  Recently, heat treatment between 250 C and 500 C has been attempted to
improve quality factor 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, eleven 1.3 GHz 1-cell cavities were
treated with different temperatures at a small furnace. The average quality
factor has reached 3.6E10 when the gradient is 16 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. The average quality factor has reached 3.8E10
when the gradient is 16 MV/m.
