A New Rb Lamp Exciter Circuit for Rb atomic clocks and Studies on Transition from Ring to Red mode

TL;DR

This paper introduces a novel RF exciter circuit for rubidium lamps used in atomic clocks, discusses the transition from ring to red mode affecting signal quality, and analyzes the reasons behind this mode change.

Contribution

The paper presents a new RF exciter circuit operating at 60-65 MHz for rubidium lamps and investigates the mode transition from ring to red mode affecting atomic clock performance.

Findings

New RF exciter circuit operating at 60-65 MHz

Mode transition from ring to red mode affects signal quality

Reasons for mode change are analyzed

Abstract

In this paper we describe the development of novel RF exciter circuit for electrode less Rb lamp. The lamp exciter circuit is a RF oscillator with a a new configuration operating at 60 to 65 MHz frequency with 3 to 4 watt power. The Rb lamp is used in exciting the ground state hyperfine transitions in Rb atom in a glass cell placed inside a tuned microwave cavity, As the frequency of these hyperfine transitions is very stable it is used in the development of Rb atomic clock by phase locking the oven controlled crystal oscillator (OCXO) to this atomic transition frequency. The details of the Rb lamp exciter are presented in the paper.The Lamp is ideally operated in ring mode as in this mode the linewidth is narrow and there is no self reversal. However, high temperature and RF excitation power may drive the Rb lamp to red mode which gives rise to line broadening and self reversal. It is the experience that mode change from ring to red deteriorates the atomic signal strength and S/N. In this paper the reasons of mode change are also discussed.