Search

A superconducting energy recovery linac test facility (PKU-SETF) was built at Peking University, and a 2K cryogenic system, which is the first closed-loop 2K cryogenic system for a superconducting accelerator in China, was constructed for the 1.3 GHz 3+1/2 cell dc-SRF injector. The main accelerator consists of two nine-cell TESLA-type superconducting cavities of the PKU-SETF The commissioning and stable operation of this 2 K cryogenic system was carried out. A helium pressure stability of better than ±0.1 mbar and a total refrigeration capacity of 65 W at a temperature of 2K was reached. [ABSTRACT FROM AUTHOR]

A high intrinsic quality factor (Q0) of a superconducting radio-frequency cavity is beneficial to reducing the operation costs of superconducting accelerators. Nitrogen doping (N-doping) has been demonstrated as a useful way to improve Q0 of the superconducting cavity in recent years. N-doping researches with 1.3 GHz single cell cavities are carried out at Peking University and the preliminary results are promising. Our recipe is slightly different from other laboratories. After 250 μm polishing, high pressure rinsing and 3 h high temperature annealing, the cavities are nitrogen doped at 2.7–4.0 Pa for 20 min and then followed by 15 μm electropolishing. Vertical test results show that Q0 of a 1.3 GHz single cell cavity made of large grain niobium has increased to 4 × 1010 at 2.0 K and medium gradient. [ABSTRACT FROM AUTHOR]