Small Aperture Telescopes for the Simons Observatory

Ali, Aamir; Adachi, S.; Arnold, K.; Ashton, Peter; Bazarko, A. O.; Chinone, Yuji; Coppi, Gabriele; Corbett, Lance; Crowley, Kevin D.; Crowley, Kevin T.; Devlin, Mark J.; Dicker, Simon; Duff, Shannon M.; Ellis, Christopher G.; Galitzki, Nicholas; Goeckner-Wald, N.; Harrington, Kathleen; Healy, Erin; Hill, Charles A.; Ho, Shuay Pwu Patty; Hubmayr, Johannes; Keating, Brian; Kiuchi, K.; Kusaka, A.; Lee, Adrian T.; Ludlam, M.; Mangu, Aashrita; Matsuda, Frederick; McCarrick, Heather; Nati, F.; Niemack, Michael D.; Nishino, Hitoshi; Orlowski-Scherer, John; Rao, Mayuri Sathyanarayana; Raum, Christopher; Sakurai, Y.; Salatino, Maria; Sasse, Trevor; Seibert, Joseph; Sierra, Carlos; Silva-Feaver, Maximiliano; Spisak, Jacob; Simon, Sara M.; Staggs, Suzanne T.; Tajima, O.; Teply, G. P.; Tsan, Tran; Wollack, Edward J.; Westbrook, B.; Xu, Zhilei; Zannoni, M.; Zhu, Ningfeng

doi:10.1007/s10909-020-02430-5

Cited by 35 publications

(30 citation statements)

References 24 publications

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“…In the LATR, 13 OTs require 156 coaxial cables and 2400 DC wires to be routed without introducing unacceptable thermal loading. To address this, the SO developed the modularized universal readout harness (URH; for both the LATR and the small-aperture telescopes (Ali et al 2020). One URH contains 48 coaxial cables penetrating three temperature stages from 300 K to 4 K. In addition, each URH carries 600 DC cryogenic wires so as to bias detectors and amplifiers, and convey flux ramps.…”

Section: Detector Readout Interfacementioning

confidence: 99%

“…The Simons Observatory (SO; Galitzki et al 2018; The Simons Observatory Collaboration 2019) is a next-generation CMB experiment consisting of three 0.42 m small-aperture telescopes (SATs; Ali et al 2020) and one 6 m Large Aperture Telescope (LAT; Parshley et al 2018) in the Atacama Desert of Chile. The LAT utilizes a crossed-Dragone optical design with a pair of 6 m mirrors (Gallardo et al 2018;Gudmundsson et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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The Simons Observatory Large Aperture Telescope Receiver

Zhu

Bhandarkar

Coppi

et al. 2021

ApJS

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The Simons Observatory is a ground-based cosmic microwave background experiment that consists of three 0.4 m small-aperture telescopes and one 6 m Large Aperture Telescope, located at an elevation of 5300 m on Cerro Toco in Chile. The Simons Observatory Large Aperture Telescope Receiver (LATR) is the cryogenic camera that will be coupled to the Large Aperture Telescope. The resulting instrument will produce arcminute-resolution millimeter-wave maps of half the sky with unprecedented precision. The LATR is the largest cryogenic millimeter-wave camera built to date, with a diameter of 2.4 m and a length of 2.6 m. The coldest stage of the camera is cooled to 100 mK, the operating temperature of the bolometric detectors with bands centered around 27, 39, 93, 145, 225, and 280 GHz. Ultimately, the LATR will accommodate 13 40 cm diameter optics tubes, each with three detector wafers and a total of 62,000 detectors. The LATR design must simultaneously maintain the optical alignment of the system, control stray light, provide cryogenic isolation, limit thermal gradients, and minimize the time to cool the system from room temperature to 100 mK. The interplay between these competing factors poses unique challenges. We discuss the trade studies involved with the design, the final optimization, the construction, and ultimate performance of the system.

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Section: Detector Readout Interfacementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Simons Observatory Large Aperture Telescope Receiver

Zhu

Bhandarkar

Coppi

et al. 2021

ApJS

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“…PB-2c is building an identical CHWP for observation at 220 and 270 GHz, and the Simons Observatory has adopted the presented system, with some system-dependent modifications, for cryogenic polarization modulation on their small aperture telescopes. 73,74 Additionally, several of its core strengths, such as its low-noise encoder and easy-to-operate driver, make the PB-2b CHWP system portable to future CMB experiments including CMB Stage-4. 75 its AR coating.…”

Section: Discussionmentioning

confidence: 99%

A cryogenic continuously rotating half-wave plate mechanism for the POLARBEAR-2b cosmic microwave background receiver

Hill

Kusaka

Ashton

et al. 2020

Review of Scientific Instruments

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We present the design and laboratory evaluation of a cryogenic continuously rotating half-wave plate (CHWP) for the POLARBEAR-2b (PB-2b) cosmic microwave background (CMB) receiver, the second installment of the Simons Array. PB-2b will observe at 5,200 m elevation in the Atacama Desert of Chile in two frequency bands centered at 90 and 150 GHz. In order to suppress atmospheric 1/f noise and mitigate systematic effects that arise when differencing orthogonal detectors, PB-2b modulates linear sky polarization using a CHWP rotating at 2 Hz. The CHWP has a 440 mm clear aperture diameter and is cooled to ≈ 50 K in the PB-2b receiver cryostat. It consists of a low-friction superconducting magnetic bearing (SMB) and a low-torque synchronous electromagnetic motor, which together dissipate < 2 W. During cooldown, a grip-and-release mechanism centers the rotor to < 0.5 mm, and during continuous rotation, an incremental optical encoder measures the rotor angle with a noise level of 0.1 µrad/ √ Hz. We discuss the experimental requirements for the PB-2b CHWP, the designs of its various subsystems, and the results of its evaluation in the laboratory. The presented CHWP has been deployed to Chile and is expected to see first light on PB-2b in 2020 or 2021.

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“…The Simons Observatory (SO [15]), with its Small Aperture Telescopes (SATs), will produce high-sensitivity maps of the CMB polarization at the degree-scale across 10% of the sky (∼ 4, 000 deg 2 ) across a broad range of frequencies (27 − 280 GHz) [26]. In order to achieve its goal of constraining r at the level of σ(r) 0.002, 1 SO will need to tackle both instrument and analysis challenges.…”

Section: Jcap05(2021)032mentioning

confidence: 99%

The Simons Observatory: gain, bandpass and polarization-angle calibration requirements for B-mode searches

Abitbol

Alonso

Simon

et al. 2021

J. Cosmol. Astropart. Phys.

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We quantify the calibration requirements for systematic uncertainties for nextgeneration ground-based observatories targeting the large-angle B-mode polarization of the Cosmic Microwave Background, with a focus on the Simons Observatory (SO). We explore uncertainties on gain calibration, bandpass center frequencies, and polarization angles, including the frequency variation of the latter across the bandpass. We find that gain calibration and bandpass center frequencies must be known to percent levels or less to avoid biases on the tensor-to-scalar ratio r on the order of ∆r ∼ 10 −3 , in line with previous findings. Polarization angles must be calibrated to the level of a few tenths of a degree, while their frequency variation between the edges of the band must be known to O(10) degrees. Given the tightness of these calibration requirements, we explore the level to which residual uncertainties on these systematics would affect the final constraints on r if included in the data model and marginalized over. We find that the additional parameter freedom does not degrade the final constraints on r significantly, broadening the error bar by O(10%) at most. We validate these results by reanalyzing the latest publicly available data from the BICEP2/Keck Array collaboration within an extended parameter space covering both cosmological, foreground and systematic parameters. Finally, our results are discussed in light of the instrument design and calibration studies carried out within SO.

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Small Aperture Telescopes for the Simons Observatory

Cited by 35 publications

References 24 publications

The Simons Observatory Large Aperture Telescope Receiver

The Simons Observatory Large Aperture Telescope Receiver

A cryogenic continuously rotating half-wave plate mechanism for the POLARBEAR-2b cosmic microwave background receiver

The Simons Observatory: gain, bandpass and polarization-angle calibration requirements for B-mode searches

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