CYCLOPS - A SINGLE-BEAM 1.3 MILLIMETER POLARIMETER

We present the design of a broad band, 1.3 mm polarimeter for astronom ical observations and the results of first light observations at the H einrich Hertz Telescope (HHT). The systematic polarization of the inst rument plus telescope is 1.1%. The observed linear polarization of DR 21, P = 1.65% +/- 0.14% and theta = 16 degrees +/- 2 degrees, is consi stent with previous measurements. Our 0.9% upper limit on the linear p olarization of Cepheus A is the first 1.3 mm measurement reported. Wit h Cyclops it is possible to map the magnetic fields in several of the brightest molecular cloud dust cores in the Milky Way. We comment on t he expected performance of an achromatic Rexolite half-waveplate for l ambda = 800 mu m to 1.3 mm.