Lecture Notes in Physics

3 Laser-Triggered Nuclear Reactions 37
Table 3.2. Some proton-induced reactions. Cross-sectional and decay data are taken
from [57] and from [58], respectively. Only the strongest γ-lines of the decaying
reaction products are indicated
Target Reaction Product t1/2 γ-Line Eth Emax σmax
Nucleus Nucleus (keV) (MeV) (MeV) (mbarn)
65 Cu (p,n)
65 Cu (p,p+n)
63 Cu (p,n)
63 Cu (p,2n)
63 Cu (p,p+2n)
11 B (p,n)
13 C (p,n)
65 Zn 244.3 d 1115.5 2.13 10.9 760
64 Cu 12.7 h 1345.8 9.91 25 490
63 Zn 38.47 min 669.6 4.15 13 500
62 Zn 9.186 h 596.56 13.26 23 135
61 Cu 3.33 h 656.0 19.74 40 323
11 C 20.39 min 511 3 8 300
13 N 9.96 min 511 3 6 150
upper energy detection limit is given only by the number of induced reactions
in the stack and the sensitivity of the gamma-detector, whereas the limit
for the detection of low-energy protons is given by the reaction threshold of
4MeV.
Another technique that involves only one single copper foil takes advantage
of the different proton-induced reactions in the natural occuring isotopes 65 Cu
and 63 Cu, which are listed in Table 3.2 [5]. Some of these reaction cross sections
are plotted in Fig. 3.4. Again, from the known cross-sectional data and the
measured number of induced reactions the proton spectrum is derived. Since
the cross sections of these reactions peak at energies from 10 to 40 MeV, and
the lowest threshold energy is 2 MeV, proton spectra in the range of 2–40 MeV
can be measured.
Other proton-induced reactions have been demonstrated as well. In particular
the (p,n)-reactions in 11 B, 13 C, and 18 O [65] are of potential interest
for future applications in the production of isotopes for positron emission
tomography (PET) as is discussed in Sect. 3.4.
Ion-Induced Nuclear Reactions
As shown in Sect. 3.2, ions heavier than protons can be accelerated by the
same mechanism that leads to protons acceleration. 12 C, 16 O – both of which
originate from hydrocarbon and water contaminations on the target surfaces –
as well as ions from the target material itself, such as 27 Al, 56 Fe [9, 34, 37], or
deuterons [12], were accelerated. It has been shown that the ion energies can
reach 10 MeV/nucleon, which results in 650 MeV energy for Fe-ions [9]. These
ions can react with a secondary target: they may fuse and form highly excited
compound nuclei, which evaporate neutrons, protons, and alpha-particles [9,
37]. Depending on their initial excitation, that is, incident ion energy the
reaction channel may be different, corresponding to a different cross section