Atomic beam device

Details Atomic beam device Atomic beam device

1979-06-25

1982-10-12

Anderson, Bruce C.

Radiant energy

Electrically neutral molecular or atomic beam devices and...

H01S 100

Patent

active

043541089

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to an atomic beam device for frequency standards using an atomic or molecular beam, and in more detail, to a newly designed compact, rigid and inexpensive cesium beam tube which is easy to maintain.
An atomic beam tube which utilizes the atom spectrum of cesium (Cs) for a frequency standard generally includes the basic structure as shown in FIG. 1.
In FIG. 1, the cesium oven 1 which is used as the cesium beam source heats the cesium Cs to a temperature of 80.degree. to 100.degree. C. so that it is vaporized and thereby generates the Cs beam through the collimator.
This Cs beam enters the detector 7 through the first state selection magnet 2 for producing a magnetic field A, high frequency transition part 3, including the microwave cavity 5 placed in the field, for producing a magnetic field C, and the second state selection magnet 6 for producing a magnetic field B. On the other hand, a microwave signal is supplied to an RF input circuit 8. When the frequency of this microwave signal coincides with the transition frequency of the Cs atoms, resonance of the Cs atoms occurs in the cavity 5, resulting in the maximum output of the detector 7. Therefore, a highly stabilized oscillation frequency can be obtained by using closed loop control for the oscillation frequency of the microwave oscillator, for example, such as a crystal controlled oscillator, so that the microwave signal frequency is maintained at the center of the resonance spectrum of the Cs atom. The transition frequency of the Cs atom in the ground state is 9192.631770 MHz.
An example of the conventional cesium beam tube which is configurated by combining the above-mentioned basic elements is shown in the Japanese patent publication No. Toku-Ko-Sho 42-27517 (corresponding U.S. Pat. No. 3,323,008). Moreover, an example of another conventional cesium beam tube is also disclosed in the Japanese patent laid-open application No. Toku-Kai-Sho 51-64895 (corresponding U.S. Pat. No. 3,967,115). The structure of the cesium beam tube in accordance with these prior art references is shown in FIG. 2 in the form of a cross-section.
In FIG. 2, the atomic beam generator 1, A magnetic field unit 2, high frequency transition part 3, B magnetic field unit 6, detector 7, C magnetic field unit 4 and magnetic shield 10 are rigidly and levelly mounted on the mount 9 as shown in FIG. 2. Each element is arranged on the mount 9 so that the atomic beam generated from the atomic beam generator 1 reaches the detector through the specified route G. The mount 9, which is holding each element mentioned above, is provided at the inside of the case 11 which ensures a hermetically sealed structure in combination with the cover 13. The high frequency input circuit 8 is engaged with the case 11 and projected to the outside, and moreover is held to the mount 9 at the section D thereby resulting in a sufficient seal. In addition, at the above-mentioned high frequency signal input port 8, which is coupled to the microwave signal to be supplied from the external circuit, a sealing material 14 is provided, through which said microwave signal effectively passes. In order to hermetically seal each element accommodated in the case 11, the cover 13 is mounted to the case 11 and the area around the joint, namely the part E, is sealed by a means such as welding. In the above-mentioned structure of the atomic beam device, an air exhaust system and vacuum ion pump are connected to an air exhaust port which is provided on case 11 but which is not illustrated in FIG. 2, so that the inside of the atomic beam device is maintained in a vacuum condition. In this case, the ion pump may be built inside of the device or provided as an additional unit outside of the device. After the air in the atomic beam device is exhausted until a vacuum is obtained, the air exhaust system is removed. Then, by sealing said air exhaust port, the atomic beam device can be completed. The part 12 is an airtight electrical connection terminal engaged with the case 11, and is

REFERENCES:
patent: 3323008 (1967-05-01), Holloway et al.
patent: 3348040 (1967-10-01), Vessot
patent: 3397310 (1968-08-01), Holloway et al.
patent: 3967115 (1976-06-01), Kern

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