We report an experimental study on the temperature and number evolution of cold cesium atoms diffusively cooled inside a wall-coated glass cell by measuring the absorption profile of the 62S1/2 （F = 4） →62P3/2（F= ...We report an experimental study on the temperature and number evolution of cold cesium atoms diffusively cooled inside a wall-coated glass cell by measuring the absorption profile of the 62S1/2 （F = 4） →62P3/2（F= 5） transition line with a weak probe laser in the evolution process. We found that the temperature of the cold atoms first gradually decreases from 16 mK to 9 mK, and then rapidly increases. The number of cold atoms first declines slowly from 2.1 × 109 to 3.7×108 and then falls drastically. A theoretical model for the number evolution is built and includes the instantaneous temperature of the cold atoms and a fraction p, which represents the part of cold cesium atoms elastically reflected by the coated cell wall. The theory is overall in good agreement with the experimental result, and a nonzero value is obtained for the fraction p, which indicates that the cold cesium atoms are not all heated to the ambient temperature by a single collision with the coated cell wall. These results can provide helpful insight for precision measurements based on diffuse laser cooling.展开更多
Superconducting hot electron bolometer(HEB)mixers are the most sensitive heterodyne detectors at frequencies beyond 1 THz,and are used for many astronomical observations.HEB,consisting of a narrow and short supercondu...Superconducting hot electron bolometer(HEB)mixers are the most sensitive heterodyne detectors at frequencies beyond 1 THz,and are used for many astronomical observations.HEB,consisting of a narrow and short superconducting thin film patch connected to an antenna via contact pads,is brought into a highly sensitive operating regime by applying a DC current and a certain amount of local-oscillator power.Potentially,superconducting HEB mixers are capable of exhibiting high sensitivity for frequencies up to several tens of THz,as their output noise and conversion gain are nearly frequency independent according to the mixing mechanism.Moreover,the understanding of mixing mechanism has evolved over time from lumped-element model to distributed hot-spot model.In this review,we provide an overview of theoretical and experimental studies on HEBs and their applications,especially in astronomical observations on ground,airborne and space telescopes.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11304177)
文摘We report an experimental study on the temperature and number evolution of cold cesium atoms diffusively cooled inside a wall-coated glass cell by measuring the absorption profile of the 62S1/2 （F = 4） →62P3/2（F= 5） transition line with a weak probe laser in the evolution process. We found that the temperature of the cold atoms first gradually decreases from 16 mK to 9 mK, and then rapidly increases. The number of cold atoms first declines slowly from 2.1 × 109 to 3.7×108 and then falls drastically. A theoretical model for the number evolution is built and includes the instantaneous temperature of the cold atoms and a fraction p, which represents the part of cold cesium atoms elastically reflected by the coated cell wall. The theory is overall in good agreement with the experimental result, and a nonzero value is obtained for the fraction p, which indicates that the cold cesium atoms are not all heated to the ambient temperature by a single collision with the coated cell wall. These results can provide helpful insight for precision measurements based on diffuse laser cooling.
基金supported partly by NSFC under Grants U1831202,U1731119,U1931123,11773083,and 11873099the National Key R&D Program of China under Grants 2017YFA0304003 and 2018YFA0404701,CAS under Grants QYZDJ-SSW-SLH043 and GJJSTD20180003Jiangsu Province under Grant BRA2020411.
文摘Superconducting hot electron bolometer(HEB)mixers are the most sensitive heterodyne detectors at frequencies beyond 1 THz,and are used for many astronomical observations.HEB,consisting of a narrow and short superconducting thin film patch connected to an antenna via contact pads,is brought into a highly sensitive operating regime by applying a DC current and a certain amount of local-oscillator power.Potentially,superconducting HEB mixers are capable of exhibiting high sensitivity for frequencies up to several tens of THz,as their output noise and conversion gain are nearly frequency independent according to the mixing mechanism.Moreover,the understanding of mixing mechanism has evolved over time from lumped-element model to distributed hot-spot model.In this review,we provide an overview of theoretical and experimental studies on HEBs and their applications,especially in astronomical observations on ground,airborne and space telescopes.
