On Friday, 2nd September 2011, the first infra-red SNOM image was collected using radiation from the ALICE IR-FEL at Daresbury Laboratory by a Cockcroft Institute team comprising of partners from Daresbury Laboratory and University of Liverpool. SNOM, an abbreviation for Scanning Near-field Microscopy, is a technique utilising small aperture fibre-optics to probe a sample surface at finer spatial detail than the diffraction limit of the illuminating radiation would normally allow. It gives topographical and spectral information and to get data at single, selectable wavelengths, requires very high IR intensities distributed over many pulses at a high frequency and is only possible using FEL radiation (driven either by room temperature linear accelerators as in the Vanderbilt University FEL facility in USA or preferably driven by superconducting Continuous Wave linear accelerators such as in the ALICE facility in UK), offering an advantage over various conventional laser-based OPA techniques (Optical Parametric Amplification).
This very first images show topographical information gathered from an aluminium sample stub on a spatial scale of better than one micron using 6.6 micron wavelength IR illumination from the ALICE FEL and exhibits a total height variation across the image area of less than 1.5 micron. Striations across the image arise from variations in FEL output power, which have not been normalised in the production of this image.
The use of SNOM on the ALICE IRFEL is a major new initiative in the Cockcroft Institute, known as FELIS (FEL Integration with Snom), to exploit the ALICE FEL radiation for one-of-a-kind pioneering scientific investigations and to establish its unique scientific capability for the community. Successfully bringing together stable operation of the FEL, delivery of FEL radiation to the ALICE Diagnostics Room and commissioning of a SNOM on loan from CNR-Rome marks a significant milestone for the team comprising scientific and technical members from the Cockcroft Institute its stakeholding partners among others — the University of Liverpool and ASTeC (STFC) — as well as collaborators from CNR-Rome. The achievement is particularly encouraging for them as the FELIS project in which they are collaborating only began in mid-July. The team has a clear programme of improvements they intend to make in the coming months, and are now confident that the next stage of recording high resolution spectral images of biologically and medically significant relevant samples such as oesophagus and oesophageal adenocarcinoma cells, in the mid-IR, can be achieved using the ALICE FEL in the coming months, opening up new avenues for research in cancer diagnostics.
