Reaching 5E-13 short term frequency stability of the integrating sphere   cold atom clock
  We present an improvement of short term frequency stability of the integrating sphere cold atom clock after increasing the intensities of clock signals and optimizing the feedback loop of the clock. A short term frequency stability of $5.0\times10^{-13}\tau^{-1/2}$ has been achieved and the limiting factors have been analyzed. 
P Liu, Y L Meng, J Y Wan, X M Wang, Y N Wang, L Xiao, H D Cheng, and L   Liu
physics.atom-ph