Development of a Micro Mercury Trapped Ion Clock Prototype Employing a Spindt Cathode Ionization Source

We have developed a prototype mercury ion clock in a miniature pumpless vacuum quadrupole trap tube employing a Spindt-type field-emitter array (FEA) as an electron source for ionization, an external 194-nm micro-plasma lamp for optical pumping, and a 40.5-GHz CMOS-based microwave synthesizer creating a clock capable of achieving the 10−14-stability level in one day. The physics package consists of the sealed 30cc vacuum tube with one layer of magnetic shielding, light source, and detector assembly. The complete system's SWaP (size, weight, and power) is 1.1 L, 1.2 kg, and < 6 W of power. System stability level is comparable to the widely used, much larger rack-mounted Microchip 5071A cesium frequency standard. Prototype clocks have operated for over 30 months.