Energy Loss of Coasting Gold Ions and Deuterons in RHIC

The total energy loss of coasting gold ion beams at two different energies and deuterons at one energy were measured at RHIC, corresponding to a gamma of 75.2, 107.4 and 108.7 respectively. We describe the experiment and observations and compare the measured total energy loss with expectations from ionization losses at the residual gas, the energy loss due to impedance and synchrotron radiation. We find that the measured energy losses are below what is expected from free space synchrotron radiation. We believe that this shows evidence for suppression of synchrotron radiation which is cut off at long wavelength by the presence of the conducting beam pipe.