A compensated multi-pole linear ion trap mercury frequency standard for ultra-stable timekeeping

Area of Science:

• Atomic Physics
• Metrology
• Timekeeping Technology

Background:

• The Jet Propulsion Laboratory (JPL) has been developing a multi-pole linear ion trap frequency standard (LITS).
• Previous LITS development focused on achieving high stability for frequency standards.

Purpose of the Study:

• To demonstrate long-term field operation of the LITS technology.
• To enhance the performance of the LITS for advanced timekeeping applications.
• To assess the LITS's suitability for metrology and space-based systems.

Main Methods:

• Implemented enhancements to the LITS system.
• Developed a scheme for compensating the second-order Doppler shift.
• Conducted continuous, unattended field operation for 9 months.
• Utilized the LITS as a frequency reference for a geodetic receiver (JPLT).
• Performed comparisons with cesium fountain clocks and international primary frequency standards.

Main Results:

• Achieved a record line Q of 5 x 10^12 for a room temperature microwave atomic transition.
• Demonstrated a short-term fractional frequency stability of 5 x 10^-14 / τ^(1/2).
• Reduced combined sensitivity to primary LITS systematic effects below 5 x 10^-17 fractional frequency.
• Showed a systematic floor of less than 2 x 10^-16 when compared to JPL's cesium fountain clock.
• Exhibited a frequency deviation less than 2.7 x 10^-17 / day when compared to international primary frequency standards.

Conclusions:

• The multi-pole LITS technology is suitable for long-term field operation and reliable timekeeping.
• The enhanced LITS demonstrates high precision and stability, making it valuable for metrology laboratories.
• The robustness and performance of the LITS are ideal for space applications.