A Microwave Blackbody Target for Cosmic Microwave Background Spectral Measurements in the 10-20GHz range

TL;DR

This paper details the design, construction, and testing of a cryogenically cooled microwave blackbody target for precise spectral measurements of the cosmic microwave background in the 10-20 GHz range.

Contribution

It introduces a novel, highly stable, and thermally homogeneous blackbody calibration target optimized for the Tenerife Microwave Spectrometer.

Findings

Achieved temperature stability of +/- 1 mK/h

Ensured high emissivity (>= 0.999)

Demonstrated thermal homogeneity with gradients <= 25 mK

Abstract

The Tenerife Microwave Spectrometer (TMS) is a ground-based radio-spectrometer that will take absolute measurements of the sky between 10-20 GHz. To ensure the sensitivity and immunity to systematic errors of these measurements, TMS includes an internal calibration system optimised for the TMS band, and cooled down to 4 K. It consists of an Aluminium core, composed of a baseplate and a bed of pyramidal elements coated with an absorber material and a metallic shield. The absorber coating is made of a commercial resin ECCOSORB CR/MF 117. To achieve the high stability (+/- 1 mK/h), temperature homogeneity (thermal gradients {AT <= 25 mK), and emissivity (e>= 0.999) requirements of the reference unit, careful consideration has been given to the RF and thermal properties of the materials, as well as their geometry. In summary, this paper presents a comprehensive account of the design, characterisation, and test results of the TMS reference system.