We summarize the technical specifications of TIME, the Tomographic Ionized-carbon Mapping Experiment, which is designed to probe the structure and evolution of the universe by using line intensity mapping to measure carbon monoxide (CO) and ionized carbon ([C ii]) with a mm-wavelength grating spectrometer. We present detector count, spectral coverage and resolution, and give an update on the current status of the project. TIME was installed at the Arizona Radio Observatory 12 m telescope in 2019 and returned for further engineering, commissioning, and observing in 2022. Data taken during the 2022 season demonstrate the ability of TIME to compensate for field rotation through the use of a K-mirror system, as well as spectro-imaging functionality broadly in line with expectations given the current state of the instrument. TIME will return to ARO for science observations for the Winter 2024 season. We discuss hardware and software updates and preliminary data analysis in preparation for science scans.
The Terahertz Intensity Mapper (TIM) is designed to probe the star formation history in dust-obscured star-forming galaxies around the peak of cosmic star formation. This will be done via measurements of the redshifted 157.7 µm line of singly ionized carbon ([CII]). TIM employs two R~250 long-slit grating spectrometers covering 240 to 420 µm. Each is equipped with a focal plane unit containing four wafer-sized subarrays of horn-coupled aluminum kinetic inductance detectors (KIDs). We present the design and performance of a prototype focal plane assembly for one of TIM’s KID-based subarrays. The overall detector package must satisfy thermal and mechanical requirements, while maintaining high optical efficiency and a suitable electromagnetic environment for the KIDs. In particular, our design manages to strictly maintain a 50 µm air gap between the array and the horn block. The prototype detector housing in combination with the first flight-like quadrant were tested at 250 mK. A frequency scan using a vector network analyzer shows 823 resonance features, which represents ⪆90% yield, indicating a good performance of our TIM detector wafer and the whole focal plane unit. Initial measurements also showed that many resonances were affected by collisions and/or very shallow transmission dips as a result of a degraded internal quality factor. This is attributed to the presence of an external magnetic field during cooldown. We report on a study of magnetic field dependence of the quality factor of our quadrant array. We implemented a Helmholtz coil to vary the magnetic field at the detectors by (partially) nulling earth’s. Our investigation shows that the earth magnetic field can significantly affect our KIDs’ performance by degrading the quality factor by a factor of two to five, well below those expected from the operational temperature or optical loading. We find that we can sufficiently recover our detectors’ quality factor by tuning the current in the coils to generate a field that matches earth’s magnetic field in magnitude to within a few µT. We emphasize that it is impractical to fly a Helmholtz coil on TIM and dynamically “null” earth’s. Therefore, it is necessary to employ a properly designed magnetic shield enclosing the TIM focal plane unit. Based on the results presented in this paper, we set a shielding requirement of |B| ⪅3 µT.
The Terahertz Intensity Mapper (TIM) is a balloon-borne far-infrared imaging spectrometer designed to characterize the star formation history of the universe. In its Antarctic science flight, TIM will map the redshifted 158um line of ionized carbon over the redshift range 0.5-1.7 (lookback times of 5-10 Gyr). TIM will spectroscopically detect ~100 galaxies, determine the star formation rate history over this time interval through line intensity mapping, and measure the stacked CII emission from galaxies in its well-studied target fields (GOODS-S, SPT Deep Field). TIM consists of a 2-meter telescope feeding two grating spectrometers that that cover 240-420um at R~250 across a 1.3deg field of view, detected with 7200 kinetic inductance detectors and sampled through a novel RF system-on-chip readout. TIM will serve as an important scientific instrument, accessing wavelengths that cannot easily be studied from the ground, and as a testbed for future FIR space technology.
TIM, the Terahertz Intensity Mapper, is a NASA far-infrared balloon mission designed to perform [CII] intensity mapping of the peak of cosmic star formation. To achieve this goal, TIM will fly two grating spectrometers that together cover the 240 to 420 um wavelength range at an R~250. Each spectrometer will require large format arrays (4x~900 detectors) of dual-polarization sensitive detectors, which are photon noise limited at 100 fW of loading. We will present the design of a fully-aluminum lumped-element kinetic-inductance detector (KID) that incorporates a novel “chain-link” absorber design. Operating at 215 mK, we demonstrate that this detector achieves a photon noise limited performance at 80 fW of optical loading with a white noise spectrum down to 1 Hz. Informed by dark measurements, we except these KIDs to achieve a detector limited NEP of 2e-18 W/rt(Hz) at a loading <10 fW. In addition, we shall show our design of a kilopixel array and its initial performance measurements.
TIME is an instrument being developed to study emission from faint objects in our universe using line intensity mapping (LIM) to understand the universe over cosmic time. The TIME instrument is a mm-wavelength grating spectrometer with Transition Edge Sensor (TES) bolometers measuring in the frequency range of 200-300 GHz with 60 spectral pixels and 16 spatial pixels. TIME will measure [CII] emission from redshift 5 to 9 to probe the evolution of our universe during the epoch of reionization. TIME will also measure low-redshift CO fluctuations and map molecular gas in the epoch of peak cosmic star formation from redshift 0.5 to 2. This instrument and the emerging technique of LIM will provide complementary measurements to typical galaxy surveys and illuminate the history of our universe. TIME was recently installed on the 12m ALMA prototype antenna operated by the Arizona Radio Observatory on Kitt Peak for an engineering test and will return for science observations in 2020.
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