Fabrication Development for SPT-SLIM, a Superconducting Spectrometer for Line Intensity Mapping

• Main Authors: Cecil, T., Albert, C., Anderson, A. J., Barry, P. S., Benson, B. A., Cotter, C., Chang, C., Dobbs, M., Dibert, K., Gualtieri, R., Karkare, K. S., Lisovenko, M., Marrone, D. P., Montgomery, J., Pan, Z., Robson, G., Rouble, M., Shirokoff, E., Smecher, G., Wang, G., Yefremenko, V.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: IEEE 2023
• Subjects: Electrical and Electronic Engineering; Condensed Matter Physics; Electronic; Optical and Magnetic Materials; South pole
• Online Access: https://doi.org/10.1109/tasc.2023.3259919

Line Intensity Mapping (LIM) is a new observational technique that uses low-resolution observations of line emission to efficiently trace the large-scale structure of the Universe out to high redshift. Common mm/sub-mm emission lines are accessible from ground-based observatories, and the requirements on the detectors for LIM at mm-wavelengths are well matched to the capabilities of large-format arrays of superconducting sensors. We describe the development of an R = λ/Δλ = 300 on-chip superconducting filter-bank spectrometer covering the 120–180 GHz band for future mm-LIM experiments, focusing on SPT-SLIM, a pathfinder LIM instrument for the South Pole Telescope. Radiation is coupled from the telescope optical system to the spectrometer chip via an array of feedhorn-coupled orthomode transducers. Superconducting microstrip transmission lines then carry the signal to an array of channelizing half-wavelength resonators, and the output of each spectral channel is sensed by a lumped element kinetic inductance detector (leKID). Key areas of development include incorporating new low-loss dielectrics to improve both the achievable spectral resolution and optical efficiency and development of a robust fabrication process to create a galvanic connection between ultra-pure superconducting thin-films to realize multi-material (hybrid) leKIDs. We provide an overview of the spectrometer design, fabrication process, and prototype devices. © 2023 IEEE. The work of M. Dobbs, J. Montgomery, and M. Rouble was supported in part by the Natural Sciences and Engineering Research Council of Canada and in part by the Canadian Institute for Advanced Research. The work at Argonne, including use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences and Office of High Energy Physics, under Grant DE-AC02-06CH11357. This work was supported in part by Fermilab under Grant LDRD-2021-048 and in part by the National ...