A three cell 8 GHz accelerator structure fabricated from bulk niobium, was processed in a tin vapor atmosphere at 1050 °C. The structure was operated in a π/2 standing wave mode. At 4.2 K a surface resistance of 1.1 μΩ and an accelerating field of 2.7 MV/m was obtained. This corresponds to peak surface fields of E = 10 MV/m and B = 20 mT. The fields were limited by fast magnetic thermal breakdowns. The temperature dependence of the rf surface resistance yielded a transition temperature of Tc= (18.0 ± 0.2)K and an energy gap of 2Δ (0) = (4.6 ± 0.2)kTc.
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Arnolds et al. (1977) studied this question.
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