Abstract: Apparatus for non-invasively inspecting an object, such as an item of luggage, for explosives material comprises a multi-channel thermal neutron inspection system having a plurality of neutron irradiation chambers. Simultaneous operation of several channels increases maximum system throughout several times. Each chamber has a lithium neutron source which is stimulated to neutron production by a proton beam. Beam switching magnets are energized by pulsing to divert a common proton beam to each source in turn. The initial beam is generated by a radio frequency quadrupole accelerator. The advantages of this system are very low residual source activity and controllable neutron production thereby minimizing safety hazards. The irradiation chamber may contain several different gamma ray detectors to identify the presence elements present in explosives material. In addition a neutron radiography imaging means may be employed to identify the presence of potential shielding materials.

Abstract: Residual core material can be detected inside hollow cast articles using positron emission tomography. Positron radio-isotope material is inducted into any residual core material present by immersing a cast article in an aqueous solution of radio-isotope emitter, for example gallium. Absorbed gallium subsequently emits positrons which are annihilated in collisions with electrons emitting two 511 KeV gamma rays in diametrically opposite directions. The emissions are detected and tracked by a PET camera and the resulting images correlated with a sectioned image of the article as a check on the location of detected core material. Initially a low-dose-rate solution for the purpose of merely establishing the presence of core material is used but a second optional process step introduces a more active solution allowing a PET camera to collect sufficient data to image absorbed isotope.

Abstract: The temperature of an object (10) is measured by monitoring the thermal Doppler broadening of resonances in its neutron transmission characteristics, as neutrons (11) pass through it from a source (12) to a detector (14). Various surfaces (18, 20, 24) of the object are each plated with a different element, such as platinum, iridium and rhenium respectively. By monitoring the Doppler broadening of resonances due to platinum, the temperature of the platinum surface (18) can be determined; and the temperatures of the iridium surface (20) and the rhenium surface (24) are determined likewise.

Abstract: A method of non-invasively measuring strain and temperature of an object, substantially simultaneously, using neutrons of selected energy levels is described. A pulsed neutron source is made to emit thermal and epithermal neutrons in a collimated beam directed at a target object. Temperature is monitored by observing the thermal Doppler broadening of resonances in the neutron transmission characteristic for the epithermal neutrons and strain is measured from observations made of changes to the thermal neutron diffraction pattern.

Abstract: To produce an image of a component of part of an engineering structure such as an aero-engine using a positron emission tomography (PET) technique it is proposed to provide the component or part of the structure of interest with a surface coating containing a radioisotope labelling material. The radioisotope label may be provided by applying a film of lacquer, paint or the like containing the isotope, or the component etc. may be bombarded by suitably energetic ions in order to induce a reaction in which a selected isotope is produced.

Abstract: A representation of oil flow in a gas turbine engine is obtained by injecting a compatible radioactive isotope label into the engine oil flow and detecting the radiation emitted from within the body with detectors mounted outside the body to produce signals representative of the quantity and direction of the radiation; the detector output signals are compensated for attenuation on passing through the engine in accordance with attenuation signals derived from a representation of the spatial distribution of the engine and of its materials, and signals from non-viable directions are discounted. The compensated detector output signals are used to generate a number of focal-plane tomograms from which an image in a desired plane may be re-constructed. The image may be formed on a background of the engine in the relevant plane generated from the representation thereof.

Abstract: Carrier particles, e.g., of metal or metal oxide, are doped with a positron-emitting isotope and injected into fluid flowing in a body, such as a gas turbine engine. The positrons decay on coming to rest, giving two gamma rays which are detected, and a 3D image is built up. The particles are capable of stopping a portion of the positions before they escape from the particles into the surroundings; thus the gamma rays indicate more accurately the position at which the positron was emitted, and give a clearer image.

Abstract: In order to produce a visual image on a screen of the movement of gas flows inside hollow bodies, e.g. gas turbine or internal combustion engines, or wind tunnels, a gaseous tracer material including a short-lived radio-active isotope is injected into the hollow body. Radiation detectors 32 are positioned around a gas turbine engine 10 and linked to a computer 36 which is programmed using an image reconstruction algorithm to reconstruct the flow path of the isotope in suitable form. One suitable isotope is produced by irradiating carbon tetrafluoride using a stream of deuterons from a cyclotron 12. The resulting reaction produces an isotope of Fluorine which has a half-life of 11.56 seconds, and decays producing radiation at approximately 1.6 Mev. The activity of the isotope is raised to the highest feasible level by continuously irradiating the tracer material in a chamber 14 as it is pumped around a circuit prior to injection. The half lives of the isotopes used are in the range 3 seconds to 2 minutes.

Abstract: Cold neutron radiation of energy less that 0.025 eV having a flux greater than 1.times.10.sup.3 neutrons/square centimeter/second is used to diagnose temporal information about the spatial distribution of hydrocarbon fuel and lubrication oils in internal combustion engines, gas turbine engines and fuel systems.Images of the movement of fuel or oil are recorded by directing a beam of neutrons through an engine and using an image intensifier responsive to low light levels to intensify an image formed by neutrons which have been directed through the engine onto a fluorescent screen. The output image from the intensifier is recorded by a video or cine camera.