The National Astronomical Observatory of Japan (NAOJ) is promoting the “ALMA 2” project, a major upgrade of the Atacama Large Millimeter/submillimeter Array (ALMA) for the 2030s. As part of this effort, NAOJ is participating in the internationally coordinated Wideband Sensitivity Upgrade (WSU) program. NAOJ developed the current Band 8 receiver (observing frequency: 385–500 GHz) in the construction phase of ALMA. As part of WSU, NAOJ continues to lead the design and development aimed at expanding the instantaneous observing bandwidth to 4–18 GHz range, while reducing the receiver’s noise temperature to achieve higher sensitivity.

The development team has been working to reconfirm the specifications and performance of the current Band 8 receiver. At the same time, they have reexamined the design and reevaluated the performance of each individual component that will make up the new receiver while pursuing further performance improvements through research and development. These efforts are carried out in collaboration with universities, research institutes, and companies in Japan and abroad. Based on these efforts, the team presented a design proposal capable of meeting the enhanced scientific requirements for the new receiver. The proposal was evaluated by an expert panel during the Preliminary Design Review.

The preliminary design review is a key process for evaluating the validity of the receiver system requirements and external interfaces derived from these scientific requirements, along with development progress, design feasibility, and potential risks. Expert reviewers from Japan and abroad specializing in the receiver and its component technologies conducted the review and discussed a wide range of technical issues and challenges they face in advancing the development. The participants also visited laboratories on the NAOJ Mitaka campus and a cleanroom that is used to manufacture the superconducting devices forming the core of the receiver. This provided a unique opportunity to directly observe the development environments and evaluation systems actually in use.

The review committee concluded that, for the preliminary design for the Band 8 receiver upgrade, the overall design approach and interfaces have been appropriately organized, and the feasibility of addressing the main technical challenges has been clearly demonstrated. In addition, the committee provided a number of recommendations that will benefit future development. Based on the evaluation and recommendation received in this preliminary design review, the Band 8 receiver upgrade team will proceed to the next stage, a critical design phase, and continue working toward the realization of a high-performance “ALMA 2” system.

Related Links:
ALMA 2 Project has begun (2023.04.27)
ALMA2030 Wideband Sensitivity Upgrade (WSU) –Next Frontier for ALMA