In fig 31 where the presence of an azimuthal b eld fig

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Unformatted text preview: the foil, entering from the nonirradiated side in (a) and from the opposite, laser-irradiated side in (c). The inversion of the deflection pattern reveals the effect of a toroidal B field [the asymmetrical pattern in (c) is due to a nonideal intensity distribution in the focus]. (b), (d) Particle tracing simulations for the conditions of (a) and (c) assuming a suitably parametrized B field. From Cecchetti et al., 2009. 782 Andrea Macchi, Marco Borghesi, and Matteo Passoni: Ion acceleration by superintense laser-plasma . . . FIG. 32 (color online). The left shows the proton imaging setup with increased dynamical range in the time domain (Quinn et al., 2009a, 2009b). By placing a wire target at an angle with respect to the probe beam it is possible to resolve the propagation at a velocity close to c of a field front along the laser-irradiated wire, as shown in the right (top: experimental images, bottom: particle tracing simulations). From Quinn et al., 2009a. has been revealed with mesh deflectometry by either a compression or outward dilation of the mesh lines, depending on whether the B field has clockwise or counterclockwise direction compared to the propagation direction of the probe beam. The divergence of the probe beam also implies that the effective probing time is a function of the position on the image plane because of the different time of flight for protons at different angles. This effect has to be taken into account for measurement of field structures propagating at relativistic speeds (Kar et al., 2007; Quinn et al., 2009a) and actually may improve the capability to characterize such structures, as it was obtained by a slightly modified arrangement (Quinn et al., 2009b). This allowed one to observe the ultrafast, transient field front associated with the early stage of TNSA where electromagnetic effects come into play (see Fig. 32). A proton streak deflectometry technique for obtaining continuous temporal mapping (but only one spatial dimension is resolved) has also been proposed in which the energy resolution is achieved by means of magnet dispersion (Sokollik et al., 2008). B. Production of warm dense matter Laser-driven ions have found application in a number of experiments aimed to heat up solid-density matter via isochoric heating, and create so-called warm dense matter (WDM) states, i.e., matter at 1–10 times solid density and temperatures up to 100 eV (Koenig et al., 2005) of broad relevance to material, geophysical, and planetary studies (Ichimaru, 1982; Lee et al., 2003). The high-energy flux and short temporal duration of laser-generated proton beams are crucial parameters for this class of applications. WDM states can be achieved by several other means, e.g., x-ray heating (Tallents et al., 2009) and shock compression (Kritcher et al., 2008). However, when studying fundamental properties of WDM, such as the equation of state (EOS) or opacity, it is desirable to generate large volumes of uniformly heated material; ion b...
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This document was uploaded on 09/28/2013.

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