In the beam technique, the lifetime is measured by counting the absolute number of protons with a fiducial volume while continuously monitoring the absolute neutron flux. We completed this experiment in 2003 and reported a value of (886.8 +/- 3.4) s where the uncertainty was dominated by systematic effects associated with the neutron counting. Since that time, the group has successfully refined the ability to measure absolute neutron fluence at the level of 0.06%, and with this improvement, neutron counting is no longer the limiting systematic effect. In 2013 we published an improved value of the neutron lifetime using the new neutron counting results, and we are also working on a new experiment to measure the lifetime at the level of 1 s uncertainty.
In the upcoming run of this experiment, we expect that the apparatus will achieve an overall uncertainty on the lifetime near 1 s. Work is in progress on assembling the components needed to operate the experiment and also studying many of the critical systematics effects associated with the measurement. The collaboration expects to mount the experiment on the NG-C beamline in the near future.