D.I. Sevost\'yanov - Advanced Energy Technologies Ltd. (Skolkovo). E-mail: dmitry.sevost.mephi@gmail.com A.V. Sivak - Advanced Energy Technologies Ltd. (Skolkovo). E-mail: sanyoker@mail.ru S.S. Losev - National Research Nuclear University «MEPhI» (Moscow). E-mail: losevsts@gmail.com Yu.V. Mas\'yan - National Research Nuclear University «MEPhI» (Moscow). E-mail: i23591326@gmail.com R.I. Fishman - Advanced Energy Technologies Ltd. (Skolkovo). E-mail: f_raf@mail.ru V.V. Vasil\'ev - P.N. Lebedev Physical Institute of RAS (Moscow). E-mail: vvv@okb.lpi.troitsk.ru S.A. Zibrov - Ph. D. (Phys.-Math.), P.N. Lebedev Physical Institute of RAS (Moscow). E-mail: szibrov@yandex.ru V.L. Velichansky - Ph. D. (Phys.-Math.), P.N. Lebedev Physical Institute of RAS (Moscow). E-mail: vlvlab@yandex.ru

An overview of the methods of manufacturing atomic cells filled with alkali metals and buffer gases with a typical size of less than about 5 mm is given in the Introduction section of the paper. A cell fabrication technique implementing the glass welding technology is compared to a method based on the anode diffusion bonding of silicon and Pyrex that is used by Symmetricom, Inc. The advantages and disadvantages of the two approaches are discussed. The details of the experimental setup used for the production of the glass atomic cells are presented. The frequency dependence of a CPT resonance on the cell temperature has opposite signs in case of Ar and Ne buffer gases. These dependences for different pressure ratios of buffer gases were studied. A particular attention was paid to the determination of the ratio of Ar and Ne gases resulting in a minimal temperature shift coefficient. A proper selection of the partial pressures of buffer gases can significantly reduce the requirements for the stability of the cell temperature. Laser welding together of the cell body and the second window occurs in the chamber filled with the needed buffer-gas mixture. Due to the heating of the cell and the enclosed gas its pressure becomes greater than that of the chamber and some part of it escapes from the cell. As a result, pressure in the cell after cooling is smaller than that in the chamber. By measuring and comparing of the pressure induced shifts in small and large cells performed at the same temperature the following ratios were found. When pure Ne is filled in the cells its pressure in the enclosed small cells is 1.6 times smaller than that in the chamber. For Ar the corresponding ratio is 1.3. The scatter in the pressure of small cells does not exceed 20%. The accomplished systematic measurement of metrological properties of the produced cells supports the conclusion that the developed technology provides high-quality references for CSACs with frequency stability of 10⁻¹¹ per hour.

 

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