BerILL: The ultimate humidity chamber for neutron scattering

We present the design and the performances of a precision humidity chamber for neutron diffraction which is the result of a very fruitful collaboration between the Helmholtz-Zentrum Berlin and the Institut Laue-Langevin. The sample temperature can be set between 10 and 85°C. The relative humidity is controlled from 10 to 99.9 % ± 0.01 % by controlling the temperatures of the sample and a water bath at the millidegree Celsius scale. Sample exchanges are extremely easy and the operation only requires entering two parameters: sample temperature and relative humidity. The performances are confirmed by neutron diffraction measurements performed on DMPC and DOPC.