Detectors made with semiconductors such as silicon can be efficiently used for detecting and imaging neutrons when coated
with suitable materials. They detect the charged reaction products resulting from the interaction of thermal neutrons with
materials with high capture cross section like 10B, 6Li, and 6LiF. This work describes the performance of a thermal neutron
detector system, GAMBE, which is based on silicon sensors and a layer of neutron-sensitive material, such as a lithium
fluoride film or a lithium-6 foil, in a sandwich configuration. This arrangement has a total detection efficiency of 4 ± 2 %,
7 ± 1 %, and12 ± 1 % for 7 μm 6LiF film, 40 μm and 70 μm 6Li foil respectively. Also, it enhances the rejection of
fake hits using a simple coincidence method. The coincidence that defines a true neutron hit is the simultaneous signal
recorded by the two sensors facing the conversion layer (or foil). These coincidences provide a very good method for
rejecting the spurious hits coming from gamma-rays, which are usually present in the neutron field under measurement.
The GAMBE system yields a rejection factor at the level of 108 allowing very pure neutron detection in high gamma
background conditions. However, the price to pay is a reduction of the detection efficiency of 1 ± 1 % or 0:9 ± 0:3 % for
7 μm 6LiF film and 40 μm 6Li foil respectively.