How do the biofilms of soil microbes affect the transport of accidental radioactive contaminants? How are domain interfaces in low-cost organic photovoltaic materials organized? How do lightweight polymer-based matrix materials fail under strain? X-ray microscopes provide unique capabilities to address these questions, since they have mesoscale spatial resolution and the penetrating power to image materials with real-life thicknesses. One can therefore study soil microbe communities with a thickness equal to that of multiple overlying bacteria; or organic photovoltaics as cast on electrodes and capped with antireflective, anti-oxidative layers. However, organic materials can suffer shrinkage under x-ray irradiation, and hydrated organics such as those in soil microbial communities show severe changes due to radiolytical reactions at the water/organic interface. For these reasons, electron microscopy studies on organic materials are best carried out under cryogenic conditions where radiolysis, mass loss, and shrinkage of organics are minimized. Inspired by this, Xradia has developed the worlds only commercial cryogenic x-ray microscope which provides the same degree of radiation damage resistance as has shown to be essential in electron microscopy. We propose to develop an essential complementary tool for Xradias cryogenic x-ray microscopes: a Cryogenic Correlative Confocal Light Microscope (C3LM). This instrument will allow one to calibrate the new views of materials that x-ray microscopes provide with a view more familiar to most customers and scientific users: that of light microscopy. Because cryogenic sample conditions only halt secondary radiation damage effects (shrinkage; mass loss; bubbling in hydrated specimens) as long as the specimen remains cold, one must carry out light microscopy investigations with a cold sample and one must have the ability to carry out light microscopy after x-ray microscopy when one has cracking at non-pre-determined positions, or after x-ray fluorescence has been used to identify the region in a biofilm where plutonium has been sequestered. The microscope must be confocal for 3D imaging of samples with the thickness that x-ray microscopes can study, for delivering high light concentration to buried photovoltaic interfaces, and for visualizing the distribution of fluorescently-tagged molecules. The C3LM will join two highly complementary, but so far disconnected microscopy techniques together to provide a novel and unified platform for true correlative studies of materials important to the DoE.
