Thermostatic chamber for Doppler broadening temperature measurement

With the redefinition of the Boltzmann constant and the basic international temperature unit of Kelvin, the international agreement on temperature scale is gradually transferred to the thermodynamic temperature scale. Based on the Doppler broadening of the cesium atom' absorption spectrum the thermodynamic temperature of cesium atom cell can be measured. The accuracy of temperature measurement and the verification of experimental principle depend on the surrounding temperature stability of the absorption cell. In this paper, a thermostatic chamber with precise temperature control system was designed and realized. The thermostatic chamber consists of an aluminum cavity, a support layer, a shielding layer, a heat insulation layer and a copper column. The influence of size and material parameters on temperature control effect was analyzed by finite element method. Based on theoretical analysis, the structure of the chamber was optimized. In the experiment, circulating water cooling was used to provide the base temperature for the cavity. A negative feedback control program was developed to regulate the heating power of the electric heating film to achieve rapid temperature regulation and stabilization. The maximum temperature difference of the copper column inside the constant temperature chamber with a length of 380 mm and a diameter of 210 mm was less than 8 mK. The temperature fluctuation within 12 hours were less than 1 mK and the temperature stability was less than 0.16 mK, and the standard uncertainty of the camber temperature was 11.02 mK. This study will improve the development of the calibration-free, chip-scale thermodynamic temperature sensors.