of the kSZ power at $\ell = 3000$ to be $D^{\rm kSZ}_{3000} < 2.8\,\mu{\rm K}^2$ at 95% confidence in the absence of tSZ-CIB correlations. When correlations were allowed, this constraint relaxed to $D^{\rm kSZ}_{3000} < 6.7\,\mu{\rm K}^2$ at 95% confidence. @dunkley13 constrain the amplitude of the kSZ power to be $D^{\rm kSZ}_{3000} < 8.6\,\mu{\rm K}^2$ at 95% confidence with a uniform prior of $\xi \in [0, 0.2]$. When this prior was relaxed to $\xi < 0.5$ in @sievers13, the kSZ constraint was weakened to $D^{\rm kSZ}_{3000} < 9.4\,\mu{\rm K}^2$ at 95% confidence.

The kSZ power can be interpreted as a constraint on reionization. @zahn12 [hereafter Z12] used reionization simulations to show that when all of the kSZ power in the baseline model R12 is interpreted to be from reionization (a more conservative assumption in the case of this upper limit than attributing some of it to homogeneous kSZ), the upper limit on the duration of the period in which the universe goes from an average ionization of $\bar{x}_{e}$ =0.20 to 0.99 is $\Delta z \equiv z_{\xhii=0.20}-z_{\xhii=0.99} \le 4.4$ (95% confidence). Z12 report a yet more conservative limit of $\Delta z \le 7.9$ (95% confidence) when allowing for tSZ-CIB correlation.

This 