Development of thermodynamic temperature measurement system based on quantum voltage noise source at NMIJ

We have been developing a Johnson noise thermometer (JNT) at NMIJ toward redefinition of the Boltzmann constant k. The JNT system measure thermal noise power of a resistor installed at the triple point of water and power of a reference signal generated with a Quantum Voltage Noise Source (QVNS) alternatively in order to obtain k precisely. Relative differences between experimentally obtained k and the current CODATA value was 7 part in 10
^-5
. Relative statistical uncertainty of k for 18 hours measurement was 2 parts in 10
^-5
.