MEASUREMENTS OF COSMIC BACKGROUND-RADIATION ANISOTROPY AT INTERMEDIATE ANGULAR SCALE

Results from an Antarctic ground-based experiment devoted to the searc h for fluctuations in the cosmic background radiation (CBR) are presen ted. We have developed an off-axis telescope with a Gaussian beam resp onse of 50' FWHM and with a beam-throw adjustable from 0-degrees to 2- degrees. The detector was a He-3 bolometer working at 0.35 K and opera ting at 2.2 mm wavelength. The data collected show evidence of fluctua tions at a level of DELTAT(rms)/T = 4.5 x 10(-5) at an angular scale o f 40'. The expected fluctuations obtained by extrapolating the COBE re sult down to this angular scale, in a cold dark matter scenario, are a factor 2.5 lower (1.8 x 10(-5)). If residual systematic effects or co ld galactic dust emission are responsible for the signal detected, our result should be considered as an upper limit to CBR anisotropy.