Abstract
TIME is a mm-wavelength grating spectrometer array that will map fluctuations of the 157.7-\(\mathrm {\upmu m}\) emission line of singly ionized carbon ([CII]) during the epoch of reionization (redshift z \(\sim \) 5–9). Sixty transition-edge sensor (TES) bolometers populate the output arc of each of the 32 spectrometers, for a total of 1920 detectors. Each bolometer consists of gold absorber on a \(\sim \) 3 \(\times \) 3 mm silicon nitride micro-mesh suspended near the corners by 1 \(\times \) 1 \(\times \) 500 \(\upmu \)m silicon nitride legs targeting a photon-noise-dominated NEP \(\sim 1 \times 10^{-17}\,\mathrm {W/\sqrt{Hz}}\). Hafnium films are explored as a lower-\(T_\mathrm{c}\) alternative to Ti (500 mK) for TIME TESs, allowing thicker support legs for improved yield. Hf \(T_\mathrm{c}\) is shown to vary between 250 and 450 mK when varying the resident Ar pressure during deposition. Magnetic shielding designs and simulations are presented for the TIME first-stage SQUIDs. Total axial field suppression is predicted to be \(5 \times 10^7\).
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Acknowledgements
JH is supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469. AC is supported by the National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship under Grant No. 1602677.
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Hunacek, J., Bock, J., Bradford, C.M. et al. Hafnium Films and Magnetic Shielding for TIME, A mm-Wavelength Spectrometer Array. J Low Temp Phys 193, 893–900 (2018). https://doi.org/10.1007/s10909-018-1906-3
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DOI: https://doi.org/10.1007/s10909-018-1906-3