On the development and application of a photon counting imaging system for broad spectrum luminescence analysis
Creators: name: McCulloch, Iain
Publisher: name: The Australian National University
Year: 2014
Subjects: subject: Photon detectors
subject: Luminescence spectroscopy
subject: Imaging systems

description: Novel luminescence equipment, the Photon Counting Imaging System (PCIS), with broad spectrum high sensitivity imaging capabilities, incorporating both thermal and multi-source optical stimulation, and providing flexible facilities for the optical filtering of signals, was designed and constructed. Capable of high quantum efficiency, low-noise imaging from infrared to near UV (~ 1050 - ~ 200 nm), the PCIS is based on a liquid Nitrogen-cooled charge-couple device (LN-CCD) detector, and very wide spectrum, high photon capture optics. The three element expanded Offner reflective optical design avoids chromatic aberration and meets the spectral requirements, but demands extreme precision of manufacture and assembly. A highly rigid, adjustable and focusable optics assembly was designed and constructed, and special optical alignment tools and methods were developed and applied. A bespoke programmable control unit (the IICU) was designed and built, providing independent numerical control of multiple optical stimulation sources, with programmable generic interfaces to support a wide range of ancillary equipment and experiment designs. Configurable control tables installed in the IICU define synchronised sequences of functions which implement a highly flexible range of basic luminescence operations. A PCIS hardware simulation environment supports the development and testing by experimenters of new IICU control tables. Custom PCIS control software, with an informative graphical user interface, uses the IICU control table functions to implement sophisticated, high level luminescence protocols and experimental sequences. Flexible parameterised protocol templates have been developed for the Single Aliquot Regeneration (SAR) dating protocol using Optically Stimulated Luminescence (OSL), and for the exploratory broad spectrum analysis of materials with thermoluminescence (TL). A developer's version of the PCIS control software is integrated with hardware and software PCIS simulators to provide a fully-functioned development environment for the construction and testing of luminescence protocols before samples are committed to the imaging system. A comprehensive, three-level logging scheme ensures that all runs, including simulator runs, can be fully audited and verified, and can be precisely repeated at any time. Studies undertaken with the PCIS include analyses of quartz, Sodium Chloride (table salt), Calcium Fluoride, porcelain, mobile phone SIM cards, and samples of specialised glasses designed to detect ionising radiation. Future PCIS applications are surveyed, as are future developments of the PCIS, including re-development around an electron-multiplying charge-coupled device (EM-CCD) to give the PCIS upgraded temporal and spatial resolution, and improved low-signal sensitivity. Initially intended in this project to address unresolved questions in karst geomorphology involving sedimentary processes and structures at the Jenolan Caves and Naracoorte Caves World Heritage Areas, the PCIS has proved to have great capability for wider applications in dating, sedimentary process studies, analysis of minerals and other materials, radiological event analysis, and for the direct study of luminescence, fluorescence, phosphorescence and tenebrescence phenomena. In conjunction with novel micro-sampling and OSL site survey techniques, the PCIS may enable entirely new methodologies, transforming the role of luminescence in archaeology, palaeontology, and Quaternary geomorphology.