Progress on the3H-3He mass difference using the compensated Penning trap spectrometer

The use of the compensated Penning trap to measure an ion's mass relative to some calibration ion is described along with the leading systematic effects which must be considered. In this respect, magnet stability should no longer be a major limitation. Sideband techniques are described that center ions in the trap and equilibrate the cyclotron motion. The spectrometer's accuracy has been checked at the 1-ppb level by comparing the same atom with different charge states. The present application determines preliminary atomic masses of both 3 H and 3 He. These can be combined to yield an endpoint energy for the tritium decay (relative to neutral ground states) of 18 588(10)eV.