Small-angle anisotropies in the CMBR from active sources

We consider the effects of photon diffusion on the small-angle microwave background anisotropies due to active source models. We find that fluctuations created just before the time of last scattering allow anisotropy to be created on scales much smaller than allowed by standard Silk damping. Using simple models for string and texture structure functions as examples, we illustrate differences in the angular power spectrum of the intrinsic and Doppler components of the anisotropy on scales of the order of a few arcminutes. In particular, we find that the Doppler peak heights are modified by 10-50% and small-angle fall-off is power law rather than exponential.