Full-sky beam convolution for cosmic microwave background applications

Duivenvoorden, Adriaan J.; Gudmundsson, J. E.; Rahlin, A.

doi:10.1093/mnras/stz1143

Cited by 14 publications

(19 citation statements)

References 82 publications

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“…This is likely due to the higher index of refraction of silicon which increases polarization dependence (see Section 4E). Simulations presented in [53] suggest that systematics due to the beam ellipticities of these two designs would not have a significant impact on the science goals of a 4th-generation CMB satellite experiment searching for a primordial B-mode polarization signal.…”

Section: Ellipticitiesmentioning

confidence: 99%

Geometrical and physical optics analysis for mm-wavelength refractor telescopes designed to map the cosmic microwave background

Gudmundsson¹

2020

Appl. Opt.

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We present a compact two-lens HDPE f /1.6 refractor design that is capable of supporting a 28-deg diffractionlimited field of view at 1-mm wavelengths and contrast it to a similar two-lens refractor using silicon lenses. We compare the optical properties of these two systems as predicted by both geometrical and physical optics. The presented analysis suggests that by relaxing telecentricity requirements, a plastic two-lens refractor system can perform comparably to a similar silicon system across a wide field of view and wavelengths up to 1 mm. We show that for both telescope designs, cold stop spillover changes significantly across the field of view in a way that is somewhat inconsistent with Gaussian beam formalism and simple f -number scaling. We present results that highlight beam ellipticity dependence on both pixel location and pixel aperture sizean effect that is challenging to reproduce in standard geometrical optics. We show that a silicon refractor design suffers from larger cross-polarization compared to the HDPE design. Our results address the limitations of solely relying on geometrical optics to assess relative performance of two optical systems. We discuss implications for future refractor designs.

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Section: Ellipticitiesmentioning

confidence: 99%

Geometrical and physical optics analysis for mm-wavelength refractor telescopes designed to map the cosmic microwave background

Gudmundsson¹

2020

Appl. Opt.

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“…Using this technique, we can predict the nominal beam response for the different frequency bands in the SO LAT. W e generate an ensemble of physical optics simulations using an application programming interface (API) that couples to TICRA Tools (formerly GRASP) [33]; a similar approach was described in [34,35]. 3 The physical optics simula- Fig.…”

Section: Physical Optics a Basic Model Setupmentioning

confidence: 99%

The Simons Observatory: modeling optical systematics in the Large Aperture Telescope

Gudmundsson¹,

Gallardo²,

Puddu³

et al. 2021

Appl. Opt.

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We present geometrical and physical optics simulation results for the Simons Observatory Large Aperture Telescope. This work was developed as part of the general design process for the telescope, allowing us to evaluate the impact of various design choices on performance metrics and potential systematic effects. The primary goal of the simulations was to evaluate the final design of the reflectors and the cold optics that are now being built. We describe nonsequential ray tracing used to inform the design of the cold optics, including absorbers internal to each optics tube. We discuss ray tracing simulations of the telescope structure that allow us to determine geometries that minimize detector loading and mitigate spurious near-field effects that have not been resolved by the internal baffling. We also describe physical optics simulations, performed over a range of frequencies and field locations, that produce estimates of monochromatic far-field beam patterns, which in turn are used to gauge general optical performance. Finally, we describe simulations that shed light on beam sidelobes from panel gap diffraction.

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“…Using the updated version of beamconv, we simulate one year of satellite scanning for 50 detectors. We use a similar scan strategy as in Duivenvoorden et al (2019), which is based on Gorski (2008); Wallis et al (2017). The satellite spins around its principal axis with a period of 600 seconds.…”

Section: Simulated Scanningmentioning

confidence: 99%

“…4) of monochromatic input skies, beams and HWP Mueller matrices. The memory costs and computational scaling of the algorithm have thus gained a linear scaling with 𝑛 𝜈 compared to the algorithm in Duivenvoorden et al (2019) but are unchanged otherwise. The algorithm allows for efficient time-domain simulations that include all-sky beam convolution with asymmetric beams and non-ideal HWPs.…”

Section: Data Modelmentioning

confidence: 99%

“…We also simulate the interaction between the HWP non-idealities and a realistic polarized beam and point out the importance of this potential systematic. To produce these simulations, we extend the beamconv 1 code, first described in Duivenvoorden et al (2019). The new code allows us to simulate the effects of nonideal HWPs on the time-ordered data (TOD) of CMB experiments.…”

Section: Introductionmentioning

confidence: 99%

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Probing frequency-dependent half-wave plate systematics for CMB experiments with full-sky beam convolution simulations

Duivenvoorden,

Adler,

Billi

et al. 2020

Preprint

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We study systematic effects from half-wave plates (HWPs) for cosmic microwave background (CMB) experiments using full-sky time-domain beam convolution simulations. Using an optical model for a fiducial spaceborne two-lens refractor telescope, we investigate how different HWP configurations optimized for dichroic detectors centred at 95 and 150 GHz impact the reconstruction of primordial 𝐵-mode polarization. We pay particular attention to possible biases arising from the interaction of frequency dependent HWP non-idealities with polarized Galactic dust emission and the interaction between the HWP and the instrumental beam. To produce these simulations, we have extended the capabilities of the publicly available beamconv code. To our knowledge, we produce the first time-domain simulations that include both HWP non-idealities and realistic full-sky beam convolution. Our analysis shows how certain achromatic HWP configurations produce significant systematic polarization angle offsets that vary for sky components with different frequency dependence. Our analysis also demonstrates that once we account for interactions with HWPs, realistic beam models with non-negligible cross-polarization and sidelobes will cause significant 𝐵-mode residuals that will have to be extensively modelled in some cases.

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Full-sky beam convolution for cosmic microwave background applications

Cited by 14 publications

References 82 publications

Geometrical and physical optics analysis for mm-wavelength refractor telescopes designed to map the cosmic microwave background

Geometrical and physical optics analysis for mm-wavelength refractor telescopes designed to map the cosmic microwave background

The Simons Observatory: modeling optical systematics in the Large Aperture Telescope

Probing frequency-dependent half-wave plate systematics for CMB experiments with full-sky beam convolution simulations

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