ALMA Band 5 receiver cartridge. Design, performance, and commissioning

We describe the design, performance, and commissioning results for the new ALMA Band 5 receiver channel, 163–211 GHz, which is in the final stage of full deployment and expected to be available for observations in 2018. This manuscript provides the description of the new ALMA Band 5 receiver cartridge and serves as a reference for observers using the ALMA Band 5 receiver for observations. At the time of writing this paper, the ALMA Band 5 Production Consortium consisting of NOVA Instrumentation group, based in Groningen, NL, and GARD in Sweden have produced and delivered to ALMA Observatory over 60 receiver cartridges. All 60 cartridges fulfil the new more stringent specifications for Band 5 and demonstrate excellent noise temperatures, typically below 45 K single sideband (SSB) at 4 K detector physical temperature and below 35 K SSB at 3.5 K (typical for operation at the ALMA Frontend), providing the average sideband rejection better than 15 dB, and the integrated cross-polarization level better than –25 dB. The 70 warm cartridge assemblies, hosting Band 5 local oscillator and DC bias electronics, have been produced and delivered to ALMA by NRAO. The commissioning results confirm the excellent performance of the receivers

Direct Measurement of Superconducting Tunnel Junction Capacitance

Abstract-Superconductor-Insulator-Superconductor (SIS) is the key component for millimeter and submillimeter mixers for radio astronomy and environmental science. The capacitance of the SIS mixer determines both the RF and IF performances. Previously, the measurements of this capacitance have been followed with high uncertainty levels. Herein, we present the characterization of the SIS junction capacitance at cryogenic temperature (~4 K) by direct measurement of the SIS junction impedance at microwave frequencies allowing accurate characterization of the SIS junction capacitance. The proposed calibration method uses only one short-circuit reference. The SIS junction capacitance measurement is realized by biasing the junction at the different parts of its current-voltage characteristic, thus eliminating a separate measurement of shortcircuit standard. In order to verify the acquired measurement results, thin-film capacitors with known capacitance were also characterized. The capacitances of four SIS junctions with various areas were measured. The absolute uncertainty of the proposed measurement method was found to vary from 5 to 6.8 % amongst different junction areas