Near-field beam pattern measurement of ALMA band 8 (385 – 500 GHz) first cartridge

In this paper, the optical performance of the ALMA band 8 (385-500 GHz) cartridge receiver (S/N 01), which is the first one of 80 shipments, was investigated. ALMA Band 8 cartridge receiver consists of a corrugated horn, an ortho-mode transducer, an elliptical mirror, a local oscillator, IF amplifiers, and superconducting-insulator-superconducting (SIS) mixers which cover IF frequency range from 4 to 8 GHz. The amplitude and phase of electric field at near-field were probed, and then the far-field co-polar and cross-polar patterns of the receiver were transferred. The far-field patterns are symmetrical, low side-lobe and compatible with physical optics simulations down to -30 dB. We confirmed that the aperture efficiency at sub-reflector of 12-m antenna are around 80 % and cross-pol. efficiency are about - 20 dB at five frequencies.