There is a marginal increase in TD-slow flux with surface temperature, but it is difficult to discern trends, because the variation over the wide range of surface temperatures is small. The angular distributions of O at Ts = 1023 K and 1623 K for FiberForm are shown in Figure (Supplementary Material). The TD-prompt fluxes can be fit well with a cosine-power distribution, cos n θf, with n = 1.27 at Ts = 1023 K and n = 1.56 at Ts = 1623 K. The angular distribution of the IS flux for FiberForm is much broader than for vitreous carbon, as would be expected for a rough surface. Finally, the thermal fluxes are higher in the decreasing temperature sweep compared to the increasing temperature sweep. This is a manifestation of a hysteresis effect that is discussed below.