A Micro-Computerized Facility For On-Line Spectroscopic Plasma Diagnostics

Temperature distributions and species densities can be determined in cylindrical plasmas by using the Abel inversion technique to obtain the volumetric emission coefficient from lateral radiance measurements on optically thin spectral lines. These diagnostics are especially useful for studying arcs and glow discharges. Extensive spectroscopic measurements and data analysis routines are required for each determination, and user-interactive judgements are required at several points in the analysis. We have interfaced a Polymorphic 8813 microprocessor-based computer with our spectroscopic instruments for this task. The computer speaks BASIC and has 56 kbytes of user-available RAM. An S-100 compatible analog interface board is used for control of an optical spectrometer and a translation stage, as well as for digitization of the data in real time. Software was written for filing the data on minifloppy disks, performing data analysis, and printing or plotting the results with a small line printer or with an X-Y recorder. We were able to obtain a reliable and productive facility without large capital equipment outlays because of the modest cost of the microprocessorbased computer and its ability to interact with the expensive equipment that was already on hand.