Up Close: The National Center for Electron Microscopy at Lawrence Berkeley Laboratory
- PDF / 1,079,660 Bytes
- 2 Pages / 604.8 x 806.4 pts Page_size
- 46 Downloads / 181 Views
The National Center for Electron Microscopy (NCEM) was established in 1984 in response to a perceived need for a facility offering a broad range of transmission electron microscope techniques for advanced materials characterization. Its inception was motivated by the desirability of sharing major resources in the face of spiraling instrument costs during a period of stable or reduced equipment budgets, and the identified need for better materials characterization capabilities to support the nation's energy-related research programs. Full and continuing support for the Center is provided by the Basic Energy Sciences, Division of Materials Sciences of the U.S. Department of Energy. Generous DOE policy guidelines, including use of the facilities by qualified microscopists. at no cost for nonproprietary research, provide ready access to a wide spectrum of users from universities, industry, and government laboratories. Operation of the NCEM is guided by a Steering Committee currently chaired by J. Hren of North Carolina State University. Instrumentation
At the heart of the NCEM are two high voltage microscopes — the 1.5 MeV Kratos HVEM and the 1 MeV JEOL Atomic Resolution Microscope (ARM). The HVEM, which has the highest accelerating voltage available in the United States, is an a l l - p u r p o s e instrument designed primarily for 54
dynamic in situ studies. It is equipped with a variety of heating, cooling and straining stages and an environmental (or gas reaction) cell for performing experiments in a controlled gaseous atmosphere. An excellent specimen chamber vacuum (cryopumped to better than 107 torr), LaB6 filament, and highresolution, low-light-level 80 mm television camera complements its other capabilities. One of the main research objectives at the NCEM is to characterize microstructures at the atomic level. This goal motivated the design and construction of the ARM. Since being installed in 1983, its performance has been progressively improved, mainly by mechanical and acoustical vibration suppression, to where atomic columns with spacings less than 0.15 nm can be resolved. The high-resolution asset of the ARM is enhanced further by the high-angle biaxial tilt goniometer stage which allows images to be obtained (at full resolution) along any zone axis in the stereographic triangle. In these respects the ARM can provide additional structural information not obtainable on its progeny, the JEOL 4000CX. An essential complement to the instrumental performance is computer image simulation. This component of the NCEM facilities is now fully operational and provides users with a variety of services. In addition to user-friendly programs for image simulations from
structure models, averaging methods are available for enhancing image quality. Also, links between the computer and various microscopes are being established that streamline the procedures for alignment and performance optimization and greatly increase the microscopist's efficiency. The third major instrument in the Center is a JEOL 200CX TEM/STEM Analy
Data Loading...
