Ames Laboratory Feature
CRYSTAL ANALYSIS INSTRUMENT GOES MODERN
Ames Laboratory’s updated Laue crystal orientation system offers speed, safety
An old method for analyzing crystal orientation receives some high-tech updates in new instrumentation installed at the U.S. Department of Energy’s Ames Laboratory. Real-time digital photography and motorized joy-stick controls on the Laue back-reflection X-ray diffraction system give researchers greater ease of operation and improved protection from X-ray radiation.
The Laue technique uses X-ray diffraction to produce images, called Laue patterns, which reveal the structural arrangement of atoms in a single crystal sample and is most often used to determine the orientation of crystal planes with respect to the sample surface. X-rays impinge on a single crystal sample, and the beams scatter, or diffract, when they interact with planes of atoms within the crystal. The diffracted beams are intercepted by an X-ray sensitive area detector. The Laue patterns consist of dots that combine to create striking geometrical patterns. Each dot in an image corresponds to a reflection from a plane of atoms in the crystal, and crystals of different symmetries produce different characteristic patterns. The diffraction patterns of the crystal are recorded by a digital camera device, and Laue images are displayed in real-time |
Laue back-reflection X-ray diffraction system |
on a nearby computer monitor. Real-time digital display of Laue images is one of the main advantages of the new system over previous versions that collected Laue patterns on Polaroid film, requiring an often tedious cycle of waiting for the image to develop, making small adjustments, and again waiting for an image. Now Laue patterns can be viewed immediately and the crystal sample can be reoriented quickly.
“The new Laue system saves time and resources. It is much faster and more efficient,” said Alan Goldman, Ames Lab physicist and interim director of Ames Lab, who is overseeing the Laue system. “Old systems also wasted a lot of Polaroid film. The new Laue system eliminates that waste.”
The new instrument also offers a joystick-controlled motorized sample mount. The joystick, in conjunction with a low-powered laser representing the X-ray path, is used to position the sample prior to scanning and to make adjustments during a series of scans. Prior Laue systems required users to stop the X-ray scan and manually adjust the sample, perhaps many times, to achieve the desired position. The joystick speeds up the process of taking many scans across the crystal sample to examine its structure from different angles.
The joystick is a safety feature as well. Since crystal samples can be positioned using the joystick at a distance, the Laue instrument remains completely enclosed during all scans. An automated interlock system ensures that the X-ray beams are not emitted unless all enclosure doors are closed, protecting users from exposure.
“The new Laue system offers enhanced safety for people with limited X-ray experience,” said Goldman.
Ames Lab scientists will use the Laue instrument in a variety of research and material preparation projects.
~ Breehan Gerleman, Public Affairs, 515-294-9750