JPS5921558Y2 - Light source lamp for rubidium atomic frequency standard instrument - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubidium gas cell type light source lamp for an atomic frequency standard instrument that utilizes optical pumping (more specifically, to temperature maintenance of the light source lamp).

To generate a highly stable frequency, a crystal oscillator has conventionally been used in many cases, and has been put into practical use with long-term stability of about 1o-11/day.

The main part of a crystal oscillator The crystal oscillator is made by artificial work such as polishing the crystal piece, and over a long period of time it will change over time, so no significant improvement in stability can be expected.

Therefore, in order to meet the demand for highly stable frequency standards, which are typically used in the fields of telecommunications, measuring instruments, etc., there is a method of using microwaves to utilize quantum mechanical vibrations of molecular atoms as a frequency standard.

FIG. 1 is a block diagram of a rubidium gas cell type atomic frequency standard (hereinafter referred to as an Rb atomic oscillator), and FIG. 2 is a block internal diagram of the optical microwave resonator 10 of FIG. 1.

In the Rb atomic oscillator, a double resonance method using optical pumping is used.

The Rb atoms participating in resonance are sealed in a resonance cell 22 with a suitable buffer gas and placed in a microwave cavity resonator 23.

Pumping light from a light source lamp 20 sealed together with Rb atoms and an inert carrier gas such as krypton, neon, or argon passes through a filter cell 21 and a resonance cell 22 and reaches a photodetector 24, where the amount of transmitted light is detected by a solar cell. It is electrically detected by etc.

26 is a C magnetic field coil, and 27 is a heater. Rubidium D light as pumping light has two components (wavelength 7
948 A, 7800 A), and the filter cell 21 is not an essential component because the filter cell 21 is arranged to increase pumping efficiency.

Due to the incidence of the pumping light, the Rb atoms in the resonant cell are deviated from the thermal equilibrium state and enter a negative temperature state.

When a microwave having a frequency equal to the transition frequency is inserted therein from the diode 25, stimulated emission occurs.

Since the ejected atoms absorb the pumping light again and are optically pumped, the amount of transmitted pumping light decreases.

That is, microwave transitions used in the standard are detected as changes in the amount of pumping light.

The output of this optical microwave section draws a resonance curve that is absorbed at the transition frequency, but since the microwave is modulated at a low frequency, there is a 180 degree phase difference above and below the center of resonance. obtain a resonance signal.

This resonance signal is applied to a crystal oscillator 15 through an amplifier 11 and a phase discriminator 12, through different low-pass filters.

The servo amplifier 13 has an integral element and eliminates long-term fluctuations.

The crystal oscillator 15 is a VCX having a part of the tuning capacitance that has an element such as a Varicab whose capacitance can be changed by voltage.

(Voltage controlled crystal oscillator, Voltage Cont
roledCrystal 0scillator)
If the microwave frequency and transition frequency differ, control is added to pull back the oscillation frequency of the crystal oscillator.

The microwave signal drawn from the diode 25 is produced by modulating the output of the crystal oscillator 15 and the output of the low frequency oscillator 14 with a frequency modulator 16 and further multiplying with a frequency multiplier 17.

The standard signal taken out to the outside has a frequency of I MHz, 5 MHz, etc. through a frequency synthesizer 18.

Therefore, in a controlled steady state, the relationship between the oscillation frequency of the crystal oscillator and the transition frequency of the atoms is determined by frequency synthesis,
Since it is determined only by the frequency multiplication method, a standard frequency stabilized to the stability of the atomic transition frequency can be extracted from the crystal oscillator.

As mentioned above, the resonant frequency itself of the quantum mechanical vibration of the reference molecule or atom remains unchanged as long as the environmental conditions are constant. However, in order to construct an atomic oscillator based on this vibration, the following steps must be taken. A problem arises.

That is, in the rubidium gas cell type atomic frequency standard, rubidium as a reference is sealed in a glass container, but it is difficult to accurately control the amount of rubidium in the container.

FIG. 3 is a schematic diagram of an apparatus for enclosing rubidium metal into a lamp.

31 is a light source lamp, 32 is a reaction tube, 33 is an exhaust port/filled gas inlet, and 34 is a reaction sample.

First, the reaction tube 32 and the lamp 31 are evacuated to a vacuum of 10 -6 mmHg or more, and then rubidium is forced into the lamp 31 as a metal vapor. There are mainly two methods.

The first method is to use an Rb ampoule as a reaction sample by breaking it in a reaction tube 32 in a nitrogen atmosphere, and the second method is to reduce rubidium chloride with calcium hydride to produce rubidium. This is the way to proceed.

Currently, the second method is the mainstream because rubidium belongs to an alkali metal and has strong reactivity.

In any case, the reaction tube is heated with a gas burner, etc., and the metal vapor is driven into the lamp, and after filling with an appropriate gas, it is sealed, and the amount of metal that has entered the lamp is
It is not possible to strictly define the condition only by visually observing the state of adhesion to the inner wall of the lamp.

However, if the amount of Rb in the lamp is too large, the noise will increase and the operation will become unstable, while if it is too small, the life of the lamp will be shortened, which is an important factor.

The present invention eliminates the above-mentioned drawbacks and is a light source lamp in which only the necessary amount of rubidium metal sealed in the lamp can contribute to light emission.

A light source lamp filled with rubidium does not have an electrode inside the tube, and uses an electrodeless discharge that is excited by wrapping an excitation coil around the outside of the tube.

First, it starts with a discharge of the enclosed gas, Rb metal vapor increases as the temperature rises, and Rb becomes the main source of light emission.

In addition, since the profile of the emission spectrum differs depending on the temperature, a constant temperature T (usually 90°C to 12°C) is required.
Normally, the entire lamp is maintained at about σC.

The present invention divides the interior of the lamp into a main temperature section and a sub-temperature section, and controls the amount of rubidium metal contributing to the emission spectrum by maintaining the main temperature section at the main temperature TM and the sub-temperature section at the sub-temperature T5. It is something.

FIG. 4 shows an example of the shape and configuration of the lamp section according to the present invention.

41 is the main temperature section, 42 is the sub-temperature section, 43 is the main temperature source, 4
4 is a sub-temperature section, and 45 is an excitation coil.

The main temperature source 43 and the sub-temperature section 44 can be maintained at a desired temperature by several methods, such as winding a coil or the like and passing a current to generate heat, or using heat dissipation from a transistor, etc. If it's possible, the method doesn't matter.

The Rb metal within the lamp is sealed and becomes Rb metal vapor at a rate determined by external factors such as holding temperature and excitation power.

Therefore, if the holding temperature is increased, as long as Rb metal remains, the amount of Rb metal vapor will increase, and the spectral intensity will become stronger before self-absorption and self-inversion phenomena occur.

In FIG. 4, the main temperature section is maintained at a temperature T (90°C to 120°C) that is conventionally used, and the sub-temperature section is maintained at a temperature T5 lower than this main temperature TM.
The amount of Rb metal that does not vaporize can be made larger in the sub-temperature section than in the main temperature section.

That is, when excessive Rb metal is enclosed, the sub-temperature T8
By lowering the temperature, it is possible to control the amount of Rb metal vapor that contributes to light emission in the main temperature section, that is, affects the spectral intensity.

Therefore, according to the present invention, if an amount of Rb metal that is more than enough to contribute to light emission is sealed in the lamp, by changing the temperature difference between the main temperature part and the sub-temperature part, the main temperature part will be affected during light emission. It becomes possible to bring the amount of Rb metal vapor present to the most desired value.

In particular, in the present invention, the sub-temperature section is made smaller than the main temperature section, and works together with the second heater to adjust the amount of rubidium metal evaporated within the lamp, and since the sub-temperature section is small, The amount of rubidium metal evaporated can be quickly adjusted according to the adjusted temperature of the second heater, and the combination of the first heater facing the main temperature section and the second heater facing the sub-temperature section allows for light emission and Since the amount of evaporation can be adjusted in tandem, it has solved the problems of noise and instability caused by enclosing too much rubidium metal, and shortened lamp life due to too little.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a rubidium gas cell type atomic frequency standard. FIG. 2 is an internal diagram of the optical microwave resonance section 10 in FIG. 1. FIG. 3 is a simplified diagram of an apparatus for enclosing rubidium metal into a lamp. FIG. 4 is a diagram illustrating an example of the configuration of the lamp section according to the present invention. In FIG. 1, 10... optical microwave resonator, 11... amplifier, 12... phase discriminator, 15... crystal oscillator, 17... ...Frequency multiplier, 18...Frequency synthesizer, in Fig. 2, 20...Light source lamp, 21...
・Filter cell, 22... Resonance cell, 23.
...Microwave cavity resonator, 24...Photodetector, 25...Diode, 26...
・C magnetic field coil, in Figure 3, 31...
Light source lamp, 34...Reactant, in Fig. 4, 41...Main temperature section, 42...Sub-temperature section, 43...Main temperature source , 44...Sub-temperature section, 45...Excitation coil.

Claims (1)

[Scope of utility model registration request] In a light source lamp filled with rubidium metal and an inert gas, a main temperature section and a sub-temperature section are integrally formed in the lamp body, the sub-temperature section is formed to be smaller than the main temperature, and the outer periphery of the main temperature section is A light source lamp for a rubidium atomic frequency standard, characterized in that a first heater and an excitation coil are opposed to each other, and a second heater is provided around the outer periphery of the sub-temperature section to adjust the amount of vapor of rubidium metal within the lamp. .