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kind of measurements allow to characterise the spallation process. High energy neutrons emitted at
low angles are representative of the first stage of the collision while low energy neutrons emitted
isotropically correspond to the evaporation phase. Measurements done with thicker targets are
representative of the inter-nuclear cascade leading to the multiplication and moderation of neutrons.
Figure 4. Neutron production double-differential cross-sections measured in 1.2 GeV induced
reactions on a 2-cm thick Pb target [8]. The histograms represent calculations using the Bertini INC
Code [9] while the dotted lines corresponds to calculation done with the Cugnon INC Code [10].
4. Residue production in spallation reactions
Residue production in spallation reactions can be investigated using two different experimental
approaches. In the standard one, the reaction is induced in direct kinematics, the light-energetic
projectile hits a heavy target. In this case the recoil velocity of the residues produced in the reaction is
not sufficient to leave the target and -spectroscopy or mass spectrometry techniques are used to
identify those residues. The main limitation of this technique is that for most of the residues the
measurement is done after decay and consequently only isobaric identification is possible.
Better suited seems to be the measurement of the spallation residues in inverse kinematics. In this
case the heavy nucleus is accelerated at relativistic energies and impinges a light target. Due to the
kinematical conditions, the reaction residues leave easily the target and can be identified in a short
time using the appropriate technique.
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