Mass measurements near the $r$-process path using the Canadian Penning Trap mass spectrometer

The masses of 40 neutron-rich nuclides from Z = 51 to 64 were measured at an average precision of delta m/m = 10(-7) using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a Cf-252 spontaneous fission source in a helium gas catcher, approach the predicted path of the astrophysical r process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in beta-endpoint measurements. Differences in mass excess from the 2003 Atomic Mass Evaluation of up to 400 keV are seen, as well as systematic disagreement with various mass models.