Improvements to JPL's Compensated Multi-Pole Linear Ion Trap Standard and Long-Term Measurements at the 10-16 Level

The Multi-pole Linear Ion Trap Standard (LITS) being developed at the Jet Propulsion Laboratory (JPL) has demonstrated excellent short and long-term stability. The technology has now demonstrated long-term field operation providing a new capability for timekeeping standards. Recently implemented enhancements have resulted in a record room temperature microwave line Q of 5times10¹², a short-term fractional frequency stability of 5times10^-14/tau^1/2 and reduction of the combined sensitivity to the primary LITS systematic effects below 5times10^-17 fractional frequency. Initial comparisons to JPL's cesium fountain clock show a systematic floor of less than 2times10^-16. The multi-pole LITS at JPL has been operating continuously and unattended since October, 2006 and is used as the frequency reference for the JPL geodetic receiver known as JPLT, enabling comparisons to any clock used as a reference for an IGS site. Initial comparisons with UTC over a 6-month period show a frequency deviation equivalent to less than 2.5times10^-17/day. In the capacity of a stand-alone ultra-stable flywheel, such a standard could be invaluable for long-term timekeeping applications in metrology labs while its simplicity and robustness make it ideal for space applications as well.