Stability evaluation of systematic effects in a compensated multi-pole mercury trapped ion frequency standard

A compensated multi-pole linear ion trap standard (LITS) using trapped ¹⁹⁹Hg+ has recently demonstrated a fractional frequency deviation from the laser-cooled primary standards and the post-processed version of TAI known as TT(BIPM) of < 2.7(0.4)x10^-17/day over a 9-month period. A subsequent stability evaluation performed after the 9-month comparison is in statistical agreement with the measured instability. We will describe the largest remaining sources of instability including a first measurement of the Hg+/Hg pressure shift of +3.8(7.2)x10^-8/Pa. We also describe initial results using a sealed vacuum system. Finally we are beginning an investigation of ²⁰¹Hg+ and will describe a proposed frequency comparison between ²⁰¹Hg+ and ¹⁹⁹Hg+ that may be able to place a new limit on fundamental constant variation.