Research on Vacuum Transfer Equipment in NIM

By the end of 2018, the 26th Congress of Metrology and Weights (Conférence Générale des Poids et Mesures, CGPM) had been held. A new definition of mass unit has been approved on the meeting of CGPM. Mise en pratique-kg includes the guide of dissemination after the redefinition of kilogram. The traditional dissemination of mass unit is carried out in air. The new method for dissemination from Planck constant to primary mass standard or from primary mass standard to secondary mass is implemented under vacuum. The dissemination method after the redefinition of mass unit will be changed from Planck constant to primary mass standard or from primary mass standard to secondary mass standard. The measurement of weights under vacuum will replace the measurement of weights in air. To transfer weights from vacuum vessel to vacuum mass comparator, a vacuum transfer equipment (VTE) is developed by National Institute of Metrology, China (NIM). A multistage manipulator system is designed to transfer weight under vacuum between VTE and vacuum mass comparator or Joule Balance. The experimental results show that the performance of VTE is efficient for transferring the weights under vacuum.