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Extreme Ultraviolet Schwarzschild Microscope with Sub-picosecond Temporal ResolutionExtreme ultraviolet (EUV) microscopy is an attractive technique because the fundamental resolution limit scales as the wavelength of light. Thus, an image can theoretically have 50 times better resolution at a wavelength of 10 nm than at a typical visible wavelength of 500 nm. Due to the high absorption and large photon energy in the extreme ultraviolet regime, compound materials tend to be radiation damaged during short wavelength imaging experiments. This is particularly true for organic materials and living tissue. One way in which to avoid the effects of radiation damage is rapid data acquisition. Up to now, however, high-resolution imaging on these time scales has not been possible because an image with sufficient signal to noise could not be obtained sufficiently quickly.
Figure 1. Schematic drawing of the Schwarzschild X-ray Microscope. Principles of operationThe light source for this experiment consists of rare-gas clusters illuminated by a fast high-intensity laser. The clusters are produced by introducing cooled gas to the vacuum system through a custom-designed nozzle. The gas then condenses into droplets consisting of clusters of a few hundred or thousand atoms of near-solid density. This system is an efficient source of EUV radiation, and the EUV is produced with a pulse duration almost as short as the laser pulse. This light is then collected by a condensor that focuses the light on the sample and fills the primary mirror of the microscope. The microscope is coated with a multilayer that efficiently reflects in a narrow wavelength region. The image is magnified 500-1000X and is projected onto an EUV sensitive CCD a few meters downstream. Expected resolution is 20 nm to 100 nm.
Figure 2. The freshly coated mirrors for the microscope. For more information contact Charles Tarrio. Online: May 1998 by Charles Tarrio. |