The CEPC 650 MHz 2-Cell superconducting cavity is vertically tested to the standard (2020-06-15)

On June 12, the 650 MHz 2-Cell Superconducting Cavity in the Ring Electron-positron Collider (CEPC) has successfully completed vertical testing with N doping at Peking University. The test results show that: At 2 k temperature, when the accelerating gradient E_acc reaches 22 mv/m, Q value can be more than 6 e10 (corresponding to the microwave surface resistance of only 4.7 nΩ), which exceed the CEPC vertical measurement index (Q = 4 e10 @ Eacc = 22 mv/m). It makes a new record, also can match with international leading level.

In the testing process, the 650 MHz 2-Cell superconducting cavity was first treated with buffering chemical polishing (BCP), and vertical measurement before N doping was completed . Subsequently, the researchers doped it with nitrogen, and completed the vertical test after N doping, the Q value was greatly improved, which reached 8E10 under the low field (~10MV/m), and quench at 25MV/m. The next step is to increase the accelerating gradient of the superconducting cavity by electropolishing (EP) etc.

This research is supported by the CEPC pre-research project and the PAPS project.