Measurement of the degree of polarization of the spectra from laser produced recombining Al plasmas

Abstract

Using a polarization-resolved UV-visible spectrometer, the degree of polarization of the spectra from laser produced Al plasmas was measured. The polarization resolution was achieved by using either a dichroic polarizer or a calcite crystal. The degree of polarization of Al III 4s(2)S(1/2)-4p(2)P(o)(3/2) transition at 569.66 nm was measured at different positions from a target surface. The degree of polarization was observed to be 2.1+/-0.13% at a distance of 220 microm from the target and decreased as the distance from the target increased, vanishing at a distance of about 1.3 mm from the target. To avoid the possible error due to the shot-to-shot variation of the line intensity, a calcite crystal was used to simultaneously observe the two polarization components, obtaining a similar result. The electron temperature of about 3 eV and the density of 2 x 10(17) cm(-3) measured spectroscopically indicates that the plasma was in the recombining phase. This is a report on the observation of the polarization of a transition in a laser-produced recombining Al plasma.

Spatial prisoner’s dilemma game with volunteering in Newman-Watts small-world networks

“…Therefore, the spatial structure may greatly affect their activities. Since Axelrod [7] suggested ideas of the PDG on a lattice, spatial prisoner's dilemma games (SPDG) have been extensively explored in various kinds of network models in the past few years, including regular lattices [8,9,10], random regular graphs [11], random networks with fixed mean degree distribution [12], small-world networks [13,14,15] and realworld acquaintance networks [16], etc. In the general SPDG, each agent can take one of two strategies (or states): cooperator (C) and defector (D).…”

“…For convenience, following Refs. [10,11,14, 15], we set s = p = 0, r = 1, σ = 0.3, and 1 < t < 2. We define t − r as the relative temptation quantity (shortly RTQ) reflecting the extent of the temptation and cursorily partition the networks into three regions: lattice, small-world and random graphs corresponding to the variational range of Q: (0.0001, 0.001), (0.001, 0.3) and (0.3, 1) respectively.…”

“…Following Ref. [14], the payoffs earned by the agents are calculated as average and not accumulated from round to round. To start the next round, agents are allowed to inspect the profits collected by their neighbors and adjust their strategies.…”

Comparison of the polarisation of line and continuum emission in a laser produced plasma

“…The origin of the polarisation in this study was postulated to be an anisotropic electron distribution function caused by steep density gradients which result in polarized recombination radiation [6]. Similarly, studies on the visible emission from an Al plasma showed that the line emission can also be partially polarized [3]. In this study, the degree of polarisation in the Al 2+ doublet at 569.6 and 572.3 nm was found to be on the order of 3 %.…”

“…The technique of PPS has been applied to laser produced plasmas where partial polarisation has been observed in the x-ray and visible spectral ranges [2,3]. Importantly, a particular application of PPS known as polarisation-resolved laser induced breakdown spectroscopy (PRLIBS) exploits this partial polarisation in order to enhance the signal to background ratio over traditional LIBS measurements [4].…”