Soft x-ray contact microscopy using laser-generated plasma sources

Julian H. Fletcher; Robin A. Cotton; Colin E. Webb

doi:10.1117/12.138728

13 January 1993 Soft x-ray contact microscopy using laser-generated plasma sources

Julian H. Fletcher, Robin A. Cotton, Colin E. Webb

Author Affiliations +

Proceedings Volume 1741, Soft X-Ray Microscopy; (1993) https://doi.org/10.1117/12.138728
Event: San Diego '92, 1992, San Diego, CA, United States

Abstract

Of the three main approaches to soft x-ray microscopy currently being investigated (contact, scanning, and direct imaging), we believe that, at present, contact microscopy provides the only solution to the problems of user access to working x-ray microscope systems and radiation damage to biological specimens. A small, transportable, discharge pumped, UV pre- ionized KrF laser system has been developed for the exclusive use of contact microscopy. By employing an injection seeded unstable confocal resonator, a beam of 2.5 times the diffraction limited divergence and energy of the order of magnitude 2 J is generated. By focusing this beam onto the surface of a suitable target material with an intensity of the order of magnitude 10¹² W/cm², a plasma is created which emits largely in the water window region of the spectrum with an efficiency of up to 20%. These x-rays are used to illuminate a biological specimen which is placed in close contact with a photosensitive resist such as polymethyl methacrylate. The specimen may be hydrated and requires no prior preparation such as staining or fixation. A transmission map of the specimen is recorded in the resist within 25 ns, before radiation damage can effect the specimen's structure. After chemical development, during which exposed areas of the resist are preferentially dissolved resulting in a relief map of the x-ray transmission of the specimen, the resist is viewed in an SEM or alternatively an atomic force microscope (AFM). Images of various biological specimens are presented.

Citation Download Citation

Julian H. Fletcher, Robin A. Cotton, and Colin E. Webb "Soft x-ray contact microscopy using laser-generated plasma sources", Proc. SPIE 1741, Soft X-Ray Microscopy, (13 January 1993); https://doi.org/10.1117/12.138728

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