The Terahertz Intensity Mapper (TIM) is a NASA-funded balloon-borne telescope that aims to measure the [CII] emission from star forming galaxies over an enormous cosmic volume. TIM’s cryogenic receiver, based on the BLAST-TNG design, utilizes a three-stage He sorption refrigerator backed by a 280-liter liquid helium tank to achieve a base temperature of 250 mK, which enables photon noise-limited performance for its MKID detectors. Two low-impedance multi-channel heat exchangers enhance cooling efficiency, contributing to a designed hold time of 20 days under ground conditions. Preliminary simulations and assembly tests showcase the cryostat's reliability, and data validation is anticipated by the summer of 2024. We will present the design and current status of the TIM cryogenic receiver and our ongoing characterization effort toward an Antarctic flight in 2026.
We present preparation for fabrication and deployment of science-grade kilo-pixel Kinetic Inductance Detector (KID) based arrays for the Terahertz Intensity Mapper (TIM). TIM is a NASA-funded balloon-borne experiment planning its Antarctic flight for 2026. TIM employs two focal planes, each with four subarrays of ~900 hexagonal-packed, horn-coupled aluminum KIDs. Fabrication yield is high, and we have successfully mapped KID resonant frequencies to spatial locations with our LED mapper. The spatial and frequency information associated with every yielded pixel allows a study of spatial coincidences as cosmic rays interact with the array, as well as interpretation of a covariance analyses performed on the noise timestreams. We also describe the improvement on the science-usable yield of our 864-pixel array achieved by (1) the lithographic trimming that de-collides resonators, and (2) our characterization of interpixel crosstalk. This pioneering work on the postprocessing will pave the way for science with our large KID arrays.
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.
The BLAST Observatory is a proposed super-pressure balloon-borne polarimeter designed for a future ultra- long duration balloon campaign from Wanaka, New Zealand. To maximize scientific output while staying within the stringent super-pressure weight envelope, BLAST will feature new 1.8m off-axis optical system contained within a lightweight monocoque structure gondola. The payload will incorporate a 300 L 4He cryogenic receiver which will cool 8,274 microwave kinetic inductance detectors (MKIDs) to 100mK through the use of an adiabatic demagnetization refrigerator (ADR) in combination with a 3He sorption refrigerator all backed by a liquid helium pumped pot operating at 2 K. The detector readout utilizes a new Xilinx RFSOC-based system which will run the next-generation of the BLAST-TNG KIDPy software. With this instrument we aim to answer outstanding questions about dust dynamics as well as provide community access to the polarized submillimeter sky made possible by high-altitude observing unrestricted by atmospheric transmission. The BLAST Observatory is designed for a minimum 31-day flight of which 70% will be dedicated to observations for BLAST scientific goals and the remaining 30% will be open to proposals from the wider astronomical community through a shared-risk proposals program.
The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter polarimeter designed to map interstellar dust and galactic foregrounds at 250, 350, and 500 microns during a 24-day Antarctic flight. The BLAST-TNG detector arrays are comprised of 918, 469, and 272 MKID pixels, respectively. The pixels are formed from two orthogonally oriented, crossed, linear-polarization sensitive MKID antennae. The arrays are cooled to sub 300 mK temperatures and stabilized via a closed cycle 3He sorption fridge in combination with a 4He vacuum pot. The detectors are read out through a combination of the second-generation Reconfigurable Open Architecture Computing Hardware (ROACH2) and custom RF electronics designed for BLAST-TNG. The firmware and software designed to readout and characterize these detectors was built from scratch by the BLAST team around these detectors, and has been adapted for use by other MKID instruments such as TolTEC and OLIMPO.1 We present an overview of these systems as well as in-depth methodology of the ground-based characterization and the measured in-flight performance.
The Next Generation Balloon-Borne Large Aperture Submillimeter Telescope (BLAST-TNG) was a unique instrument for characterizing the polarized submillimeter sky at high-angular resolution. BLAST-TNG flew from the Long Duration Balloon Facility in Antarctica in January 2020. Despite the short flight duration, the instrument worked very well and is providing significant information about each subsystem that will be invaluable for future balloon missions. In this contribution, we discuss the performance of telescope and gondola.
The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter mapping experiment planned for a 28 day long-duration balloon (LDB) flight from McMurdo Station, Antarctica during the 2018-2019 season. BLAST-TNG will detect submillimeter polarized interstellar dust emission, tracing magnetic fields in galactic molecular clouds. BLAST-TNG will be the first polarimeter with the sensitivity and resolution to probe the ~0.1 parsec-scale features that are critical to understanding the origin of structures in the interstellar medium.
BLAST-TNG features three detector arrays operating at wavelengths of 250, 350, and 500 m (1200, 857, and 600 GHz) comprised of 918, 469, and 272 dual-polarization pixels, respectively. Each pixel is made up of two crossed microwave kinetic inductance detectors (MKIDs). These arrays are cooled to 275 mK in a cryogenic receiver. Each MKID has a different resonant frequency, allowing hundreds of resonators to be read out on a single transmission line. This inherent ability to be frequency-domain multiplexed simplifies the cryogenic readout hardware, but requires careful optical testing to map out the physical location of each resonator on the focal plane. Receiver-level optical testing was carried out using both a cryogenic source mounted to a movable xy-stage with a shutter, and a beam-filling, heated blackbody source able to provide a 10-50 C temperature chop. The focal plane array noise properties, responsivity, polarization efficiency, instrumental polarization were measured. We present the preflight characterization of the BLAST-TNG cryogenic system and array-level optical testing of the MKID detector arrays in the flight receiver.
The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter mapping experiment planned for a 28 day long-duration balloon (LDB) flight from McMurdo Station, Antarctica during the 2018-2019 season. BLAST-TNG will detect submillimeter polarized interstellar dust emission, tracing magnetic fields in galactic molecular clouds. BLAST-TNG will be the first polarimeter with the sensitivity and resolution to probe the ∼0.1 parsec-scale features that are critical to understanding the origin of structures in the interstellar medium. With three detector arrays operating at 250, 350, and 500 μm (1200, 857, and 600 GHz), BLAST-TNG will obtain diffraction-limited resolution at each waveband of 30, 41, and 59 arcseconds respectively. To achieve the submillimeter resolution necessary for its science goals, the BLAST-TNG telescope features a 2.5 m aperture carbon fiber composite primary mirror, one of the largest mirrors flown on a balloon platform. Successful performance of such a large telescope on a balloon-borne platform requires stiff, lightweight optical components and mounting structures. Through a combination of optical metrology and finite element modeling of thermal and mechanical stresses on both the telescope optics and mounting structures, we expect diffractionlimited resolution at all our wavebands. We expect pointing errors due to deformation of the telescope mount to be negligible. We have developed a detailed thermal model of the sun shielding, gondola, and optical components to optimize our observing strategy and increase the stability of the telescope over the flight. We present preflight characterization of the telescope and its platform.
Polarized thermal emission from interstellar dust grains can be used to map magnetic fields in star forming molecular clouds and the diffuse interstellar medium (ISM). The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) flew from Antarctica in 2010 and 2012 and produced degree-scale polarization maps of several nearby molecular clouds with arcminute resolution. The success of BLASTPol has motivated a next-generation instrument, BLAST-TNG, which will use more than 3000 linear polarization- sensitive microwave kinetic inductance detectors (MKIDs) combined with a 2.5 m diameter carbon fiber primary mirror to make diffraction-limited observations at 250, 350, and 500 µm. With 16 times the mapping speed of BLASTPol, sub-arcminute resolution, and a longer flight time, BLAST-TNG will be able to examine nearby molecular clouds and the diffuse galactic dust polarization spectrum in unprecedented detail. The 250 μm detec- tor array has been integrated into the new cryogenic receiver, and is undergoing testing to establish the optical and polarization characteristics of the instrument. BLAST-TNG will demonstrate the effectiveness of kilo-pixel MKID arrays for applications in submillimeter astronomy. BLAST-TNG is scheduled to fly from Antarctica in December 2017 for 28 days and will be the first balloon-borne telescope to offer a quarter of the flight for “shared risk” observing by the community.
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