Recent improvements to a transportable neutron spectrometer (TNS)

This paper reviews the design, operation and future development of a transportable neutron spectrometer (TNS). Analogue signal processing techniques are used to condition the signals from an array of radiation sensors, comprising five gas-filled sensors and a hydrogenous oil-filled scintillator. This high reliance on analogue signal processing techniques is because of the nano-second rise time of the pulses produced from the sensor array. The analogue circuitry requires a high degree of expertise from the operator and frequent instrument calibration. An overview of the present instrument will be given together with a description of how the raw data from the individual sensor channels are combined to give a continuous neutron energy spectrum. Digital processing techniques are now being applied to the TNS to handle some of the more complex analogue functions, particularly neutron/γ-ray pulse-shape discrimination for the photo-scintillator column. Potential advantages of this approach are on qualities such as usability, reliability, testability, repeatability and portability of the instrument. The paper will report on the progress to date and give the latest results from experiments using a mixed neutron/γ-ray radiation source.