• H. Hahn, I. Ben-Zvi, L.R. Hammons, W. Xu
  BNL, Upton, Long Island, New York

The development of Higher Order Mode dampers for a five-cell cavity is being persued at this laboratory. The physics needs and technical requirements for several future electron-ion collider projects are under study, which all involve Energy Recovery Linacs. The envisioned Ampere class currents make effective HOM damping mandatory which will be achieved with capacitive probes and inductive loops. Longitudinal space requirements constrain the space between the cavities in the linac chain. Two five-cell copper cavities are assembled with minimal separation to simulate the space available for fundamental power coupler, beam position pickup probe, and two HOM dampers. The location of the dampers is chosen in the connecting beam tubes to balance fundamental mode suppression and HOM damping. Measured and simulated Cu cavity results are compared with those for the ferrite-damped superconducting ERL.