Cosmic microwave background observations with the Jodrell Bank-IAC interferometer at 33 GHz

This paper presents the first results obtained with the Jodrell Bank-IAC tw o-element 33-GHz interferometer, The instrument was designed to measure the level of the cosmic microwave background (CMB) fluctuations at angular sca les of 1 degrees-2 degrees. The observations analysed here were taken in a strip of the sky at Dec. = +41 degrees with an element separation of 16.7 l ambda, which gives a maximum sensitivity to similar to 1.degrees 6 structur es on the sky. The data processing and calibration of the instrument are de scribed. The sensitivity achieved in each of the two channels is 7 mu K per resolution element. A reconstruction of the sky at Dec. = +41 degrees usin g a maximum entropy method shows the presence of structure at a high level of significance, A likelihood analysis, assuming a flat CMB spatial power s pectrum, gives a best estimate of the level of CMB fluctuations of Delta T- l = 43(-12)(+13)mu K for the range l = 109 +/- 19; the main uncertainty in this result arises from sample variance. We consider that the contamination from the Galaxy is small. These results represent a new determination of t he CMB power spectrum on angular scales at which previous results show a la rge scatter; our new results are in agreement with the theoretical predicti ons of the standard inflationary cold dark matter models.