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We report on the effects of cosmic ray interactions with the kinetic inductance detector (KID)-based focal plane array for the terahertz intensity mapper (TIM). TIM is a NASA-funded balloon-borne experiment designed to probe the peak of the star formation in the Universe. It employs two spectroscopic bands, each equipped with a focal plane of four ∼ 900-pixel, KID-based array chips. Measurements of an 864-pixel TIM array show 791 resonators in a 0.5 GHz bandwidth. We discuss challenges with resonator calibration caused by this high multiplexing density. We robustly identify the physical positions of 788 (99.6 %) detectors using a custom LED-based identification scheme. Using this information, we show that cosmic ray events occur at a rate of 2.1 events / min / cm 2 in our array. 66 % of the events affect a single pixel, and other 33 % affect < 5 KIDs per event spread over a 0.66 cm 2 region (2 pixel pitches in radius). We observe a total cosmic ray dead fraction of 0.0011 % and predict that the maximum possible in-flight dead fraction is ∼ 0.124 %, which demonstrates our design will be robust against these high-energy events.

Imaging and spectroscopy at (sub-)millimeter wavelengths are key frontiers in astronomy and cosmology. Large area spectral surveys with moderate spectral resolution ( R = 50 –200) will be used to characterize large-scale structure and star formation through intensity mapping surveys in emission lines such as the CO rotational transitions. Such surveys will also be used to study the the Sunyaev Zeldovich (SZ) effect, and will detect the emission lines and continuum spectrum of individual objects. WSPEC is an instrument proposed to target these science goals. It is a channelizing spectrometer realized in rectangular waveguide, fabricated using conventional high-precision metal machining. Each spectrometer is coupled to free space with a machined feed horn, and the devices are tiled into a 2D array to fill the focal plane of the telescope. The detectors will be aluminum lumped-element kinetic inductance detectors (LEKIDs). To target the CO lines and SZ effect, we will have bands at 135–175 and 190–250 GHz, each Nyquist-sampled at R ≈ 200 resolution. Here, we discuss the instrument concept and design, and successful initial testing of a WR10 (i.e., 90 GHz) prototype spectrometer. We recently tested a WR5 (180 GHz) prototype to verify that the concept works at higher frequencies, and also designed a resonant backshort structure that may further increase the optical efficiency. We are making progress towards integrating a spectrometer with a LEKID array and deploying a prototype device to a telescope for first light.

CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn) is a low-resolution Fourier transform spectrometer dedicated to the study of star-forming galaxies and clusters of galaxies in the transparent millimeter windows from the ground. It is characterized by a wide instantaneous 18.6 arcmin field of view, operates at 130–310 GHz, and was installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5 100m above sea level. CONCERTO’s double focal planes host two arrays of 2 152 kinetic inductance detectors and represent a pioneering instrument to meet a state-of-the-art scientific challenge. This paper introduces the CONCERTO instrument and explains its status, shows the first CONCERTO spectral maps of Orion, and describes the perspectives of the project.

As the Earth's climate has changed, Arctic sea ice extent has decreased drastically. It is likely that the late‐summer Arctic will be ice‐free as soon as the 2030s. This loss of sea ice represents one of the most severe positive feedbacks in the climate system, as sunlight that would otherwise be reflected by sea ice is absorbed by open ocean. It is unlikely that CO2 levels and mean temperatures can be decreased in time to prevent this loss, so restoring sea ice artificially is an imperative. Here we investigate a means for enhancing Arctic sea ice production by using wind power during the Arctic winter to pump water to the surface, where it will freeze more rapidly. We show that where appropriate devices are employed, it is possible to increase ice thickness above natural levels, by about 1 m over the course of the winter. We examine the effects this has in the Arctic climate, concluding that deployment over 10% of the Arctic, especially where ice survival is marginal, could more than reverse current trends of ice loss in the Arctic, using existing industrial capacity. We propose that winter ice thickening by wind‐powered pumps be considered and assessed as part of a multipronged strategy for restoring sea ice and arresting the strongest feedbacks in the climate system. Key Points To prevent strong positive feedbacks in the climate system, it may be necessary to artificially increase sea ice thickness in the Arctic We calculate that 1.4 m of seawater pumped to the surface freezes more readily and increases ice thickness by 1.0 m in one winter We describe a method employing devices using wind power to pump water and thicken ice, and discuss the feasibility and effectiveness of deploying such devices over the Arctic

BFORE is a NASA high-altitude ultra-long-duration balloon mission proposed to measure the cosmic microwave background (CMB) across half the sky during a 28-day mid-latitude flight launched from Wanaka, New Zealand. With the unique access to large angular scales and high frequencies provided by the balloon platform, BFORE will significantly improve measurements of the optical depth to reionization τ , breaking parameter degeneracies needed for a measurement of neutrino mass with the CMB. The large-angular-scale data will enable BFORE to hunt for the large-scale gravitational wave B -mode signal, as well as the degree-scale signal, each at the r ∼ 0.01 level. The balloon platform allows BFORE to map Galactic dust foregrounds at frequencies where they dominate, in order to robustly separate them from CMB signals measured by BFORE, in addition to complementing data from ground-based telescopes. The combination of frequencies will also lead to velocity measurements for thousands of galaxy clusters, as well as probing how star-forming galaxies populate dark matter halos. The mission will be the first near-space use of TES multichroic detectors (150/217 GHz and 280/353 GHz bands) using highly multiplexed mSQUID microwave readout, raising the technical readiness level of both technologies.

We present a design of a high performance horn operating at 700 GHz. The feed, which comprises three smooth-walled conical sections, is easy to machine and yet has comparable performance to a corrugated horn. The measured radiation patterns show high main beam circularity, low sidelobe level and good agreement with theoretical predictions. The cross-polar level is below −20 dB across a frequency bandwidth of 140 GHz. The new design allows the fabrication of high performance, large format feed arrays cheaply and rapidly.

We report on the effects of cosmic ray interactions with the Kinetic Inductance Detector (KID) based focal plane array for the Terahertz Intensity Mapper (TIM). TIM is a NASA-funded balloon-borne experiment designed to probe the peak of the star formation in the Universe. It employs two spectroscopic bands, each equipped with a focal plane of four \\(\\sim\\,\\)900-pixel, KID-based array chips. Measurements of an 864-pixel TIM array shows 791 resonators in a 0.5\\(\\,\\)GHz bandwidth. We discuss challenges with resonator calibration caused by this high multiplexing density. We robustly identify the physical positions of 788 (99.6\\(\\,\\)%) detectors using a custom LED-based identification scheme. Using this information we show that cosmic ray events occur at a rate of 2.1\\(\\,\\mathrm{events/min/cm^2}\\) in our array. 66\\(\\,\\)% of the events affect a single pixel, and another 33\\(\\,\\)% affect \\(<\\,\\)5 KIDs per event spread over a 0.66\\(\\,\\mathrm{cm^2}\\) region (2 pixel pitches in radius). We observe a total cosmic ray dead fraction of 0.0011\\(\\,\\)%, and predict that the maximum possible in-flight dead fraction is \\(\\sim\\,\\)0.165\\(\\,\\)%, which demonstrates our design will be robust against these high-energy events.

Microwave sounding is the leading driver of global numerical weather forecasting, but is limited by the scalability of such instruments. With modern machining and commercial microwave components, it is now possible to design low size, weight, power, and cost (SWaP-C) microwave spectrometers while maintaining wide bandwidth performance. Here we report on the status of CubeSounder, a spectrometer tailored for water vapor radiometry that utilizes passive wave guide filter banks. After developing a prototype and high altitude balloon payload, we demonstrated CubeSounder on commercial stratospheric balloon flights. We report on our design process, especially the simulation and fabrication of the custom millimeter-wave filter banks. We also report the initial results of the data collected from the balloon flights.

The CCAT Observatory's primary science instrument, Prime-Cam, is nearing readiness for deployment to the Fred Young Submillimeter Telescope (FYST) in the Atacama Desert in northern Chile. When fully deployed, Prime-Cam will field approximately 100,000 kinetic inductance detectors (KIDs) across seven instrument modules making both broadband and polarimetric measurements. Meanwhile, in-lab characterization of the first CCAT instrument module, a 280 GHz broadband camera fielding over 10,000 KIDs, is currently underway in the testbed instrument Mod-Cam. Both Mod-Cam and Prime-Cam will employ 46 cm long low-thermal-conductivity flexible circuits (\"stripline\") between 4 K and 300 K to connect large-format arrays of multiplexed KIDs in each instrument module to readout electronics. The 280 GHz camera currently installed in Mod-Cam uses six of these striplines to read out its over 10,000 detectors. We have examined the thermal and electrical performance of the stripline installed in Mod-Cam. We begin by characterizing the OFHC copper in the stripline traces, allowing for the estimation of thermal loading through these flexible circuits in their configurations in both Mod-Cam and Prime-Cam. We then directly measure the thermal conductivity of the stripline, finding it is best described by \\(kA = 22\\pm6~T^{0.84\\pm0.09}~\\mathrm{\\mu~W~m~K^{-1}}\\) for temperature ranges of 6 K < T < 20 K and \\(kA~=~0.6\\pm0.3~T^{-0.4\\pm0.1}~\\mathrm{mW~m~K^{-1}}\\) for ranges from 20 K < T < 80 K. Following our thermal characterizations, we report on the transmission and crosstalk properties of the Mod-Cam readout chain, isolating elevated crosstalk to SMP-SMA transition printed circuit boards (PCBs) that interface with the stripline. This finding validates the stripline circuit as a viable high-density cabling option for large-format array readout.

CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn) is a low-resolution Fourier transform spectrometer dedicated to the study of star-forming galaxies and clusters of galaxies in the transparent millimeter windows from the ground. It is characterized by a wide instantaneous 18.6 arcmin field of view, operates at 130-310 GHz, and was installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5100 m above sea level. CONCERTO's double focal planes host two arrays of 2152 kinetic inductance detectors and represent a pioneering instrument to meet a state-of-the-art scientific challenge. This paper introduces the CONCERTO instrument and explains its status, shows the first CONCERTO spectral maps of Orion, and describes the perspectives of the project.