Scattering centre detector assembly and method

An assembly which comprises (a) a duct (22) for transmission of fluids, said duct having longitudinal axis, (b) at least one emitter (301) capable of exciting a beam of radiation (21) in the form of a cone having root angles and , which may be the same or different, into a cross section area of a duct to be analysed in a direction downstream of fluid flow in the duct at an angle λ from the plane perpendicular to the longitudinal axis of the duct, the angle λ being between 5° to 45°, (c) a detector (23, 304) sensitive to radiation radiated by scattering centres in the fluid over at least 1% of the cross sectional area of the duct, the direction of the central axis of the emitter cone being at an angle α to the direction of the central axis of the detector cone, the detector cone having root angles and , which may be the same or different and the detector cone having angle λ perpendicular to the longitudinal axis of the duct, the direction of the detector being downstream of fluid flow in the duct, the angle α being in the range 0° to 180° and angle λ being between 5° to 45°, the detector collecting scattered radiation and the detector being coupled to (d) a collator (310) for collecting data from the detector.