1. A method for analysing an object by neutron interrogation, by the associated particle technique, wherein a device is used which includes a sealed-tube neutron generator equipped with an alpha-particle detector and at least one gamma radiation detector, where the alpha particle detector allows neutrons emitted by the generator in a given solid angle to be monitored by detecting alpha particles associated with the neutrons emitted, where the gamma radiation detector allows gamma radiation emitted by the object to be detected when the object is placed in the given solid angle and receives the emitted neutrons, and the device is placed in a given position relative to the object, where the object is placed in the given solid angle, the method comprising: sending neutrons from the generator towards the object; carrying out acquisition of the data which is then provided by the alpha particle detector and gamma radiation detector; processing the data thus acquired in order to obtain a three-dimensional mapping of the object; performing at least one displacement of the device around the object, in order to place the device in another given position in relation to the object, where the object is kept fixed in the given solid angle; repeating the sending, carrying and processing steps for the other position of the device; correcting each three-dimensional mapping geometrically in order to allow the mapping to be updated relative to a set of all the three-dimensional mappings; and combining the three-dimensional mappings with each other in order to obtain a single three-dimensional mapping.