High spatial resolution silicon-based neutron detectors

This project has contributed to the expansion of methodological expertise and capacity in neutron research in Norway and will promote full utilization of Norway's membership of the European Spallation Source (ESS). The aim of this project was to bring advanced silicon detector technology to the world of neutron scattering. Silicon-based neutron sensors with a spatial resolution on the micrometer scale are paired with efficient neutron converters, thus providing a portfolio of new instruments with superior performance for the ESS. Neutron sensors from SINTEF were tested in a thermal neutron beam at the reactor at IFE/Kjeller. Results show that silicon- based neutron sensors can clearly detect thermal neutrons and that the detector response and the efficiency are as expected from simulations. Pyramidial 3D structures on the sensor surface which increase the effective area of the detector, do not improve the detector efficiency.

Using existing micro-machining technology, SINTEF has fabricated silicon radiation detectors with 3-dimensional structures aiming to improve the probability of neutron capture in a neutron converter while maintaining a short distance for the secondary pro ducts to enter the detector's sensitive volume. On-going efforts to investigate various micro-structures such as micro-pillars and pyramidal structures have been carried out at SINTEF since 2011 due to the increasing interest in high spatial resolution ne utron sensors in material science and neutron imaging. The deposition of neutron converters both for their incompatibility with silicon fabrication as well as their adhesion on such microstructures remains a challenge. The PhD student will carry out an in vestigation of these advanced sensors by studying the detection efficiencies with respect to different converter materials, their corresponding deposition methods and a range of various 3-dimensional structures. The study will include the characterization using neutron sources and neutron beam lines e.g. at IFE, GEANT 4 simulations and an investigation of neutron coating methods. Radiation hardness and detectors' lifetimes will also be studied. The results of the investigation will demonstrate and identif y the suitability of these advanced silicon detectors for the European Spallation Source.