Or surface density of impurity protons in the target

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Unformatted text preview: t processes. We refer, in particular, to hot electron properties (see Sec. II.B.2) such as conversion efficiency h , temperature Th , density nh , cutoff energy, and beam divergence angle div . These quantities may in principle be modeled and/or measured but most times are not precisely known. Finally, some models include purely phenomenological parameters such as the ion acceleration time tacc (see Sec. III.C.2) and numerical parameters determined by fitting set of experimental data or numerical simulations. The experimental and theoretical uncertainties and the different nature of the model parameters inevitably impose some limitations to the conclusions that one could draw from a quantitative comparison. 15 See, e.g., Krushelnick et al. (2005), Borghesi et al. (2006, 2008), Fuchs et al. (2006b), Robson et al. (2007), and Perego et al. (2011). Rev. Mod. Phys., Vol. 85, No. 2, April–June 2013 769 We briefly touch on this problem following the work by Perego et al. (2011). The descriptions which have been selected in this paper are the fluid expansion models proposed by Mora (2003, 2005), the quasistatic approaches of Schreiber et al. (2006) and Passoni and Lontano (2008), and the ‘‘hybrid’’ descriptions by Albright et al. (2006) and Robinson, Bell, and Kingham (2006) (see Sec. III.C). The calculations used to implement these models and evaluate E max are also summarized. To perform the comparison a database containing an extensive collection of published experimental parameters and results, referring to a wide range of laser and target parameters, has been considered. This analysis shows that, despite all the uncertainties, the predictions of the TNSA models can be considered quite good, and in some cases remarkable, for a wide range of experimental parameters. In particular, quasistatic models, especially the one proposed by Passoni and Lontano (2008), appear more suitable for the prediction of E max . These conclusions are strongly affected by the estimates of the required parameters, and a more realistic approach to evaluate these quantities could improve the predicting capability of both expansion and hybrid models. The possibility to compare model predictions with experimental parametric studies under well-defined and controlled laser conditions, aimed at providing reliable and clear scaling laws, can significantly enhance the effectiveness of the analysis. Figure 19 shows results from a parametric study of the dependence of E max on laser power and duration (Zeil et al., 2010). Several other parametric investigations of the dependence of E max on laser pulse irradiance, duration, energy, and fluence have been reported (Fuchs et al., 2006b; Nayuki et al., 2006; Robson et al., 2007; Flippo, Workman et al., 2008; Flacco et al., 2010) as well as attempts in interpreting part of these findings (Passoni et al., 2009; Passoni, Bertagna, and Zani, 2010a; Zani, Sgattoni, and Passoni, 2011). FIG. 19 (color online). Experimental sca...
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This document was uploaded on 09/28/2013.

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