Speaker
Description
Construction of the low-energy section of Superconducting Linear Accelerator 3 (SCL3), a key component of the Rare Isotope Accelerator complex for ON-line experiments (RAON), was completed. During the construction, field emission (FE) was one of the most critical performance-limiting factors in the vertical test (VT) process. The VT is performed at 4.2 K and 2 K to analyze the temperature-dependent characteristics. The field enhancement factor, which is the main parameter for quantifying FE characteristics, is obtained separately from the Q0 and X-ray measurement results. It is confirmed that the 4.2 K test results show a larger Q0-based field enhancement factor than those at 2 K, even for the same X-ray pattern. As the BCS resistance and its temperature derivative are much larger at 4.2 K than at 2 K, it is suspected that FE-induced electron collisions generate additional BCS resistance. In this study, three HWR cavities that show the same X-ray pattern are chosen to evaluate the FE-induced BCS resistance and the effective thermal resistance as a function of FE power. A correction calculation based on the effective thermal resistance is conducted for 27 of the 4.2 K datasets that have a different X-ray pattern at 2 K. Validation of the correction is confirmed by comparing it with the ratio of the X-ray- and Q0-based field enhancement factors at 2 K. From this study, the effect of the FE-induced BCS resistance is eliminated, and a more accurate Q0-based field enhancement factor is obtained at 4.2 K.