Technology Enhancements for Next Generation Radiation Detectors

Portable radiation detectors are becoming widely used across various industries, particularly the security industry to roll out networks of portable detectors for illicit nuclear material detection. The capabilities of modern detectors have rapidly increased in recent years, largely with the use of advancements in photonics technology. This research program demonstrates two versatile methods of maximising the use of state of the art solid state photo multiplier technology and dual gamma neutron scintillation material, by using low power digital and analogue methods where low power consumption in portable devices is essential for longer operation times between battery charges.

A 25 million sample per second analogue to digital converter system is developed and its performance analysed for methods of gamma event energy capture using a basis of well-established principles used in radiation detection. Its architecture flexibility allows the embedding of different applications, where firstly using it similar to a traditional peak capture circuit is evaluated for gamma energy capture. Secondly, the system is evaluated when using continuous or triggered sampling of a silicon photo multiplier array output both with and without prior stages of analogue signal processing, in order to accurately capture the radiation event signal for digital processing of gamma radiation events. The results show 8-bit peak capture accuracy using generated semi – Gaussian input signals simulating scintillation requirements as fast asusing a 1 μS shaping time at 250,000 events per second. The results also show that the ADC system is able to continuously sample a scintillation event, where the captured data is re-plotted for evaluation, where further on device digital processing methods can yield radiometric information.

A low power analogue based circuit is also developed and evaluated for use with the dual gamma neutron scintillator CLLB. Current pulse shape discrimination methods rely on offline processing of pulse datasets to distinguish between a gamma and a neutron event, where the common method used relies on integration windows. This method when implemented in electronic circuitry as a timer controlled gated integrator can prove challenging to design efficiently and can consume excessive amounts of power which is a disadvantage for a battery powered product. The method used in the implemented analogue circuit relies on a combination of amplitude ratio windowing and pulse height discrimination, where successful discrimination between gamma and neutron events was achieved, and where the circuit depending on configuration and application consumes as low as 14 mW of power.