  A new method for measuring chance-coincidence backgrounds during the
collection of coincidence data is presented. The method relies on acquiring
data with near-zero dead time, which is now realistic due to the increasing
deployment of flash electronic-digitizer (waveform digitizer) techniques. An
experiment designed to use this new method is capable of acquiring more
coincidence data, and a much reduced statistical fluctuation of the measured
background. A statistical analysis is presented, and used to derive a figure of
merit for the new method. Factors of four improvement over other analyses are
realistic. The technique is illustrated with preliminary data taken as part of
a program to make new measurements of the prompt fission neutron spectra at Los
Alamos Neutron Science Center. It is expected that the these measurements will
occur in a regime where the maximum figure of merit will be exploited.
