Page 169 - 00. Complete Version - Progress Report IPEN 2014-2016

Nuclear Science and Technology | Progress Report 169

ry in USP’s Physics Institute, the possibility to
use gamma-gamma-particle coincidence mea-
surements 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-
ies Institute of the Aeronautic Technological
Center (IEAv/CTA) and CERN, damage induced
by irradiation with electrons, heavy particles Fig 16. Energy spectra of 7Li and 4He ions produced
by neutron capture in 10B layers in in a gas detec-
and fast neutrons in both regular and aero- tor for layer thicknesses of 0.5, 1.0, 2.5 and 5.0 µm..
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 (7Li and 4He ions) must
have enough energy to leave the boron layer
and enter the gas region, which is the sensi-
tive part of the detector. If the boron layer is
very thick, most of the 7Li and 4He ions are
absorbed in the layer and will not enter the
gas to produce a signal. There is a maximum
Fig 17. Dependence of the efficiency on the thick-
thickness for the layer, for which the 7Li and ness of layers for neutron detectors mounted with sev-
4He ions can cross and enter the gas region. eral layers of boron deposited on thick-GEM plates.
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 Car-
lo toolkit in order to obtain the optimal thick-
ness for several configurations. The simulated
energy spectra of the ions that enter the gas
are presented in Figure 16 for several values of
boron thickness. Figure 17 shows the depen-
dence of the efficiency on the boron thickness
for several layers and Figure 18 shows the ef-
ficiency and optimal thickness depending on
the number of layers used to build the detec-
tor. The results of these calculations will give Fig 18. Efficiency and optimal thickness for bo-
ron layers of thick-GEM detectors mount-
support for the building of real detectors. ed with several plates coated with boron.