X-ray microscope 904792 213748200 2008-05-20T18:00:03Z 207.62.177.227 Sliced thinly and then dried? Bloody useless mess that would produce. An '''X-ray microscope''' uses [[electromagnetic radiation]] in the soft [[X-ray]] band to produce images of very small objects. Unlike visible [[light]] [[microscope]]s, X-rays do not reflect or refract easily, and they are invisible to the human eye. Therefore the basic process of an X-ray microscope is to expose film or use a [[charge-coupled device]] (CCD) detector to detect X-rays that pass through the specimen. It is a contrast imaging technology using the difference in absorption of soft x-ray in the water window region (wavelength region: 2.3 - 4.4 nm, photon energy region: 0.28 - 0.53 keV) by the carbon atom (main element composing the living cell) and the oxygen atom (main element for water). Early X-ray microscopes by [[Paul Kirkpatrick]] and [[Albert Baez]] used [[grazing-incidence]] [[reflective optics]] to focus the X-rays, which grazed X-rays off [[parabolic]] curved mirrors at a very high [[angle of incidence]]. An alternative method of focusing X-rays is to use a tiny [[fresnel]] [[zone plate]] of concentric gold or nickel rings on a [[silicon dioxide]] substrate. Sir [[Lawrence Bragg]] produced some of the first usable X-ray images with his apparatus in the late 1940's. [[Image:Hohlraum irradiation on NOVA laser.jpg|thumb|right|200px|Indirect drive laser [[inertial confinement fusion]] uses a "hohlraum" which is irradiated with laser beam cones from either side on it its inner surface to bathe a fusion microcapsule inside with smooth high intensity X-rays. The highest energy X-rays which penetrate the hohlraum can be visualized using an X-ray microscope such as here, where X-radiation is represented in orange/red.]] In the 1950's [[Sterling Newberry |Newberry]] produced a shadow X-ray microscope which placed the specimen between the source and a target plate, this became the basis for the first commercial X-ray microscopes from the [[General Electric Company]]. In the present Berkeley's XM-1 uses an X-ray lens to focus X-rays on a CCD, in a manner similar to an optical microscope. The ALS is also home to the world's first soft x-ray microscope designed for biological and biomedical research. This new instrument, XM-2 was designed and built by scientists from the National Center for X-ray Tomography (http://ncxt.lbl.gov). XM-2 is capable of producing 3-Dimensional tomograms of cells. Sources of soft X-rays suitable for microscopy, such as [[synchrotron]] radiation sources, have fairly low brightness of the required wavelengths, so an alternative method of image formation is scanning transmission soft X-ray microscopy. Here the X-rays are focused to a point and the sample is mechanically scanned through the produced focal spot. At each point the transmitted X-rays are recorded with a detector such as a [[proportional counter]] or an [[avalanche photodiode]]. This type of Scanning Transmission X-ray Microscope (STXM) was first developed by researchers at Stony Brook University and was employed at the [[National Synchrotron Light Source]] at [[Brookhaven National Laboratory]]. The resolution of X-ray microscopy lies between that of the optical microscope and the [[electron microscope]]. It has an advantage over conventional [[electron microscopy]] in that it can view biological samples in their natural state. Electron microscopy is widely used to obtain images with nanometer level resolution but the relatively thick living cell cannot be observed as the sample has to be chemically fixed, dehydrated, embedded in resin, then sliced ultra thin. However, it should be mentioned that [[cryo-electron microscopy]] allows the observation of biological specimens in their hydrated natural state. Until now, resolutions of 30 nanometer are possible using the Fresnel zone plate lens which forms the image using the soft x-rays emitted from a synchrotron. Recently, more researchers have begun to use the soft x-rays emitted from laser-produced plasma rather than synchrotron radiation. Additionally, X-rays cause [[fluorescence]] in most materials, and these emissions can be analyzed to determine the [[chemical element]]s of an imaged object. Another use is to generate [[diffraction]] patterns, a process used in [[X-ray crystallography]]. By analyzing the internal reflections of a diffraction pattern (usually with a computer program), the three-dimensional structure of a [[crystal]] can be determined down to the placement of individual atoms within its molecules. X-ray microscopes are sometimes used for these analyses because the samples are too small to be analyzed in any other way. [[Image:Be foil square.jpg|thumb|right|250px|A square [[beryllium]] foil mounted in a steel case to be used as a window between a vacuum chamber and an X-ray microscope. Beryllium, due to its low Z number is highly transparent to X-rays.]] ==See also== * [[Synchrotron X-ray tomographic microscopy]] ==External links== *[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12379938 Application of X-ray microscopy in analysis of living hydrated cells] *[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11972376 Hard X-ray microbeam experiments with a sputtered-sliced Fresnel zone plate and its applications] [[Category:X-rays]] [[Category:Microscopes]] [[de:Röntgenmikroskopie]] [[ja:X線顕微鏡]]