B24 is the full-field transmission microscope at Diamond designed specifically to meet the rising demand for tomographic imaging of biological specimens under near physiological conditions.
The technique bridges the resolution gap that exists between electron microscopy and conventional light microscopy and allows acquisition of tomographic data from both native and fluorescent-labelled samples. So far we have the most experience with collecting data on cells grown adherently on 3mm grids (as used in electron microscopy) but we have also collected data on bacteria and structures containing lipidic networks. The common theme is that all samples are mounted on 3mm EN grids and vitrified in liquid nitrogen cooled liquid ethane.
At present B24 is operating at 500eV (in the “water window”) where the image contrast is generated by the preferential absorption of the X-rays by carbon with the surrounding water/ice is relatively transparent. In due course operation of the beamline will extend outside the water window particularly to higher energies. This should allow data to be collected either side of an absorption edge so that certain elements within a sample (e.g. Fe) can be highlighted. In addition it is planned to offer Zernike phase contrast at 2.5keV.
It is expected that, in the longer term, we will also upgrade the beamline to permit the study of samples which require Containment Level 3 facilities. The precise details of how this will be achieved will be established in due course. The timescale for this upgrade is at present unknown.
The beamline is currently in the commissioning stage and expecting first users within 2015.
Current operation parameters
500eV (water window)
40nm zone plate
Diamond Light Source is the UK's national synchrotron science facility, located at the Harwell Science and Innovation Campus in Oxfordshire.
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