May 2005 Archives

A joint research group from Russia, the Ukraine and the USA has developed a table-top microscope, consisting of a pulsed extreme ultraviolet (EUV) capillary discharge laser emitting at 46.9 nm, a Schwarzschild condenser, a zone plate objective, and a CCD camera. To reduce image-degrading effects such as speckle and interference, the team shortened the laser's capillary tube length from 36 to 18 cm to give a low-coherence beam with a pulse energy of around 0.1 mJ. The spatial resolution is currently 100 nm. Typical exposure time is 20~70 seconds. For more information, see the paper, "Reflection mode imaging with nanoscale resolution using a compact extreme ultraviolet laser", F. Brizuela et al., Optics Express, 435, 1210-1213 (2005), http://www.opticsexpress.org/abstract.cfm?URI=OPEX-13-11-3983

Recently, a very old copy of Archimedes' writings, which had been erased, written over and even painted over during the past 1,000 years, has been analyzed by X-ray fluorescence with a sub-micron X-ray beam at Stanford Synchrotron Radiation Laboratory, California, United States. The palimpsest, which is preserved at Walters Art Museum in Baltimore, is a goatskin parchment on which a 10th-century scribe copied some of Archimedes' manuscripts originally written around 220 B. C. Later, the ink was erased by being scraped off with a pumice stone. Further damage was done when forgers painted Byzantine religious images on four pages. Archaeologists have successfully analyzed much of the 174-page palimpsest by conventional methods using visible and ultraviolet light, but several pages, including those under the paintings, remained obscured. The main idea behind the work at Stanford is that the ink contains iron pigment, and therefore the analysis is basically the mapping of iron K X-ray fluorescence. As the ink is only 1-2 microns thick, the use of a sub-micron beam was crucial. The analysis revealed that the hidden text on two of the pages is about floating bodies and the equilibrium of planes. Surprisingly, the third page is a previously unknown introduction to Archimedes' Method of Mechanical Theorems. The main source of the news is an article by Heather Rock Woods, Stanford University,http://news-service.stanford.edu/news/2005/may25/archimedes-052505.html
For further details, contact Neil Calder, Stanford Linear Accelerator Center, Phone +1-650-926-8707, or Uwe Bergmann, Stanford Synchrotron Radiation Laboratory, Phone +1-650-926-3048, bergmann@SLAC.Stanford.EDU

A joint research group from the Universities of Sheffield and Warwick (both in the United Kingdom) and the European Synchrotron Radiation Facility (ESRF) in Grenoble, France have recently reported an interesting application of a dispersive XAFS (X-ray absorption fine structure) spectrometer, which has no moving parts and is thus inherently more stable than a conventional step-scanning instrument, thereby permitting comparative measurements to be taken rapidly. The measurements were performed on a FeCo alloy thin film located between the poles of a magnet, which induces a saturating field in the sample. The magnets were rotated via a stepping motor such that the induced magnetization, causing the strain, lies either along or perpendicular to the X-ray polarization vector. Transmitted X-ray intensity measurements were made repeatedly at every 90 degree angle between the magnetization vector and the polarization vector. An entire four-quadrant measurement took about 1s, with repeated measurements accumulated over a 2h period. The differential absorption spectra obtained in this way can give atomic displacements due to magnetostriction. The research group demonstrated that it is possible to observe the movement of atoms with a resolution of 0.01 Å i.e., an improvement of 100 times on the previous level. For further details, see the paper, "Measurement of femtometre-scale atomic displacements by X-ray absorption spectroscopy", R. F. Pettifer et al., Nature, 435, 78-81 (2005).