorter laser pulse. X-ray emission was measured in the soft and hard X-ray region (0.7 to 8 keV) using various X-ray filters. A nano-particle coated target is found to yield a larger flux as well as velocity of ions as compared to polished target when the laser polarization is parallel to the plane containing target normal and detector axis. However, no X-ray enhancement has been observed in the wavelength range 1.5 to 20 Å.