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2.0 Development of an integrated superconducting spectrometer for science-grade astronomical observations Akio Taniguchi (Nagoya University, Japan) Kenichi Karatsu, Yoichi Tamura, Tatsuya Takekoshi, Tom J. L. C. Bakx, Tai Oshima, Juan Bueno, Bruno Buijtendorp, Yasunori Fujii, Kazuyuki Fujita, Robert Huiting, Tsuyoshi Ishida, Shun Ishii, Ryohei Kawabe, Kotaro Kohno, Akira Kouchi, Nuria Llombart, Jun Maekawa, Vignesh Murugesan, Shunichi Nakatsubo, Alejandro Pascual Laguna, David J. Thoen, Paul P. van der Werf, Stephen J. C. Yates, Shahab Dabironezare, Sebastian Hähnle, Jochem J. A. Baselmans, Matthijs Gouwerok, Matus Rybak, Keiichi Matsuda, Stefanie Brackenhoff, Anne-Kee Doing, Hiroki Akamatsu, Tetsu Kitayama, Akira Endo

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Integrated Superconducting Spectrometer (ISS) 2 || Key device for probing the cosmic history of dust-obscured star & galaxy formation by redshift confirmation and physics of molecular/atomic lines 1. Finding Submillimeter Galaxies over the sky mm-submm imaging cameras (e.g., A-MKID, ASTECAM) 2. Spectroscopic redshift measurement Ultra-wideband (>> 100 GHz) submillimeter spectroscopy ? Umehata et al. time, redshift 2D projection 3D space

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Integrated Superconducting Spectrometer (ISS) 3 || One of the main focal-plane instruments for the future large (D~50 m) submillimeter single-dish telescopes (e.g., LST, AtLAST) Submm Transients Nearby Galaxies Astrochemistry ? Super-massive Black Holes Galactic Plane Deep Extragalactic/Cosmological Survey Clusters of Galaxies Magellanic Clouds Planetary atmosphere Unknown Unknowns WIDE-FIELD SPECTROSCOPIC/POLARIMETRIC IMAGING HIGH-CADENCE SUBMM VLBI WIDE-FIELD HIGH-CADENCE IMAGING WIDE-FIELD MULTI-CHROIC IMAGING AREA CADENCE FREQUENCY INSTANTANEOUS IMAGING/SPECTROSCOPY © Y. Tamura

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DESHIMA: An ultra-wideband ISS for submm astronomy 4 wideband signal Dusty Star-forming Galaxies Leaky-lens antenna 347
 Filters Microwave KIDs 6.000 GHz 5.996 GHz 4.000 GHz 4.004 GHz dz~0.01 440 GHz 220 GHz F/dF = 500 from readout electronics NbTiN Al (Obreschkow 2009) ASTE 
 10 m return z=7.6 z=3.3 = DEep Spectroscopic HIgh-redshift MApper (Endo et al.)

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DESHIMA: An ultra-wideband ISS for submm astronomy 5 || DESHIMA 1.0 • A first-light experiment of ISS with ~50-GHz (322 - 377 GHz) bandwidth || Commissioning campaign on the ASTE 10-m • Detection of molecular line and continuum emission from bright astronomical objects • Excellent agreement between on-sky measurements, lab measurements, and the design DESHIMA DESHIMA x

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DESHIMA: An ultra-wideband ISS for submm astronomy 5 || DESHIMA 1.0 • A first-light experiment of ISS with ~50-GHz (322 - 377 GHz) bandwidth || Commissioning campaign on the ASTE 10-m • Detection of molecular line and continuum emission from bright astronomical objects • Excellent agreement between on-sky measurements, lab measurements, and the design Antenna Filters MKIDs DESHIMA DESHIMA x

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DESHIMA: An ultra-wideband ISS for submm astronomy 6 || DESHIMA 1.0 • A first-light experiment of ISS with ~50-GHz (322 - 377 GHz) bandwidth || Commissioning campaign on the ASTE 10-m • Detection of molecular line and continuum emission from bright astronomical objects • Excellent agreement between on-sky measurements, lab measurements, and the design DESHIMA DESHIMA readout signal line signal antenna astronomical signal line lens filter MKID aluminium absorber NbTiN ground plane 49 channels sky signal (line frequency) readout signal (5.1-6.0 GHz) sky signal (other frequencies) sky signal & readout signal filter of line frequency a b 49 channels CO(3-2) redshift z 0.02 0 (ALMA) Antenna Filters MKIDs Endo et al. 2019b Redshifted CO (3-2) from an extra-galaxy VV114 45 GHz (49 channels)

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DESHIMA: An ultra-wideband ISS for submm astronomy 7 || DESHIMA 1.0 • A first-light experiment of ISS with ~50-GHz (322 - 377 GHz) bandwidth || Commissioning campaign on the ASTE 10-m • Detection of molecular line and continuum emission from bright astronomical objects • Excellent agreement between on-sky measurements, lab measurements, and the design CO(3-2) 345.8 GHz HCN(4-3) 354.5 GHz HCO+(4-3) 356.7 GHz a b c d CH3OH SO 5 arcmin~0.6 pc CO HCN HCO + e g f Flux density (Jy) CO(3-2) 345.8 GHz HCN(4-3) 354.5 GHz a b c d 5 arcmin~0.6 pc e g f Antenna Filters MKIDs DESHIMA DESHIMA Orion KL region Endo et al. 2019b 40 GHz

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DESHIMA: An ultra-wideband ISS for submm astronomy 8 || DESHIMA 1.0 • A first-light experiment of ISS with ~50-GHz (322 - 377 GHz) bandwidth || Commissioning campaign on the ASTE 10-m • Detection of molecular line and continuum emission from bright astronomical objects • Excellent agreement between on-sky measurements, lab measurements, and the design nck constant, ∆F is the effective bandwidth of the filter channel, ∆Al = erconducting gap energy of aluminium, and ηpb ∼ 0.4 is the pair-breaking oreground photon-noise limited noise equivalent flux density (NEFDph), has to take into account the instrument coupling, aperture efficiency ηA, rea of the ASTE telescope Ap, and is given by NEFDph = NEPph √ 2ηpol ηinst ηfwd ηatm ηA Ap ∆F . (4) √ 2 accounts for the NEP being defined for 0.5 s integration time, and for the fact that DESHIMA is sensitive to a single linear polarization. ncy resolution ow that the signal-to-noise-ratio (SNR) for a single ISS channel matched uency of an astronomical line is maximum when the channel frequency Photon (Poisson) Photon (Bunching) quasiparticle recombination NEP ph = 2P MKID (hF + P MKID /ΔF) + 4Δ Al P MKID /η pb Noise Equivalent Flux Density (Jy s0.5 / b) model measure ments Endo et al. 2019b (galaxy) (star)

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DESHIMA 2.0: ISS for science-grade astronomical observations 9 Readout signal (4-6 GHz) Sky signal line 220 GHz 440 GHz Leaky lens antenna MKID Aluminium absorber Filter NbTiN ground plane Amorphous Si 337 spectral channels 1.0 2.0 332 - 377 GHz Frequency range 220 - 440 GHz 45 GHz Band width 220 GHz 49 Nchannels 347 2% Instrument efficiency 8 - 16% Readout signal (5.1-6.0 GHz) Line signal Antenna Sky signal line 332 GHz 377 GHz Silicon lens MKID Aluminium absorber NbTiN ground plane Sky signal (line frequency) Sky signal (other frequencies) Filter at line frequency 49 spectral channels

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DESHIMA 2.0: ISS for science-grade astronomical observations 9 Readout signal (4-6 GHz) Sky signal line 220 GHz 440 GHz Leaky lens antenna MKID Aluminium absorber Filter NbTiN ground plane Amorphous Si 337 spectral channels 1.0 2.0 332 - 377 GHz Frequency range 220 - 440 GHz 45 GHz Band width 220 GHz 49 Nchannels 347 2% Instrument efficiency 8 - 16% Readout signal (5.1-6.0 GHz) Line signal Antenna Sky signal line 332 GHz 377 GHz Silicon lens MKID Aluminium absorber NbTiN ground plane Sky signal (line frequency) Sky signal (other frequencies) Filter at line frequency 49 spectral channels wide-band chip design wide-band optics design

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DESHIMA 2.0: ISS for science-grade astronomical observations 10 || Ready for detection of the atomic carbon lines from bright high-z galaxies 2.0 1.0 [CII] flux from a galaxy with LFIR = 5 x 1013 Lsun assuming 5σ detection in an 8 hr observation DESHIMA 2.0 detectable frequency-flux space! goal baseline assuming 5σ detection in an 8 hr observation

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DESHIMA 2.0: ISS for science-grade astronomical observations 10 || Ready for detection of the atomic carbon lines from bright high-z galaxies 2.0 1.0 [CII] flux from a galaxy with LFIR = 5 x 1013 Lsun assuming 5σ detection in an 8 hr observation DESHIMA 1.0 detectable frequency-flux space DESHIMA 2.0 detectable frequency-flux space! goal baseline assuming 5σ detection in an 8 hr observation

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DESHIMA 2.0: Observation setup and key techniques 11 || Both hardware and software are being developed to detect faint lines dusty star-forming galaxy (target) ASTE 10-m DESHIMA Chajnantor, Chile (alt. 4860 m) atmosphere Earth's astronomical signal atmospheric noise Remote control and quick look from base camp and Japan

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DESHIMA 2.0: Observation setup and key techniques 11 || Both hardware and software are being developed to detect faint lines dusty star-forming galaxy (target) ASTE 10-m DESHIMA Chajnantor, Chile (alt. 4860 m) atmosphere Earth's astronomical signal atmospheric noise Wideband chip Wideband optics Fast sky position chopper Atmospheric noise removal Remote control and quick look from base camp and Japan

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DESHIMA 2.0: Wide-band chip design 12 || Fabrication of a telescope chip with full band-width is ongoing • The first telescope chip covers 222 - 425 GHz (92% of the spec. band-width) • High yield rate of operational KIDs (> 90%) is achieved • Scatter of center frequency and Q-factor requires optimization Si lens Filter bank ↑ MKID ↓ MKID ↓ Filter ↓ MKID ~0.28 mm 62 mm

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DESHIMA 2.0: Wide-band chip design 13 || Fabrication of a telescope chip with full band-width is ongoing • The first telescope chip covers 222 - 425 GHz (92% of the spec. band-width) • High yield rate of operational KIDs (> 90%) is achieved • Scatter of center frequency and Q-factor requires optimization Filter responses of the first telescope chip (preliminary result)

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DESHIMA 2.0: Wide-band chip design 13 || Fabrication of a telescope chip with full band-width is ongoing • The first telescope chip covers 222 - 425 GHz (92% of the spec. band-width) • High yield rate of operational KIDs (> 90%) is achieved • Scatter of center frequency and Q-factor requires optimization Filter responses of the first telescope chip (preliminary result)

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DESHIMA 2.0: Wide-band quasi-optics design 14 || Application of novel wide-band leaky-lens antenna (Hähnle+20) • Sufficient telescope-to-chip optical coupling (aperture efficiency of η > 55%) over the entire frequency range of DESHIMA 2.0 (Dabironezare, Ph.D thesis) Quarter wavelength Matching layer centred at 340 GHz • Parylene, hm = 136.3 μm Performance for 250 - 500 GHz band DESHIMA: Quasi-Optical Design Here no feeding line or Si are assumed and no apertu of the beam Quarter wavelength Matching layer centred at 340 GHz Parylene, ℎ𝑚 = 136.3 𝜇𝑚 Here fe SiN m not a Performance for 240-480 GHz band DESHIMA: Quasi-Optical Design © S. Dabironezare, Ph.D thesis Aperture efficiency of the full system Si lens Leaky slot design - Summary 600 $% • Leaky Slot with !" = 500 '( and ) = 35°, ," = 351 '( • Membrane: 1'( thick SiN • Ground plane: NbTiN with sheet inductance of 1 pH/□ • Absorbing layer at 385 '( above the ground plane with diameter of 4 mm. (The field outside this diameter is put to zero). • Membrane is a square with side length of 600 '(. • Example of CPW feeding for the antenna: § CPW line of 2.4-3-2.4 '( on SiN membrane § Quarter wavelength transformer 1: 6 = 70.9 '(, 2-3.4-2 'm on SiN membrane § Quarter wavelength transformer 2: 6 = 76.4 '(, 2-5-2 'm on SiN membrane § CPW line of 2-2.8-2 '( on SiN-Si § CPW line of 2-2-2 '( on Si 10 '( 25 '( Center of the geometry Airgap 10 !" 1 !" SiN membrane NbTiN Ground plane Air Si 375 !" 13.332 "" Filter bank and KIDs read out line 385 !" ? Mesh abs.1 Mesh abs.2 4 "" 600 !" •Leaky Slot with L_a=500 µm and γ=35°, w_a=351 µm •Membrane: 1µm thick SiN, 0.6 x 0.6 mm •Ground plane: NbTiN with sheet inductance of 1 pH/□ •AR coating of 136 um Parylene (centred @ 340 GHz) •Absorbing layer at 385 µm above the ground plane with diameter of 4 mm. (The field outside this diameter is put to zero). •CPW feeding for the antenna (option 1 - aligned to membrane edge): §CPW line of 2.4-3-2.4 µm on SiN membrane §Quarter wavelength transformer 1: l=70.9 µm, 2-3.4-2 µm on SiN membrane §Quarter wavelength transformer 2: l=76.4 µm, 2-5-2 µm on SiN membrane §CPW line of 2-2.8-2 µm on SiN-Si CPW line of 2-2-2 µm on Si 13.265 mm leaky slot CPW 62 mm

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DESHIMA 2.0: Fast sky position chopper 15 || Fast switching between on- and off-source positions • Sky position separation: 234 arcsec (sufficient to observe high-z sources) • Switching frequency: 10 Hz (single on-off cycle of 0.1 s) • On-source fraction over the total observation time: 40% (goal), 30% (baseline) Sky position 1 (off-source) Sky position 2 (on-source) Path to ASTE cabin ~4 arcmin throw ASTE cabin OFF ON

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DESHIMA 2.0: Atmospheric noise removal 16 || End-to-end system noise simulator (TiEMPO; Huijten+2020) • Simulated time-series spectra of various observation modes can be made || Novel data-scientific method to estimate signals (SPLITTER; Brackenhoff+) • "Detection" of line and continuum emission with a √2 times better sensitivity Simulated noise budgets of DESHIMA 2.0 Noise (W Hz-1/2)

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DESHIMA 2.0: Atmospheric noise removal 17 || End-to-end system noise simulator (TiEMPO; Huijten+2020) • Simulated time-series spectra of various observation modes can be made || Novel data-scientific method to estimate signals (SPLITTER; Brackenhoff+) • "Detection" of line and continuum emission with a √2 times better sensitivity Detection of simulated line and continuum emission using SPLITTER molecular/atomic lines

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Summary 18 || DESHIMA 2.0 • An integrated superconducting spectrometer covering 220 GHz in submm || Current status and observation strategies on ASTE in 2022 • Chip: first full wide-band chip with filter measurements is achieved • Optics: leaky-lens antenna covers wide-band with sufficient efficiency • Strategies: fast on-off chopping and data-scientific noise removal are developed DESHIMA 1.0 DESHIMA 2.0 Frequency 332 - 377 GHz 220 - 440 GHz Nchannels 49 347 Instrument efficiency 2% 8 - 16% on-source fraction 8% 30 - 40% Readout signal (4-6 GHz) Sky signal line 220 GHz 440 GHz Leaky lens antenna MKID Aluminium absorber Filter NbTiN ground plane Amorphous Si 337 spectral channels