SBIR-STTR Award

While the Principal Investigator was on leave at Lawrence Liverniore, a new class of microwave elements was developed, fabricated, and tested. The design of these elements combines the principles of microwave twist reflectors with those of digital holography. The result is a single reflector which, in an independent fashion, controls both the phase and polarization of an incident wavefront in a nearly arbitrary fashion. Two such elements are currently being installed in TNLX-U at Lawrence Liverniore and they represent a fourfold iniprovenient in efficiency over the previous waveguide systeni. However, the components designed for TNIX did not function exactly as predicted and deficiencies were identified in the theory of operation for these components. These deficiencies need to be renioved if the concept is to be generalized to the niore coniplex designs required for other fusion systems. At present, a nuniber of important questions reniain concerning the theory, design, fabrication, and application of these elements. The goal of the Phase I effort is to complete the analytical description for the operation of these novel reflector components and to begin development of the computer software required for general designs. In the Phase 11 effort the goal will be to develop the industrial base required for the design and manufacture of the new components.AnticipatedResults Potential Commercial Applications as described by the awardee:At present, these elements are planned for use in NIFTFB and there niay be applications in the systenis at Princeton, NI.I.T., and Oak Ridge. Other possible applications include use of these new components with gyrotron microwave sources to help produce pure niode patterns.

In Phase I, two of the most important theoretical questions relating to the operation of Holographic Microwave Elements (HOMES) have been addressed. The twist polarizer problem has been solved, and the results are being implemented in software. Also, the study of design methods for systems containing more than one HOME has begun. In Phase II, the theoretical questions of sampling rate and algorithm convergence, as they relate to HOME design and fabrication, will be addressed. These questions relate directly to the computer time required in the HOME design and to the milling machine time required for manufacture. Unless the sampling rate used can be reduced and the algorithm convergence improved, the design of a lm x lm HOME could require up to 1 h of Cray time and take 100 h of actual machine time. However, as previously noted and again verified by some sample designs that recently have been run on a VAX 11-780, there is reason to believe that the sampling requirements can be reduced. No work on algorithm convergence rates has been completed. Also in phase II, an attempt will be made to secure funds from the Indiana Corporation for Science and Technology to set up a fabrication facility at Fairfield Manufacturing Company of Lafayette. Fairfield owns two 5-axis mills. There should be great efficiency in setting up a fabrication facility at the same time theoretical questions relating to fabrication are addressed. In this way unanticipated fabrication problems may change the focus of the theoretical efforts.Anticipated Results/Potential Commercial Applications as described by the awardee:Future rf heating systems will most likely use gyrotrons, which produce very complex field patterns. The HOME components may be essential for changing these patterns into linearly polarized wave fronts at the plasma. At present the HOME is believed to be the only viable technology for this task. This is why HOMEs are planned for use in the Mirror Fusion Test Facility-B (MFTF-B).