ALMA Band 3 Receivers

Work continues on the development of the Band 3 receivers, extremely sensitive low-noise 84–116GHz receivers that are a critical element of the Atacama Large Millimetre Array Radio Telescope project (ALMA). This project will culminate with the delivery of 73 receivers to ALMA.

Project Manager: Keith Yeung
Project Engineer: Stéphane Claude
Project Scientist: Doug Johnstone

The NRC Herzberg Institute of Astrophysics (NRC-HIA) is currently involved in the development of 73 84–116 GHz heterodyne receivers for the international Atacama Large Millimetre array (ALMA). ALMA will be located at 5000 m elevation in the Chajnantor Plain of northern Chile — the best accessible submillimetre astronomy site in the world. ALMA will be the world's pre-eminent radio astronomy facility of the next decades; its resolution and sensitivity will constitute a great leap forward compared to existing facilities.

The receiver development program consists of two stages. The prototype development phase (2002–08) involves the development of 8 prototype cartridges that meet the stringent ALMA specifications. The second phase will be the production of the final sixty-five (65) receiver units, which will be delivered to the Front End Integration Centres (FEICs) in Charlottesville, Virginia, Oxford, U.K., and Taipei, Taiwan, starting in April 2008 and ending in December 2011.

The first twelve Band 3 have been shipped to the North American Integration Centre including SN 2 to 6 (as shown in picture below). Eleven other Band 3 cartridges have been fully assembled and tested on the NRC-HIA Cartridge Test Bed and are ready to be delivered to the three FEICs.

Image of Band 3 receiver cartridges

The nucleus of the receiver is a superconductor-insulator-superconductor (SIS) tunnel diode mixer which downconverts the RF signal collected by the radio telescope to an intermediate frequency (IF) signal centred at 8 GHz with a bandwidth of 8 GHz. The SIS detector must operate at a temperature of 4 Kelvin. A cryogenic high electron mobility transistor (HEMT) amplifier is used to amplify the IF signal by 40 dB before it is delivered to the ALMA Back-End System.

The receiver specifications are extremely demanding. The RF coverage is 84–116 GHz, and the IF bandwidth is 8 GHz. The receiver noise temperature must be below 17 K over 80% of the RF operating band, and must be below 27 K at all frequencies for double-side band responses. The gain and phase stability of the receivers must be less than one part in 10⁴ per second. These design specifications constitute a significant technical challenge.

Related links

NRC-HIA ALMA project web page

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Related Information

Institutes:

• NRC Herzberg Institute of Astrophysics