US3667066A - Optically pumped alkali atomic beam frequency standard - Google Patents

Optically pumped alkali atomic beam frequency standard Download PDF

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US3667066A
US3667066A US840139A US3667066DA US3667066A US 3667066 A US3667066 A US 3667066A US 840139 A US840139 A US 840139A US 3667066D A US3667066D A US 3667066DA US 3667066 A US3667066 A US 3667066A
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frequency
atoms
level
levels
state
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Alfred Kastler
Maurice Arditi
Pierre Cerez
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Bpifrance Financement SA
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Agence National de Valorisation de la Recherche ANVAR
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H3/00—Production or acceleration of neutral particle beams, e.g. molecular or atomic beams
    • G—PHYSICS
    • G04—HOROLOGY
    • G04F—TIME-INTERVAL MEASURING
    • G04F5/00—Apparatus for producing preselected time intervals for use as timing standards
    • G04F5/14—Apparatus for producing preselected time intervals for use as timing standards using atomic clocks

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  • the frequency standard comprises an oven producing a beam of Rb and Rb", a lamp using Rb for enriching the level F
  • Foreign Application Priority Data 1 of the fundamental state of the atoms of Rb a hyperfrequency cavity equalizing the population of the levels F 1, July 8, 1968 France ..l5824l p 0 and F: 2, "1F: 0 of this State a lamp using Rb or natural Rb filtered by a vat containing Rb for producing transitions between the levels F l of the fundamental state and an excited level, and a detector completed by an elec- [58] Field of Search 33 l/3, 94, 324/.5 F manic unit coupfing a quartz ,oscmamr to the atomic resonance.
  • An object of this invention is to provide a standard or clock having a very great stability of frequency, especially in the long term, and constituting a primary or absolute standard of frequency, its resonance frequency being very near to the Bohr frequency of the free atom.
  • an atomic clock or frequency standard which uses a beam of atoms, in particular alkali atoms and more particularly still rubidium, comprising at least three levels of progressively increasing energy, namely two levels E and E in the fundamental state and one level E in the excited state, is characterized by the fact that this beam of atoms passes, in a vacuum, successively through a zone of optical pumping in which it is illuminated by a source of nonpolarized radiation at a frequency corresponding to the interval of energy between one of the fundamental levels E or E and the excited state E a radiofrequency cavity in which it is subjected to a magnetic field of frequency corresponding to the interval of energy between the levels E and E of the fundamental state, and a zone of optical detection in which it is illuminated by a source of non-polarized radiation at a frequency corresponding to the interval of energy between the other level of the fundamental state IE or E and the excited level E
  • the invention will be well understood with the aid of the following complementary description and the accompanying drawings, which are, of
  • FIG. 1 represents schematically an atomic frequency standard or clock using a beam of rubidium, constructed according to this invention
  • FIG. 2 is a longitudinal axial section through the rubidium oven of the clock of FIG. 1;
  • FIGS. 3 and 4 are cross-sectional views, respectively along lines III-III and IVIV of FIG. 2 in the directions of the arrows;
  • FIG. 5 represents the energy levels of an atom of rubidium
  • FIG. 6 represents the lines (or transitions) of atoms of rubidium 85 and rubidium 87 between the two levels of the fundamental state and a level of the excited state;
  • FIG. 7 illustrates the lines (or transitions) used in the rubidium clocks ofthe prior art
  • FIG. 8 illustrates the lines (or transitions) used in the rubidium clock of FIG. 1;
  • FIGS. 9 to 11 illustrate the lines (or transitions) which can be used in three variants of the clock of FIG. 1, these variants also being constructed according to this invention.
  • FIG. 12 represents the derivative signal obtained experimentally in the clock according to FIG. 1 with two separate radiofrequency cavities and with only a single radiofrequency cavity.
  • an atom in particular an alkali atom, has a fundamental state S and excited states P, D, of increasing energy.
  • the level of the fundamental state is called the level S and the first excited state has two levels P and P because of the fine structure which explains the double lines of the alkali atoms (such as the double line of sodium corresponding to the transitions between the levels P and P on the one hand, and the level S on the other hand).
  • H of constant intensity H the different levels of energy are subdivided into Zeeman sublevels whose spacing is proportional to H in a weak field.
  • FIG. 5 which represents the energy levels of rubidium 87 (Rb”), shows:
  • the magnetic transition between the two levels F 2 and F 1 of the fundamental state S for m; 0, is used to obtain a frequency standard, since this transition is not very sensitive to the effects of the magnetic field.
  • the level B being constituted practically by the levels P P
  • rubidium 87, E E, 6834.6 MHz and E E, or E E, E E is about 7,800-7,950 A.
  • a first magnet (Stem- Gerlach) is used for separating the atoms of the level F 4 and of the level F 3 (whose magnetic moments are of opposite signs) of a beam of atoms of cesium 133 coming from an oven; the atoms of the level F 3 are'deviated, whereas the atoms of the level F 4 move towards the axis and pass through a cavity or rather a pair of cavities in which they undergo a hyperfine transition between the levels F and F,,, a certain number of atoms falling back to the level F After having undergone this hyperfine transition, the atoms in the two states F 3 and F 4 are subjected to the influence of a second magnet which focuses the particles in one of the states onto a detector of the surface ionization type constituted by a tungsten wire heated to 1,000 K, the output current of this
  • the optical pumping method of one of the inventors namely Mr. Alfred Kastler, is used between the levels E, and E .'It is then necessary to irradiate the vapor of rubidium 87 of the cell by radiation of frequency f (E, E, )/(h).
  • the frequency f is very near to the frequency f (E, E, )l( h); it is thus difficult if not impossible to separate the lines f and f by means of ordinary interference-type filters; it 'has been proposed to take advantage of the natural coincidence between the optical lines f,;, of the two isotopes rubidium 85 and rubidium 87 (the lines f, of these two isotopes are distinct).
  • the rubidium 87 of the cell is lit by means of a Rb resonance light source through a filter constituted by a vat containing Rb which only allows the frequency f, E, is thus impoverished while enriching the level E according to the arrow f of FIG. 7.
  • the width of the resonance line is decreased and the effectiveness of the optical pumping is increased by introducing into the cell, in addition to the rubidium 87, an inert gas such as helium, nitrogen, neon or argon.
  • an inert gas such as helium, nitrogen, neon or argon.
  • the collisions of the atoms of Rb with molecules of the buffer gas produce a considerable frequency shift, which is dependent on the nature and the pressure of the buffer gas, sensitive-to the temperature and also sensitive to the intensity of the pumping light.
  • the result is that the resonance frequency of the cell must be determined by calibration.
  • the apparatus can therefore only serve as a secondary frequency standard.
  • the clock essentially comprises (FIG. 1):
  • this zone 6 is subjected to a continuous magnetic field II; of weak constant intensity H (about 50 milligauss) to resolve the degeneracy by splitting the levels F l and F 2; magnetic shielding 8 isolates this zone 6 from external magnetic fields; this continuous field IT; is parallel to the direction of the hyperfrequency magnetic field, and perpendicular to the direction of the beam of atoms in order to avoid a widening of the resonance lines due to the Doppler effect.
  • the field H is produced by four longitudinal wires 34 through which passes a direct current of constant intensity;
  • detection means comprising a Rb" resonance lamp 9 (or a lamp using natural rubidium), a vat 10 containing Rb and an inert gas at high pressure (for example neon at 50 torr), this vat having the role of stopping the component of frequency f while allowing the frequency f, of the Rb to pass (as explained in more detail hereafter with reference to FIG. 6), a collimation lens 11, a lens 12 for collecting the light which is not absorbed by the beam of atoms and a detector 13, advantageously constituted by a photomultiplier, on which is concentrated, by the lens 12, the light which has passed through the beam;
  • an electronic unit 14 annexed to the atomic clock proper and comprising a quartz oscillator which is coupled to the clock, this unit being described in more detail below.
  • the oven 2 (FIGS. 2, 3, 4) comprises a base 15 constituted by an insulating disc made of steatite, a body 16 comprising a foot 17 fixed on the disc, an ejector 18 carried by the neck 19 of the body 16 and a sleeve 20 screwed on the neck 19.
  • the body 16 comprises a blind axial bore 21 for the rubidium and peripheral channels 22 in which heating resistances (not shown) are housed.
  • the ejector 18 is traversed by a series of longitudinal channels constituted by nickel tubes 23 having a cross-section of about a square millimeter. Into the central bore 21 is introduced some natural rubidium, which is covered by octane.
  • This beam is made up of 75% of Rb atoms and 25% of Rb atoms. In the preferred embodiment, only the atoms of Rb in the beam will be used, this beam traveling from the bottom towards the top in the elongated container 2.
  • FIG. 5 shows in detail the lowest energy levels of Rh.
  • the optical resonance line is a double line D,, D comprising the two components of fine structure D, (5 S 5 P and D (5 S, 5 P represented by the double arrows at 7,947.6 A and 7,800 A respectively.
  • the hyperfine structures of the first excited state 5 P are in general smaller than the Doppler width and will thus be neglected, as will the difference between D, and D whereas the hyperfine structure of the fundamental state 5 S is in general greater than the Doppler width.
  • the lines D, and D thus each separate into two hyperfine components due to the structure of the fundamental state.
  • the effects of the lines D, and D are additive.
  • the lines of resonance of the mixture of atoms of Rb and Rb thus comprise four principal components A and B for Rb" and a and b for Rb; as can be seen in FIG.
  • the optical pumping has the effect of transferring part of the atoms fromthe level E to the level E, thus enriching this latter level and impoverishing the level E
  • the beam arrives in the detection zone 25 (before its condensation at 24) with a level E, enriched with respect to the level E
  • the resonance lamp 9 using natural Rb or Rb" emits the four components A, B, a, b; the vat 10 containing Rb only allows the components B and b to pass, but only the component b is active which has just the frequency (E,, E,)/ (h) which permits it to be absorbed by the atoms of Rb of the beam which are in the level E, (arrow f, of FIG.
  • the electronic unit 14 comprises an audiofrequency amplifier 26 amplifying the output from the photomultiplier 13, a quartz oscillator 27, a system 28 automatically servo-coupling the frequency of the oscillator 27 to the frequency of the atomic resonance at 6,834.6 MHz and a frequency synthesizing device 29 which pemlits shifting from the frequency of the oscillator (which is a frequency at a sub-multiple of 6,834,682,614 Hz) to a frequency at a round number such as MHz, as well as to the usual frequencies of l and 0.1 MHz.
  • the servo-control system 28 comprises: a frequency multiplier 30 which multiplies the frequency of v the oscillator 27 (about 5 MHz) by a number such that the multiple frequency is equal to 6,834.6 MHz;
  • a modulator 31 at very low frequency which frequency-modulates the output of the multiplier 30 in order to scan the resonance line in the cavity 7, which is translated as an amplitude modulation at the same very low frequency of the luminous beam striking the detector 13 and hence of the current I delivered by the amplifier 26 (this point will be discussed later with reference to FIG. 12);
  • phase detector 32 which determines the phase difference between the applied modulation (at 30 Hz) and the reestablished modulation (that of the current I) and constitutes the error signal which controls the frequency of the quartz oscillator 27 bymeans of the frequency device 33.
  • the curves I and 1 represent the variation of the amplitude of the current I as a function of the frequency of the signal applied to the cavity 7 in the case in which this cavity is a single cavity (having a length equal to the length through which the atom beam passes in a single branch) and a U-shaped cavity (as illustrated) respectively. It can be seen that the width of the resonance line is much narrower in the second case: in fact the width is inversely proportional to the total length of the single cavity in the first case or of the distance between the cavities in the second case.
  • the width of the resonance line is in fact equal to iF/L; by using thepresent invention, the slow atoms are given an advantage, and hence the resonance line is reduced further.
  • the modulation of the phase of the oscillator at very low frequency and the use of synchronous detection (phase detection) of the very low frequency signal delivered by the detector 13 result in the derivative curve I of I and I of 1 respectively.
  • the slope of in the neighborhood of 6,834.6 MHz is much greater than the slope of I,; the error signal which is proportional to this slope is thus greater in the case of a double cavity: for a frequency variation of df the error signal is di.
  • a positive or negative error signal is obtained according as the frequency is on one side or the other of the resonance frequency.
  • This error signal serves, in the servo-control system, for holding the frequency of the quartz oscillator at the frequency of the hyperfine resonance of Rb" (6,834.6 MI-Iz).
  • the detection light produced by the system 9, 10, 11 can be made to pass several times through the beam, for example by using mirrors. Nevertheless it is necessary to avoid an excess of detection light for an excess of such a light could have a tendency to depopulate the level E, more rapidly than the pumping by the system 4, 5 can populate this level, which would lead to the disappearance of a sharp maximum of current I at the resonance and hence a decrease of the signal/noise ratio.
  • the rubidium beam atomic clock which has just been described with reference to FIGS. 1 to 6, 8 and 12 has numerous advantages with respect to the prior art cesium beam clocks or rubidium vapor clocks whose principles have been explained above.
  • the clock according to this invention gives a primary frequency standard or absolute frequency standard, in the sense that the frequency of the resonance is very close to the Bohr frequency of the free atom.
  • the frequency of the resonance is very close to the Bohr frequency of the free atom.
  • the atoms of Rb travel in a vacuum, there are no frequency shifts due to collisions of the atoms of Rb with the molecules of the buffer gas as in the clocks using alkali vapor cells. For the same reason, the effect of temperature is minimized.
  • the regions of optical pumping and of optical detection are clearly separated from the regions of interaction of the hyperfrequency fields, and accordingly, frequency shifts due to the virtual transitions induced by the pumping light are avoided; this effect is particularly troublesome and difficult to eliminate in the case of clocks using alkali vapor cells; here, it is possible, by careful construction, to avoid leakage of the-pumpinglight or of the detection light in the region of interaction of the fields of high frequency.
  • the aperture angle of the beam of atoms is not limited by the air gaps of focusing or deflection magnets, relatively intense atom beams can be used which thus considerably increases thesignal/noise ratio during detection.
  • the optical detection is relatively simple with respect to the detection by surface ionization used in the clocks of the Rabi type, which (detection by surface ionization) often necessitates the use of a mass spectrograph.
  • the effective mean speed is then given by fdN fv -e' 'dv 'rr a 1r m
  • a supplementary factor l/v for the pumping and a factor I/vfor the detection namely a factor l/v A factor of 2 is thus gained in the fineness of the line with respect to the magnetic deflection methods.
  • the atomic clock of the type illustrated in F IGS. l to 4 can nevertheless consume more atoms of alkali metal than a clock of the Rabi type. In order to reduce the consumption, recirculation of the rubidium can be provided. It will be noticed that the system is symmetrical from the physical point of view: the
  • the apparatus of FIGS. 1 to 4 could also operate by using the atoms of Rb of the beam, the optical pumping being produced at the base by a Rb lamp filtered by a vat of Rb", whereas the optical detection at the top of the beam would be effected by a non-filtered Rb" lamp, the frequency of excitation of the U-shaped hyperfrequency cavity now being 3,036 MHz, the hyperfine spacing between the levels E (F 3) and E (F 2) of the fundamental state of Rb as can be seen in FIG. 6.
  • FIG. 10 illustrates the use of such optical pumping and optical detection for the atoms of rubidium 85.
  • the pumping at the base by the lamp of Rb filtered by the Rb has the effect of making the atoms of Rb pass from the level E, to the excited level (arrow f whence they fall back to the levels E and E (arrows fi and fa hus the level E is enriched with respect to the level E,.
  • the optical detection has the effect of making atoms of Rb pass from the level E to the level 15;, (arrow f).
  • the saturation of the resonance line (E E,)/(h) at 3,036 MHz by the hyperfrequency cavity has the effect of equalizing the population of the levels E and E and consequently of reducing the overpopulation of E realized by the optical pumping, which leads to a reduction of the detection light from the Rb lamp during passage of the beam. There is thus a maximum of the current delivered by the detector fac ing the Rb detection lamp during the passage through the resonance.
  • the variant illustrated in FIG. 11 can be adopted, in which the pumping is effected, according to the arrow f between the levels E and E, by a non-filtered Rb lamp, whereas the detection is effected, according to the arrow f by a lamp of Rb filtered by a vat of Rb.
  • FIGS. 8, 9, 10 and 11 which represent this invention, are characterized by the fact that optical pumping is realizedbetween one of the levels E or E of the fundamental state and the excited level E and optical detection is realized between the other level (E or E, respectively) of the fundamental state and the excited level E the hyperfrequency cavity being supplied at the frequency corresponding to the spacing between the two levels E and E of the fundamental state.
  • the action of the light and of the radiofrequency field is also sequential in time
  • the different operations of optical pumping, of interaction with the radiofrequency field, and of optical detection take place in different regions of space, in the vacuum container, and are produced by the movement of the atoms in space rather than by a square-wave modulation of the light or of the radiofrequency field.
  • the pumping light or the detection light and the radiofrequency field are emitted in a continuous manner. The result is a simplification of the electronic excitation and servo-control systems.
  • the duration of the passage of the atoms in the region of illumination by the pumping light is very brief, about 0.2 milliseconds, and in order to obtain a good signal/noise ratio it is necessary to use intense beams with a wide opening, and this particular technique, which is absent in the alkali vapor cells is a feature of the present invention.
  • This patent is concerned with a thallium beam atomic clock of the conventional Rabi-Ramsey type. Although a beam of alkali atoms, in a vacuum, is used, the optical pumping and the optical detection which are features of the present invention are not mentioned.
  • the beam magnets produce a separation between the alkali atoms belonging to difierent hyperfine levels, in order to preserve, for example, only the atoms of the higher energy level which are then focused onto an ionization detector.
  • the atoms are not separated, but, by the optical pumping, the populations of atoms in one of the hyperfine energy states is enriched.
  • the detection is made-by an optical method which detects the change of populations produced by the radiofrequency.
  • Atomic beam frequency standard comprising a source of a beam of alkali atoms having at least three levels of progressively increasing energy, namely'two levels E and E in the fundamental state and one level E in the excited state and means for projecting said beam of atoms in a vacuum successively through: a zone of optical pumping in which it is illuminated by a source of non-polarized radiation at a frequency corresponding to the interval of energy between one of the fundamental levels E, or E and the excited state E a radiofrequency cavity in which the beam is subjected to a magnetic field of frequency corresponding to the interval of energy between the levels E, and E, of the fundamental state;
  • Atomic beam frequency standard comprising, in combination: an evacuated elongated container; an oven disposed in said container at one end of the container, said oven being adapted to project said beam of atoms in the direction of the other end of the container; means for optical pumping between one of the fundamental levels of the atoms of the beam and a level of an excited state of said atoms; a said cavity of the double type, through which the beam passes after having undergone the optical pumping; means for producing in said cavity an alternating magnetic field, parallel to the continuous field and at a frequency corresponding to the difference of energy between the two levels of the fundamental state of said atoms; optical detection means for directing, on the beam which has passed through the cavity, a detection light at the frequency corresponding to the difference of energy between the other level of the fundamental state
  • means comprise a resonance lamp usingnatural rubidium or Rb filtered by a vat of Rb, the detector receiving the light emitted by the last cited lamp which light has passed through said vat and the beam.
  • Atomic beam frequency standard wherein the oven contains natural rubidium and produces a beam of atoms of Rb" and Rb; the optical pumping means comprise a resonance lamp using natural rubidium or Rb" filtered by a vat of Rb for enriching the level E, (F 2) of the fundamental state with respect to the level E, (F 1) of this state of the atoms of Rb"; the cavity is supplied at a frequency equal to 6,834.6 MHz; and the optical detection means comprise a resonance lamp using Rbfithe detector receiving the light emitted by the last cited lamp which light has passed throu the beam. k
  • an audiofrequency amplifier amplifying the current of the optical detection means, a quartz oscillator operating on a frequency whichis an exact sub-multiple of the frequency of the transition between the two levels of the fundamental state, a frequency multiplier multiplying the frequency of the oscillator for deducing the frequency of the pre-cited transition, means for modulating at low frequency the frequency of the multiplier, aphase detector comparing the phase of the modulation with the phase of the current delivered by the amplifier, means for controlling the frequency of the oscillator in response to the signal emitted by the phase detector and av frequency synthesizer deducing, from the frequency of the oscillator, frequencieswhich are integral numbers in the decimal system.
  • Atomic beam frequency standard wherein the oven contains natural rubidium and produces a beam of atoms of Rb" and Rb; the optical pumping means comprise a Rb resonance lamp filtered by a vat of Rb for enriching the level E (F 2) of the fundamental state with respect to the levels E (F l) of this state of the atoms of Rb; the cavity is supplied at a frequency equal to 3,036 MHz; and the means for optical detection comprise a resonance lamp using natural rubidium or Rb", the detector being a photomultiplier, receiving the light emitted by the last cited lamp which light has passed through said vat and the beam.
  • Atomic beam frequency standard according to claim 1, wherein said alkali atoms are sodium, potassium or cesium, wherein at least one of the means for optical pumping and means for the optical detection comprise alkali vapor cells placed in an intense magnetic field for modifying the frequency by the Paschen-Back effect.
  • Atomic beam frequency standard according to claim 1, wherein said alkali atoms are sodium, potassium or cesium, wherein at least one of the means for optical pumping and means for the optical detection comprise a semi-conductor laser.
US840139A 1968-07-08 1969-07-07 Optically pumped alkali atomic beam frequency standard Expired - Lifetime US3667066A (en)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3903481A (en) * 1973-04-05 1975-09-02 Ernst Jechart Gas cell atomic frequency standard having selected alkali vapor isotope ratios
US4454482A (en) * 1981-10-09 1984-06-12 Demarchi Andrea Atomic or molecular beam frequency standard with optical pumping and open resonator
FR2671913A1 (fr) * 1991-01-23 1992-07-24 Lorin Christian Machine a resonance solitonique par superfluidite.
US6314215B1 (en) 1998-09-17 2001-11-06 New Mexico State University Technology Transfer Corporation Fast all-optical switch
US20070120563A1 (en) * 2005-11-28 2007-05-31 Ryuuzou Kawabata Magnetic field measurement system and optical pumping magnetometer
US20070247241A1 (en) * 2006-04-19 2007-10-25 Sarnoff Corporation Batch-fabricated, rf-interrogated, end transition, chip-scale atomic clock
US20160146909A1 (en) * 2013-08-02 2016-05-26 Hitachi, Ltd. Magnetic field measurement device
US11166342B1 (en) 2020-07-30 2021-11-02 Microchip Technology Incorporated Ovens for atomic clocks and related methods
RU2811394C1 (ru) * 2023-11-07 2024-01-11 Федеральное Государственное Унитарное Предприятие "Всероссийский Научно-Исследовательский Институт Физико-Технических И Радиотехнических Измерений" (Фгуп "Вниифтри") Источник атомов

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3323008A (en) * 1962-10-29 1967-05-30 Hewlett Packard Co Atomic beam apparatus with means for resiliently supporting elements in an evacuatedtube to prevent thermal distortion
US3360740A (en) * 1966-07-18 1967-12-26 Hewlett Packard Co Critical temperature range for oxygenated tungsten ionizing detector in thallium beam tubes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3323008A (en) * 1962-10-29 1967-05-30 Hewlett Packard Co Atomic beam apparatus with means for resiliently supporting elements in an evacuatedtube to prevent thermal distortion
US3360740A (en) * 1966-07-18 1967-12-26 Hewlett Packard Co Critical temperature range for oxygenated tungsten ionizing detector in thallium beam tubes

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3903481A (en) * 1973-04-05 1975-09-02 Ernst Jechart Gas cell atomic frequency standard having selected alkali vapor isotope ratios
US4454482A (en) * 1981-10-09 1984-06-12 Demarchi Andrea Atomic or molecular beam frequency standard with optical pumping and open resonator
FR2671913A1 (fr) * 1991-01-23 1992-07-24 Lorin Christian Machine a resonance solitonique par superfluidite.
US6314215B1 (en) 1998-09-17 2001-11-06 New Mexico State University Technology Transfer Corporation Fast all-optical switch
US20070120563A1 (en) * 2005-11-28 2007-05-31 Ryuuzou Kawabata Magnetic field measurement system and optical pumping magnetometer
US7656154B2 (en) * 2005-11-28 2010-02-02 Hitachi High-Technologies Corporation Magnetic field measurement system and optical pumping magnetometer
US7468637B2 (en) * 2006-04-19 2008-12-23 Sarnoff Corporation Batch-fabricated, RF-interrogated, end transition, chip-scale atomic clock
US20090066430A1 (en) * 2006-04-19 2009-03-12 Alan Michael Braun Batch-fabricated, rf-interrogated, end transition, chip-scale atomic clock
US20070247241A1 (en) * 2006-04-19 2007-10-25 Sarnoff Corporation Batch-fabricated, rf-interrogated, end transition, chip-scale atomic clock
US7852163B2 (en) 2006-04-19 2010-12-14 Sarnoff Corporation Batch-fabricated, RF-interrogated, end transition, chip-scale atomic clock
US20160146909A1 (en) * 2013-08-02 2016-05-26 Hitachi, Ltd. Magnetic field measurement device
US10162021B2 (en) * 2013-08-02 2018-12-25 Hitachi, Ltd. Magnetic field measurement device
US11166342B1 (en) 2020-07-30 2021-11-02 Microchip Technology Incorporated Ovens for atomic clocks and related methods
WO2022025972A1 (en) * 2020-07-30 2022-02-03 Microchip Technology Incorporated Ovens for atomic clocks and related methods
RU2811394C1 (ru) * 2023-11-07 2024-01-11 Федеральное Государственное Унитарное Предприятие "Всероссийский Научно-Исследовательский Институт Физико-Технических И Радиотехнических Измерений" (Фгуп "Вниифтри") Источник атомов

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