c. Conversion Two types of conversion devices have been considered, the amplitron - a crossed field amplifier (CFA) and the klystron - a linear beam device. The amplitron envisioned for the SPS would utilize open construction (i.e., no tube envelope) for low weight, a platinum metal cathode for long life, samarium cobalt magnets for low weight, and pyrolytic graphite radiators for waste heat rejection. The klystron would also utilize open construction, as well as a hot cathode and heat pipes. These two devices are depicted in Exhibit 18. The de to rf conversion device has been identified as a critical technology item requiring early development. These devices contribute the greatest power losses in the system, they must have excellent phase stability, and their noise output must be low. Further in-depth study and development are needed to address these factors. The amplitron offers the greater promise for long life, high efficiency, low cost and lower weight at less risk than the klystron. Other factors that must be considered include: For both amplitron and klystron: • Harmonic filters at the rf generators are needed to meet commercial service regulations. • Radio astronomy and similar sensitive receiving systems will need notch filters to protect against SPS harmonics. • Multiple SPS installations require further in-depth investigation. For the amplitron: • A bandpass filter is needed to improve performance relative to radio astronomy noise regulations. • Noise level with filter added is estimated to exceed radio astronomy isotropic regulations between 2.3 GHz and 2.7 GHz, and to exceed radio astronomy 60 dB antenna regulations above 1.9 GHz. Early development of the amplitron and filters is required to establish noise characteristics.
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