Improved linear ion trap physics package

The authors describes an improvement in the architecture of the physics package used in the linear ion trap (LIT) based frequency standard developed at the Jet Propulsion Laboratory. This new design is based on the observation that ions can be moved along the axis of an LIT by applied DC voltages. The state selection/interrogation region can be separated from the more critical microwave resonance region where the multiplied local-oscillator signal is compared to the stable atomic transition. This separation relaxes many of the design constraints of the present units. Improvements include increased frequency stability, and a substantial reduction in size, mass, and cost of the final frequency standard