Material properties of a low contraction and resistivity silicon-aluminum composite for cryogenic detectors

We report on the cryogenic properties of a low-contraction silicon-aluminum composite, namely Japan Fine Ceramics SA001, to use as a packaging structure for cryogenic silicon devices. SA001 is a silicon--aluminum composite material (75% silicon by volume) and has a low thermal expansion coefficient ($\sim$1/3 that of aluminum). The superconducting transition temperature of SA001 is measured to be 1.18 K, which is in agreement with that of pure aluminum, and is thus available as a superconducting magnetic shield material. The residual resistivity of SA001 is 0.065 $\mathrm{\mu \Omega m}$, which is considerably lower than an equivalent silicon--aluminum composite material. The measured thermal contraction of SA001 immersed in liquid nitrogen is $\frac{L_{293\mathrm{K}}-L_{77\mathrm{K}}}{L_{293\mathrm{K}}}=0.12$%, which is consistent with the expected rate obtained from the volume-weighted mean of the contractions of silicon and aluminum. The machinability of SA001 is also confirmed with a demonstrated fabrication of a conical feedhorn array, with a wall thickness of 100 $\mathrm{\mu m}$. These properties are suitable for packaging applications for large-format superconducting detector devices.Comment: 8 pages, 4 figures, 1 table, accepted for the Journal of Low Temperature Physics for the LTD19 special issu

TiEMPO: Open-source time-dependent end-to-end model for simulating ground-based submillimeter astronomical observations

The next technological breakthrough in millimeter-submillimeter astronomy is 3D imaging spectrometry with wide instantaneous spectral bandwidths and wide fields of view. The total optimization of the focal-plane instrument, the telescope, the observing strategy, and the signal-processing software must enable efficient removal of foreground emission from the Earth's atmosphere, which is time-dependent and highly nonlinear in frequency. Here we present TiEMPO: Time-Dependent End-to-End Model for Post-process Optimization of the DESHIMA Spectrometer. TiEMPO utilizes a dynamical model of the atmosphere and parametrized models of the astronomical source, the telescope, the instrument, and the detector. The output of TiEMPO is a time-stream of sky brightness temperature and detected power, which can be analyzed by standard signal-processing software. We first compare TiEMPO simulations with an on-sky measurement by the wideband DESHIMA spectrometer and find good agreement in the noise power spectral density and sensitivity. We then use TiEMPO to simulate the detection of a line emission spectrum of a high-redshift galaxy using the DESHIMA 2.0 spectrometer in development. The TiEMPO model is open source. Its modular and parametrized design enables users to adapt it to design and optimize the end-to-end performance of spectroscopic and photometric instruments on existing and future telescopes.Comment: Presented at SPIE Astronomical Telescopes + Instrumentation 2020. Full published paper, poster and video available at https://doi.org/10.1117/12.2561014 Open-source Python package of TiEMPO: https://pypi.org/project/tiempo-deshima/ Open-source code of TiEMPO: https://zenodo.org/record/4279086#.X_jAsdhKg2

First light demonstration of the integrated superconducting spectrometer

Ultra-wideband 3D imaging spectrometry in the millimeter-submillimeter (mm-submm) band is an essential tool for uncovering the dust-enshrouded portion of the cosmic history of star formation and galaxy evolution. However, it is challenging to scale up conventional coherent heterodyne receivers or free-space diffraction techniques to sufficient bandwidths ($\geq$1 octave) and numbers of spatial pixels (>$10^2$). Here we present the design and first astronomical spectra of an intrinsically scalable, integrated superconducting spectrometer, which covers 332-377 GHz with a spectral resolution of $F/\Delta F \sim 380$. It combines the multiplexing advantage of microwave kinetic inductance detectors (MKIDs) with planar superconducting filters for dispersing the signal in a single, small superconducting integrated circuit. We demonstrate the two key applications for an instrument of this type: as an efficient redshift machine, and as a fast multi-line spectral mapper of extended areas. The line detection sensitivity is in excellent agreement with the instrument design and laboratory performance, reaching the atmospheric foreground photon noise limit on sky. The design can be scaled to bandwidths in excess of an octave, spectral resolution up to a few thousand and frequencies up to $\sim$1.1 THz. The miniature chip footprint of a few $\mathrm{cm^2}$ allows for compact multi-pixel spectral imagers, which would enable spectroscopic direct imaging and large volume spectroscopic surveys that are several orders of magnitude faster than what is currently possible.Comment: Published in Nature Astronomy. SharedIt Link to the full published paper: https://rdcu.be/bM2F

TiEMPO: Open-source time-dependent end-To-end model for simulating ground-based submillimeter astronomical observations

The next technological breakthrough in millimeter–submillimeter astronomy is three-dimensional imaging spectrometry with wide instantaneous spectral bandwidths and wide fields of view. The total optimization of the focal-plane instrument, the telescope, the observing strategy, and the signal-processing software must enable efficient removal of foreground emission from the Earth’s atmosphere, which is time-dependent and highly nonlinear in frequency. Here, we present Time-dependent End-to-end Model for Post-process Optimization (TiEMPO) of the DEep Spectroscopic HIgh-redshift MApper (DESHIMA) spectrometer. TiEMPO utilizes a dynamical model of the atmosphere and parameterized models of the astronomical source, the telescope, the instrument, and the detector. The output of TiEMPO is a time stream of sky brightness temperature and detected power, which can be analyzed by standard signal-processing software. We first compare TiEMPO simulations with an on-sky measurement by the wideband DESHIMA spectrometer, and find good agreement in the noise and sensitivity. We then use TiEMPO to simulate the detection of the line emission spectrum of a high-redshift galaxy using the DESHIMA 2.0 spectrometer in development. The TiEMPO model is open source. Its modular and parametrized design enables users to adapt it to optimize the end-to-end performance of spectroscopic and photometric instruments on existing and future telescopesISSN:2329-4221ISSN:2329-412

TiEMPO: Open-source time-dependent end-to-end model for simulating ground-based submillimeter astronomical observations

The next technological breakthrough in millimeter-submillimeter astronomy is three-dimensional imaging spectrometry with wide instantaneous spectral bandwidths and wide fields of view. The total optimization of the focal-plane instrument, the telescope, the observing strategy, and the signal-processing software must enable efficient removal of foreground emission from the Earth's atmosphere, which is time-dependent and highly nonlinear in frequency. Here, we present Time-dependent End-to-end Model for Post-process Optimization (TiEMPO) of the DEep Spectroscopic HIgh-redshift MApper (DESHIMA) spectrometer. TiEMPO utilizes a dynamical model of the atmosphere and parameterized models of the astronomical source, the telescope, the instrument, and the detector. The output of TiEMPO is a time stream of sky brightness temperature and detected power, which can be analyzed by standard signal-processing software. We first compare TiEMPO simulations with an on-sky measurement by the wideband DESHIMA spectrometer, and find good agreement in the noise and sensitivity. We then use TiEMPO to simulate the detection of the line emission spectrum of a high-redshift galaxy using the DESHIMA 2.0 spectrometer in development. The TiEMPO model is open source. Its modular and parametrized design enables users to adapt it to optimize the end-to-end performance of spectroscopic and photometric instruments on existing and future telescopes