| 摘要 |
<p>The standard comprises (a) an optical pumping device comprising (i) a light source of given spectral component, (ii) a cell contg. gaseous alkali metal, receiving the light, internally covered with a nondisorienting layer, pref. polyethylene, organo-silane or a silicone, (iii) a detector providing a signal representing transmitted light and (iv) a coil subjecting the cell to constant magnetic field, (b) an arrangement for subjecting the cell to an electromagnetic wave inducing a hyperfine spectral transition of metal ats., increasing absorption of light by the cell and (c) a controller responsive to signals from (iii), modifying wave frequency to centre it on the frequency of the hyperfine spectral transitions. The arrangement produces a progressive electromagnetic wave, widening the line of absorption of the cell by Doppler effect to permit a redn. in the control time constant. The standard is useful in environments subject to vibration or shock, and for navigation or communications. The control time constant is much less than that of high performance standards, but sufficient for these hostile environments, and the structure, is much reduced size and is simplified over standards using a microwave cavity.</p> |
