Performance and on-sky optical characterization of the SPTpol instrument

George, E. M.; Aird, K. A.; Austermann, J. E.; Beall, James A.; Becker, D.; Bender, A. N.; Benson, B. A.; Bleem, L. E.; Britton, J.; Carlstrom, J. E.; Chang, C. L.; Chiang, H. C.; Cho, H-M.; Crawford, T. M.; Crites, A. T.; Datesman, A.; Haan, T. de; Dobbs, M.; Everett, W.; Ewall‐Wice, Aaron; Halverson, N. W.; Harrington, N. L.; Henning, J. W.; Hilton, G. C.; Holzapfel, W. L.; Hoover, S.; Huang, N.; Hubmayr, Johannes; Irwin, K. D.; Karfunkle, M.; Keisler, R.; Kennedy, James E.; Lee, A.T.; Leitch, E. M.; Li, D.; Lueker, M.; Marrone, Daniel P.; McMahon, Jeff; Mehl, J.; Meyer, S. S.; Montgomery, J.; Montroy, T. E.; Nagy, Johanna; Natoli, T.; Nibarger, J. P.; Niemack, Mike; Novosad, V.; Padin, S.; Pryke, C.; Reichardt, Christian; Ruhl, J. E.; Saliwanchik, B. R.; Sayre, J. T.; Schaffer, K. K.; Shirokoff, E.; Story, K. T.; Tucker, C.; Vanderlinde, K.; Vieira, J. D.; Wang, G.; Williamson, A. R.; Yefremenko, V.; Yoon, K. W.; Young, E.

doi:10.1117/12.925586

Cited by 18 publications

(13 citation statements)

References 13 publications

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“…The predicted noise levels agree to within the 10-20% systematic uncertainties of preliminary on-sky noise measurements. 38 projected map depths for SPTpol also agree with a simple scaling from SPT-SZ using its measured focal plane sensitivity and survey map depth, which already include all overheads, data cuts, and observing inefficiencies, and would similarly predict final SPTpol survey depths of ∼ 9 and ∼ 5µK-arcmin for the 90 and 150 GHz bands, respectively.…”

Section: Projections and Performancesupporting

confidence: 64%

“…39,40 This low-noise system introduces a small current-noise term that is sub-dominant to other noise sources under normal operating parameters. 38 For SPTpol we multiplex 12 resonant channels on each SQUID, 19 with frequency separation between channels of ∼ > 60 kHz to minimize crosstalk. A total of 144 SQUIDS are used to readout the 1536 optical TES channels in addition to various dark TES bolometers and other calibration channels.…”

Section: Readoutmentioning

confidence: 99%

“…Details of these measurements can be found elsewhere in these proceedings. 18,19,38 Non-idealities in the Year 1 SPTpol band-passes 38 have lead to a noise performance that is slightly less than optimal. In Austral summer 2012/2013, the SPTpol filtering will be modified to optimize the high band-edge of both the 90 and 150 GHz bands, and the low band-edge waveguide cutoff of the 150 GHz pixels.…”

Section: Projections and Performancementioning

confidence: 99%

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SPTpol: an instrument for CMB polarization measurements with the South Pole Telescope

Austermann¹,

et al. 2012

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SPTpol is a dual-frequency polarization-sensitive camera that was deployed on the 10-meter South Pole Telescope in January 2012. SPTpol will measure the polarization anisotropy of the cosmic microwave background (CMB) on angular scales spanning an arcminute to several degrees. The polarization sensitivity of SPTpol will enable a detection of the CMB "B-mode" polarization from the detection of the gravitational lensing of the CMB by large scale structure, and a detection or improved upper limit on a primordial signal due to inflationary gravity waves. The two measurements can be used to constrain the sum of the neutrino masses and the energy scale of inflation. These science goals can be achieved through the polarization sensitivity of the SPTpol camera and careful control of systematics. The SPTpol camera consists of 768 pixels, each containing two transition-edge sensor (TES) bolometers coupled to orthogonal polarizations, and a total of 1536 bolometers. The pixels are sensitive to light in one of two frequency bands centered at 90 and 150 GHz, with 180 pixels at 90 GHz and 588 pixels at 150 GHz. The SPTpol design has several features designed to control polarization systematics, including: singlemoded feedhorns with low cross-polarization, bolometer pairs well-matched to difference atmospheric signals, an improved ground shield design based on far-sidelobe measurements of the SPT, and a small beam to reduce temperature to polarization leakage. We present an overview of the SPTpol instrument design, project status, and science projections.

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Section: Projections and Performancesupporting

confidence: 64%

Section: Readoutmentioning

confidence: 99%

Section: Projections and Performancementioning

confidence: 99%

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SPTpol: an instrument for CMB polarization measurements with the South Pole Telescope

Austermann¹,

et al. 2012

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“…This matches how many focal planes are designed, e.g. the Planck (Maffei et al 2010), SPTpol (George et al 2012) and ACTpol (Thornton et al 2016) receivers. The focal planes for SO will also be at least partly composed of such combinations of detector orientations (Galitzki et al 2018).…”

Section: Introductionmentioning

confidence: 62%

Controlling systematics in ground-based CMB surveys with partial boresight rotation

Thomas

McCallum

Brown

2019

Monthly Notices of the Royal Astronomical Society

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Future CMB experiments will require exquisite control of systematics in order to constrain the B-mode polarisation power spectrum. One class of systematics that requires careful study is instrumental systematics. The potential impact of such systematics is most readily understood by considering analysis pipelines based on pair differencing. In this case, any differential gain, pointing or beam ellipticity between the two detectors in a pair can result in intensity leakage into the B-mode spectrum, which needs to be controlled to a high precision due to the much greater magnitude of the total intensity signal as compared to the B-mode signal. One well known way to suppress such systematics is through careful design of the scan-strategy, in particular making use of any capability to rotate the instrument about its pointing (boresight) direction.Here, we show that the combination of specific choices of such partial boresight rotation angles with redundancies present in the scan strategy is a powerful approach for suppressing systematic effects. This mitigation can be performed in analysis in advance of map-making and, in contrast to other approaches (e.g. deprojection or filtering), results in no signal loss. We demonstrate our approach explicitly with time ordered data simulations relevant to next-generation ground-based CMB experiments, using deep and wide scan strategies appropriate for experiments based in Chile. These simulations show a reduction of multiple orders of magnitude in the spurious B-mode signal arising from differential gain and differential pointing systematics.

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“…Indeed, our early devices were going unstable at operating bias points of ∼ 0.8 R N , near typical operating points for our 150 GHz detectors. 31 We tested several TES geometries to find an appropriate transition shape and deposited a non-superconducting metal, palladium gold ("bling"), around each TES to increase the detectors' time constants. We found that having a solid bar for the TES and extending the bling over the edge of the microstrip leads heading to the TES and into the TES region itself lowered α sufficiently while keeping 150 GHz detector loop gains in transition at an acceptable level.…”

Section: Dark Propertiesmentioning

confidence: 99%

Feedhorn-coupled TES polarimeter camera modules at 150 GHz for CMB polarization measurements with SPTpol

Henning¹,

Aird

Austermann³

et al. 2012

SPIE Proceedings

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The SPTpol camera is a dichroic polarimetric receiver at 90 and 150 GHz. Deployed in January 2012 on the South Pole Telescope (SPT), SPTpol is looking for faint polarization signals in the Cosmic Microwave Background (CMB). The camera consists of 180 individual Transition Edge Sensor (TES) polarimeters at 90 GHz and seven 84-polarimeter camera modules (a total of 588 polarimeters) at 150 GHz. We present the design, dark characterization, and in-lab optical properties of the 150 GHz camera modules. The modules consist of photolithographed arrays of TES polarimeters coupled to silicon platelet arrays of corrugated feedhorns, both of which are fabricated at NIST-Boulder. In addition to mounting hardware and RF shielding, each module also contains a set of passive readout electronics for digital frequency-domain multiplexing. A single module, therefore, is fully functional as a miniature focal plane and can be tested independently. Across the modules tested before deployment, the detectors average a critical temperature of 478 mK, normal resistance R N of 1.2 Ω, unloaded saturation power of 22.5 pW, (detector-only) optical efficiency of ∼ 90%, and have electrothermal time constants < 1 ms in transition.

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Performance and on-sky optical characterization of the SPTpol instrument

Cited by 18 publications

References 13 publications

SPTpol: an instrument for CMB polarization measurements with the South Pole Telescope

SPTpol: an instrument for CMB polarization measurements with the South Pole Telescope

Controlling systematics in ground-based CMB surveys with partial boresight rotation

Feedhorn-coupled TES polarimeter camera modules at 150 GHz for CMB polarization measurements with SPTpol

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