Broadband Excitation of ECR Plasmas
79776S Electron-cyclotron-resonance (ECR) sources are under investigation for accelerators in nuclear physics research. Recent data indicated substantial performance differences when the same ECR source was operated with a klystorn as opposed to a traveling wave tube (TWT) amplifier. Specifically, the TWT drive provided the same ion beam performance as the klystron while requiring only half the radio frequency (RF) power. Because the only substantial difference between these two RF sources was the intrinsic bandwidth of the RF source, these data provide convincing evidence of the potential benefits of increasing the excitation bandwidth of the RF power system. This project will compare the operational characteristics of one or more ECR sources by filling the gain-bandwidth curve of its klystron amplifier with a variety of different RF spectral density functions. The approach will take advantage of a special RF circuit, recently developed for another application, which is capable of producing, under software control, virtually any RF excitation spectrum imaginable. Phase I will modify the RF circuit to provide RF power at frequencies typical of ECR sources (6.5 GHz, 10.5 GHz, and 14.5 GHz). The modified circuit then would be used as the RF excitation source in at least two operating ECR sources to demonstrate the efficacy of the approach and to identify efficient RF spectral density functions. Commercial Applications and Other Benefits as described by the awardee: The modified RF circuit could be marketed as a simple add-on device to improve ECR source operation. The cost of such a device would be relatively modest and could instantly and significantly improve the performance of virtually any ECR source in the world. The device also should find application in other ECR plasma systems such as sources of singly charged ions for ion implantation; in plasma etching systems used in semiconductor fabrication; and in light-ion sources used for proton therapy, isotope production, and other light-ion accelerator applications.
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