Tutorial Session 3B - Passive Atomic Frequency Standards

This tutorial is an introduction to the basic physics and electronics of passive atomic frequency standards (AFS). A passive AFS is the most common type of atomic clock. It uses a crystal oscillator or other frequency source to excite a passive atomic discriminator that produces a correction signal in a frequency control loop to lock the oscillator to the atomic reference. The crystal oscillator then provides a stable output frequency. The types of atomic resonator (physics package) in these devices include the rubidium gas cell, the cesium beam tube (magnetically selected or laser pumped/detected), the passive hydrogen maser, the trapped mercury ion, cesium or rubidium fountains, several types of optical standards, and, most recently, devices using coherent population trapping, including the chip-scale atomic clock. The rubidium gas cell frequency standard, by far the most widely used such device, will be covered in the most detail.