  The demand for new thermal neutron detectors as an alternative to 3He tubes
in research, industrial, safety and homeland security applications, is growing.
These needs have triggered research and development activities about new
generations of thermal neutron detectors, characterized by reasonable
efficiency and gamma rejection comparable to 3He tubes. In this paper we show
the state of the art of a promising low-cost technique, based on commercial
solid state silicon detectors coupled with thin neutron converter layers of
6LiF deposited onto carbon fiber substrates. A few configurations were studied
with the GEANT4 simulation code, and then calibrated at the PTB Thermal Neutron
Calibration Facility. The results show that the measured detection efficiency
is well reproduced by the simulations, therefore validating the simulation tool
in view of new designs. These neutron detectors have also been tested at
neutron beam facilities like ISIS (Rutherford Appleton Laboratory, UK) and
n_TOF (CERN) where a few samples are already in operation for beam flux and 2D
profile measurements. Forthcoming applications are foreseen for the online
monitoring of spent nuclear fuel casks in interim storage sites.
