Introduction to neutron gas detectors for scattering science.

3He was often used as the neutron convertor for detectors in neutron scattering science, but this gas has become rare and expensive since 2008. The growing lack of Large Area Neutron Detectors becoming a major concern in most of the research neutron institutes, the development of techniques based on alternative convertors is of the highest priority. 10B is one of them; it can be used either in solid scintillators, or in proportional counters as thin films (10B or 10B4C) or gas compound (10BF3). The ILL is also still active in developing 3He detectors: large area curved detectors for powder and single crystal diffraction, Multi-tube detectors for reflectometry and SANS, and the high resolution MILAND multi-purpose detector developed in FP6.
After recalling basic principles of neutron gas detectors, these developments will be illustrated by several examples of detectors considered as workhorse in their category.