Advancing Readout of Large-Format Far-IR Transition-Edge Sensor Arrays

Advances in superconducting detector technology are essential to enabling national science priorities in far-infrared (far-IR) astrophysics. The 2020 Decadal Survey recommendation for a far-IR Probe mission beginning in 2030 clearly emphasizes the need for technology development. A key area identified by the Cosmic Origins Program (COS) as a Tier-1 technology gap is cryogenic multiplexing of tens of thousands of superconducting detectors, which requires a unique low power, low noise and scalable solution. To address this challenge, this proposal focuses on the development of time-domain multiplexing for superconducting Transition-Edge Sensor (TES) bolometers. The TES bolometer is a mature detector technology that has been employed in numerous pioneering sub-orbital millimeter and far-IR instruments. Specifically, the absorber-coupled TES bolometer is uniquely versatile. It can be used to efficiently detect light across the entire 1–1000μm range and is the most promising candidate for achieving ultra-low noise operation with high optical coupling efficiency in the infrared. A new generation of two-dimensional time-domain multiplexer (2dMUX) array will be designed, fabricated, and tested that permit significantly higher multiplexing factors (≥128) over current implementations. The circuit and physical design of the multiplexer unit cell has improved greatly through existing efforts to build 2dMUXs for the X-ray Integral Field Unit on the Advanced Telescope for High Energy Astrophysics (ATHENA – L-Class ESA mission), which uses an array of 3,168 TES micro-calorimeters. The advances made in the design and performance of the 2dMUX for X-IFU are immediately applicable to the multiplexing of far-IR TES bolometers. For example, the latest innovation is a two-level row address switch that dramatically reduces the number of wires needed to address the readout. A reduction in the number of wires directly translates to a lower dissipation at the coldest stage of a cryogenic focal plane and longer cryogenic hold time. Further improvements in the physical layout of the multiplexer unit cell promises will lead to a 30% reduction in the 2dMUX array size, which translates to a reduction in size of the focal plane assembly. The new generation of 2dMUX arrays will have better noise performance, dissipate less power, and require significantly less row address wires. The first year of the program will focus on the design and integrating two-level switching into an array format. In the second year, two 32(row)×16(col) 2dMUX arrays will be hybridized to a fanout board and read out as a 64(row)×16(col). The end-to-end performance of the multiplexer chips will be assessed with an array of 1024 low-noise TES pixels that will be placed on the fanout board.

The Strategic Astrophysics Technology program (SAT) supports focused development efforts for key technologies to the point at which they are ready to feed into major missions in the three science themes of the Astrophysics Division: Exoplanet Exploration, Cosmic Origins, and the Physics of the Cosmos. This program is specifically designed to address middle technology readiness level (TRL) "gaps" between levels 3 and 6: the maturation of technologies that have been established as feasible, but which are not yet sufficiently mature to incorporate into flight missions without introducing an unacceptable level of risk. NASA does not require a data management plan for proposals to SAT.

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