Semi-Dry Cooling Solutions for Future Superconducting Accelerator Structures

Cryogenic dry cooling solutions for Superconducting RF cavities allow for synergies with modern cavity production methods based on vacuum coating and A15 SC layer deposition methods. A proof-of-concept cryogenic performance test stand will study relevant parameters of low-temperature cooling loops with respect to the RF performance of a 1.3 GHz prototype cavity. The paper describes cooling options concerning helium forced flow heat transfer at the capillary surface plus the conduction pathway and the consequent temperature distribution in the cavity itself. Such novel and drastically reduced helium content cooling schemes can be applied to a wide variety of SC cavity or magnet assemblies. The results of the numerical evaluation of heat transfer and pressure drop relations for two-phase and single-phase supercritical flow are cited. These data form the basis for future experimental validation campaigns in the temperature range of 4.2 K to 25 K and helium pressures of up to 2.2 MPa. Special attention is paid to possible new introduced effects of mechanical vibrations or temperature gradients along the cooling capillary when compared to a stagnant He bath cooling.