JPS6362118B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lamp cell for a gas cell type atomic oscillator.

Atomic oscillators control crystal oscillators based on the permanently unchanging resonance frequencies of atoms and molecules.
Because of its extremely high long-term frequency stability, it is used as a frequency standard. Such atomic oscillators can be classified into active maser type, passive absorption type, atomic beam type, gas cell type, etc. Among them, optical pumping method is used. Since the passive gas cell type atomic oscillator can be constructed in a relatively small size, it is used as a frequency standard for various devices.

For example, such a rubidium gas cell type atomic oscillator has the configuration shown in FIG. That is, the optical microwave section 11 and the voltage controlled crystal oscillator 12
The optical microwave section 11 includes a lamp cell 1, a lamp excitation coil 2, a reflector 3, a lamp exciter 4, a filter cell 5, a cavity resonator 6, a gas cell 7, and a photodetector. 8, an amplifier 9, a multiplier 10, etc. Rubidium Rb exists in nature as two isotopes, Rb ⁸⁷ and
Rb ⁸⁵ is present, Rb ⁸⁷ is sealed in the lamp cell 1, Rb ⁸⁵ is sealed in the filter cell 5, and Rb ⁸⁷ is sealed in the gas cell 7. The high frequency output from the lamp exciter 4 is applied to the lamp excitation coil 2, and the lamp cell 1 emits discharge light. In addition to Rb ⁸⁷ , this lamp cell 1 is generally filled with one type of gas such as neon Ne, argon Ar, krypton Kr, etc. as a buffer gas.

Among the wavelength components of the light generated from the lamp cell 1, unnecessary wavelength components are absorbed by the filter cell 5, and only the light of the desired wavelength component is incident on the gas cell 7. Further, the oscillation output of the voltage controlled crystal oscillator 12 is outputted by the frequency multiplication synthesizer 13 and the multiplier 10.
The resonant frequency of Rb ⁸⁷ is multiplied to 6834.68...MHz and applied to the cavity resonator 6.

When the microwave applied to the cavity resonator 6 matches the resonant frequency of Rb ⁸⁷ in the gas cell 7, the light passing through the gas cell 7 is absorbed by optical microwave double resonance, thereby detecting the photodetector 8. Detection output decreases. This is identified and amplified by the amplifier 9 and used as the control voltage for the voltage controlled crystal oscillator 12. The oscillation frequency of the voltage controlled crystal oscillator 12 is as follows.
Since it is controlled based on the extremely stable resonance frequency of Rb ⁸⁷ , it is accurate and highly stable.

The present invention relates to improvements to lamp cells in such atomic oscillators.

Conventionally, when lighting such a light source lamp,
Several tens of excitation coils are wound around one lamp cell.
High-frequency power of ~100 MHz is applied to excite the gas within the lamp cell, causing discharge and lighting. Even after lighting, the high-frequency power is applied while maintaining the power at the time of lighting, and the lighting (discharging) state is maintained by the magnetic field of the high-frequency power. In this lighting and maintenance means, the same power is applied continuously when lighting is maintained as when starting lighting, which shortens the life of the lamp and also reduces the temperature characteristics and long-term stability of the atomic oscillator. It gets worse. If the value of high-frequency power is made small, the life of the lamp will be improved, but lighting will become difficult.
Also, in place of conventional means, for example, as shown in FIG. 2, when the lamp cell 21 is lit,
A method has also been taken in which a high voltage pulse is applied from the pulse generator 22 to force the discharge (lighting) to start. Note that 23 is a lamp exciter for maintaining lighting. According to such lighting means, discharge can be maintained after lighting using low high frequency power.
Therefore, the lamp life, temperature characteristics as an atomic oscillator, long-term stability, etc. are improved. However, in such a means, the pulse generator 2
2 is required, which is not preferable in constructing an atomic oscillator that requires smaller size and higher reliability.

It is an object of the present invention to eliminate the problems of the prior art and to more easily start lighting (discharging) a lamp cell.

Therefore, according to the present invention, in a lamp cell of a gas cell type atomic oscillator that controls a voltage-controlled oscillator, the metastable level voltage of the first gas together with the atom is set to a Two different gases with a relationship greater than the ionization voltage of the second gas are confined, the first gas becomes a metastable state, then the metastable state of the first gas ionizes the second gas, and the second gas becomes a metastable state. We propose a lamp cell for a gas cell type atomic oscillator, which is characterized in that by starting the gas discharge, the final transition to atomic discharge light emission occurs.

Hereinafter, a lamp cell of a rubidium gas cell type atomic oscillator to which the present invention is applied will be described in detail using examples.

In addition to rubidium (Rb), neon (Ne) and argon (Ar) are sealed in the lamp cell according to the present invention. The metastable level voltage (V) and ionization voltage (Vi) of neon and argon are Vm (Ne) = 16.6, 16.7v Vi (Ne) = 21.5v Vm (Ar) = 11.5, 11.7v Vi (Ne) = 15.8 v (unit of numerical value is electron volt).

In this way, since Vm(Ne) > Vi(Ar), in the first stage of discharge, a metastable state of neon (Ne _* ) is created, and in the second stage, this metastable state of neon effectively depletes argon. to ionize. Therefore, once the argon discharge starts, it becomes possible to finally shift to rubidium discharge light emission as in the conventional lamp cell.

That is, the present invention utilizes the metastable state of the enclosed gas atoms (Ne, Ar) and the ionization voltage to first facilitate the discharge of the enclosed gas, and finally to cause the emission of light from the rubidium atoms.

According to the present invention, the light emission of rubidium is guided through three stages as described above, and it is possible to light the light with lower excitation power than before, which is useful for extending the lifespan and improving the reliability of the atomic oscillator. It's advantageous. Further, although a combination of neon and argon is shown in this embodiment, the type of gas is not limited to this. Generally, between two gases a and b, Vm(a)>Vi
If the relationship (b) holds true, the same effects as above can be expected. It is also possible to further facilitate discharge by combining the third and fourth gases.

Although the present invention has been described using a rubidium gas cell type atomic oscillator as an example, it can also be applied to other atomic oscillators that utilize optical pumping, and has great advantages.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the atomic oscillator, and FIG. 2 is a detailed diagram of the light source lamp section.

Claims (1)

[Claims] 1. In a lamp cell of a gas cell type atomic oscillator that controls a voltage-controlled oscillator based on the permanent resonant frequency of atoms, the metastable level voltage of the first gas together with the atoms is lower than the ionization voltage of the second gas. Confining two different gases that have a large relationship, bringing the first gas into a metastable state, and then the metastable state of the first gas ionizing the second gas,
1. A lamp cell for a gas cell type atomic oscillator, characterized in that by starting a discharge of a second gas, the final transition to atomic discharge light emission occurs.