Abstract
Following a literature survey into neutron detection methods, a conceptual design for a novel dose meter was proposed consisting of a pair of CdZnTe (CZT) detectors with a thin sandwiched layer of 6LiF between, achieved by coating one of the detectors with 6LiF. A detector was constructed using two 10x10x2 mm CZT detectors, of which one was coated with a 4 μm 6LiF layer. Coincidence counting of the alpha particle and triton arising from the 6Li (n, α) 3H reaction was used to reduce the gamma background. Development of this design was carried out by undertaking experimental work on a simple prototype and by conducting Geant4 simulations. The Geant4 simulation work included comparison of simulations with experimental data to validate the modelling work carried out. Results from this work show that neutron detection is possible using this technique, using a 6LiF layer of a few microns thickness, and that inference of neutron energy from the detector response is possible in principle. Also identified as a result of the modelling work were drawbacks and limitations with the use of CZT, notably the opacity of the 2 mm thick detectors used in the experimental work to thermal neutrons. This affected detector performance significantly, leading to detector separation playing a key role in detector efficiency, with efficiency also varying strongly with neutron field direction. The presence of neutrons was detected in a mixed neutron and gamma field, although 5 cm of lead shielding was required in order to detect a response above background. A review of the different methods of neutron detection is also presented with a discussion on their applicability to monitoring worker dose in the workplace. Having reviewed the performance of available dose meters, it has been concluded that there is scope for improved novel instruments as the response of existing instruments available has a strong energy dependence.