Real-time imaging enhances fusion experiments
At the Centre Canadien de Fusion Magnetic (CCFM; Varennes, Quebec, Canada), Fernando Meo, Pierre de Villers, and their colleagues have developed a real-time digital imaging system for researching magnetically defined plasmas in the study of thermonuclear fusion. To capture and analyze plasma images, the system uses two synchronized RS-170 cameras connected to a personal-computer-based frame-grabber board. Using direct memory access, images are delivered to PC memory via the PC`s 32-bit EISA bus.
After acquisition, the plasma images are compressed and saved to the hard drive. The personal computer allows the scientists to control the acquisition, processing, and analysis of images through a graphical user interface (GUI) that was built with IDL software from Research Systems (Boulder, CO). After computer processing, the images and the details of the experimental conditions are compressed and saved on disk.
"Much of the data-processing and image-analysis software at CCFM is written in IDL," says de Villers, "because IDL supports such file formats as HDF, JPEG, and TIFF; it is portable across different computers; it permits the acquisition, display, and storage of images on the PC, and it then transfer the images to the VMS server for archiving. As a result of this portability, image analysis can be performed on either the VMS or PC platform," he adds. Moreover, image-analysis sessions can be active during acquisition sessions, allowing the researchers to maximize analysis productivity.
By means of routines initiated through the GUI pull-down menus, the scientists are able to analyze and enhance images with processing routines defined in the configuration file. "The system is also upgradeable," Meo explains, "by adding other image-processing and compression routines to the software." Fast Fourier transforms, filtering, and enhancement routines have helped the researchers study particle-flow patterns and understand the effects of impurities such as carbon in the main plasma.
Meo says, "The imaging system is used to analyze visible radiation of the magnetically confined plasma and gain information on plasma shape and position. The cameras have interference filters that block all the light except that from carbon, hydrogen, or even helium, depending on the filter."
After images have been analyzed, they are compressed and stored for future study. Meo`s application supports LZW and JPEG compression schemes, enabling users to specify which method to use according to the quality of the archiving required. The LZW scheme is used primarily for scientific data because of its "lossless" format, whereas JPEG is used mainly for qualitative analysis.
