This paper reports the specific application of an electrostatic glass motor (EGM) into the Swiss Continuous Caesium Clock Fountain (FOCS) developed at the Observatoire cantonal de Neuchâtel (ON) in collaboration with the Swiss Federal Office of Metrology and Accreditation (METAS) [1].
The fountain delivers a frequency standard based on a continuous beam of cold and slow Caesium atoms. In comparison with the pulsed fountains, the continuous operation of the fountain presents several advantages [2] which will be exposed here. The Cesium atoms are cooled by a laser. This light should be kept leaking into the measurement chamber, where it would induces small resonance frequency shifts. This decoupling of the laser light from the continuous flux of atoms is achieved by a small turbine rotating at an appropriate constant speed. The motor of this light-trap shutter consists of a glass rotor facing a stator with a 3-phased array of electrodes. The substrate of the electrode is made out of Al2O3 and the silver-palladium electrodes are patterned using a thick-film photolithographic process. The system can be described as parallel capacitors; hence charges separate in the glass within several seconds and would disappear with the same time-constant if the power supply is cut. If the voltages on the stator are commuted, these charges exert a lateral force sufficient to move the rotor.
The proposed novel use of EGM for ultra-high vacuum applications is a viable way of moving objects under these harsh conditions, as well as chopping light beams or precisely positioning optical elements such as mirrors or lenses. It establishes that EGM, being one of the rare examples of an industrially exploitable electrostatic motor at macroscopic scale, is particularly suited for laboratory vacuum experiments and space applications.
|