The Simons Observatory: Rotation Performance of Cryogenic Half-Wave Plate Polarization Modulators

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Hauptverfasser: Yamada, Kyohei, Bixler, Bryce, Sugiyama, Junna, Sasaki, Daichi, Sakurai, Yuki, Arnold, Kam, Day-Weiss, Samuel, Galitzki, Nicholas, Johnson, Bradley R., Kusaka, Akito, Page, Lyman A., Sueno, Yoshinori
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Veröffentlicht: 2026
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author Yamada, Kyohei
Bixler, Bryce
Sugiyama, Junna
Sasaki, Daichi
Sakurai, Yuki
Arnold, Kam
Day-Weiss, Samuel
Galitzki, Nicholas
Johnson, Bradley R.
Kusaka, Akito
Page, Lyman A.
Sueno, Yoshinori
author_facet Yamada, Kyohei
Bixler, Bryce
Sugiyama, Junna
Sasaki, Daichi
Sakurai, Yuki
Arnold, Kam
Day-Weiss, Samuel
Galitzki, Nicholas
Johnson, Bradley R.
Kusaka, Akito
Page, Lyman A.
Sueno, Yoshinori
contents We present the on-site rotation performance of the first three cryogenic continuously rotating half-wave plate (HWP) polarization modulators for the Simons Observatory small aperture telescopes (SATs). The SATs operate at an altitude of 5200 m in the Atacama Desert in northern Chile, and measure the degree-scale cosmic microwave background polarization to search for primordial $B$-mode polarization. To this end, the SATs employ a 505 mm diameter 50 K cryogenic HWP polarization modulator to suppress atmospheric $1/f$ noise and to mitigate systematic uncertainties. We present methods for reconstructing the rotation of our polarization modulators, enabling detailed evaluations of their rotation angle accuracy, stability, displacements, and vibrations. We achieve the required rotation angle accuracy in more than 99.9% of observations, with a median noise level of 0.16 $μ$rad$\sqrt{\text{s}}$. We also achieve one-dimensional measurement of the rotor displacement with an accuracy of 0.06 $μ\text{m}\sqrt{\text{s}}$. Our results demonstrate the on-site rotation performance, rotation angle reconstruction method, and robustness of the polarization angle modulators. This is a crucial step towards achieving the SAT science goals.
format Preprint
id arxiv_https___arxiv_org_abs_2605_27056
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The Simons Observatory: Rotation Performance of Cryogenic Half-Wave Plate Polarization Modulators
Yamada, Kyohei
Bixler, Bryce
Sugiyama, Junna
Sasaki, Daichi
Sakurai, Yuki
Arnold, Kam
Day-Weiss, Samuel
Galitzki, Nicholas
Johnson, Bradley R.
Kusaka, Akito
Page, Lyman A.
Sueno, Yoshinori
Instrumentation and Methods for Astrophysics
We present the on-site rotation performance of the first three cryogenic continuously rotating half-wave plate (HWP) polarization modulators for the Simons Observatory small aperture telescopes (SATs). The SATs operate at an altitude of 5200 m in the Atacama Desert in northern Chile, and measure the degree-scale cosmic microwave background polarization to search for primordial $B$-mode polarization. To this end, the SATs employ a 505 mm diameter 50 K cryogenic HWP polarization modulator to suppress atmospheric $1/f$ noise and to mitigate systematic uncertainties. We present methods for reconstructing the rotation of our polarization modulators, enabling detailed evaluations of their rotation angle accuracy, stability, displacements, and vibrations. We achieve the required rotation angle accuracy in more than 99.9% of observations, with a median noise level of 0.16 $μ$rad$\sqrt{\text{s}}$. We also achieve one-dimensional measurement of the rotor displacement with an accuracy of 0.06 $μ\text{m}\sqrt{\text{s}}$. Our results demonstrate the on-site rotation performance, rotation angle reconstruction method, and robustness of the polarization angle modulators. This is a crucial step towards achieving the SAT science goals.
title The Simons Observatory: Rotation Performance of Cryogenic Half-Wave Plate Polarization Modulators
topic Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2605.27056