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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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