Terrestrial and Space-based Applications of Microchannel Plate X-ray Optics
thesisposted on 19.01.2011, 11:38 by James Peter Nussey
This thesis describes the continued development of square pore microchannel plate (MCP) X-ray optics with a view to their application on terrestrial and space-based instrumentation. The development of a lab-based Imaging X-ray Fluorescence Spectrometer (IXRFS) is described, incorporating an MCP optic to relay fluorescent flux, excited from uniformly illuminated target samples onto a Charge Coupled Device (CCD). Applications in mineralogy and scientific instrument calibration are investigated, with elemental maps spatially correlated to observed sample features in each case. The soft X-ray focusing properties of one planar and two slumped MCP optics are evaluated with a view to their application on the future Lobster-ISS all-sky monitor. Best FWHM foci of 9.4' x 7.5' (planar) and 9.1' x 9.1' (slumped) are reported. Observed temporal variation in the angular resolution of a slumped MCP optic is attributed to the mechanical deformation of the optic during focusing. Multifibre misalignment is determined to be the major source of error in the focusing properties of the planar MCP. The metallisation of the reflecting surfaces of MCP optics improves their high energy and wide angle response; metal films of iridium, ruthenium and nickel, deposited onto MCP optics using the Atomic Layer Deposition (ALD) and Electroless Nickel (EN) methods are characterised using the techniques of Auger Electron Spectroscopy (AES) and X-ray Reflectivity (XRR). Ruthenium and nickel-coated MCPs exhibit a shortfall in low-grazing angle reflectivity, not observed in the case of iridium, which is modelled with an RMS surface roughness of 26 Å. The Lobster-ISS all-sky monitor is modelled to a range of specifications using a Monte-Carlo raytrace code to optimise performance. Iridium-coated MCP optics are found to provide the best modelled sensitivity for a variety of astrophysical objects. In this configuration, Lobster-ISS is modelled to have a 1 day limiting sensitivity of 0.32 mCrab.