RevModPhys.85.751

Of medical interest eg for pet diagnostic see sec vd

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Unformatted text preview: relevance for astrophysical nucleosynthesis, would require intensities above 3 Â 1022 W cmÀ2 that may be available with next-generation short-pulse laser facilities. Neutrons are an important product of the above mentioned nuclear reactions, with potential applications in cancer therapy, neutron radiography, radiation damage of materials, and transmutation of nuclear waste. The potential for laser-driven neutron sources is considerable and offers advantages over accelerator- and reactor-driven sources in terms of cost, compactness, brightness, and short duration for applications such as fast neutron radiography (Lancaster et al., 2004) and studies of impulsive damage of matter (Perkins et al., 2000). This has motivated several experiments on the production of neutrons initiated by laser-driven proton beams on secondary targets. Experiments carried out at the VULCAN laser facility revealed neutron yields up to 4 Â 109 srÀ1 per pulse at a laser intensity of 3 Â 1020 W cmÀ2 (Yang et al., 2004a), produced via the 11 Bðp; nÞ11 C and 7 Liðp; nÞ7 Be reactions. The latter was also investigated by Youssef, Kodama, and Tampo (2006) as a diagnostic of proton acceleration. Neutron production was also observed in interactions with solid targets containing deuterium (typically deuterated plastic), which can be either directly irradiated by high-intensity laser pulses (Norreys et al., 1998; Disdier et al., 1999; Habara et al., 2003, 2004b; Willingale et al., 2011a) or irradiated by ions accelerated on a separate target (Fritzler et al., 2002; Karsch et al., 2003). In both cases the neutrons are produced in the course of fusion reactions of the type Dðd; nÞ3 He involving laser-accelerated deuterium ions as also observed in gaseous targets (Ditmire et al., 1997; Grillon et al., 2002). Numerical modeling and theoretical investigations of laserdriven neutron production have been carried out; see, e.g., Toupin, Lefebvre, and Bonnaud (2001), Macchi (2006), Davis and Petrov (2008, 2011), and Ellison and Fuchs (2010). Application of laser-accelerated ions in particle physics requires ‘‘by definition’’ the ions to be relativistic, i.e., their total energy must exceed the rest energy whose value per nucleon is $mp c2 ’ 0:94 GeV. Presently, observed cutoff energies are more than an order of magnitude below this threshold. Nevertheless, the scalings inferred from either experiments or theoretical models and the foreseen availabil29 Typical short-lived positron emitters include 11 B, 11 C, 13 N, 15 O, and 18 F. Related experiments have been reported, by Nemoto et al. (2001), Fritzler et al. (2003), Ledingham, McKenna, and Singhal (2003), Clarke et al. (2006), Fujimoto et al. (2008, 2009), and Ogura et al. (2009). 18 O, Rev. Mod. Phys., Vol. 85, No. 2, April–June 2013 ity of higher laser powers in a few years suggests that GeV ions may eventually be produced and applied in selected particle physics experiments. Moreover, it should be noted that the very lo...
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