Abstract: Gas-filled detector for locating the presence in space of particles or radiations. The detector according to the invention comprises a curved body containing a gaseous fluid under pressure, and being provided with a window, and on the inside, an elongated element forming means of picking-up an avalanche of elements, said means being constituted by a structure of the type with at least one curved conducting strip held in such a way by the body that it projects into the enclosure and that one of its longitudinal edges is parallel to the axis of the window. The invention finds an application in X-ray crystallography.