NeuLAND - FAIR

events
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Figure B.8.: Reconstructed relative energy spectrum for the Neutron MRPC from a
Monte Carlo simulation. Simulated is the one-neutron emission from 132 Sn
for 600 AMeV energy with a relative energy of 100 keV. The detector is
placed at 35 m distance to the target.
In order to be able to reconstruct the relative energy, an algorithm was developed, which
selects those hits in the simulation that can be used to determine the momenta of the
incoming neutrons correctly. The hit multiplicity increases as the number of impinging
neutrons increases and there is a fair separation between the appearing peaks in the
spectrum as is seen in figure B.7. Therefore, this was used to determine the number of
incoming neutrons in an event (n). This provides us the so-called identification matrix
which contains correlation percentages between the expected and deduced number of
incoming neutron (see e.g., B.1). The hit selection algorithm is based on the clustering
of the hits with an adjustable distance parameter, which is combined with a causality
check between the clusters. The remaining hits were ordered according to their latent
speed calculated from the hit position and time of detection. The first n number of hits
were used for the momentum and relative energy reconstruction. As an example such a
reconstructed relative energy spectrum is shown in figure B.8.
According to the simulations, the MRPC-based setup is able to detect single neutrons
with high efficiency. There is some limited capability, as well, to disentangle multineutron
events and reconstruct the relative energy of nuclear reaction products. The
multi-neutron performance is, however, much worse than that of the scintillator-based
concept (see section 4.5).
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