Noise evaluation of a digital neutron imaging device

To assess the applicability of neutron radiography technology, it is important to compare the performance characteristics of different neutron detection systems and their implementations. Although widely used in X-ray imaging, performance evaluation measures, such as the noise power spectrum (NPS) and the detective quantum efficiency (DQE), have not been readily applied to neutron radiography. This paper introduces the concepts of NPS and DQE and presents an adopted procedure for the calculation of NPS and DQE, using an in-house developed digital neutron radiography device as an example. This low-cost radiography apparatus has remarkable features such as using an off-the-shelf digital camera modified by open-source code and a front surface aluminized mirror made of 6Li-doped glass. The results show that a high spatial resolution does not necessarily translate to better detectability of faint details and noise evaluation has to be taken into account. In order to improve the poor DQE of the evaluated system, it is suggested to reduce the fast neutron content and increase the light collection efficiency. Such improvements would bring the output signal-to-noise ratio (SNR) much closer to the input quantum noise, which would consequently increase DQE.