Conveners
Evaluating the Suitability of Organic Semiconductor Detectors for Nuclear Security: Evaluating the Suitability of Organic Semiconductor Detectors for Nuclear Security
- Aled Horner (Queen Mary University of London)
Description
Feasible alternatives for thermal neutron detectors based on 3He have been searched for
over the past near 20 years. These can be used in a wide variety of industries: nuclear
security and safeguarding, the medical industry for neutron therapy beam monitoring,
non-destructive imaging, and as part of nuclear and particle physics experiments. A
number of different alternatives exist to the gas-based 3He detectors, including the
organic semiconducting detectors utilising boron for boron-neutron capture which are
described here. Organic materials allow for high scalability, generally low costs of
manufacture, and excellent tuneability, however a number of drawbacks still remain to
this technology. Low counting efficiencies lead to expensive bespoke read-out equipment
requirements.
In this presentation, work done investigating the suitability of this technology for the specific
context of nuclear security will be given. With reference to two real-life scenarios, the
capability of the detectors fabricated in-house at Queen Mary University of London,
London, UK, will be discussed based on a suite of alpha irradiation data obtained
at Queen Mary and neutron irradiation data at external neutron sources based at
the National Physical Laboratory, Teddington, UK, and at the University of Glasgow,
Glasgow, UK. A number of brief studies are discussed on the improvement on the existing
technology: improvements to the qualities of films are reported, environmental effects
investigated, and gamma blindness from numerous sources considered. A number of
organic materials are used throughout this project. One of the three isomer forms of a
novel material is particularly highlighted, oCbT2-NDI, a polymer in which an icosahedral
carborane (a cluster of boron, carbon, and hydrogen) is included in the monomer backbone.
Here is described the first successful alpha and neutron radiation detection using
this type of material.
This presentation also introduces the findings that a large component of the signal being
read out by these detectors under alpha irradiation in fact originates with ionisation of
air. This phenomenon is discussed in detail as well as suggestions on how to improve
the organic detector technology further when moving to the future with this project.
