Speaker
Description
For over a decade, the National Physical Laboratory in Teddington UK has used novel scintillators for nuclear metrology within the laboratory for measurements of industrial application as well as more fundamental blue-sky research. The high light yield, possibility for low internal background, suitable energy resolution and low cost of the devices make them attractive counters for coincidence counting in the metrological regime and beyond.
Currently these measurements are made on the second generation National Nuclear Array (NaNA) device [1,2], which utilises up to 20 CeBr$_3$ in a 3D printed spherical geometry allowing for auxiliary detectors such as HPGe, Si and TDCR (liquid scintillation) counters to be added to the system for individualised experimental setups. This improvement has shown promise in the metrological context from the previous version comprised of 12 LaBr$_3$ detectors which contributes more internal background leading to more uncertainty in count rate for coincidence counting. Measurements on both generations of the device will be presented from primary standardisations: i.e. the realisation of the Becquerel – in the case of the $\gamma$-$\gamma$ emitting $^{60}$Co [3] and $\gamma$-X emitting $^{125}$I, to measurements of nuclear structure – validation of the $2^+\rightarrow0^+$ lifetime in $^{166}$Er - and measurements regarding the lifetime of positronium in different media.
These works, and other smaller scale studies with other different scintillator detectors at NPL have created expertise that have allowed the Nuclear Metrology Group to be involved in a fleet of experiments and collaborations worldwide. This talk will provide an overview of the work done at the NPL site and in outside experiments, as well as future work planned with these detectors.
[1] Shearman, R., et al, 2017. Commissioning of the UK NAtional Nuclear Array. Radiation Physics and Chemistry 140, 475–479. https://doi.org/10.1016/j.radphyschem.2017.02.007
[2] Regan, P.H., et al, 2015. Development of NANA: A Fast-Scintillator, Coincidence Gamma-ray Array for Radioactive Source Characterisation and Absolute Activity Measurements at the UK National Physical Laboratory. J. Phys.: Conf. Ser. 620, 012005. https://doi.org/10.1088/1742-6596/620/1/012005
[3] Collins, S.M., et al, 2018. Investigation of γ-γ coincidence counting using the National Nuclear Array (NANA) as a primary standard. Applied Radiation and Isotopes 134, 290–296. https://doi.org/10.1016/j.apradiso.2017.07.056