Research On Doppler Broadening Thermometry Based On Cesium Atomic Absorption Spectroscopy

Fixing Boltzmann constant in SI unit revolution directly impact temperature measurement regarding to merging current used the international scaled temperature scale to thermodynamic temperature scale.In order to reach a quantum thermodynamic temperature sensing,this research implemented a doppler broadening thermometry which takes advantages of direct laser absorption spectroscopy on Cs¹3333 D1(6S^1/2→6P¹/2/2 transition)line to retrieve Doppler broadened linewidth,and calculated the thermodynamic temperature of the thermal equilibriumed atomic gas.The details are as follows:（1）Design of laser frequency stabilization and sweeping system.In order to capture the atomic absorption characteristics better,it is necessary to control the laser output frequency accurately.By locking the output frequency of the laser on the high precision wavelength meter,the relative frequency stability of 1000s laser output can reach 8.97E-10.（2）Design of probe laser power stabilization system.In order to improve the signal-to-noise ratio and the uncertainty of spectral fitting,we need to probe laser power steadily.A closed-loop feedback loop is constructed by splitting the light path,and and the signal-to-noise ratio of power in 1 hour is within 1000:1.That is,the first-order light passing through the AOM is divided into two paths,one of which is converted into an error signal by the high-speed servo controller as a current optical power feedback signal,and is input to the RF source and then modulated to output the AOM to form a closed-loop feedback loop;another as the probe laser.（3）Design of vacuum thermostat system.In order to improve the accuracy and reliability of Doppler broadening thermometry system,a vacuum Thermostatic chamber was designed based on the advantages of other chamber designs.Finally,the 24-hour fluctuation of the ambient temperature of the absorption chamber was achieved.（4）Experimental and spectral data processing analysis.The temperature measurement experiment was carried out by changing the incident power at a target temperature of 28℃,and the temperature measurement results were different under different incident powers.When the incident power is 110μw,the temperature measurement error of the measured high-precision platinum resistance is 0.02%.The experiment was repeated an other day,and the reproducibility of different power points was 0.2%.（5）Uncertainty analysis.The main sources of system uncertainty and the estimated values are given.The reproducibility of the temperature measurement results is 0.15%by multiple experiments at the same power point.