Improving Band 9 Sensitivity by Advanced Tuning Algorithms

Principal Investigator: Ronald Hesper

Institute: Netherlands Research School for Astronomy, The Netherlands


The scientific driver for the proposed study is an improvement of the sensitivity of the existing ALMA Band 9 receivers that have been delivered by the NOVA Submillimeter Instrumentation Group to the observatory, without any hardware intervention. This ties in with the Recommended Development Path number 2 (“Larger bandwidths and better receiver sensitivity”) in the ASAC recommendations for ALMA 2030. It also corresponds to Pathway No. 05 (“Sensitivity: Lower noise Rxs”) in the ALMA Development Working Group Report “Pathways to Developing ALMA”.

We expect that the noise temperature of a significant number (likely considerably more than half) of the delivered mixers can be improved by about 10K, and some as much as 20K, by developing advanced tuning algorithms. Since the typical double sideband (DSB) noise temperature of the mixers is of the order of 100K, this means an increase of about 10% (and possibly more) in sensitivity for the entire array “for free”. The investment to be made for this is the currently proposed study and the effort of implementing it in the ALMA front end software.

Of course, any insights gained in this study can also be used in other instruments that use the ALMA Band 9 mixers (CHAMP+, Sepia, LLama), and, with proper modifications, likely with other SIS-based bands as well.