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Recently, heat treatment between 250 °C and 500 °C has been attempted to improve quality factor (Q) of superconducting radio-frequency cavities at FNAL and KEK. Experiments of such medium temperature (mid-T) bake with furnaces have also been carried out at IHEP. Firstly, over ten 1.3 GHz 1-cell cavities were treated with different temperatures at a small furnace, which all demonstrated improvement of Q and anti-Q-slope phenomenon. The average quality factor has reached 3.6×10 10 when the gradient is 16 MV/m，while the highest Q is 4.9×10 10 @16MV/m; the maximum gradients of these 1-cell cavities are between 25.1 and 36.9 MV/m. Then, the recipe of mid-T furnace bake at 300 °C for 3 hours has been applied to six 1.3 GHz 9-cell cavities at a new big furnace, which have all shown higher Q and anti-Q-slope at medium field (16~24 MV/m). The average quality factor has reached 3.8×10 10 when the gradient is 16 MV/m. The maximum gradients of the 9-cell cavities are between 22.7 and 26.5 MV/m.

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In this paper, studies on applying a new electrolyte to treat the surfaces of Nb sheets, which was called buffered electropolishing (BEP), were reported. Through studies of the BEP I-V characteristic and optimization of main parameters such as acid agitation, temperature, etc., much faster Nb polishing rate and smoother surface finish were achieved in comparison with those obtained from the conventional electropolishing (EP). The average polishing rate could reach around 2:5 m= min . It was over 7 times faster than that of the traditional EP. Meanwhile, the average surface mean square root roughness was around 50 nm over an area of ð200 Â 200Þ m 2 . This study shows BEP has a great potential to replace the traditional EP process and becomes a new generation of technology for treating Nb superconducting radio frequency cavities.

Quadricyclane (tetracyclo[3.2.02,7.04,6]heptane) is a strained, saturated cyclic hydrocarbon and a potential environmental contaminant because of uses in solar energy and optical memory storage devices and as a recently proposed additive to jet fuel. Quadricyclane is very unstable in both soil and water, and in the environment it exists as abiotic transformation products, tricyclo[2.2.1.02,6]heptan-3-ol and bicyclo[2.2.1]hept-5-en-2-ol. In soils, tricyclo[2.2.1.02,6]heptan-3-ol is microbially transformed to a C7H8O intermediate which we postulate to be tricyclo[2.2.1.02,6]heptan-3-one. This compound is subsequently biodegraded over several months. Elevated respiration rates in soils amended with tricyclo[2.2.1.02,6]heptan-3-ol provide evidence that it is mineralized to CO2, while bicyclo[2.2.1]hept-5-en-2-ol concentrations in soil microcosms remained unchanged over a period of 8 months.Key words: quadricyclane, biotransformation, biodégradation, tricyclo[2.2.1.02,6]heptan-3-ol, bicyclo[2.2.1]hept-5-en-2-ol.

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