Oscillators – Molecular or particle resonant type
Patent
1994-11-03
1995-10-24
Grimm, Siegfried H.
Oscillators
Molecular or particle resonant type
331 3, H03L 726
Patent
active
054613469
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an atomic beam resonator, particularly with cesium-beam, advantageously to produce a reference frequency for the frequency stabilization of a quartz oscillator, and comprising, arranged in series in the direction of the beam, an atomic beam source, a first state selector, an interrogating area including a waveguide body constituting a Ramsey-type two arms resonant cavity, the arms of which are transversally traversed by the atomic beam, a second state selector, a photon sensor device for producing the useful output signal of the resonator and a device for injecting into the resonant cavity an interrogating signal produced from the signal from said oscillator, so as to produce in each arm of said cavity a microwave interrogating field interacting with the atomic beam atoms, the interrogating area being surrounded by a magnetic shielding.
Atomic beam resonators of this type are already known. The injection of the microwave energy is usually realized by a magnetic coupling by means of a T-H. In this case, the two microwave interrogating fields are in phase and the response of the resonator exhibits a maximum at the resonance frequency.
These known resonators exhibit important drawbacks from electrical and mechanical points of view. Thus, the coupling through a T-shaped waveguide element renders the resonator cumbersome. This coupling using a waveguide T which must cross the magnetic shielding produces important disturbances of the static magnetic field, which is unfavorable for obtaining good long term frequency stability and good accuracy. Moreover, owing to the fact that the response of the resonator has a maximum at the resonant frequency, the short term frequency stability of the resonator is limited by the shot noise associated with the atomic flux detected at the resonance. On the other hand, for this response of the resonator having a maximum at the resonant frequency, the amplitude of the frequency modulation applied to the interrogating signal must be relatively high, which causes important shiftings of the frequency of the atomic resonance in case for example of an untuning of the cavity.
SUMMARY OF THE INVENTION
The present invention has for purpose to provide an atomic beam resonator which does not have the drawbacks of the technical state, which have just been stated.
To attain this purpose, the resonator according to the invention is characterized in that the injection means of the microwave energy in the resonant cavity is constituted by a coupling device which is adapted to prescribe in the cavity an odd number of modes so that the two interrogating fields are in phase opposition and that the response of the resonator exhibits a minimum at the resonant frequency.
According to a feature of the invention, the coupling device is an electrical coupling-type device.
According to another feature, the electrical coupling device is realized in the form of an antenna extending into the resonant cavity through a passage realized in the wall of the waveguide body so that the axis of the antenna crosses the intersection of the planes of symmetry of the cavity.
According to an advantageous feature of the invention, the antenna is constituted by the central conductor of a coaxial cable an end of which is connected to the generator of the interrogating signal and the other end of which is connected to the waveguide constituting the resonant cavity, and which crosses the shielding sheathing through a hole of small diameter corresponding to the cable diameter and located at a selected location for not disturbing the static magnetic field.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and other purposes, features, details and advantages thereof will appear more clearly during the explanatory description which will follow made in reference to the accompanying schematic drawings given only by way of example illustrating an embodiment of the invention and in which:
The FIG. 1 is a perspective view of an atomic beam resonator ac
REFERENCES:
patent: 3967115 (1976-06-01), Kern
patent: 4661782 (1987-04-01), Weidemann
Audoin Claude L. A.
Cerez Pierre J. C.
Giordano Vincent P.
Petit Pierre H. F.
Grimm Siegfried H.
Tekelec Airtronic Cites des Bruyeres
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