High-significance Sunyaev-Zel'dovich measurement:: Abell 1914 seen with the Arcminute Microkelvin Imager

We report the first detection of a Sunyaev - Zel'dovich (S - Z) decrement using the Arcminute Microkelvin Imager ( AMI). We have made commissioning observations towards the cluster of galaxies A1914 and detected the S - Z effect with a significance of 17 sigma in a uv-tapered map at a mean frequency of 15.75 GHz. The integrated S - Z flux density of - 8.6 +/- 0.5 mJy is consistent with a simple X-ray derived model for the intracluster gas. We find that the spectrum of the decrement, measured in the six channels between 13.5 - 18 GHz, fits well to that expected for the S - Z effect. The sensitivity of the telescope is consistent with the figures used in our simulations of cluster surveys with AMI.