A revised uncertainty budget for measuring the Boltzmann constant using the Doppler broadening technique on ammonia

We report on our on-going effort to measure the Boltzmann constant, kB, using the Doppler broadening technique. The main systematic effects affecting the measurement are discussed. A revised error budget is presented in which the global uncertainty on systematic effects is reduced to 2.3?ppm. This corresponds to a reduction of more than one order of magnitude compared with our previous Boltzmann constant measurement. Means to reach a determination of kB at the part per million accuracy level are outlined.