• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method for manufacturing a cesium atomic micro-clock microcell having a reversal temperature greater than 80 ° C comprising a step of generating a cesium vapor by heating a pellet comprising cesium, the buffer gas used comprising neon and helium.
    公开号:CH710305A2
    申请号:CH01496/15
    申请日:2015-10-16
    公开日:2016-04-29
    发明作者:Boudot Rodolphe；Gorecki Christoph；Maurice Vincent；Kroemer Eric；Fouilland Bernard
    申请人:Thales Sa；Centre Nat De La Rech Scient (Cnrs)；Univ Franche Comte；Ecole Nat Superieure De Mec Et Des Microtechniques；
    IPC主号:
    专利说明:

    [0001] The field of the invention relates to cesium atomic micro-clocks. More specifically, the invention relates to the buffer gas used in cesium micro-clock microcells.
    [0002] The performance of many compact and portable systems depends on the frequency stability of the reference or standard they use. A GPS receiver, acronym for Global Positioning System, in English or Global Positioning System, in French, for example, is based on the principle of measuring the propagation times of electromagnetic waves emitted by a constellation of orbiting satellites. around the Earth and synchronized with each other by atomic clocks. The accuracy of the positioning of the GPS receiver depends essentially on the quality of the measurement of the travel time of the waves emitted by a satellite orbiting the Earth to said GPS receiver. The GPS satellite waves are encoded or modulated to carry the GPS constellation reference time information in the form of a navigation message and a pseudo-random code. To use this information, the GPS receiver must have its own clock which will allow it to date the instant of reception of each wave upon reception. Thus, the GPS receiver knows how to compare this reception date with the transmission time information transported in an encoded manner by the received wave.
    [0003] The a priori knowledge with high precision of the time of the GPS constellation by the GPS receiver thanks to a high precision clock allows it to provide more robust GPS navigation in cases where the reception of the signals is likely to be disturbed, interrupted or discontinuous. It can also contribute to the safety and integrity of navigation when this is made necessary, for example for the purposes of air navigation and the transport of passengers.
    [0004] A frequency standard is a physical device, such as for example an atomic clock, providing a periodic signal the frequency of which is stable and known with great precision.
    [0005] Today, the evolution of systems requiring high robustness and a high degree of security requires a stable frequency reference, typically the reference frequency variation must be less than one microsecond per day.
    [0006] Currently, the best frequency references are atomic clocks. Atomic clocks exploit the transition frequency between two energy levels of an atomic species whose value depends on the Bohr relation. Compared to an oscillating signal delivered by a quartz resonator, for example, whose frequency depends on the dimensions of the material or other experimental parameters, the frequency of an atomic clock depends only on the intrinsic physical constants of the atomic species, these constants are independent of the experimental conditions and do not vary over time.
    [0007] FIG. 1 represents a frequency standard, in this case an atomic clock, comprising two basic elements:- an atomic reference 1 corresponding to the transition frequency of an atom between two energy levels of the spectrum of the atom considered. The two energy levels being related by the Bohr relation E2 – E1 = h. at, h being Planck's constant, and- a macroscopic oscillator 2 which provides a useful signal of frequency close to the transition frequency at of the atom of atomic reference 1.
    [0008] The atomic reference 1 is used to calibrate the frequency of oscillator 2 and thus to transfer the stability of the frequency from the atomic reference 1 to the macroscopic oscillator 2.
    [0009] Historically, cesium has been chosen to define the International System second, clocks based on the cesium atom isolated from its environment are therefore considered primary standards. Clocks based on atoms other than cesium or on non-isolated cesium atoms are said to be secondary and must be calibrated using so-called primary clocks.
    [0010] An atomic clock must deliver a signal of known and stable frequency based on atomic resonance. To do this, we make an electromagnetic field, the frequency of which is generated from the frequency delivered by an oscillator of frequency osc, interact with an atom having a resonance at the frequency at = (E2 – E1) / h.
    [0011] The response of the atomic system depends on the mismatch δ = - at between the frequency of the signal from the oscillator and the atomic resonance. The response is maximum when the difference or disagreement δ is zero. The measured detuning makes it possible to construct an error signal and the correction which must be applied to the frequency of oscillator 2. The objective of this correction process is to bring the frequency of the oscillator Osc back to the resonant atomic frequency.
    [0012] To date, the most compact atomic standards are rubidium atomic clocks.
    [0013] This type of clock has dimensions of the order of ten centimeters and consumes several watts of electrical power. The relatively large dimensions of conventional compact atomic clocks and their high power consumption limit their use for on-board or portable systems.
    At the start of the 2000s, the miniaturization of portable systems became a major issue.
    We seek to achieve miniature atomic clocks having frequency stability performance much better than those obtained with a quartz oscillator, of at least one or two orders of magnitude, and having a volume between 1 and 15 cm <3> and consuming up to 150 mW.
    The examples of applications, cited above, require clocks having a very high level of performance.
    [0017] Other applications have more modest performance constraints but much more stringent sizing and energy consumption constraints.
    [0018] Compact rubidium clocks are well known. Conventional clocks include an optical part and a microwave part separated in time and geographically.
    [0019] The principle of operation of a rubidium clock can be summed up in two stages.
    [0020] In a first step, the rubidium atoms are optically pumped by a laser into one of the clock energy levels.
    [0021] Optical pumping is understood to mean the ability to manipulate atoms with the aid of a laser beam to populate a given energy level.
    [0022] In a second step, an additional 6.8 GHz microwave signal is applied to make the atoms oscillate between the two energy levels that one seeks to excite.
    This type of clock, although relatively compact, remains relatively large in size. Indeed, this type of clock requires the use of a resonant cavity, the dimensions of which are adapted to the wavelength that one seeks to excite.
    [0024] A miniaturization of compact atomic clocks is made possible by a physical principle called coherent population trapping, better known by the term “Coherent Population Trapping”, in English, or CPT and the development of micro-manufacturing techniques.
    The principle of the coherent trapping of the CPT population, shown in FIG. 2, consists in making an all-optical interrogation.
    A three-level atomic system consists of two ground states (1) and (2) with energies E1 and E2, respectively, coupled to a common excited state (3).
    A dichromatic laser beam from a laser diode (the frequency of which is directly modulated at 4.6 GHz, corresponding to the frequency half of the transition of the cesium atom) comprises two waves and separated by 9.192 GHz .
    This laser beam will interact with the cesium atoms which will be trapped in a particular atomic state called "black state" in which the cesium atoms do not absorb photons, the light transmitted through the atomic vapor is then increased which makes it possible to obtain at output a resonance signal which can be used to correct the frequency of the local oscillator modulating the laser diode.
    In other words, there is in a CPT micro-clock a spatio-temporal uniqueness of the step of trapping the atoms in a particular state of excitation, corresponding to the black state and the step d oscillation between two energy levels of the ground state at the frequency of the clock transition.
    This all-optical interrogation or excitation makes it possible to overcome the resonant metal cavity which is located around the microcell, and whose dimensions must be in accordance with the wavelength that one seeks to excite.
    [0031] The absence of a resonant cavity allows for a much smaller clock than conventional rubidium compact clocks.
    CPT atomic micro-clocks can be integrated into GPS receivers, in particular, to replace the previously used quartz clocks.
    By atomic micro-clock is meant an atomic clock including:the volume is between a few cm <3> and 15 cm <3>,the total consumption is less than 150 mW, andthe relative frequency stability is 10 <–> <11> at one day of integration, or, in other words, 1 µs of drift per day.
    An atomic micro-clock, as shown in FIG. 3, comprises, in a simplified manner, three parts: a microcell 3 in which there are the cesium atoms 4 which interact with the laser beam 5, an optical module for shaping the light beam, comprising in particular the laser diode 6 which emits the laser beam 5 and an electronic part 7 which in particular produces the signal at 9.192 GHz.
    [0035] In this case, the microcell 3 can be likened to a small cavity whose dimensions are of the order of a millimeter.
    [0036] It comprises a vapor of cesium atoms. The cesium-4 atoms are thermally stirred, they move at a speed of around 230 m.s <–> <1>.
    [0037] The impact of the cesium 4 atoms with the internal walls 3a of the microcell causes the loss of atomic coherence, the cesium 4 atom is then depolarized, which attenuates the clock signal.
    [0038] The goal of an atomic clock is to observe the cesium-4 atoms for as long as possible.
    [0039] The impact of the cesium atoms inside microcell 3 against the internal walls 3a of microcell 3 must therefore be minimized to improve the quality of the clock signal by extending the life of atomic coherence.
    [0040] For this, it is necessary to increase the flight time of the cesium atoms between two impacts against the walls 3a.
    The most commonly used technique to increase the life of the CPT coherence in the microcell 3 is to dilute the alkaline vapor, in this case the cesium vapor, using gas pressure, said buffer gas 8.
    In the presence of this gas, the cesium atoms 4 make numerous collisions against the neighboring buffer gas 8 atoms.
    Thus, the time that the alkali or cesium atoms 4 take to collide against an internal wall 3a of the microcell is prolonged.
    Now, the longer the time of flight of the cesium 4 atoms, the narrower the peak width at the resonant frequency, and the more the relative frequency stability of the clock is improved.
    [0045] However, the collisions between the cesium 4 atoms and the buffer gas 8 atoms will displace the energy levels of the cesium 4 atom and will induce an S shift in the clock frequency.
    This shift S of the clock frequency of a few hundred hertz per torr, depends directly on the nature of the buffer gas 8, the temperature T and the pressure of the buffer gas 8 inside the microcell.
    In a limited temperature range, the displacement S of the frequency due to the buffer gas 8 can be written as follows:S = P [a + b (T – T0) + c (T – T0) <2>]P is the buffer gas pressure at a reference temperature T0 = 0 ° C,T is the measurement temperature,a is the coefficient of displacement in pressure,b and c are, respectively, the linear and quadratic coefficients of temperature displacement.
    This frequency shift S will therefore have a direct impact on the stability of the frequency of the clock.
    Usually, to overcome this drawback, the buffer gas 8 is a mixture of two gases: a first gas which induces a displacement of the clock frequency towards higher frequencies and a second gas which induces a displacement of the frequency d clock to lower frequencies. Adjusting the proportions of the two gases constituting the buffer gas mixture 8 makes it possible to obtain a desired so-called "inversion" temperature.
    In this case, the frequency displacement S can be written as follows:S = P [(r1a1 + r2a2) + (r1b1 + r2b2). (T – T0) + (r1c1 + r2c2) <2> (T – T0) <2>]a1, a2, b1, b2, c1, c2 are the coefficients specific to the gases constituting the buffer gas 8,r1 and r2 translate the percentage compared to the total pressure of the gases, we have r1 + r2 = 1
    The derivative with respect to T of this relationship depends on the partial pressures of the gases constituting the buffer gas 8. It is, consequently, important to control the partial pressures of the gases when filling the cell.
    The term “inversion temperature” is understood to mean a temperature at which the sensitivity of the clock frequency to temperature variations cancels out to the first order.
    [0053] In other words, the effects of each of the two gases constituting the buffer gas mixture 8 are compensated for at a certain temperature called the inversion temperature. At this temperature, the clock will be much less sensitive to temperature variations.
    [0054] The existence of an inversion temperature is thus a strong point for improving the frequency stability of the clock in the medium and long term.
    [0055] Generally, the buffer gas mixture 8 used comprises nitrogen and argon.
    In the United States, research teams have developed micro-clocks comprising a cesium vapor generated by a chemical reaction prior to or subsequent to the step of closing the microcell 3. This microcell uses a buffer gas 8 comprising a Ar – N2 mixture.
    This type of microcell 3 allows in particular high temperature applications, typically above 85 ° C.
    However, this Ar – N2 buffer gas mixture 8 is incompatible with a method of manufacturing the microcell 3 in which the cesium vapor is generated using a pellet comprising cesium subsequent to the tight closure of the chamber. microcell 3, described in the publication by M. Hasegawa, RK. Chutani, C. Gorecki, R. Boudot, P. Dziuban, V. Giordano, S Clatot - “Microfabrication of cesium vapor cells with buffer gas for MEMS atomic docks” - Sensors and Actuators A: Physical 167 (2), 594–601 , 2011).
    An object of the invention is to provide a buffer gas mixture 8 with an inversion temperature greater than 80 ° C compatible with a method of manufacturing microcells, as described in the publication cited above, including The step of generating the cesium vapor is subsequent to the step of closing the microcell.
    [0060] Thus, according to one aspect of the invention, there is provided a method of manufacturing a cesium atomic micro-clock microcell with an inversion temperature greater than 80 ° C comprising:a first step of manufacturing a micro-clock microcell structure, so as to obtain a first and a second cavities connected to each other by channels,a second step of fixing a lower plate under the structure of the microcell so as to create a first and a second closed cavities on the lower side of the structure,a third step of introducing a pellet comprising cesium into the first cavity,a fourth step of introducing a gas mixture comprising neon and helium into the structure of the microcell,a fifth step of fixing a top plate so as to seal off the first and second cavities, anda sixth step of heating the pellet comprising cesium.
    The use of a gas mixture comprising neon and helium allows in particular the manufacture of microcells according to a particular process consisting in generating a cesium vapor subsequent to the tight closing of the microcell by heating the pellet comprising cesium.
    Advantageously, the first step of manufacturing the structure of the microcell comprises:a first sub-step of forming two cavities in a silicon monolith, anda second sub-step of making the channels.
    Advantageously, the formation of the two cavities is carried out by a deep reactive ionic etching process.
    [0064] Advantageously, the heating of the pellet is carried out using a laser making it possible to locally reach temperatures of the order of 700 ° C necessary for the generation of the cesium vapor.
    [0065] Advantageously, the lower plate and the upper plate comprise borosilicate glass.
    Advantageously, the second and fifth steps of fixing the lower and upper plates are steps of anodic welding by heating to a temperature of 350 ° C and by applying a potential difference of 900 V between the plate respectively. lower and the structure and between the upper plate and the structure allowing a tight closure of the microcell so that the highly volatile helium gas does not escape.
    [0067] Advantageously, the percentage of helium in the Ne-He mixture depends on the inversion temperatures that one wishes to obtain. Typically, inversion temperatures are between 80 ° C and about 140 ° C.
    [0068] Advantageously, the pressure of the Ne-He mixture inside the microcell is between 10 and 150 Torr at a temperature of 0 ° C.
    According to another aspect of the invention, there is provided a microcell of a cesium atomic micro-clock with an inversion temperature of greater than 80 ° C comprising a mixture of gases comprising cesium, neon and helium.
    The invention will be better understood and other advantages will become apparent on reading the following description given by way of non-limiting example, and, thanks to the appended figures, among which: FIG. 1, already cited, represents the operating principle of an atomic clock according to the known art, FIG. 2, already cited, illustrates the principle of the coherent population trapping effect, FIG. 3, already cited, represents the principle and the main elements constituting a cesium atomic micro-clock, FIGS. 4a to 4f illustrate the stages in the development of a microcell according to the invention, FIG. 5 is a diagram of a microcell according to the invention, FIG. 6 illustrates an example of a resonance peak according to the CPT principle of a clock signal detected by a Cs-Ne-He microcell, according to one aspect of the invention, and FIGS. 7a to 7d are graphical representations of the clock frequency as a function of the cell temperature Cs-Ne-He for different buffer gas compositions, these figures show the inversion temperature for these different mixtures, and the table 1 summarizes the observations and deductions from the curves of FIGS. 7a to 7d.
    [0071] Figs. 4a to 4f illustrate the steps in the development of a cesium microcell described in the publication by M. Hasegawa et al. cited above.
    [0072] In this case, the cesium vapor of the microcell is generated only after the final closure step of microcell 3.
    In a first step (fig. 4c), the structure 31 of the microcell 3, shown in fig. 4a is carried out.
    By structure 31 is meant the block or monolith of material 30 comprising the first 32 and second 33 cavities interconnected by channels.
    In this case, the structure 31 is made from a block of silicon 30 or "wafer" of silicon in which are etched two cavities 32 and 33. Advantageously, the silicon monolith is hollowed out by a method of engraving such as the acronym DRIE for "Deep Reactive Ion Etching", in English. Alternatively, other methods can be implemented, such as KOH chemical etching.
    In a second step (fig. 4c), a lower plate 34a is fixed under the structure 31. Advantageously, the fixing of the plate 34a is carried out by anodic welding up to a temperature of 350 ° C and by applying a potential difference between the lower plate 34a and the material of the structure 31, typically the material of the structure is silicon.
    Is introduced in a third step (Fig. 4d) a pellet 35 or bread comprising cesium.
    The term “cesium bar or lozenge” means a solid element comprising in particular cesium and intended to allow the creation of a cesium vapor inside the microcell under the effect of temperature.
    [0079] Analyzes have shown the presence of other materials and in particular zirconium in the cesium pellet 35 used to generate the cesium vapor.
    Studies have shown that the zirconium present in the cesium-35 pellet absorbs the nitrogen of the N2 – Ar buffer gas, usually used, which explains the fact that the N2 – Ar mixture cannot be used in a method of making a microcell using a cesium pellet. In fact, the nitrogen present in the buffer gas 8 is absorbed and the mixture no longer plays its role of buffer gas.
    In a fourth step (Fig. 4e), the buffer gas mixture 8 is introduced according to the invention. In this case, the buffer gas mixture 8 comprises neon and helium prior to the fifth step of closing the structure 31 by a top plate 34b on top of the structure 31.
    The buffer gas mixture 8 comprising neon and helium is not absorbed by the cesium pellet 35 and makes it possible to achieve inversion temperatures above 80 ° C.
    Typically, the different Ne-He buffer gas compositions make it possible to achieve temperatures between 80 ° C and about 140 ° C.
    In a sixth step of heating the cesium pellet to a temperature of 700 to 800 ° C, the cesium vapor is generated. The cesium vapor will then migrate to the other cavity via channels 36.
    [0085] FIG. 5 is a perspective view of microcell 3, according to one aspect of the invention.
    The microcell 3 comprises a first 32 and a second 33 cavities. In this case, the first cavity 32 is circular and the second cavity 33 is square in shape, however it is specified that the shapes of these cavities 32 and 33 are not of particular importance, so the cavities can be of any shape. The two cavities 32 and 33 are also connected to each other by narrow channels 36.
    Furthermore, inside one of the cavities 32 and 33, in this case, inside the second cavity 33, is arranged a pellet or bar comprising cesium 35 in the form of an alloy. metallic.
    The cavity 32 is filled with a mixture of buffer gas 8, not visible in FIG. 5, the mixture comprising neon and helium. After the final closure of the microcell by fixing the upper plate 34b, heating by laser to a temperature of 700–800 ° C of the pellet comprising cesium 35 generates a cesium vapor inside the microcell 3.
    [0089] Figs. 7 are graphical representations of frequency versus temperature for different compositions of buffer gas 8 including neon and helium. The various conclusions resulting from these curves are summarized in Table 1.
    More particularly, these curves demonstrate the movement S of clock frequency as a function of the temperature of the microcell 3 comprising a cesium vapor and a buffer gas mixture 8 to demonstrate the presence of a temperature. inversion for which the sensitivity of the clock frequency to temperature variations is canceled out to the first order.
    To achieve these curves, a laser diode is used emitting a laser beam resonating at a wavelength of 894.6 nm (D1 line of the cesium atom), the beam is introduced into a modulator which modulates the beam using a local oscillator generating a signal of 4.596 GHz, corresponding to half of the cesium clock frequency (9.192 GHz). The optical spectrum is then made up of two separate lines of 9.192 GHz.
    The laser beam is sent to the Cs-Ne-He microcell, the microcell being temperature regulated. In addition, the microcell is placed in a magnetic field of a few micro-tesla so as to isolate the clock transition. The transmitted light power is detected by a photodiode.
    To detect the CPT resonance, the frequency of the local oscillator which controls the modulator is scanned and the change in the light power transmitted through the cell is measured. When the frequency separation between the two optical lines at the output of the modulator is strictly equal to the hyperfine transition frequency of the atoms, the cesium atoms are trapped in a particular state, called the black state, in which they no longer absorb photons. incidents. The light power transmitted through the cell is then maximum and a resonance peak (fig. 6) is detected at the output of the cell. An electronic module allows the frequency of the local oscillator to be slaved to the peak of the CPT signal: the atomic clock is thus formed.
    The different curves of FIGS. 7 highlight the fact that the inversion temperature directly depends on the partial pressures of neon and helium.
    The curve 41 of FIG. 7a was produced with a cell according to the invention comprising a mixture of buffer gas 8 comprising 2.4% helium and 97.6% neon. Curve 41 has a quadratic shape, the point at the top corresponding to the inversion temperature. In this case, the inversion temperature is 89.7 ° C.
    The curves 43 and 44 have similar shapes to the shape of the curve 41, only the proportion of helium is modified, for a percentage of helium of 3.3% the inversion temperature is 94, 6 ° C.
    We understand that the more the proportion of helium in the buffer gas 8 increases, the more the inversion temperature increases.
    These results suggest that for larger proportions of helium, it would be possible to further increase the inversion temperature and potentially to reach inversion temperatures of the order of 110 ° C or even 140 ° vs.
    Micro-clocks made with a neon-helium mixture could be used in an on-board device for applications in high temperature environments.
    [0100] Obviously, a buffer gas 8 comprising a Ne-He mixture can very well be used in other types of microcells not using in particular a cesium 35 pellet.
    权利要求:
    Claims (10)
    [1]
    1. A method of manufacturing a cesium atomic micro-clock microcell with an inversion temperature greater than 80 ° C comprising:- a first step of manufacturing a micro-clock microcell structure (31), so as to obtain a first (32) and a second (33) cavities interconnected by channels (36),- a second step of fixing a lower plate (34a) under the structure (31) of the microcell so as to create a first (32) and a second (33) closed cavities on the lower side of the structure (31),- a third step of introducing into the first cavity (32) a pellet (35) comprising cesium,- a fourth step of introducing a gas mixture (8) comprising neon and helium in the structure (31) of the microcell,- a fifth step of fixing an upper plate (34b) so as to seal the first (32) and second cavities (33), and- a sixth step of heating the pellet (35) comprising cesium.
    [2]
    2. The method of claim 1 wherein the first step of manufacturing the structure (31) of the microcell comprises:- a first sub-step of forming the two cavities (32; 33) in a silicon monolith, and- a second sub-step of making the channels (36).
    [3]
    3. Method according to one of claims 1 or 2 wherein the two cavities are produced by a deep reactive ionic etching process.
    [4]
    4. Method according to one of the preceding claims, in which the heating of the pellet (35) is carried out using a laser.
    [5]
    5. Method according to one of the preceding claims, wherein the lower plate (34a) and the upper plate (34b) comprise borosilicate glass.
    [6]
    6. Method according to one of the preceding claims wherein the second and fifth steps of fixing the lower (34a) and upper (34b) plates comprise an anodic welding step.
    [7]
    7. Method according to one of claims 5 or 6 wherein the anodic soldering steps are carried out by heating to a temperature of 350 ° C and by applying a potential difference of 900V between the upper plate (34b). and the structure (31) and the bottom plate (34a) and the structure (31).
    [8]
    8. Method according to one of the preceding claims, in which the percentage of helium in the Ne-He gas mixture depends on the desired inversion temperature.
    [9]
    9. Method according to one of the preceding claims, in which the pressure of the Ne-He mixture inside the microcell is between 10 and 150 Torr at a temperature of 0 ° C.
    [10]
    10. Cesium atomic micro-clock microcell with an inversion temperature greater than 80 ° C comprising a mixture of gases (8) comprising cesium, neon and helium.
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    同族专利:
    公开号 | 公开日
    CH710305B1|2019-07-15|
    US9864340B2|2018-01-09|
    FR3027416A1|2016-04-22|
    US20160109859A1|2016-04-21|
    FR3027416B1|2016-12-09|
    引用文献:
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    JP6031787B2|2011-07-13|2016-11-24|株式会社リコー|Method for manufacturing atomic oscillator|
    FR2996962B1|2012-10-12|2016-01-01|Centre Nat Rech Scient|ALKALINE STEAM CELL PARTICULARLY FOR ATOMIC CLOCK AND METHOD OF MANUFACTURING THE SAME|
    JP6135308B2|2012-11-21|2017-05-31|株式会社リコー|Alkali metal cell, atomic oscillator and method for producing alkali metal cell|CN106647225B|2016-12-21|2018-12-18|兰州空间技术物理研究所|A kind of CPT atomic clock light channel structure|
    法律状态:
    2016-08-15| PUEA| Assignment of the share|Owner name: THALES, FR Free format text: FORMER OWNER: CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE (CNRS), FR |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1402343A|FR3027416B1|2014-10-17|2014-10-17|GAS MIXTURE MICROCELLULAR MICROCELL PAD MICRO CLOCQUER AT CESIUM|
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