Page 22 - PR 2014 2016 07 Nuclear Science and Technology

164 Nuclear Science and Technology | Progress Report

value should probably be reassessed.

In a collaboration with the Pelletron labora-
tory in USP’s Physics Institute, the possibility
to use gamma-gamma-particle coincidence
measurements to determine nuclear reactor
cross sections was studied, and the results
proved that this can indeed be a very useful
technique in these measurements.

In another collaboration with the Pelletron
laboratory, together with the Advanced Stud- Fig 16. Energy spectra of Li and He ions produced by
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neutron capture in 10B layers in in a gas detector for
ies Institute of the Aeronautic Technological layer thicknesses of 0.5, 1.0, 2.5 and 5.0 µm..
Center (IEAv/CTA) and CERN, damage induced
by irradiation with electrons, heavy particles
and fast neutrons in both regular and aero-
space-specific electronic devices is under study.

Scientific Computing

The efficiency of TGEM detectors for neutrons
increases with the number of boron coated
plates. The boron layers absorb neutrons and
the produced particles ( Li and He ions) must
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have enough energy to leave the boron layer
and enter the gas region, which is the sensitive
part of the detector. If the boron layer is very
Fig 17. Dependence of the efficiency on the thickness
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thick, most of the Li and He ions are absorbed of layers for neutron detectors mounted with sever-
in the layer and will not enter the gas to pro- al layers of boron deposited on thick-GEM plates.
duce a signal. There is a maximum thickness
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for the layer, for which the Li and He ions can
cross and enter the gas region. Besides that,
when several layers are placed in series, there
is an optimal thickness, which depends on the
number of layers. Calculations were performed
with the GEANT4 Monte Carlo toolkit in order
to obtain the optimal thickness for several
configurations. The simulated energy spectra
of the ions that enter the gas are presented
in Figure 16 for several values of boron thick-
ness. Figure 17 shows the dependence of the
efficiency on the boron thickness for several
layers and Figure 18 shows the efficiency and Fig 18. Efficiency and optimal thickness for bo-
ron layers of thick-GEM detectors mounted
optimal thickness depending on the number with several plates coated with boron.

Instituto de Pesquisas Energéticas e Nucleares