Abstract: Frequency stabilization of an atomic system is improved by closed loop stabilization of the power level of an atomic excitation signal. A second harmonic atomic Rabi response varies with excitation power level so that power modulation of the atomic excitation and demodulation of the second harmonic response produces a power error signal for closed loop power level control using a voltage controlled attenuator. The atomic system also includes conventional frequency stabilization closed loop control using a voltage controlled oscillator. Both power and frequency modulation of the excitation signal generate a complete atomic response from which both power and frequency error signals are generated for both power and frequency closed loop stabilization.

Abstract: An electrodeless discharge lamp having a gas filling consisting of a gas mixture for generating gas-specific resonance radiation, wherein the lamp vessel is made of glass. To facilitate replacement and mounting of the electrodeless lamp, the discharge lamp is arranged within a metallic housing and the lamp vessel is disposed together with the high frequency coil as well as any electronic elements on a printed circuit board which is connected with the cover of the lamp housing.

Abstract: The microwave field intensity of a cell type atomic clock is stabilized through time division feedback control of the power of the microwave signal implemented by a microcontroller. The depth of the microwave dip is calculated from differences in measurements of the optical signal when the microwave signal is dithered around the atomic transition frequency of the active medium, and measurements taken when the optical signal is dithered around the optical wavelength of the active medium while the microwave signal is adjusted to produce no microwave absorption, either by reducing the microwave power to zero or by detuning it from the atomic transition frequency of the active medium. RF synthesizers suitable for regulating microwave power include a synthesizer using a step recovery diode for frequency multiplication and having the power to a driver amplifier or the bias applied to the diode regulated. A digital synthesizer can also be used to generate a regulated microwave signal.

Abstract: A method and apparatus for compensating for the long term drift of an oscillator. Signals from hydrogen clouds are received and processed to generate an adjustment signal, which is used to adjust the frequency of the oscillator. The adjustment signal is derived from a frequency spectrum midpoint estimated from the signal strength of the received signals.

Abstract: An atomic maser includes a circuit (25) for effecting a shift in the frequency of a signal injected into a resonant cavity (4) so as to generate alternately a first and a second signal portion having respectively a frequency greater than and less than the natural frequency of stimulated emission, the first and second signal portions having a periodicity corresponding to a predetermined interrogation period. Circuitry (31,32,33,51,52) is responsive to a signal detected in the cavity (4) to produce an error signal representing the difference between the amplitude of the detected signal in response to the injection of the first and second signal portions. Further circuitry (53,54) adjusts the resonant frequency of the cavity in response to the error signal. A pulse generator 26 and a mixer 28 periodically apply both the first and second signal portions for a limited duration only during the interrogation period.

Abstract: A rubidium atomic oscillator includes a voltage-controlled oscillator (VCO) producing a first microwave signal for an output, and a light source producing pumping light of which the wavelength is externally controlled. The oscillator further includes a division part for dividing the pumping light into a first light and a second light, a wavelength shift part changing a wavelength of the second light to produce a third light, and a cavity resonator, oscillated by a second microwave signal, which absorbs the first light and the third light, the cavity resonator having a resonance cell filled with a rubidium gas. In an electrical control part, the second microwave signal is produced based on the first microwave signal from the VCO, a level of the first light passed through the cavity resonator is detected, and a frequency of the VCO is controlled so that the first light is maximally absorbed in the cavity resonator.

Abstract: In the generation of frequency-modulated interrogation frequencies for atomic frequency standards, the modulation characteristics can be tailored to the frequency discrimination characteristics of a physics package. The rate of phase change of a digital pulse train providing a frequency-modulated component of interrogation frequency for an atomic frequency standard can be varied, for example, by multiplexing a plurality of differently phased (delayed) pulse trains to vary the rate of phase change in a digital interrogation frequency component, or by effecting phase delays and phase advances through the addition and subtraction of pulses of a digital interrogation frequency component.

Abstract: A physics package interrogation signal can be digitally synthesized for use in an atomic frequency standard with one or more sets of integrally-related sub-multiples of a clock frequency in which one of the integrally-related sub-multiple frequencies is varied to provide frequency modulation between integrally-adjacent sub-multiple frequencies through the use of preloadable counters, the controlled delay and the synchronization of digital pulse trains and operation in plural modes. The method and apparatus can reduce false lock possibilities, optimize the ability of the physics package to remain locked, and reduce phase noise in the output of an atomic frequency standard.

Abstract: A rubidium atom oscillator has an increased allowable temperature range in which a frequency fluctuation due to change in the ambient temperature is suppressed. The frequency is stabilized in an increased temperature range as compared to the conventional rubidium atom oscillator. The rubidium atom oscillator oscillates a microwave having a predetermined stable frequency by using an optical pumping effect of rubidium gas. A rubidium lamp radiates a resonance light. A cavity resonator accommodates a gas cell containing rubidium gas and a photodetector detecting an amount of the resonance light passing through the gas cell. It is determined whether or not an ambient temperature of the cavity resonator is within a predetermined temperature range between a lower-limit temperature and an upper-limit temperature. A temperature correction signal is generated based on the determination. A current determined by the temperature correction signal is supplied to a coil surrounding the cavity resonator.

Abstract: A frequency synthesizer having two atomic frequency standard inputs that is adapted to provide seamless switching or transition between the atomic frequency standard inputs with no change in the synthesizer output phase and frequency. The synthesizer includes a multichannel phase comparison system, each channel adapted for handling an atomic frequency standard input, a digital phase lock loop, a digital to analog converter, and a voltage controlled crystal oscillator which provides the synthesizer output. The phase comparison system is adapted to continually monitor the integrity of the atomic frequency standard inputs and to continually estimate the phase differences between the two atomic frequency standard inputs. The phase difference is used to estimate the proper phase and frequency offset between the primary and secondary inputs.

Abstract: A miniature atomic frequency standard utilizes a tubular vapor cell extending transversely through a TE.sub.210 microwave cavity. In one embodiment of the invention, the vapor cell is heated directly by electric heaters secured to ends of the tubular vapor cell which extend outside the microwave cavity. The vapor cell is insulated by thermal insulation inside the microwave cavity and between the microwave cavity and a magnetic shield. In another embodiment of the invention, the entire microwave cavity is heated which eliminates the need for thermal insulation inside the cavity and thus it can be made smaller, but additional thermal insulation is provided between the microwave cavity and the magnetic shield. Preferably, the C-field coil is wound on the thermal insulation just inside the magnetic shield to reduce heat loss by conduction.

Abstract: The atomic frequency oscillator comprises a resonance cell (41) placed in a microwave resonator (53) surrounded by an electromagnetic shield (58). A laser module (10) emits a light beam which reaches the resonance cell and is used for optically pumping rubidium into the resonance cell. The light beam is conducted from the laser module to the resonance cell by an optical fiber (14) passing through the electromagnetic shield. The optical path traveled by the light beam does not include any beamsplitter. At least one controller uses the light beam conducted by the optical fiber for controlling the injection current and/or the temperature of the laser diode so as to stabilize the light emission frequency. The resonance cell serves both as resonance cell for controlling an oscillator (54) generating via a frequency multiplier (55) the signal for exciting the microwave resonator and as cell for controlling the laser diode (11).

Abstract: A resonator package can comprise a microwave container which does not have to be tuned, such as an untuned waveguide, carrying an absorption cell and forming an optical path through its open end and the absorption cell and leading to a light detection means, and a microwave loop adjustably carried by the microwave container between the absorption cell and the light detection means. The microwave loop can be carried by a carrier slidably engaging a slot formed in the waveguide, and can be tuned by adjusting its position with respect to the adjacent face of the absorption cell. The resonator package can thus eliminate a microwave cavity and the need for the precise dimensions of a microwave cavity and the problems of separately tuning a microwave cavity and loop, and can permit smaller resonator assemblies without the use of dielectric loading and the use of a loop that also functions as a very simple and inexpensive microwave multiplier/mixer.

Abstract: A digital controller time multiplexes dithering of the microwave frequency control signal and a laser wavelength control signal in a miniaturized cesium vapor atomic frequency standard. A unique common charge/sample and dump integrator amplifies the photodetector output for the + and - dither of both the laser current and microwave frequency. To suppress error in the integrated photodetector output attributable to noise generated by the digital processor, the processor is placed in a sleep mode during the integration intervals. To further suppress errors, the cesium vapor electric heaters are not energized during the intervals when the microwave signal is being dithered.

Abstract: A laser diode has its frequency locked to the frequency of an absorption line of rubidium (water and oxides of nitrogen are also disclosed). The level of absorption, and hence the frequency relationship of the laser light with respect to the absorption line is detected by a photodetector. The absolute frequency of the laser light is guaranteed by initially adjusting the temperature of the diode until the frequency of the light is brought into coincidence with a first absorption line, subsequently maintaining the temperature at a constant level, and adjusting the drive current of the diode until the frequency of laser light achieves coincidence with an adjacent transition line. This ensures that the diode frequency is locked to the same absorption line each occasion the diode is switched on. Additionally, the change in drive current between coincidence with the two adjacent absorption lines is monitored as a further check that the correct transition line has been selected.

Abstract: A novel atomic frequency standard includes an absorption cell containing a first volume of atoms for varying an intensity of light energy passing therethrough; at least one dielectric resonator for generating an evanescent electromagnetic field that effects hyperfine energy level transitions of the first volume of atoms; a waveguide for housing the absorption cell and one or more dielectric resonator(s); a photo detector mounted near an end of the waveguide for receiving light energy; and an electromagnetic energy injector for electromagnetically exciting the dielectric resonator(s). Preferably, a filter cell is positioned adjacent to a dielectric resonator between the absorption cell and the light source.

Abstract: A method of reducing the interrogation signal phase noise in passive, compact, low-cost commercial atomic standards, particularly phase noise occurring at a Fourier frequency equal to twice the modulation frequency, 2f.sub.mod. The method involves selecting the modulation frequency so that 2f.sub.mod is on the order of, or greater than, the atomic bandwidth (full width at half maximum signal value).

Abstract: An apparatus for providing excitation of a vapor discharge lamp includes a control circuit for controlling an oscillator circuit during an ignition mode of the vapor discharge lamp to establish and maintain a substantially constant DC voltage at an output of an oscillator transistor and to establish a current flow through the oscillator transistor at a first current level sufficient to ignite the vapor discharge lamp, and for controlling the oscillator after ignition of the vapor discharge lamp to maintain the substantially constant DC voltage at the output of the oscillator transistor while reducing the current flow through the oscillator transistor from the first current level to a second current level, and in preferred embodiments, includes circuitry to suppress unwanted blocking oscillations and optimize the dynamic range of the control circuitry.

Abstract: An atomic beam resonator, particularly a cesium beam resonator, suitable for producing an extremely stable reference frequency. The resonator comprises, arranged in series in the beam direction, a source (1) of the atomic jet (2), a first state selector (3), an interrogating region (4) with a Ramsey-type cavity resonator having two arms (17, 18), a second state selector (5) an atom detector (6) for producing the useful output signal of the resonator, and a device for injecting an interrogation signal into the cavity resonator to generate a microwave interrogation field in each arm of said cavity. Said interrogating region (4) is surrounded by a magnetic shield (10). The resonator is characterized in that the device for injecting microwave energy (25) into the the cavity resonator is a coupling device which forms an odd number of modes in the cavity so that both interrogating regions are of opposite phase and the resonator response is at its lowest at the resonant frequency.

Abstract: Optical pumping devices use light reflected from reflecting surfaces to provide a portion of the light incident on the photodetector. Conventional optical pumping devices experience a decay, over time, of the initial light intensity incident on the photodetector. The optical pumping device of the invention experiences reduced light intensity decay. The invention passivates the reflecting surfaces to eliminate tarnish and oxidation by pretarnishing the surfaces or covering the surfaces with a material whose reflectivity does not vary over time, such as gold.

Abstract: A variable energy radio frequency quadrupole linac for emitting focused and accelerated beams by changing radio frequency energy levels, wherein the accelerating cavity is divided by a plane perpendicular to the beam direction and in a radio frequency sense, and the radio frequency power level in the downstream accelerating cavity is made to be lower than that in the upstream accelerating cavity, one of the divided cavities being self oscillated, and the other being separately oscillated, a separating plate being provided between separated electrodes, the radio frequency phases in the upstream cavity and the downstream cavity being relatively changeable, and a thin plate region being provided in the periphery of a beam passing window on the separating plate, thereby the power in the cavity can be lowered without expanding the energy spread of the emitted beams so much.

Abstract: The wavelength of light generated by a diode laser optically pumping vapor in the gas cell of an atomic time-standard is stabilized against variations in ambient temperature by application of pressure to the semiconductor laser by a piezoelectric transducer, preferably implemented as thin films on the diode structure. Closed loop control of the pressure is provided by feeding back a detector signal, which is a measure of light transmitted through the vapor, to a null seeking servo the output of which is converted to a control signal which is a function of temperature/pressure. The control signal, which is applied to the piezoelectric transducer, which in turn is preferably implemented as a thin film on the diode structure, can be dithered to sense and maintain the desired resonant atomic transition frequency. The vapor is additionally excited by a microwave signal locked to an atomic transition frequency through feedback of the detector signal.

Abstract: A linear ion trap for frequency standard applications is provided with a plurality of trapping rods equally spaced and applied quadrupole rf voltages for radial confinement of atomic ions and biased level pins at each end for axial confinement of the ions. The trapping rods are divided into two linear ion trap regions by a gap in each rod in a common radial plane to provide dc discontinuity, thus dc isolating one region from the other. A first region for ion-loading and preparation/fluorescence is biased with a dc voltage to transport ions into a second region for resonance/frequency comparison with a local oscillator derived frequency while the second region is held at zero voltage. The dc bias voltage of the regions is reversed for transporting the ions back into the first region for fluorescence/measurement. The dual mode cycle is repeated continuously for comparison and feedback control of the local oscillator derived frequency.

Abstract: The atomic frequency standard has a heating element (58) surrounding an enclosure (43) which defines a microwave resonance cavity (42). The heating element supplies heat to an absorption cell (41) located in the cavity. The absorption cell (41) is surrounded by electrodes (45a-45d) which act to enhance and orient the oscillating magnetic field in the region of the absorption cell. Thermally conductive members (47a-47d) connect the electrodes (45a-45d) to the enclosure (43) to better control the temperature of the cell while retaining the advantages due to the presence of the electrodes (45a-45d).

Abstract: An atomic clock system employs one of a family of ion trap configurations confining an ion in a potential well, such that a vibrational frequency confined ion may be measured accurately. The ion traps disclassed for use in such atomic clock systems include configurations of ring-shaped conductive members, or sheets of conductive material having circular holes therein. The trap apparatus further has a means to apply an RF field such that the resulting electric field being generated in a space defined by the conductive members has a characteristic of a substantially quadrupole field whereby a charged particle, being injected into the space, is confined in said field, maintaining a dynamic equilibrium condition.

Abstract: A gas cell for a miniature atomic frequency standard. The gas cell functions not only to contain the cesium vapor, but also as a resonator for the microwave signal used to excite the vapor. By combining the functions of gas cell and resonator into a single structure, and by taking advantage of the intensity of light available from a laser diode, the overall size of an atomic frequency standard can be reduced by two orders of magnitude when compared to prior art devices of comparable accuracy.

Abstract: An atomic frequency standard cell having low helium permeability includes first and second windows sealed by fusible annular gaskets to sealing surfaces defined by a tubular cylindrical body. One of the windows defines an opening, and a fill tube is sealed the window adjacent the opening by a tube gasket. The gaskets are made of a lower softening point glass such as borosilicate glass, and the body, windows and fill tube are formed of a higher softening point glass such as aluminosilicate glass. The assembly is sealed together by heating it to a temperature that causes the gaskets to fuse and seal the adjacent components together.

Abstract: A cell-type atomic frequency standard utilizing a miniaturized gas cell and microwave exciter along with a diode laser light source. The intensity of the diode laser light source counterbalances the penalties associated with the small gas cell. The signal produced by an oscillator is applied to a vapor within the gas cell by a miniature helix coil, or LC gap conductor, or a microstrip exciter. With the dimensions of the gas cell not exceeding one-half the wavelength of the signal, and the associated circuitry formed on a semiconductor substrate, the resulting frequency standard is reduced in size by two orders of magnitude when compared to prior art devices of comparable accuracy.

Abstract: An RF chain having a high-frequency oscillator providing first, second and third outputs. The first output is multiplied to provide a microwave signal to an atomic beam tube; the second output is divided to provide a standard output frequency; and the third output is divided to provide a first input to a phase detector. The phase detector receives a second input from a low-frequency oscillator which is controlled by a servo signal from the atomic beam tube. The output of the phase detector provides a control signal to the high-frequency oscillator.

Abstract: An improved atomic beam clock apparatus and method are disclosed. The invention substantially reduces errors arising from Rabi pulling and variations in the frequency standard resulting from variations in the amplitude of the microwave signal used to excite the atomic beam. The invention includes a servo loop that adjusts both the microwave frequency and amplitude. The servo loop measures the output of a beam detector at two pairs of microwave frequencies. The output of the detector at each frequency in each pair of frequencies is measured for two different microwave amplitudes. The amplitude data is used to adjust the microwave power such that the output of the detector is maximized at each pair of frequencies. The amplitude modulation scheme of the present invention may also be applied very advantageously to conventional two point frequency modulation schemes.

Abstract: A compact frequency standard having a dielectrically loaded microwave resonant cavity. One embodiment uses light from a single laser at the frequency that causes F=4.fwdarw.F'=5 transitions in cesium, circularly polarizes a portion of the light to optically pump a cesium beam and uses another linearly polarized portion of the light to detect fluorescence after the beam passes through the microwave cavity. The microwave cavity is preferably dielectrically loaded cavity which is resonant in the TE.sub.011 or TE.sub.013 modes. The dielectric within the microwave cavity is in the form of a hollow cylinder with varying sidewalls displacing the effective axis of the microwave cavity from the geometric axis to produce a Ramsey resonance in a single cavity and creating inhomogeneities in the static field that cause narrow resonance anomalies in the cesium spectrum, which resonances may be locked onto to provide improved frequency standards.

Abstract: A beam tube atomic standard employing optical pumping for state preparation and magnetic state selection of atoms is disclosed. Atoms selected from the group consisting of the alkali metal family (Cesium, Rubidium, Potassium, Sodium and Lithium) are emitted from a source thereof to a state preparation region. A laser by optical pumping changes the state of atoms emitted by the source from a first energy state to a second energy state. A microwave cavity in which a magnetic field is induced receives atoms whose energy state has been changed to the second energy state by the laser, and due to resonance phenomenon changes the state of the atoms in the second energy state. A magnet receives in a gap thereof atoms from the cavity and deflects the received atoms having the changed energy state towards an atomic detector.

Abstract: A control system for controlling a radio frequency resonant cavity type linear accelerator so as to be power-supplied always at a resonance frequency of a resonat cavity constituting the accelerator. The system consists essentially of a signal pick-up coil inserted in the resonat cavity, a voltage-controlled oscillator assembly, a phase detector for detecting a phase difference between a signal picked up from the cavity by the signal pick-up coil and an output from the voltage-controlled oscillator assembly. An output from the phase detector controls the voltage-controlled oscillator assembly so as to make it oscillate at a frequency equal to a resonance frequency of the resonant cavity.

Abstract: Improved atomic clocks and frequency standards of the type where the frequency of an oscillator is stabilized by locking via a phase lock loop to an atomic resonator and where the output of the clock is taken from this oscillator. Protective means are provided to maintain a high accuracy when such clock is exposed to a strong magnetic field. The stabilization is based on two magnetic "C"-fields which are controlled and adjusted to maintain the accuracy of the clock.

Abstract: The passive frequency standard of this invention comprises a cell (42) containing Rb87 and a source of predetermined spectral component which, by optical pumping, empties the level F=1, m.sub.F =0 and populates the level F=2, m.sub.F =0. This source comprises a lamp (40) and an isotopic filter constituted by Rb 85 contained in the cell (42). A helicoidal resonator (44) is tuned to the transition frequency between level F=2, m.sub.F =0 and level F=1, m.sub.F =0. It receives an excitation signal for stimulating such transition from an oscillator via a connector (64). The frequency of the oscillator is slaved to the transition frequency by slave means comprising a photoelectric cell (46) which receives the light from the lamp (40) through the cell (42).

Abstract: An atomic clock of the type comprising a quartz oscillator, a tube contaig a material, the atoms of which have an hyperfine spectral transition, control means capable of generating, from the quartz oscillator, a control signal of a frequency that corresponds to the hyperfine spectral transition, and of applying this control signal to the tube to cause interaction between this signal and the atoms of the material contained in the tube, and feedback means that are sensitive to the response of the tube and are adapted to modifying the frequency of the quartz oscillator so as to substantially center the frequency of the control signal on the frequency of the hyperfine spectral transition, wherein the control means are adapted to cyclically generate test signals, the controlled frequency of which is located outside the Ramsey peak.

Abstract: A cesium oscillator includes a cesium beam tube, and an oscillator circuit which generates an oscillation signal of a frequency to be supplied to the cesium beam tube. A frequency control circuit including a sweep circuit and a feedback loop circuit continuously varies the frequency of the oscillation signal. The frequency of the oscillation signal is continuously varied two times when the frequency of the oscillation signal is to be adjusted. A hold circuit holds the highest signal level of the resonance signal supplied from the cesium beam tube when the frequency control circuit continuously varies the frequency of the oscillation signal first. A control circuit controls the frequency control circuit so as to stop continuously varying the frequency when a signal level of the resonance signal obtained by continuously varying the frequency of the oscillation signal by the frequency control circuit for the second time becomes equal to the highest signal level held by the hold circuit.

Abstract: A high accuracy atomic frequency standard and clock which utilizes a micrmputer. The microcomputer compensates for aging and temperature variations in the atomic standard and its slave crystal oscillator and generates an error signal which is used to either correct the frequency of the slave crystal oscillator or to adjust the number of clock pulses per unit time interval. No C-field adjustment is employed.

Abstract: A microwave oscillator is provided which can operate at a temperature of many degrees above absolute zero while providing very low phase noise that has heretofore generally required temperatures within a few degrees K. The oscillator includes a ring-shaped resonator element of ruby (sapphire plus chromium) or iron sapphire crystal, lying adjacent to a resonator element of sapphire, so the regenerator element lies directly in the magnetic field of the resonator element. The resonator element is substantially devoid of contact with electrically conductive material. Microwave energy of a pump frequency (e.g. 31GHz) is applied to the regenerator element, while signal energy (e.g. 10GHz) is outputted from the resonator element.

Abstract: A predetermined bias voltage is applied to the input of a summing integrator in a frequency lock loop to provide fine tuning control of a voltage controlled crystal oscillator. In this arrangement, the predetermined bias voltage is summed and integrated with a phase error signal to alter the output frequency of the voltage controlled crystal oscillator. Since the servo loop operates to null the net voltage at the input of the integrator, the circuit induces a frequency error which just compensates for the intentional voltage offset bias applied to the integrator. The offset bias arrangement produces incremental offsets within a total range of about three parts in ten to the eleventh power and permits the output frequency of an atomic frequency standard to be accurately and stably adjusted in small increments to agree closely with the frequency of a national standard or other system reference.

Abstract: A compact, self-contained and economical frequency standard uses a passive hydrogen maser to provide an accurate, repeatable, and stable standard frequency. The hydrogen dissociator and microwave cavity of the maser and circuit means coact to reduce the frequency variations possible with prior systems and to promote and emphasize the energy transfer from hyperfine hydrogen atoms to the frequency standard for its stabilization. The dissociator is accurately alignable to transfer its hyperfine hydrogen atoms of a selected state to a microwave cavity; and the microwave cavity is formed by dielectric surfaces which have been coated with a conductive coating in a predetermined configuration to suppress oscillation in undesirable modes.

Abstract: The method realizes the frequency control of a frequency standard including an atomic or molecular beam resonance apparatus with two microwave cavities, to which an electromagnetic field is fed, whose frequency is modulated in time with a sinewave signal about an interrogation frequency near to the characteristic resonance frequency of a selected transition of the atoms or molecules of the beam. In the resonance device a current is generated, proportional to the number of atoms or molecules of the beam which have undergone said transition as an effect of their passing through the cavities. The method includes the step of extracting from said current the component whose frequency is an odd harmonic of the modulation frequency of an order higher than the first, in particular the third.

Abstract: A laser diode detection and optical pumping cesium resonator in which the frequency of the laser diode is made dependent on a signal delivered by a detector picking up the fluorescence light emanating from an interaction zone created just at the output of the cesium oven by the interaction of the cesium atom jet and a part of the light beam emitted by said detection diode. In particular, a laser diode detection and optical pumping cesium resonator having a cesium oven emitting a flow of cesium atoms, a resonating cavity in the flow path, a laser diode optical pump delivering a light beam into the atom flow between the cavity and the oven at a first interaction zone and a cesium resonance frequency generator. A detector for detecting fluorencence from a second interaction zone at the cavity output resulting from the interaction of the atom stream with a third laser. The detector delivering a signal representative of the second interaction to frequency control means to control the frequency of the generator.

Abstract: The subject invention relates to an improved microwave cavity resonator and internal magnetic shield of small design for use with an atomic frequency standard.

Abstract: An evacuated wall-coated sealed alkali atom cell for an atomic frequency standard, including a cell bulb having an inner wall subjected to cleaning by means of a bakeout step and a r.f. scrubbing step under vacuum, whereupon the inner wall is provided with a deuterated paraffin coating. An alkali atom .sup.87 Rb and/or .sup.85 Rb, and/or .sup.133 Cs is sealed in the cell bulb under vacuum.

Abstract: Two collocated, weakly coupled probes, on loop and one dipole, detect the magnetic and electric fields inside a maser cavity. Signals from the probes are compared in phase, and the signal output from the phase detector is applied to a varactor, the reactance of which is coupled into the cavity by a microwave coupler. Alternatively, the varactor may be placed inside the cavity. Any deviation of phase from 90.degree. as detected by the phase detector will then produce an error signal that will change the reactance coupled into the resonant cavity to change its reactance, and thus correct its resonance frequency. An alternative to using two probes is to use a single disk probe oriented to detect both the magnetic and electric fields, and thus provide the error signal directly.

Abstract: A system is disclosed for examining the response in atomic and molecular resonators to identify and select the maximum resonant peak and the voltage used to cause said peak to be produced. The system is fabricated of modular elements electrically connected to a circuit board to facilitate its construction and transportation with the resonator. A microprocessor is utilized to perform the analysis and to generate information to select the maximum resonant peak, and the system includes means to compare the value of successively generated resonator outputs and to select the output with the maximum peak.

Abstract: An improved microwave cavity resonator for use in vapor-cell atomic frequency standards. The resonator comprises a generally-rectangular hollow metallic body designed to support the TE.sub.101 mode of standing wave. A dielectric element is positioned within the cavity to concentrate electro-magnetic field so that a compact design is achieved and so that a preselected, substantially uniform magnetic field will be coupled into an alkali metal vapor absorption cell within the resonator. Means are provided for mounting elements of an excitation circuit to preferentially excite the desired TE.sub.101 mode.

Abstract: An optical-physics package used in an atomic frequency standard is miniaturized and the performance thereof improved. The optical-physics package includes a microwave cavity in which is positioned a filter cell and an absorption cell, preferably located in close physical proximity to one another. The microwave cavity may double as an oven, and is preferably designed to operate in the TE111 mode with "E" probe microwave coupling. Dielectric loading is provided by the filter cell and absorption cell to reduce the internal dimensions of the microwave cavity.

Abstract: A highly stable voltage variable crystal controlled oscillator adapted for stand-alone use or for use with an atomic clock for further stabilizing the oscillator. A novel Colpitts crystal oscillator configuration is employed and utilizes an FET amplifier and bipolar emitter follower configured for power gain without phase shift in the feedback circuit. The oscillator output signal is derived through the crystal which then acts as its own low pass filter to improve the purity of the output signal. A novel buffer/amplifier circuit including a grounded gate FET amplifier and coupling transformer assure frequency stability despite wide ranging load impedance variations. A resilient thermal foam material is used to enclose the temperature and shock sensitive components of the oscillator to provide further frequency stability and rugged construction.