A device for delivery of a beam of X-rays provided for analysing a sample by small-angle X-ray scattering, the sample being placed at the output of said delivery device, said device comprising: - a source block comprising X-rays emission means; said device being characterised in that it comprises: - an optical block placed downstream of the source block relative to the direction of propagation of the X-rays (P RX), said optical block comprising an optical monochromator component having a reflecting surface provided for conditioning X-rays emitted by the source block according to a unidimensional or bidimensional optical effect; and - definition means of X-rays comprising: o an anti-diffusing member for spatially delimiting X-rays conditioned by the optical monochromator component, said spatial delimitation anti-diffusing member being arranged downstream of the optical monochromator component relative to the direction of propagation of the X-rays (P RX), said spatial delimitation anti-diffusing member comprising one or more plates having portions arranged to form a delimiting orifice, said portions being coated with a monocrystalline material limiting the scattering of X-rays; o a cut-off member of X-rays emitted by the source block, said cut-off member comprising X-ray absorption means arranged in the delivery device to cut off the direct X-ray beams emitted by the source block likely to reach the spatial delimitation anti-diffusing member without conditioning by the optical monochromator component, said X-ray absorption means of the cut-off member being arranged to prevent the direct X-ray beams from going beyond the optical monochromator component in the direction of propagation of the X-rays (P RX). - a source block comprising X-rays emission means; - an optical block placed downstream of the source block relative to the direction of propagation of the X-rays (P RX), said optical block comprising an optical monochromator component having a reflecting surface provided for conditioning X-rays emitted by the source block according to a unidimensional or bidimensional optical effect; and - definition means of X-rays comprising: o an anti-diffusing member for spatially delimiting X-rays conditioned by the optical monochromator component, said spatial delimitation anti-diffusing member being arranged downstream of the optical monochromator component relative to the direction of propagation of the X-rays (P RX), said spatial delimitation anti-diffusing member comprising one or more plates having portions arranged to form a delimiting orifice, said portions being coated with a monocrystalline material limiting the scattering of X-rays; o a cut-off member of X-rays emitted by the source block, said cut-off member comprising X-ray absorption means arranged in the delivery device to cut off the direct X-ray beams emitted by the source block likely to reach the spatial delimitation anti-diffusing member without conditioning by the optical monochromator component, said X-ray absorption means of the cut-off member being arranged to prevent the direct X-ray beams from going beyond the optical monochromator component in the direction of propagation of the X-rays (P RX). o an anti-diffusing member for spatially delimiting X-rays conditioned by the optical monochromator component, said spatial delimitation anti-diffusing member being arranged downstream of the optical monochromator component relative to the direction of propagation of the X-rays (P RX), said spatial delimitation anti-diffusing member comprising one or more plates having portions arranged to form a delimiting orifice, said portions being coated with a monocrystalline material limiting the scattering of X-rays; o a cut-off member of X-rays emitted by the source block, said cut-off member comprising X-ray absorption means arranged in the delivery device to cut off the direct X-ray beams emitted by the source block likely to reach the spatial delimitation anti-diffusing member without conditioning by the optical monochromator component, said X-ray absorption means of the cut-off member being arranged to prevent the direct X-ray beams from going beyond the optical monochromator component in the direction of propagation of the X-rays (P RX).