![]() One such application was the use of a multilayer film as a nanostructured sample to study the interaction of FEL pulses with matter. Multilayers with nanometer periods are now indispensable in cutting-edge experiments at FELs, not only as X-ray optics but also as samples. These capabilities were a key ingredient in the success of the Extreme Ultraviolet Lithography project carried out at LLNL and other laboratories. Lawrence Livermore National Laboratory (LLNL) is a leader in design and fabrication of multilayer x-ray optical components (including lenses, mirrors, beam splitters, synthetic holographic optical components) for the last 25 years. Such structures are necessary to efficiently reflect soft X-rays at angles of incidence steeper than the critical angle. Multilayer coatings are artificial structures that may be designed to enhance reflectivity through constructive interference of beams reflected from the many layer interfaces. The shorter the wavelength the narrower the reflectivity peak width and the higher the specifications for wavelength matching across the optic. Coherent diffractive imaging was performed with cameras operating at 32 nm, 16 nm, 13.5 nm and 4.5 nm, each utilizing a different multilayer design. Indeed, the multilayer design had to double in period over only 28 mm. To reflect scattered light over this wide angle range required a multilayer coating with a very steep lateral gradient. These contain all the details of our more ยป work on 100 nm period gratings. The remainder of this report consists of portions excerpted from Erik Anderson's thesis. Moreover, 100 nm-period gratings produced by achromatic holography are coherent over their entire area whereas gratings produced by e-beam lithography are coherent only over areas /approximately/100. The achromatic holography, on the other hand, should be capable of exposing areas well in excess of 1 cm/sup 2/ in times under 1 hour. ![]() However, the e-beam method proved to be highly impractical: exposure times of about 115 days would be required to cover an area of 1 cm/sup 2/. Erik was successful in both the e-beam and holographic approaches. This work was pursued by Erik Anderson as a major component of his Ph.D. We explored two approaches: e-beam fabrication of x-ray lithography masks, and achromatic holographic lithography. The major focus of our efforts was to develop a means of fabricating gratings of 100 nm period. These gratings are generally gold transmission gratings with spatial periods of 200 nm or less. This subcontract was initiated in order to facilitate the development at MIT of technologies for fabricating the very fine diffraction grating required in x-ray spectroscopy at Lawrence Livermore Laboratory (LLL).
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