Planck-LFI CPV: front end amplifier bias pre-tuning

Abstract

This document describes the results of the Hypermatrix pre–tuning activities. The pre–tuning is aimed at exploring the LNAs bias space changing simultaneously the four Vg biases powering each radiometer, in order to focus the bias region expected to provide the best performance. Noise Temperature is the figure of merit. It is measured roughly by calculating Y factor based on the sky – ref unbalancing over the same BEM diode when the 4KHz switching is enabled. Previous tests conducted on data from CSL campaign demonstrated that a good agreement between this rough calculation and the true Y-factor method ( basing on two reference temperatures provided by the 4K stage cooldown) is achievable.