ELECTROMAGNETIC SIMULATIONS OF COAXIAL TYPE HOM COUPLER*

The DESY-type coaxial high order mode (HOM) coupler has been used in many superconducting cavities. The electric probe tip is located at the maximum B-field inside the coupler can. For continuous wave (CW) high current applications, the heating of this tip can be severe enough to degrade the cavity performance. Electromagnetic (EM) simulations were done to estimate tip heating under a variety of conditions. Geometric remedies and detuning sensitivity effects were examined. The effect of these changes on HOM external quality factor (Qext) was also estimated. HOM probe tip heating power was calculated for the upgraded JLAB Low-Loss (LL) cavity shape and 750 MHz injector cavities