Conference Report
- PDF / 153,449 Bytes
- 1 Pages / 576 x 777.6 pts Page_size
- 79 Downloads / 178 Views
rays on a femtosecond time-scale has been highly prized by the scientific community because, at room temperature, atomic motion takes place, in most cases, on a time-scale of approximately 100 femtoseconds. With femtosecond x-ray pulses, it would be possible, for example, to track the movement of atoms in a sample of material during a phase transition (solid to liquid to gas), a chemical reaction, or any other process of physical change. The directed beams of femtosecond xrays were produced at a branch line off the 50 MeV linear accelerator that feeds electrons into the synchrotron booster. Atop this branch line is a femtosecond terawatt
near-infrared laser. The laser provides a tightly focused electron beam that is about 90 um in width; the laser produces photons in 100 femtosecond pulses. "By crossing the photon and electron beams at a right angle, we obtain scattered x-ray pulses lasting about 300 femtoseconds that travel along the direction of the electron beam," said Robert Schoenlein of the Materials Sciences Division. "The duration of the x-ray burst is determined by the transit time of the laser pulse across the waist of the focused electron beam." Once femtosecond pulses of x-rays are generated, a magnet is used to remove the electron beam. What is left are pure fem-
tosecond pulses of x-rays. The research team detected these pulses using an x-ray sensitive phosphor screen. Visible photons from the phosphor were then imaged onto a charged-coupling device camera. The images showed that the x-ray photons arrived as an elliptically shaped beam, similar to the shape of the electron beam from which they were generated. Additional measurements indicated that the beam was delivered at an energy of 30 keV and flux of about 105 photons per pulse. These results were in accordance with theoretical predictions. •
CONFERENCE REPORT
Major Topics of Small-Angle Scattering Discussed in Brazil at SAS-96 The X International Conference on Small-Angle Scattering (SAS-96), chaired by Aldo Craievich, took place on July 21-25, 1996 at Campinas, Sao Paulo State, Brazil. The choice was mainly motivated by the excellent development of this technique in Brazil and by the conclusion of the synchrotron radiation facility of the Brazilian National S. R. Laboratory at Campinas (LNLS), the first equipment of this kind in the southern hemisphere. The conference was held at the Telebras R&D Center. The exciting and pleasant conference was full of new scientific results and conducted in a friendly atmosphere. The number of participants and scientific contributions were the highest so far: 220 scientists, from 25 countries, presented 215 scientific papers and submitted 90 manuscripts for the proceedings of the Conference, to be published by the Journal of Applied Crystallography.
The different sessions, microsymposia and poster sessions received a high level of attendance. The field of small-angle scattering continues to develop rapidly, both in the extension of the scientific fields covered and in the depth of the analysis and of the t
Data Loading...
