JP3218093B2 - Atomic clock and method for controlling microwave source of atomic clock - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency standard, and more particularly to an atomic clock using, for example, a cesium beam tube.

[0002]

BACKGROUND OF THE INVENTION Many modern technology applications require a precise frequency standard, i.e., a clock. For example, very precise navigation standards are based on extremely accurate clocks. Atomic frequency standards or clocks are the basis of many such systems. One type of atomic beam standard, a widely adopted atomic clock, uses a cesium beam tube. Currently, most national standards of frequency and time are based on cesium beam devices. These standards are about one in 10 ¹³ accurate.

The cesium beam standard utilizes the quantum effects arising from the ground-state hypermagnetic structure of the cesium atom. Commonly used transitions occur by the interaction of electron spins with nuclear spins. This transition is relatively insensitive to external influences such as electric and magnetic fields. This transition defines the frequency of the microwave domain spectrum at 9,192,631,770 Hz. Basically, a cesium beam tube produces an output that is very sensitive to the frequency of the microwave source that supplies the tube with energy. The microwave source is tuned to maximize tube output. When this condition is satisfied, the frequency of the microwave source correlates in a known manner with the aforementioned transition frequency.

[0004] An ideal cesium beam tube operates as follows. A collimated beam of cesium atoms is passed through a magnetic state selector that selects cesium atoms in a first energy state. The selected atoms then traverse the microwave cavity, within which the atoms absorb energy from or impart energy to the microwave source. Some of the atoms transition to the second energy state due to the absorbed or supplied energy. The number of transitioned atoms is then determined by the analyzer. The frequency of the microwave source is continuously adjusted in the servo loop to maximize the output of the analyzer.

[0005] Conventional beam references differ from this ideal system. First, in order to optimized system to function properly, the coercive when the frequency of the microwave source is shifted to search the maximum output of the tube, the amplitude of the microwave radiation in the cavity is constant I have to drip. The microwave cavity resonates according to the physical structure of the cavity. These resonances are equivalent to the resonance of a frequency-based filter that changes the amplitude of the microwave signal in the cavity when the frequency shifts. Furthermore, small fluctuations in the intensity of the microwave source are difficult to completely eliminate. For example, such fluctuations may be caused by thermal components in the RF chain that excite the microwave cavity. Such fluctuations can further change the amplitude of the signal from the cesium beam tube. Changes in cesium beam tube output due to changes in microwave signal strength may be mistaken by the servo loop as a shift in oscillator frequency. In this case, the servo loop attempts to correct the frequency shift by shifting the microwave frequency, thereby inducing an error in the microwave frequency.

A second problem with conventional cesium beam tubes is called "Rabi pulling". The optimized system assumes that all atoms entering the microwave cavity are in the same energy state. In fact, there are atoms in several atomic states. An atom that has a spectral line near the desired transition spectral line will generate a background signal in the region of the desired spectral line. The frequency of this background signal is not constant. Thus, this signal distorts the shape of the desired spectral line. This distortion shifts the maximum position of the tube output as a function of microwave frequency, and thus introduces a second source of error in the frequency standard.

[0007]

OBJECTS OF THE INVENTION Broadly, it is an object of the present invention to provide an improved atomic beam standard. It is another object of the present invention to provide an atomic beam standard having a frequency of microwave radiation in a microwave cavity that is less sensitive to changes in intensity. Yet another object of the present invention is to provide an atomic beam standard that is less susceptible to Rabi pulling than conventional atomic beam standards.

[0008]

SUMMARY OF THE INVENTION The present invention comprises an improved atomic beam clock device and a method of controlling the same. A preferred embodiment of the present invention includes a cesium source for generating a collimated beam of cesium atoms and a first selector for selecting cesium atoms in a predetermined state. The selected cesium atoms then receive microwave radiation from a microwave source whose frequency is controlled by a controller in the device. A second selector selects cesium atoms in a predetermined state and directs the selected atoms to a detector that generates a signal regarding the number of cesium atoms incident thereon. The controller measures the steady state output of the detector at each of the four predetermined frequencies and calculates a frequency correction applied to the microwave frequency.

In a preferred embodiment of the present invention, the four frequencies comprise two pairs of frequencies, each pair being symmetrically spaced about a center frequency. One frequency of each pair is located in the positive slope region of the response curve as a function of the microwave frequency of the signal generated by the detector, and another frequency of each pair is located in the negative slope region of the response curve. positioned. In a preferred embodiment of the present invention, the steady state output of the detector at each frequency is measured at two different microwave input amplitudes. The amplitude correction applied to the microwave amplitude at each frequency pair is made by amplitude measurements.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A block diagram of the main features of a cesium beam frequency standard apparatus according to the present invention is shown in apparatus 10 of FIG. The apparatus 10 comprises a cesium beam tube 11, a voltage controlled frequency generator 13, and a controller 26. The cesium beam tube 11 operates as follows. A cesium source 12 generates a collimated beam of cesium atoms. Such atomic beam sources are well known to the expert and will not be described in detail here. It is sufficient to describe the present invention that the composite beam 15 of cesium atoms contains atoms of many different energy states. A magnetic state selector 14 is used to select atoms in a given state. The selected cesium atoms pass through a chamber 17 having a small magnetic field called the C magnetic field. Chamber 17 also includes a microwave cavity 18 through which selected cesium atoms pass. Cavity 18 has two branches that impart Ramsey resonance of cesium atoms.

The reason that Ramsey resonance is preferred is that cesium
This is because it is only necessary to carefully control the magnetic field in the region of the chamber 17 where the beam passes through the branch of the cavity 18. Some of the cesium atoms change their energy state by microwaves. Thus, when the chamber 17 is excited, the cesium beam 16 will have atoms in many different energy states.
The atoms in the desired energy state are selected using the second magnetic analyzer 20. The output of the second magnetic analyzer 20 is the detector 22
And its output is read by the controller 26.

The frequency generator 13 supplies a microwave guided into the cavity 18. The frequency of the microwave is controlled by a voltage controlled crystal oscillator 27 controlled by a controller 26. Oscillator 27 is often a 10 MHz oscillator. The output of oscillator 27 is multiplied by frequency multiplier 28 to generate the required microwave frequency for beam tube 11. As will be described in greater detail below, the controller 26 must be able to slightly change the frequency and amplitude of the microwave. This is accomplished by an adder 30 and an amplitude modulator 24 that is configured et or mixer support.

FIG. 2 shows the output of the detector 22 as a function of the frequency of the microwave radiated into the cavity 18.
The spectrum shown in FIG. 2 includes three outputs corresponding to three transitions, the desired transition shown at 40 and two adjacent transitions shown at 42 and 44. The goal of the servo strategy is to tune the oscillator 27 so that the atoms corresponding to the 33 peaks are incident on the detector. When this goal is achieved, the output of oscillator 27 is at a standard frequency. This output is provided to the user via splitter 32 and isolation amplifier 34. Note that the spectra from adjacent transitions have tails, indicated at 45 and 46, that extend into the region of the spectrum corresponding to the desired transition. Generally, these tails are not symmetric. Thus, the resulting background is skewed. It is this sloping background that generates the aforementioned rabbi pulling.

Having described the basics of the standard device, the manner in which the controller 26 controls the frequency of the oscillator 27 will now be described in more detail. Controller 26 changes the microwave frequency between the four frequencies. The output of the detector 22 is measured at each frequency and used to calculate an estimate of the oscillator frequency error. The controller 26 assumes that the output of the detector is based on the following approximate calculation. Output = A (1 + cos (πf / △ f)) + Bf ---- (1)

Where f is the frequency deviation of the microwave input to the cavity relative to the resonating microwave frequency. A and B are constants according to the physical characteristics of the cesium beam tube, and Δf is the half power width at the center peak. B = 0 when there is no rabbi pulling. Resonance is searched for by frequency modulating the microwave signal sequentially at four selected frequency increments. The adder 30 shown in FIG. 1 is used to increment or decrement the microwave frequency. If the center frequency differs from the resonance frequency by a small deviation df, the steady state output of the detector for the preferred value of the selected frequency is shown in Table 1 below as the detector output.
It described Te.

[0016]

[Table 1]

To determine the frequency error, the microwave frequencies are modulated by the above-described excursions in a convenient order. Sufficient time must be allowed to determine the output of the detector before integrating the output of the detector with a defined sampling period to estimate the output signal during each cycle.
After the complete order of the output signal has been measured, controller 26 calculates an estimate of frequency error E according to the following equation: E = (S ₂ −S ₃ ) + (S ₄ −S ₁ ) / 3 = 8Aπdf / (3 △ f) −−−− (2)

Where S ₁ -S ₄ are the respective detector outputs during cycles 1-4. Equation (2) shows that the error estimate is independent of background slope B. Therefore, the present invention corrects the rabbi pulling to a first order.

It will be clear to the expert that higher order corrections are possible by including higher order background terms according to equation (1). Such higher order correction models would require that the frequency be modulated with a number of additional excursions. Further, it will be apparent that other choices of modulation excursions can also be used. Once the exact response of the cesium beam tube to the frequency deviation is known, a response function can be used instead of equation (2), and another frequency deviation can be used to calculate the error estimate. I can do it. However, the exact response function is generally not known. Basically, this can be measured for each tube, but the accuracy required for the currently achieved performance is higher than is achievable. Unfortunately, this response function changes over time. Therefore, it is necessary to measure it regularly. Such periodic measurements require that the service of the frequency standard system be stopped. Therefore, such a calibration-based system is not preferred.

[0020] The present invention is the response function has assumptions as an even function with respect to about the frequency of the resonant frequency. When this assumption is made, four pairs of excursions are obtained under the following conditions:
Two modulation excursions are available. That is, the excursions of each pair are located symmetrically with respect to the resonance frequency,
One point of each pair must be located in the region of the positive slope of the response function, and the other corresponding point (high or low frequency) of the pair must be located in the region of the negative slope. When these conditions are met, an error estimate can be calculated from the sum and difference of the cesium tube outputs at various modulation excursions, and the resulting error estimate is dependent on the rabbi pulling until the third correction. Not done.

As mentioned above, the output of a cesium beam tube varies with microwave amplitude even if the microwave frequency is kept constant. For any given microwave frequency excursion from the resonance frequency, there is a microwave amplitude that produces the maximum cesium beam tube output. A portion of a typical response curve of a cesium beam tube as a function of microwave amplitude is shown at 50 in FIG. Note that there is another maximum of higher amplitude that is omitted from the figure. These maxima are not used since poor sexual performance than the first maximum value. These additional maxima have been omitted in FIG. 3 for simplicity of the drawing.

If the servo loop utilizes the amplitude of the sloping portion of the response curve, even a small change in microwave amplitude will induce a change in the power of the cesium beam tube.
For example, if the microwave amplitude is changed between ward values shown in 52 of FIG., The output Figure cesium beam tube 53
Will vary. However, if the servo loop uses the microwave amplitude at the maximum of the response curve, then the same change in microwave amplitude, indicated at 54,
The output of the cesium beam tube will have little or no change. Some variation in the microwave amplitude than almost always occur, it is advantageous to operate the servo loop with microwave amplitudes of the peak of the response curve. Therefore, in the preferred embodiment of the present invention, the amplitude of the microwave is controlled so that the amplitude is always close to the maximum value of the amplitude response curve.

As mentioned above, the amplitude response curve may be different at different microwave frequencies. The amplitude response curve depends on the frequency difference between the resonance frequency and the frequency at which the output of the cesium beam tube is measured. As described above, the preferred embodiment of the present invention measures the power of a cesium beam tube at two pairs of frequencies. This pair is shown in FIG. 4, which is an enlarged view of the response curve 60 of the cesium beam tube as a function of microwave frequency. The first frequency pair, designated 61 and 62, is at half the maximum point of the resonance peak.
The second frequency pair, designated 63 and 64, is at half the maximum of the adjacent peak. Each frequency pair is in a position offset by the same from the resonant frequency f _o. Therefore, the amplitude must be adjusted separately for each pair.

Next, the manner in which the amplitude is adjusted will be described with reference to FIG. FIG. 5 shows the frequency and microwave amplitude supplied to the cesium beam tube during a typical servo cycle. During the servo loop, the frequency is varied between the four frequency values mentioned above. First, the output of the cesium beam tube using microwave amplitude A ₁ is measured at a first frequency pair. Next, the microwave amplitude A ₃
Is used to measure the power of the cesium beam tube at the second frequency pair. Then, the output of the cesium beam tube is measured at a first frequency pair again using the microwave amplitude A _2. Finally, using the microwave amplitude A ₄ ,
The power of the beam tube is measured again at the second frequency pair.

Amplitude A ₁  And A _Two  Is the first pair of frequency valuesTo
Adapted microwave amplitude M ₁ Slightly deviated from,
That is, A ₁ = M ₁ -δM, A _Two  = M ₁ + δM −−−−− (3).  Similarly, the amplitude A _Three  And A _Four  Is the second pair of frequency valuesTo
Adapted microwave amplitude M ₂ Slightly deviated from,
That is, A _Three  = M _Two -δM, A _Four  = M _Two + δM −−−−− (4).

If M ₁ is located at the point of maximum of the response curve of the cesium beam tube as a function of the microwave amplitude for the first pair of microwave frequencies, A ₁ and A
The difference in the power of the cesium beam tube in the measurements made in ₂ will be zero. The difference is if it is not zero, the adjustment by M ₁ is performed. Similarly, if M ₂ is located at the point of maximum in the response curve of the cesium beam tube as a function of microwave amplitude for the second pair of microwave frequencies, A
The difference between the output of the cesium beam tube for measurements performed at ₃ and A ₄ will become zero. Difference if not zero, is adjusted by the M ₂ takes place. The magnitude δM of the amplitude modulation is a third- order effect that causes an error in determining the maximum value of the response curve.
In order to avoid the consequences, it must be as small as possible, as well as the noise of the system.

It should be noted that the constant B shown in equation (1) depends on the power of the microwave to the cavity in the cesium beam tube. Thus, if M ₁ is not equal to M ₂ , B is no longer a constant and the error estimate is different from the value calculated from equation (2). Next, the manner in which the error signal is calculated in a more general case will be described. As mentioned above, the response of a cesium beam tube as a function of microwave frequency is not known, and the function shifts with time. If Rabi pulling is not present, shows that the microwave frequency curve is an even function represented by G _e (f), where the f is the difference between the atomic resonance frequency and microwave frequency. Since G _e (f) is an even _{function, G e (f) = G} e - a (f).

If Rabi pulling is present, the beam tube current from the detector in the cesium beam tube: I (f)
Is calculated by the following equation. I = G _e (f) + B (p) f (5) where B (p) is a coefficient depending on the power of the Rabi-Pring.

[0029] As described above, the present invention preferably utilizes a modulated deflection frequency △ f ₁ and △ f ₂ two pairs of centering the microwave frequency in the frequency servo loop. When the microwave frequency differs from the resonance frequency by a slight frequency deviation ε, I ₋₁ = G _e (−Δf ₁ + ε) + B ₁ (−Δf ₁ + ε) ≒ G _e
(−Δf ₁ ) + ε (G ′ _e (−Δf ₁ ) + B ₁ ) −B ₁ Δf ₁ I ₊₁ = _Ge (Δf ₁ + ε) + B ₁ (Δf ₁ + ε) ΔG _e (△ f
₁ ) + ε (G ′ _e (△ f ₁ ) + B ₁ ) + B ₁ Δf ₁ I ₋₂ = _Ge (−Δf ₂ + ε) + B ₂ (−Δf ₂ + ε) ≒ _Ge
(−Δf ₂ ) + ε (G ′ _e (−Δf ₂ ) + B ₂ ) −B ₂ Δf ₂ I _{+ 2} = G _e (Δf ₂ + ε) + B ₂ (Δf ₂ + ε) ΔG _e (△ f
₂ ) + ε (G ′ _e (△ f ₂ ) + B ₂ ) + B ₂ Δf ₂ −−−− (6)

[0030] Here I _-1 and I ₊₁ are each modulated excursion - a beam tube current in △ f ₁ and + △ f _1, I _-2
And I ₊₂ are the beam tube currents at −Δf ₂ and + Δf ₂ . B ₁ and B ₂ are coefficients corresponding to the microwave power used when the frequency is shifted by Δf ₁ and Δf ₂ , respectively. G ' _e (△ f ₁ ) is G _e evaluated at △ f ₁
The derivative of (f). Since G _e (f) is an even function, G ′ _e (−Δf ₁ ) = − G ′ _e (Δf ₁ ).

C ₁ = I ₊₁ -I _{-1 to} 2εG ' _e (△ f ₁ ) + 2B ₁ Δf ₁ C ₂ = I ₊₂ -I _{-2 to} 2εG' _e (△ f ₂ ) + 2B ₂ △ f ₂ ------ put (7).

The goal of the error signal generator is to combine C ₁ and C ₂ to obtain an error signal independent of B ₁ and B ₂ . If C = C ₁ + αC ₂ (where α is a numerical value to be determined), the following equation is obtained. C = 2ε (G ′ _e (△ f ₁ ) + αG ′ _e (Δf ₂ )) + 2 (B
₁ Δf ₁ + αB ₂ Δf ₂ ) −−−− (8) C disappears when ε = 0, and the second term is deleted to satisfy the condition that C does not depend on B ₁ and B _2. It must be. _{Therefore, α = - B 1 △ f} 1 / (B 2 △ f 2) ------ (9)

By definition, B ₁ , B ₂ , Δf ₁ and Δf
₂ are all positive, so α is negative. Advantageously, the error detection signal C has the largest possible gain. Therefore, the coefficient of ε is selected to have the largest absolute value. This state occurs when Δf ₁ and Δf ₂ are selected so that G ′ _e (Δf ₁ ) and G ′ _e (Δf ₂ ) are maximized, and G ′ _e (Δf ₁₎ ) And G ′ _e (Δf ₂ ) have opposite signs. G _e (f) = co described above in connection with equation (1)
For the special case of s (πf / △ f), where △ f is the line width, these conditions are: △ f ₁ = １ ／ Δf and △ f ₂ = 3
/ 2 △ f. In this case, α = −B ₁ / (3B ₂ ) −−−−− (10). If the optimal power for Δf ₁ is equal to the power for Δf ₂ , then α = −３, which is the error correction value described above in connection with equations (1) and (2). Is the value used for

In the general case shown in equation (9), △ f ₁ and △ f ₂ are such that the absolute values of the derivatives G ′ _e (△ f ₁ ) and G ′ _e (△ f ₂ ) are maximized. To be selected. In this case, this can be expressed as: B ₁ / B ₂ = P ₁ / P ₂ (11) where P ₁ and P ₂ are the microwaves required to maximize the response at Δf ₁ and Δf ₂ respectively. Power. By calibrating the amplitude modulator at the output of the microwave chain, a good approximation of P ₁ and P ₂ is obtained. The measurement error of P ₁ / P ₂ imperfectly cancels the rabbi pulling, but in the actual case the pulling can be greatly reduced. The function of the amplitude servo is to remove to the first place the frequency shift due to any amplitude modulation associated with the frequency modulation. Thus, the fourth aspect of the present invention.
In addition to the point frequency modulation mechanism, the amplitude modulation mechanism of the present invention can be used very advantageously in a conventional two-point frequency modulation mechanism.

When the microwave amplitude is set to maximize the beam current at any frequency excursion, cesium
It can be seen that the beam current from the detector in the beam tube depends only on the secondary microwave amplitude components, eliminating any primary effects of any coherent amplitude. Setting the microwave amplitude for maximum amplitude modulation to the modulation frequency excursion is the optimal way to reduce frequency pulling due to coherent amplitude modulation. The main causes of coherent amplitude modulation include temperature and usually time-varying detuning of the microwave cavity, and the amplitude and frequency interdependencies of the microwave generator itself.

The conventional mechanism does not effectively control the microwave amplitude. Some conventional control mechanisms only rely on an initial adjustment to maintain that value. Another conventional mechanism detects microwave levels directly in the cavity and utilizes conventional constant leveling techniques to mitigate coherent modulation. Another conventional mechanism sets the microwave level such that the tube current is maximized at zero frequency excursion without frequency modulation. The first two types of conventional mechanisms are clearly inferior to those used in the present invention. The last conventional mechanism does not set the level to an optimal value, and thus is also inferior.

It should be noted that the servo for maximizing the beam current must operate simultaneously with the frequency servo. Amplitude servo is accomplished by small square wave modulation of the microwave signal, since this each level of the square wave occupies an integer multiple of complete frequency modulation cycles, frequency Fam amplitude modulation is obtained by the following formula . Fam = Ffm / (2N) --- (12) where Ffm is the frequency of frequency modulation and N is an integer> 0.

The present invention synchronously detects a signal caused by frequency modulation and closes the frequency servo, and also synchronously detects amplitude modulation and evenly symmetrically changes the beam tube current with respect to the frequency deviation to close the amplitude servo. This is to take advantage of the nature. These servos nullify both amplitude and frequency errors.

The same technique is used for each frequency pair of the four frequency techniques for reducing Rabi pulling.
In this case, two amplitude servos are used. That is, one is used for the inner frequency pair and the other is used for the outer frequency pair. In this case there are three servos, including a frequency servo, all of which function to reduce the amplitude and frequency errors to zero. If the microwave power is known exactly, as described above, rabbi pulling is inevitably eliminated.

By processing pairs of frequency excursions, each containing the same value of positive and negative frequency excursions, the present invention provides that the microwave signal spectrum that excites the beam tube is symmetric (slightly less). It depends only on the symmetrical properties of the guaranteed resonance line (excluding the relativistic and Bloch-Siegelt effects). If you want to use any deviation,
The actual details of the resonance line must be as accurate as the center of the line (approximately one part in 107). Since this line is not constant over time and does not have the power to achieve this accuracy, proper measurements to obtain the required accuracy cannot be made. Thus, frequency standards based on arbitrary frequency modulation are inferior to those achieved by the preferred embodiment of the present invention.

Further, it should be noted that the amplitude servo utilized in the present invention is not effective in conventional systems utilizing sinusoidal frequency (ie, phase) modulation to servo microwave frequencies. In the case of such a mechanism,
The optimum RF amplitude is the maximum beam current (or the maximum second harmonic amplitude) averaged over the modulation cycle, or
It is not the amplitude that produces the maximum beam current without deviation or frequency modulation.

Although the foregoing embodiment of the present invention uses a magnetic selector to select cesium atoms, it will be apparent to those skilled in the art that other types of selectors may be utilized. For example, the selection process can be accomplished by optical pumping. Although the invention has been described with reference to a cesium beam tube, it will be apparent to those skilled in the art that the method and apparatus of the invention may be used with other atomic clock systems.

[0043]

In the preferred embodiment of the present invention, the four microwave frequencies comprise two pairs of frequencies, each pair being symmetrically spaced about a center frequency. A higher-order frequency correction signal is obtained from the output of the detector for each frequency, and the center frequency is corrected by servo control. Also, an amplitude correction signal added to the microwave amplitude is obtained from the detector output for microwave amplitude modulation, and the amplitude is corrected. Thus, a novel control method that is insensitive to fluctuations in microwave amplitude and is less likely to be affected by rabbi pulling provides a highly accurate atomic clock that also corrects tube aging.

[Brief description of the drawings]

FIG. 1 shows a cesium alloy for explaining an embodiment of the present invention.
It is a block diagram of a beam frequency device.

FIG. 2 is a graph showing the output of a cesium beam tube as a function of microwave frequency.

FIG. 3 is a graph showing the response of a cesium beam tube as a function of the amplitude of the microwave at a given frequency.

FIG. 4 is a graph illustrating the output of a cesium beam tube as a function of microwave frequency to illustrate frequency modulation points in one embodiment of the present invention.

FIG. 5 is a graph for explaining cycling (repetition) of microwave frequency and amplitude in one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Main part of cesium beam frequency apparatus 11 Cesium beam tube 12 Cesium source 13 Voltage control frequency generator 14 Magnetic state selector (first magnetic analyzer) 15 Synthetic beam 16 Cesium beam 17 Room having C magnetic field 18 Cavity 20 second magnetic analyzer

──────────────────────────────────────────────────続 き Continued on the front page (73) Patent owner 399117121 395 Page Mill Road Palo Alto, California U.S.A. S. A. (72) Inventor Robin P. Gifard Anderson Drive, Los Altos, California, USA 770 (56) References JP-A-2-223226 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) H03L 7/26

Claims (12)

(57) [Claims] 1. The following (a) to (f)EquippedAtomic clock:  (B) a source for generating an atomic beam; (b) receiving an atom from the atomic beam,
First selecting means for selecting an atom, (c) responding to a frequency control signal,
To the frequency domain determined by the frequency control signal.
Microwave injection means for applying microwaves, (d) second selecting means for selecting atoms in the second state
(E) receiving the atoms in the second state and determining the number of atoms;
Detecting means for outputting a continuous signal,and  (F) The micros of the first, second, third and fourth frequencies
The detection means for each of the wavesEach of the steady state outputsTo
Means for measuring andThe measuredSteadyStatus outputRelated to
Means for determining a corrected frequency correction.
Responds to wave number correctionJustFor generating the frequency control signal
Control means. 2. The method according to claim 1, wherein the first and second frequencies form a pair at equal intervals above and below the center frequency, and the third and fourth frequencies form a pair at equal intervals above and below the center frequency. The atomic clock according to claim 1. 3. The method of claim 1 wherein one of said paired frequencies is located in a positively sloped region of the response curve output by said detection means as a function of the frequency of said microwave. The atomic clock according to claim 2, wherein another frequency corresponding to the frequency is located in a negatively sloped region of the response curve. 4. The apparatus according to claim 1, wherein said microwave injection means further comprises an adjusting means for adjusting the amplitude of said microwave in accordance with an amplitude control signal, said control means further comprising: means for generating said amplitude control signal. And measuring the steady state output of the detecting means at the first and second frequencies at the first microwave amplitude, and measuring the steady- state output of the detecting means at the first and second frequencies at the second microwave amplitude. the steady-state output is measured, the steady-
3. An atomic clock according to claim 2, further comprising: means for generating an amplitude correction to be added to the first and second microwave amplitudes from the measurement of the state output. 5. The control means further comprises: means for generating the amplitude control signal; and measuring a steady state output of the detection means at a third and a fourth frequency at a third microwave amplitude. the in a fourth microwave amplitude third, the steady-state output of said detection means in the fourth frequency is measured, the third from the measurement of the steady-state <br/> output, a fourth microwave amplitude An atomic clock according to claim 3, comprising: means for generating an applied amplitude correction. 6. A method for applying a microwave to an atomic beam.
The frequency of the microwaveAnd amplitudeWith adjustment means
A microwave source and the source after application of the microwave;
Related to the number of atoms in a given state in the child beam
An atomic clock having detection means for outputting a signal.
And the following description for controlling the microwave source.
Atomic clock micro including steps (a) to (b)
Wave source control method: (a) First, second, third, fourthPredeterminedThe frequency
The detection means for each of the microwavessteady stateOutput
eachEachStep to decideThe  (B) A frequency compensator for applying to the frequency adjusting means.
Steps to determine positive,and (C) the frequency of the microwave according to the frequency correction
Steps to adjust . 7. The first and second frequencies are paired at equal intervals above and below a first center frequency, and the third and fourth frequencies are equally spaced above and below a second center frequency. 7. The method of controlling a microwave generation source of an atomic clock according to claim 6, wherein the pair is separated by a distance. 8. The one frequency of each of said pairs, wherein one frequency of each of said pairs of frequencies is located in a positively sloped region of a response curve output by said detection means as a function of the frequency of said microwave. 8. The method according to claim 7, wherein another frequency corresponding to the frequency is located in a region where the response curve has a negative slope. 9. The microwave generation source further comprises adjusting means for adjusting the amplitude of the microwave, and further comprising: a stationary state of the detecting means at the first and second frequencies at a first microwave amplitude. measuring the status output, said in a second microwave amplitude first, the steady state output of said detection means to measure the second of each frequency, of said measurement
8. The method of controlling a microwave source of an atomic clock according to claim 7, further comprising the step of generating an amplitude correction to be added to the first and second microwave amplitudes from the obtained steady state output . 10. The steady- state output of said detecting means at said third and fourth frequencies at a third microwave amplitude, and said detection at said third and fourth frequencies at a fourth microwave amplitude. 8. The method of claim 7, further comprising measuring a steady state output of the means and generating an amplitude correction to be applied to the third and fourth microwave amplitudes from the measured steady state output. Control method of microwave source of atomic clock. (B) a source for generating an atomic beam, (b) first selecting means for receiving atoms from the atomic beam and selecting atoms in a first state, (c) frequency Microwave injection means for applying a microwave having a frequency determined by the frequency control signal to the atoms in the first state in response to a control signal; and (d) selecting atoms in the second state. (E) detection means for receiving the atoms in the second state and outputting a signal related to the number of the atoms, and (f) detection for each of a pair of predetermined frequencies. Means for measuring the steady state output of the means and said steady state output.
Means for determining a frequency correction from a force, the control means for generating the frequency control signal in response to the frequency correction and causing the microwave injection means to apply a microwave at the pair of predetermined frequencies. An atomic clock comprising: the microwave injection means further comprising: means for adjusting the amplitude of the microwave according to an amplitude control signal; and the control means further comprising: means for generating the amplitude control signal , and in a first microwave amplitude measured steady-state output of said detection means in said pair of predetermined frequencies, measure the steady-state output of said detection means in the pair of predetermined frequency in a second microwave amplitude and, the first from the measurement of the two steady-state output, especially in that it comprises means for generating a second microwave amplitude added amplitude correction Atomic clock to be. 12. A microwave source having means for adjusting the amplitude of a microwave for applying a microwave to an atomic beam, comprising: Atomic clock having detection means for outputting a signal related to a number, control of a microwave generating source of an atomic clock including the following steps (a) to ( c ) for controlling the microwave generating source: Method: (a) determining, at a first amplitude of the microwave, a first steady-state output of the detection means for each of the microwaves at first, second, third, and fourth frequencies , respectively. in a second amplitude of said microwave (b), first, second, third, fourth of said detecting means for each of said microwave frequency second steady state output, respectively Constant steps, and (c) said first, said first from the second steady state output, the step of determining the amplitude correction to be applied to the second amplitude.