DE1491537A1 - Atomic resonance device, in particular Maser oscillator - Google Patents

Description

Priority: October 5, 1964 - V. Ot. v. Ame

No. 401,450 and 401,751

iiie ü.rfindung relates generally Atomresonanaeinriciitungen from Gaszelientyp and insbeoondere. "-. touresonanzvorrichtun ^ s with an improved buffer gas cell and Pui ^ plichtquelle showing a greater gain or a better Rauschubstand and a lower light shift öolche improved gas cell Atomresonanzvorrichtun _ö s are especially useful as a frequency standard (atomizing) or magnetometer.

BATHROOM 0FUGP4AL

909829/0644

Attempts have already been made to obtain continuous vibrations from such a grass cell- ^ toiflresonajuzsyste -:.! under Vc.r./tndun _o of alkali metals as j ^ tonireuoni.nzLied.iuju, but jieut attempts were unsuccessful, v / eil ax parameters for determining the conditions for self-excited ochwin ^ ungen were not optimally designed, au /.continuitrlicue to obtain self-excited microwave waves. For example, the overstaffing of the den liikru ^ elxenübei'un _fj bcötiiiuiiencten jinergieniveuus is not sufficient a ^ roso . to maintain vibrations with i-iUcl ^ ic ^ .t on doii realizable quality factor of the _{cavity coupled with the transition fc.}

In a preferred embodiment of the invention it was found that the overstaffing of the internal _o ieneveaus, which are decisive for the microvial transfer of the coiuresoriciiizsysteiiis, considerably through the use of certain critical prints an extinguishing gas component ira buffer gas of the .utoinresonc.nzzelle can be increased. This ritual pressure of the release gas, for example, iron nitrogen, prevents an optical re-radiation caused by the overcrowded person. Sub-levels with higher energy of the general state of the /.toiaü, in that such undesired down-radiation is eliminated. The quenching gas thus considerably improves the amplification of the toruresonarizeinheit and, in the case of a maser, enables maser oscillation, or an improved noise clearance in a non-graining device, for example an optically pumped and over-

909829/0644 BAD origin ^ .-

woke frequency normal, as it is in the Uü patent application

J2J, 374 of August 7, 1Q61. ^ (German patent application V 22 848)

In the case of optically pumped atomic resonance devices, it has already been established that the resonance frequency of the atoms responds to changes in the intensity of the pumped light. Such changes in the resonance frequency of the high frequency (microwave) transition of the atoms with changes in intensity in the pump light are referred to as "light shifts" ^1. It was observed that the light shift was a puncture of the frequency of the pump light relative to the optical pump transition frequency of the atom. Ls it was found that the shift in light could be eliminated by shifting the frequency of the magnetic field-dependent components of the pump light radiated onto the atoms, cf. ii. Ardjti, "Physical Review", Vol. 124, Ko. 3, Noveuber 1, 1961, o. 300-809 (30ö). The pumping light components were shifted in c.er frequency by changing the magnetic field above the lamp or the filter relatively to the field above the atoms to be pumped Filter cell or lamp must be in the order of magnitude of 500 Gauss. The atoms to be pumped can hardly be relative to such v strong magnetic fields are shielded, and an elimination of light shifts in this way should therefore be avoided as far as possible.

In another embodiment of the invention, undesirable Light shifts in the atomic resonance frequency of the

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observed atoms by using two separate light sources canceled, the spectral resonance line of one being slightly above the optical pumping transition frequency of the one to be pumped Atoms, and the spectral resonance line of the other pump light source is slightly below the optical pump transition frequency of the atoms to be pumped lies, so that the positive and negative light shifts mentioned cancel each other out, whereby overall results in an effective light shift of v / ert zero. The tuning of the spectral lines of the pump light is done by Skilful choice of the carrier gas in the lamps or filters, the lamp and / or filter temperature, the isotopic composition in the lamps and / or filters, the lamp and / or filter shape and the way in which the lamp is energized. The state of a Zero light shift is easily determined by changing the intensity of both light sources simultaneously without that the intensity ratio is disturbed. Such a change must not include a change in the radio frequency or microwave resonance frequency of the pumped atoms cause when the relative intensities and frequencies of the spectral lines of the light sources are correctly selected.

The main object of the invention is to provide an improved gas cell atomic resonance device to make available that has an improved signal-to-noise ratio and / or lower light shift and which is particularly suitable, for example, as a frequency standard or magnetometer.

909829 / 06U -5-

According to one feature of the invention, an extinguishing gas component is contained in the buffer gas of the gas cell of the atomic resonance unit, and this quenching gas has a pressure in a certain optimal critical pressure range in order to amplify the atomic resonance ensemble to increase so that marsher vibrations can be obtained or an improved signal-to-noise ratio.

In particular, the extinguishing gas component of the buffer gas is nitrogen, and the critical pressure range is between 5 and 20 Torr at 20 ^° C.

According to the invention, a cavity resonator is also made available, which at the same time acts as an alkali metal gas vessel or cell serves, in which the gas-facing inner walls of the cavity are made of copper, steel, aluminum or mica, so that no separate gas container is more required and the Viandwerkstoff not with the alkali metal vapor of the atomic resonance unit reacts at operating temperatures.

Furthermore, an atomic resonance gas cell is available according to the invention made, which is a temperature coefficient of the buffer gas which corresponds to the temperature coefficient of the microwave cavity, which surrounds the gas and interacts with it, is opposite, so that a serving as a gas cell Cavity results, the microwave atomic resonance frequency of which is relatively insensitive to temperature changes in the environment.

! 0S $ 39 / Ö $ 44 ⁸

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Next, according to the invention, two light sources are used Pumping of the observed atoms is used, one of which has a positive light shift and the other a negative light shift having, the intensity ratio of the Light sources is dimensioned so that there is an essentially negligible shift in light of the pumped atoms.

In particular, according to the invention, the lamp has one light source a positive light shift and the other lamp of the

second light source a negative light shift.

Expediently, in a further embodiment of the invention two separately variable light transmission filters are provided in order to increase the intensity of the respective lamp pumping atomic accumulation of sent light.

Further features and advantages of the invention emerge from the following description in conjunction with the drawing; it ' demonstrate:

1 shows a schematic longitudinal section through an atomic fiber with features of the invention;

Pig. 2 a term scheme of Rb (not to scale);

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3 graphically shows the gain for Rb as a function of Buffer gas pressure for various buffer gases;

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Pig, 4 the gain as a function of the buffer gas partial pressure with various mixtures of nitrogen and other buffer gases;

Fig. 5 shows the gain and bandwidth as a function of the Temperature of the atomic gas cell;

6 shows a longitudinal section through a cavity resonator and gas cell with features of the invention;

Figure 7 is a cross section taken along line 7-7 in Figure 6;

8 shows the dependence of the frequency deviation on the temperature of buffer gas cell and cavity resonator;

9 shows a combination of term scheme and spectral resonance curve

87 R * S

for the optical pumping junctions for Rb 'and Rb ^;

87 Fig. 10 part of a term schema for Rb for the representation of the Effect of optical pump radiation on the microwave

87
Crossover frequency of Rb; and

11 schematically shows a cell according to the invention with an optical Pumping from two sources.

-8th-

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In Fig. 1, a rubidium burl is shown with features of the invention. In particular, a cavity resonator 1, which is dimensioned for operation in the TEqqi mode, accommodates about 2 mg of pure metallic Rb at room temperature. The cavity is then filled with a suitable buffer gas, for example pure nitrogen under a pressure of preferably about 11 torr at room temperature. Nitrogen as a component of the buffer gas has particular advantages, which are explained in more detail below. In operation, the cavity is ^{heated to about 60 0} O, at this temperature

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temperature, the metallic Rb evaporates and mixes with the buffer gas.

A wall of the cavity 1 is perforated to receive resonance radiation light for optically pumping the rubidium atoms into a higher energy level. The optical pumping mechanism will later in connection with FIGS. 2 and 3 explained. The perforated wall 2 of the cavity resonator 1 has a suitable light permeability for example 50 ^. A glass window 3 is tight placed over the perforated wall 2 so that the cavity resonator 1 can also serve as a gas cell. Usual non-magnetic Closing techniques Glass - metal are used to close the window.

87
An Rb lamp 4, for example a Varian type lamp

X-49-609 is arranged so that the light beam enters the cavity 1 through the perforated wall 2. A Rb ^Ö5 filter 5

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R7 is in the light path between cavity 1 and Rb lamp 4

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arranged to avoid certain unwanted spectral lines of the Rb-

location

Filter out the lamp so that the Rb atoms in cavity 1 are optical can be pumped. The optical pumping empties the sub-level

87
]? = 1 of the ground state of the Rb atoms, in that transitions of the atom into higher excited energy levels are effected, from which the atoms return with equal probability to the two levels F = 1 and P = 2 of the ground state; but because the level P = 1 of the ground state is constantly emptied by the optical pumping, there is an overcrowding of the level P = 2 of the ground state, and excited coherent radiation emission can be obtained from this.

A number of magnetic shieldings 6, for example closed cylinders made of MoIy Permalloy, enclose the cavity 1 in order to reduce the size of externally generated magnetic fields. In addition, a furnace 7 is disposed inside of the shields 6, to the various elements of the device to keep including the gas cell at a preferred operating temperature, for example, 6O ⁰ C.

A microwave output connection is formed by a waveguide section 8, which _{is coupled to the TE 0n} ~ mode of the cavity 1 via a diaphragm 9. A Miea-Penster 11 is gas-tight

placed via the waveguide 8 on the output flange 12. Three lower ones

right to each other, i.e. along the x, y and z axes / and in the same direction Heimholtz coil pairs 13 connected in series are arranged around the cavity 1, and are each of one

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individually adjustable direct current source 14 energized. Coil pairs 13 serve, the remaining static magnetic field in the area of the gas atoms within the cavity 1 to any desired To bring direction and size. Preferably the coils are adjusted so that they see a small, uniform one magnetic polarization field H of, for example, 1 milligauss, which is directed axially to the cavity 1.

In operation, the lamp 4 and the filter 5 form a source for optical radiation, which serves to reduce the sublevel of the hyp ^ rfine structure F = 2 of the ground state of the Rb atoms that make up the atomic resonance unit Form in cavity 1, overcrowded. The cavity resonator 1 is to the ground state hyperfine structure transition frequency (F = 2, M = O- * F = 1, M = O) matched by about 6 835 MIIz. With optimal setting of the coils 13, the pump light intensity, the cavity tuning and the temperatures of the Filter 5 and the cavity 1, the gain of the atomic resonance unit is greater than 1, so that statistical microwave transitions from the hyperfine structure energy level F = 2 to the hyperfine structure energy level F = 1 excite the cavity resonator in such a way that the fields in the cavity react back on the gas atoms, so that there is a coherent, self-sustaining continuous radiation emission at the hyperfine structure resonance frequency results. Mn part of the microwave resonance signal is then coupled out of the cavity 1 via the output connection and fed to a suitable consumer.

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ills Maser oscillator working on a field-independent transition the device according to FIG. 1 results in an extremely simple secondary frequency normal with previously unknown short-term stability from 1:10. In addition, this Maser oscillator makes a

12 Long-term stability in the order of 1:10

The maser oscillator according to FIG. 1 can be operated in more than one essentially field-independent operating mode. At a The preferred operating mode is excited radiation emission obtained from a pure hyperfine structure transition, i.e. the Zeeiuan sub-levels are frequency-wise from the desired transition (F-2, w = 0- ♦ F = 1, m = 0) separated, so that essentially only the desired field-independent transition is observed. In general, this separation of the Zeeman sub-levels is obtained, when the accumulation of Rb atoms in a magnetic polarization field H of more than 100 Hikrogauss is immersed. In this operating mode, however, the field-dependent hyperfine structure transitions do not contribute to the field-independent hyperfine structure transitions at, and the enhancement of gas atom accumulation (or the resonance exaggeration) is smaller than that obtained when the field H is less than 100 microgauss is reduced. Other parameters that determine the maser conditions need to be improved in order to increase the maser vibration obtain. In particular, it must be the temperature of the atomic cluster can be optimally chosen to improve the gain, and the quality factor of the cavity can be increased by adding a

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Larger volume cavity is used, which is in one of the higher smoke ring modes works to improve the grain conditions.

The second, essentially field-independent operating mode of the maser oscillator according to FIG. 1 is one in which the screens 6 and the coils 13 serve to reduce the magnetic field above the accumulation of gas atoms in the cavity 1 to less than 100 microgauss, so that the Zeeman sub-levels with the desired Transition (F = 2, m = 0 -? F = 1, m = 0) combine, thus increasing the gain the accumulation is increased. This combination of the Zeeman sub-levels results in a tendency to increase the gain of the whole, however, broadens the resonance line and brings some dependence on fluctuations in the magnetic Environment with itself. For applications as a frequency standard or atomic clock, the first mentioned is therefore field-independent Operating mode preferable.

The optical pumping mechanism, which is preferably used in a maser according to FIG. 1, will now be described in connection with FIG. explained. This preferred pumping technique is called "intensity" punipen and is described in "The Review of Scientific Instruments", Vol. 35, No. 7, July 1964, p. 857 ff.

In short, intensity pumping consists of an Rb filter 5 between the Rb light source 4 and the one to be pumped

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Accumulation is used. The Rb filter 5 contains a mixture

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of Rb and argon gas below 52 Torr at 20 ⁰ C and filters out certain resonance lines of the lamp 4 in order to achieve the desired overpopulation

location

of the level F = 2 of the S level of the Rb atoms, the can then be excited to pass their energy coherently to the cavity resonator 1 in a continuous, self-sustaining manner Way to deliver.

The effect of the extinguishing gas on the amplification or the resonance

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Exaggeration of the accumulation of Rb atoms is shown in FIGS. 3 and clearly. Bs was found that when using nitrogen extinguishing gas used as a component of the buffer gas for Rb in a critical range of 5-20 Torr at room temperature the gain is increased significantly, with the peak value for the gain in accumulation at a partial pressure of nitrogen of about 11 Torr (see Pig. 3). Nitrogen shows a substantial improvement in gain in comparison with other buffer gases such as neon, helium, argon or hydrogen, the amplification characteristics of which are shown in fig. are shown.

Although the maximum gain was achieved with pure extinguishing buffer gas, it is not necessary that all of the buffer gas consists entirely of extinguishing gas. It was further established that the extinguishing gas mixed with other gases such as neon, argon and helium under the critical partial pressure

87 can be. The amplification characteristics of Rb atoms in the mixtures of buffer gases containing the extinguishing gas are

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in Pig. 4 shown. From this it can be seen that for buffer gas mixtures, contain the extinguishing gas as a constituent under a partial pressure between 5 and 20 Torr Enhancement of the enhancement of the atomic aggregation results.

The complete mechanism of the gain improvement due to extinguishing gas is theoretically not clear, the following consideration should, however, come close to the actual conditions: a re-emission from the excited levels 5P empties the Levels]? = 2 and thus significantly reduces the pumping efficiency. A re-emission can be caused by collisions of the second kind with Buffer gas atoms are prevented. During these collisions, the rubidium is de-excited by transferring the energy to the quenching buffer gas atom is transmitted. This process is called "deletion" and is defined by the parameter L:

τ intensity of re-radiation with buffer gas 1

Intensity of re-emission without buffer gas 1 + γ Z

/ ² L

Y = lifetime of excited atoms Z _T = rate of extinguishing collisions

Yy

The theory and mechanism of quenching is discussed in A.G.G. Mitchell and M.W. Zeioansky, Resonance Radiation and Excited Atoms (Cambridge at the university Press, 1961), p. 192 and Peter Pringsheim,! Fluorescence and Phosphorescence (Interscience Publishers, Hew York, 1945). In most cases there are detailed calculations of the deletion process

90 ^ 829/064 *

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very complicated and the process is not completely clear in theory. Suffice it to say, however, that it is with Buffer peas such as nitrogen appears to be an almost complete one Delete.

In Pig. 5 shows the gain and bandwidth as a function of the temperature of the cavity 1; from this curve shows that the cavity should preferably be operated at about 6O ⁰ G. This temperature results in a considerable gain with a relatively small bandwidth of the desired transition (F = 2, Ui = O - * F = 1, ia = 0). This desired operating temperature is maintained with the furnace 7.

In Pig. 6 is another embodiment of a maser cavity reconator illustrated with features of the invention. The cavity is briefly described above, in detail it consists of one Liohlzylindischen main vessel 21, for example made of stainless Steel that is plated with copper on the inside in order to obtain good conductivity and thus a high quality factor. This cavity is closed at one end with a cover plate arrangement 22 which is provided with a puddle and which is gas-tight ..n a part of the tank with a similar splash 21 is connected with a gas-tight ring seal 23. The end plate assembly 22 has an inwardly protruding one End wall 24, which acts as an end wall of the cavity 1 serves. The membrane is deformable by means of a threaded spindle arrangement 25, so that the cavity over a sufficient frequency range, about + b MHz can be tuned.

90-9829 / 0844- ^: ^ original

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The other end wall of the cavity is formed by a perforated plate 26, which is provided with a plurality of bores small diameter, for example 3 mm, is provided. The openings are arranged so that the total permeability of perforated wall 26 is about $ 50. The thickness of the wall is preferably larger than the diameter of the holes so that little high frequency energy emerges from the cavity through the holes can. The main vessel 21 is sealed gas-tight at one end with a glass window 27, which over the open end a thin walled tube 28 is mounted in a manner similar to a housekeeper termination. The window arrangement 27 is with two matching flanges 29 and a seal 31 attached to the main vessel 21 in a gas-tight manner.

A hollow cylindrical, evacuated glass vessel 32 is in the room arranged between the window 27 and the perforated wall 26 to prevent undesirable absorption of the optical resonance radiation

87
from the lamp 4 by Rb gas which would otherwise fill the space between the window 27 and the perforated plate 26. In this way, an effective utilization of the resonance radiation is achieved.

The cavity 21 consists of non-reactive, non-magnetic Material that does not react with the alkali metal vapor. It was found that suitable cavity materials are less magnetic stainless steel, aluminum, copper and mica are.

909829/0844 ¹⁷

There are many other non-magnetic materials that are not suitable because they ^{react with the rubidium vapor in the operating range of 20-80 0} O, there are many unsuitable materials, only Teflon, gold and various epoxy glue should be mentioned.

The cavity resonator 21 should have as large a quality factor as possible. The surfaces of the cavity guiding the microwave field should therefore have a high conductivity. Of the non-magnetic, non-reactive materials, copper is best suited to form this inner surface that guides the field. Correspondingly, the inner surfaces of the cavity 21, which guide the face, are plated with copper. In a preferred embodiment of the cavity, the vessel 21 is made of stainless steel, in order to achieve the necessary strength, and the inner surfaces are plated with copper. In a preferred embodiment, the quality factor of the cavity is also improved in that a large ratio of cavity volume to surface is used. This is achieved in that the cavity for operation in a high TE _{Q m} ~ mode is designed, for example, the mode TE _{Q 2} -] ^f or the transition F = 2, m = 0 τ * F = 1, m = 0th

FIG. 8 shows the dependence of the resonance frequency of the maser on the temperature, specifically the frequency deviation of the resonance transition due to the buffer gas, such as Nitrogen, and the frequency shift of the cavity due to it

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the thermal expansion of the cavity resonator. Bs was found that / to achieve an against temperature changes in the environment insensitive gas cell frequency normal is possible, to compensate the temperature coefficient of the resonance cavity by a temperature coefficient of the buffer gas. In particular If the buffer gas is nitrogen and the cavity resonator is made of stainless steel, the temperature coefficients be determined in such a way that they work in opposite directions, so that they compensate each other with a suitable ratio. In this way, the grain frequency remains constant or stable over a relatively large temperature range.

The mechanism of this temperature compensation is to be understood more precisely as follows:

The coordinated cavity and the accumulation of atoms form a coupled system. When the cavity resonance frequency does not coincide with the atomic transition frequency, the compiled * set vibration frequency is not equal to the atomic resonance frequency. This effect is described by the expression

where "V = oscillation frequency

\> 0 = atomic transition frequency ν _Λ = cavity resonance frequency = cavity quality factor
= Spectral line quality factor

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From this expression it can be seen that when the atomic transition frequency 'V is not equal to the cavity resonance frequency% k, the oscillator frequency V is not equal to the atomic transition frequency XZ ₀ , in other words the frequency is drawn.

From the above equation, the pulling through the cavity results in

Sy ( )

(SL ₁

planes Rb '-Ma
This results in

In the Rb 'grain _{described above, Q is 0} ^ IO and Q ^ a * 10.

V ^ / cavity " ¹⁰
If (aaLj ^ ₁ 10 * "^ is desired , it follows that (- ^) v- * y ^ J = A ^ c. Must be less than 68 Hz.

Now let's consider the effect of temperature on pulling through the cavity

is the change in the magnetic resonance frequency with temperature,

which is mainly caused by the buffer gas.

A compensation for frequency shifts, which are caused by both the buffer gas and the cavity pulling, is achieved in the following way:

^Buffer gas = ^{+ 6 Hs} P r0 ° ^G P ^{ro cm ki} 2

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is now made negative and chosen so that the following Relationship is fulfilled:

ST ■ Ir # /

In this way, at least as a first approximation, it compensates for the frequency shift the frequency shift due to the buffer gas due to the cavity.

After this compensation, the cavity should be adjusted to the center of the * spectral line. The composite resonance frequency changes with the figure of merit and frequencies as follows:

It follows that the rate of change of the vibration frequency with the line width (Q) is only zero when the cavity is tuned

In the case of the Kb mesh, the line width or gain cannot be easily changed by changing the Rb pressure; however, the gain and Q- can easily be changed by bringing the magnetic field through the field zero state. At field zero, the effective occupation of Rb is highest because atoms in the states F = 2, m ^ O and F = 2, m _f = + 1 all contribute to the excess occupation that is available for grain effect. If the fields are large enough to resolve the various hyperfine structure Zeeman components (several 100 microgauss), only the occupation of the state F = 2, m _f = 0 contributes to the grain effect. So atomic reinforcement can easily get through

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Setting of the field modified from zero to a few 100 microgauss will. The cavity is then tuned so that the maser frequency does not change when the field is within it Area is adjusted.

In connection with FIGS. 2, 9-11 is said to be the mechanism of displacement of the light are described, followed by a description of the novel pump light source according to the invention, can be eliminated with the pump light shifts.

For an uncorrected pump source for a rubidium maser it was found that the frequency of the field-independent microwave transition (F = 2, m = 0-> F = 1, m = 0) around the high value of 40 Hz changes when the pumping light intensity is changed from zero to full. This shift in light results from the slight remote resonance of the pump line from the lamp compared to the observed accumulation of gas atoms. The term scheme of

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Rb is shown in FIG. In a preferred method of the

87 87

optical pumping, the Rb resonance radiation is

QC

The lamp is filtered in an Rb filter in order to filter out certain undesirable spectral resonance lines in the optical resonance radiation of the lamp, so that a stronger optical pumping is achieved from level F = 1 than from level F = 2. The optical pumping

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empties the sub-level F = 1 of the ground state of the Rb atoms by stimulating the transitions of the atoms into more highly excited energy states, e.g. excited P levels, from which the atoms are equally likely to move into the levels F = 1 and F = 2 des

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Return to the basic state, but share the level F = 1 dee Basic state is continuously emptied by optical pumping, there is an overstaffing of the sub-level F = 2 of the basic state, so that an energy imbalance is caused, from which microwave transitions to level F = 1 with a Crossover frequency of about 6,835 MHz can be achieved.

87
In optical pumping for Rb atoms, two primary opectral resonance lines are of interest, one at around 7,947 Λϋ and the other at around 7,800 AU. These optical transitions correspond to transitions between the level 5 ^s i / -j ^ d and the levels 5 fi / p

ρ
or 5 1 * ^ / 2 ^ ^u ^ reason for the splitting of the ground state,

Level b, split the two primary optical correspondence lines of 7,947 AU and 7,800 AS respectively into two lines, uie serves on the original lines 7,947 AU and 7,800 ^ 1. Running, split lines or doublets differ in frequency by about the microwave frequency of the hyperfine structure transition between the sub-levels of the ground state or 6- level levels.

H7

Purely the resonance line 7 800 Au of 2b are the! Doublets in Pig. 9 shown as resonance lines a and b, where a has the lower frequency of the doublet. In the Palle of the line 7 800 AE from RB the split lines of the doublet lie in terms of frequency closer together, they are shown as lines A and B, respectively. The line b of Rb 'is of course the line that the one to be pumped R7

Rb atoms should be added because this line is the sub-

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level F = 1 of the ground state of the atoms pumps, which results in an overcrowding of the sublevel F = 2. The relative positions of the hyperfine structure lines of Rb ⁸⁷ and Rb ⁵ at 7,800 AU are shown in FIG. Lines a and b are around 1,300 MHz
apart, the distance between the other lines' is greater than
2 5OU 1 · ίΗζ. By widening the buffer gas and shifting it into
lib filter, for example by increasing the argon gas pressure to 52 Torr, line A can be set so that it
line a absorbs, but line B does not absorb line b.

The opectral profiles of the lamp and filter, which are just for the
Hubidium line 7 800 A3 also apply to line 7 947 A! J. "Qi e line 7 947 AE exists for both Rb

-R

as f-uch Rb from a doublet. The low frequency component

■ 7
the Rb ⁴ "doublet is absorbed by the low-frequency line of the doublet deo Hb filter, while the high-frequency,

o'7 H 7

wanted Rb -iJublettencomponent from the Rb -lamp through the Rb filter passes through so that the Rb atoms are pumped. f

jjasf. Advantages of light shift depend on the spectral profile of the jump light in the following way: Jenn the punip light on
the low-frequency side of the atomic transition to be pumped is centered (ih lri.'i according to Fig. 10, the atomic level F = 1 is shifted to low, erer "Jiergie, v / emi aas pumplicht on the Iiochfreoue-IILe beite des .- ».Tomresonfjizüberg & ngs (h ^ in Fig. 10) is ir!

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shifted towards the value, as indicated in FIG. 10 by -hv ". Low-frequency pump radiation therefore results in a positive light shift and higher-frequency pump light results in a negative one Light shift.

In Pig. Figure 11 shows an optical pumping device with zero light shift. The device uses spectral radiation from two sources, and this radiation is adjusted so that there is one light source with positive light shift and another light source with negative light shift, and the radiations from both light sources are projected into the atomic cluster in order to pump it . A light source with positive or negative Light shift can be obtained. There are further inputs ψ directions provided with which the relative intensities of the spectral lines can be changed from the two sources so that the right intensity ratio can be selected with which a light displacement of zero results in the pumped gas cell.

The parameters of a first spectral lamp 22 are set in such a way that a negative light shift results. A suitable one Lamp 22 is, for example, a Varian X-4 ^ -609 spectral lamp

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for lib, whose parameters are set for negative light shift are. The spectral radiation from the lamp 42 is shown in FIG

87

directed the cavity resonator 1, which contains the Rb atoms, to pump them. A variable transmittance filter 43 is in the light beam of lamp 42 between the lamp and the cavity 1 arranged in order to variably regulate the intensity of the radiation coming from the lamp 42 to the cavity. A suitable one Filter 43 with variable transmittance consists, for example, of two polarization filters, an electro-optical crystal, or a Kerr cell. Between the filter 43 with variable permeability and the cavity 1 is the aforementioned Hb filter arranged, with the unwanted spectral lines of the lamp 42 are filtered out to a stronger occupation det, upper Hyperfine structure level of the basic state of the pumped To evoke rubidium atoms.

A second lamp 45, similar to lamp 42, is provided, the light beam of which is substantially perpendicular to the light beam from the first lamp 42 is directed. A semi-reflective or semi-transparent mirror 46 is at the point of intersection of the two light beams arranged and inclined 45 ° to the beam in order to reflect the optical radiation from the second lamp into the cavity 1, to pump the atomic particles in it, but at the same time to let light through from the first lamp to the cavity. The parameters of the Lamp 45 are set so that there is a positive shift in light. A filter 47 with variable permeability is in the light beam of the second lamp 45 between the lamp and the

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Mirror 46 arranged to increase the intensity of the optical radiation to be able to regulate variably from the lamp 45 to the cavity 1. That Filter 47 with variable transmission is constructed similarly to filter 43 and operates on the same level.

A second optical radiation filter 48, for example one Rb cell is in the V / eg of the ray from the second lam ^ e 45 between the transmission filter 47 and the mirror 46 are arranged in order to filter out certain undesired spectral lines of the lamp 45, P so that the optical radiation passed on by the mirror 46 into the cavity 1 overcrowds the upper hyperfine structure level of the ground state of the Rb atoms.

.Sin third filter 49 with variable permeability ibt im combined beam path for the light from both lamps 42, 45 arranged to the total intensity of the superimposed To regulate light beams. The filter 49 with variable permeability can be constructed similarly to the filters 43 and 47, respectively.

In operation, the intensity ratio of the spectral radiation is positive and negative shift in light emitted by the lamps and 45 is sent to the cavity 1, with the filters 43, 47 with variable permeability adjusted so that when there is a change of the filter 49, no light shift is observed.

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For the light shift compensation technique, it is zero necessary that the cavity 1 is precisely matched. If this condition is not met, there is a frequency shift, if the total light intensity is changed, even when the light shift is zero. The overall resonance frequency changes with the quality factor and the frequencies as follows:

with \ "= oscillation frequency of the gas cell serving

Cavity
i ~, = £ itomijche microwave or high frequency crossover frequency

l ' _c - cavity resonance frequency
• 4 = cavity quality factor

■ j-, = quality factor of the atomic line of the transition frequency.

The result is that the rate of change of the oscillation frequency with the line width (Q-,) is only zero if the cavity is tuned (f _c = t ' _r ).

In the case of the Rb mesh, the line width or gain cannot be easily changed by changing the Rb pressure; however, the gain and Q ^ can easily be changed by changing the in-line field to the field zero state. At field zero the effective occupation of the Rb is strongest because all -.toiae in the states F = 2, τψ = Ο and F = 2, m _f = + 1 all contribute to the overcrowding that is available for the grain effect. because the field strengths are large enough to handle the various Hyper

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to resolve fine-structure Zeenian components (several hundred microgauss), only the occupation of F = 2, m,. = 0 contributes to the grain effect at. The atomic gain can easily be modified by adjusting the field from zero to a few hundred microgauss. The cavity is then tuned to match the grain frequency does not change if the field is changed within this area.

The arrangement shown in FIG. 11 results in a pump light with zero light shift. The aging of the lamps 42 and 45 or however, the filters 44 and 48 can produce a change in the opectral profile of the light sources, which again results in a shift in light can result. Devices are therefore provided to automatically monitor the displacement of light, see above that there is an error Poick coupling signal with which the The intensity ratio of the two light beams is readjusted, to get the state light shift Hull for the compound Light source 4 and 5 maintain.

More precisely, the automatic light shift locking circuit consists of a light transmission modulator 52 which supplies a suitable low-frequency electrical voltage, for example of 400 Hz, to the variable filter 49 common to both beams, for example a Kerr cell. The low frequency thus effects an amplitude modulation of the two combined pump light beams. If there is a light shift in the grain output frequency, this is .frequency modulated with the low frequency.

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Mn frequency modulation detector 53 is at the output of the maser an ^ euchloütieii to determine the low frequency modulation and convert them into a low-frequency, unplitude-modulated signal to convert. The low-frequency signal obtained is then with dom ui's original modulation signal compared to that of the through-laser modulator 5 ^ is derived, namely in a phase-sensitive Detector 54, so that there is an error direct current, the d -'- m one or the other of the filters with variable Permeability, for example the filter 47, is supplied, on the intensity ratio of the light beam with positive Shift of light to the light beam with negative shift of light au regulate to correct the ratio for Li cJutver shift zero maintain.

In a preferred Ausführungsforia the optical pumping device of FIG. Constituted 11, that is, both beams exit from the same Richtug and are superimposed by means of a semi-transparent mirror 46 side, however, AES is not necessary that the light beams are superimposed on one another and from the same direction enter the cavity. For example, they can be fed into the cavity from both directions if it is provided with two perforated end walls.

The invention has been described in its application to an optically pumped continuously operating Maser oscillator, which is suitable as a frequency standard or magnetometer. The inven- '

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However, manure is just as good on optically pumped and optically Monitored atomic resonance devices can be used such as frequency standards and magnetometers, as they are in the older German Application V 13 327 IX, '42h of the applicant are described.

The atomic resonance device already mentioned is not limited to Rb atoms alone. Certain other isotopes from others Metals such as thallium, sodium, potassium and jäsi can be used. Every electron-electron orientation transition or any resonance in atoms or molecules for which the net./angular moment f of the atoms or molecules is a whole Number in quantum units of the Plank'schien .- / irkungsquan turn h, can be used. In general, it is thought that any collection of molecules or atoms with the desired Hesonance properties can be used. The term "ij.tom" is intended to therefore, in conjunction with the present description and claims, apply to both atoms and molecules.

Claims

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Claims (1)

PATENT ADVOCATE IAQI DIPL.-ING. H. KLAUS BERNHARDT ' ** * ' 8000 MÖNCHEN 23 MAINZERSTR. 5 V1 P71 D Si Patent claims: I1.) ^ Tcureüonanzvorrichtung, in particular Maser oscillator, consisting of a collection of atoms in the gaseous aggregate state in a container and a device "with which a high-frequency resonance of the atoms is caused and determined, characterized in that the container also with a Buffer gas (neon, argon) is filled, which ensures gas-gas collisions of the atoms, so that a predominant gas-gas collision restriction mechanism results, with which the diffusion time of the atoms to the walls of the container is increased, and having a Löschgasbestandtoil (nitrogen) under a partial pressure of 5 to 20 Torr at room temperature, by the results in a better response of the ä atoms. 2. Apparatus according to claim 1, characterized in that the extinguishing gas is nitrogen. 3. Apparatus according to claim 1 or 2 with one on the resonance frequency of the atoms coordinated and enclosing the atoms Honlraumresonator, of which if necessary an i / and ■ 909829/0644 - U91537 is translucent, so that an optical pump radiation can occur, characterized in that the walls of the cavity resonator directly as a gas-tight container for the atoms serve and are made of non-magnetic stainless steel, aluminum, lüca or copper. 4. Apparatus according to claim 3, characterized in that the cavity resonator (1) is so constructed, dimensioned and arranged is that its resonance frequency changes in one sense with changes in temperature, and the .atomic cluster has a temperature coefficient such that the atomic resonance frequency changes in opposite directions when the temperature changes Meaning to change the Hohlrauraresonatorresonanz changes so that the resonance frequency of the entirety of the cavity resonator - atomic collection is essentially independent of Temperature fluctuations is * 5. Device according to one of claims 1-4, characterized marked ψ is characterized in that the nuclear accumulation consisting of atoms of alkali vapor. 6. Apparatus according to claim 5, characterized in that RV
the atoms are Rb atoms. 7. Apparatus according to claim 3 and 6, characterized in that that the source for the optical pump radiation from an Rb- 85 Lamp and an Rb filter, with which certain unwanted resonance spectral lines from the radiation of the Rb lamp be filtered out. 909829/0644 H91537 ο. Device according to claim 7, characterized in that the collection of atoms arranged in a magnetic screen (ό) is that of the magnetic field in the area of the ntoae to less than 100 Mii-.rogauss, so that certain Zeeuan sub-levels the atomic resonance lines combine with the field-independent lines and get a better gain, and wünuchteni'alls a maser oscillation of the .ttoiue results. 9e device according to claim 6, 7 or -3, characterized in that the atom collection is accommodated in a furnace (7) with which the Hb atoms are kept at a temperature between 50 G and 70 ⁰ O in order to achieve a better resonance achieve. 10. Device according to one of claims 3-9, characterized in that that two pump light sources (42, 45) are provided, one of which (42) has such a spectral profile, that it irradiates the accumulation of atoms with a resonance distribution, a negative shift in light in the pumped atoms, and the other (45) has such a spectral profile that it causes the Atouansamuilung with a resonance radiation irradiated, which causes a positive light shift in the pumped atoms, and that the intensity ratio of the two pump light sources is dimensioned so that the high-frequency atomic resonance frequency of the i \ tomans £ iranung essentially independent of proportional changes in the overall intensity of the Puinplichtes. A ORIGINAL 909829/0644 ~ ^A4 ~ 3H 11. The device according to claim 10, dr.durch gekennzeichiu I that a device (49) for the variable liti.elunü ο er ü-eaamtintensitiit of the pump light is provided, io that Liehtverschiebun ^ en can be determined. 12. Apparatus according to claim 10 or 11, characterized in that that a device (47) for the variable iie ^ elation of the intensity ratio of the two PumplicLtcr · is provided, This is how the G-esaint-LichtverochifcLung Vc.riu'uel ^ ere ^ elt '.ve rden can. 13. Apparatus according to claim 11 and 12, characterized in that that the device (49) for variable regulation of the total intensity of the pumping light from a Lurchlassmodulctor (52) is controlled, which is connected to Jetektcren (53 »54), which, when the light adjustment occurs, an error signal is generated supply, the devices (47) for controlling the intensity s relation:; ses in the direction of a miniiaiile light loss P shift controls. 14. Device according to: x claim 11, λΖ oaer 13, de.'lurch characterized, üc.3 a Puraplichtquelle (42) iLre Pumpstruhlung through the translucent part (2) of the iioiilraumreson £ .tors (1) sends a semitransparent mirror ( 46) in the in 1 direction to the hollow BAD OFUGINAL 909829/0644 -A5- resonator (1) reflected, and that the device (49) for -iet.elung the accumulated intensity of the pump light between the semitransparent mirror (46) and your cavity resonator (1) is arik-iordered. 909829/0644