Specialists in frequency control are improving their crystal vibrators and atomic frequency standards. Toward better crystal devices, they are making filter crystals that operate above 30 Mc/sec; with better mathematical analysis of vibration modes to help, they are using electrode‐thickness tuning and crystal shaping to improve crystal response; they are using sound waves and x rays to investigate vibration‐mode patterns. Some are seeking new materials to replace quartz, especially endowed by nature to function as a frequency standard. Others have used quartz in a new way to make a new kind of delay line. Toward better atomic frequency standards, they are improving both stability and accuracy. All‐solid‐state versions are making rubidium gas‐cell standards and cesium‐beam standards more useful. Other improvements in atomic devices include better circuits for hydrogenbeam tubes, narrower reference lines, and better frequency stabilities, both long‐ and short‐term.
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October 1965
October 01 1965
Frequency control: Report on the 19th annual symposium…
In the two decades during which the US Army has conducted its annual frequency‐control symposia, electromagnetic oscillations from atoms in transition have joined mechanical vibrations of crystals as frequency standards. Masers, in which hydrogen, ammonia, or rubidium is the active medium, and cesium beams function alongside quartz oscillators. Current developments are turning both crystal and atomic standards into more accurate and easier‐to‐use devices.
Physics Today 18 (10), 52–58 (1965);